Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Joel, On Nov 6, 2012, at 4:06 AM, Joel A Fernandes wrote: Hi Grant, On Mon, Nov 5, 2012 at 5:58 PM, Grant Likely grant.lik...@secretlab.ca wrote: Joel A Fernandes agnel.j...@gmail.com wrote: Hi Grant, On Mon, Nov 5, 2012 at 2:14 PM, Grant Likely grant.lik...@secretlab.ca wrote: I'm open to suggestions if anyone has any. I have not objections to a fixup approach, but I'm not comfortable with anything that is fragile to modifications to the fragment. I am fairly new to the DT world so please bear with me, but how about a method that resolves symbols the same way that the linux dynamic linker does when shared libraries are loaded? A separate table (similar to .PLT/GOT sections in the ELF object format) could be created when the fragment is loaded, and the phandle references could be fixed to point to the table offsets during compile time. This table would be a second level indirection and the kernel would populate this table with the in-kernel values of the phandles that the dt fragment refers to. That's an interesting idea that is worth exploring. That would make it possible to avoid a fixup stage, but it also means that any parsing code must know how to handle the got-like table. It won't be backwards compatible with existing tools. It also wouldn't easily support the case of firmware applying the overlay and passing the resulting tree to the kernel. Hmmm Not being backwards compatible at the data level is a big problem. I really want a method that can resolve back to the current data format or is a compatible extension of it. Is it meaningful or feasible to make the table a part of the tree structure itself? the table would initially be empty. If I'm right, this is how the GOT tables in ELF objects that refer to unresolved symbols in shared libraries are implemented as well, they are a part of the object and are loaded into memory and fixed up. If the table is a part of the DT data, the tools would then be able to parse such a tree. We could enforce that the got-like tree would strictly follow a predefined format. Something along these lines would also avoid the need for a tree fix up. Do you think this reduces the difficulty of backward compatibility with the parsing tools and firmware loading? To be honest here, we are discussing a new object format. There are a few twists IMO. a) We definitely, absolutely, don't want to introduce anything that will risk compatibility with devices already out there. The binary format for device trees that don't need the dynamic resolution features we're talking about here, should be be usable for those older devices. b) Device tree is flexible enough to store the additional data in it's own node format. So we shouldn't have any kind of binary data tacked on; this ties with a) - make sure that the binary format doesn't change. c) There is no need (at least AFAIKT) of having any other resolution type than a phandle of a node. d) Finally, for some use-cases the problem is simplified by not having all the features of a true dynamic linker. For example for the capebus case the 'base' DTS won't have any references to any fragments. It is only the fragments that have unresolved references and only to the 'base' DTS. This might involve changes to the DT core, but as such, this method wouldn't suffer from the fragility problem of either base or fragment DT trees being modified. The table itself could be added to the tree by the compiler, and the phandles could point to it (fixed). such phandles could be marked for special handling to facilitate the 1-level indirection. That's part of the problem. Property values are essentially anaonymous data. There is no mechanism currently for marking data such as indicate which data values are phandles. If there were then it would be a simple matter to find all the phandles and fix them up. We could possibly add data type suppplementary properties to the tree to solve that problem. They would have to be optional for the base tree to retain backwards compatibility, but could be required on overlays. Sure, so if we add data type supplementary properties to the tree to indicate the data type as indirect phandle, then kernel could refer to the index in the got-like table to fetch the actual phandle address (1-level of indirection), instead of directly using the address in the data field. I'm fine with this. Thanks and Regards, Joel Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Tue, Nov 6, 2012 at 8:14 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: On Nov 6, 2012, at 4:06 AM, Joel A Fernandes wrote: Sure, so if we add data type supplementary properties to the tree to indicate the data type as indirect phandle, then kernel could refer to the index in the got-like table to fetch the actual phandle address (1-level of indirection), instead of directly using the address in the data field. I'm fine with this. But if the data about phandles is already in the tree, then the need for a GOT simply goes away. The phandles can be fixed up directly and it is so much better because it works with existing parsing code after the merge is applied. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Από το iPhone μου 6 Νοε 2012, 12:16, ο/η Grant Likely grant.lik...@secretlab.ca έγραψε: On Tue, Nov 6, 2012 at 8:14 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: On Nov 6, 2012, at 4:06 AM, Joel A Fernandes wrote: Sure, so if we add data type supplementary properties to the tree to indicate the data type as indirect phandle, then kernel could refer to the index in the got-like table to fetch the actual phandle address (1-level of indirection), instead of directly using the address in the data field. I'm fine with this. But if the data about phandles is already in the tree, then the need for a GOT simply goes away. The phandles can be fixed up directly and it is so much better because it works with existing parsing code after the merge is applied. Either way works. It is your call after all. I agree that your method is simpler. g. Regards -- Pantelis-- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Nov 5, 2012, at 1:22 AM, Grant Likely wrote: On Fri, Nov 2, 2012 at 8:43 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. This is actually exactly the direction I want to go with DT, which the ability to load supplemental DT data blobs from either a kernel module or userspace using the firmware loading infrastructure. g. Hi Grant, That's pretty much our use case. Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Mon, Nov 5, 2012 at 1:25 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: On Nov 5, 2012, at 1:22 AM, Grant Likely wrote: On Fri, Nov 2, 2012 at 8:43 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. This is actually exactly the direction I want to go with DT, which the ability to load supplemental DT data blobs from either a kernel module or userspace using the firmware loading infrastructure. g. Hi Grant, That's pretty much our use case. Regards Good. I'm about 80% though putting together a project plan of what is required to implement this. I'll post it for RFC shortly. I would appreciate feedback and help on flushing out the design. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Grant Likely grant.lik...@secretlab.ca [121105 06:36]: On Mon, Nov 5, 2012 at 1:25 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: On Nov 5, 2012, at 1:22 AM, Grant Likely wrote: On Fri, Nov 2, 2012 at 8:43 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. This is actually exactly the direction I want to go with DT, which the ability to load supplemental DT data blobs from either a kernel module or userspace using the firmware loading infrastructure. g. Hi Grant, That's pretty much our use case. Regards Good. I'm about 80% though putting together a project plan of what is required to implement this. I'll post it for RFC shortly. I would appreciate feedback and help on flushing out the design. Great, sounds like almost-a-plan then :) Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Grant,
On Nov 5, 2012, at 1:37 AM, Grant Likely wrote:
On Fri, Nov 2, 2012 at 12:32 PM, Pantelis Antoniou
pa...@antoniou-consulting.com wrote:
The i2c2 alias cannot be resolved at compile time; there has to be
a) A DT object format where unresolved aliases (symbols) are tracked
b) A runtime DT linker that will resolve the alias, and will insert the
i2c2-devices child nodes as children in the i2c2 node.
c) A method to trigger platform device creation for the child nodes just
inserted.
DT core changes aren't bound to be easily accepted, so without having a clear
signal from the DT maintainers that they would consider such a method people
are just hesitant to go down this road.
I do agree and will accept such a method.
g.
Understood.
I'll think about the issues and come up with a design for the format, but
let's talk about this in the open for a while.
I don't want to modify the DTB format, in order to avoid impacting any other
DT users.
So would something like this work for you?
-88
/* booting DT (all symbols are resolved) */
/* this is a valid DTB today */
/ {
i2c2: i2c@4819c000 {
compatible = ti,omap4-i2c;
#address-cells = 1;
#size-cells = 0;
ti,hwmods = i2c3; /* TODO: Fix hwmod */
reg = 0x4819c000 0x1000;
interrupt-parent = intc;
interrupts = 30;
status = on-demand;
};
/* others nodes */
/* the symbols node can be generated by the DTC */
symbols {
compatible = dt,symbols;
symbol@0 {
name = i2c2;
phandle = i2c2;
};
...
};
};
-88
/* fragment DT (not all symbols are resolved) */
/ {
i2c2-append {
compatible = dt,append;
#address-cells = 1;
#size-cells = 0;
append-at = i2c2;/* offset F00, either -1 (end of list)
*/
/* or next offset in the list of i2c2
refs. */
/* Ambient light sensor */
tsl2550@39 {
compatible = tsl,tsl2550;
reg = 0x39;
};
};
};
-88
The i2c2 value can't be resolved at compile time.
We can use a simple linked list method for keeping track of the
locations in the fragment which we need to resolve, terminating with -1.
The compiler can add the following nodes to mark the entries requiring
resolution.
For example i2c2...
dt-resolution {
i2c2 = 0xf00; /* first offset in the dtb fragment requiring */
/* resolution of i2c2 */
};
The dt-resolution node, can be appended to the dt fragment contents and
can be generated by the compiler.
Upon injection of the DT fragment the in-kernel loader can perform
symbol resolution and replace the phandles with the in-kernel values.
I know there's an aliases node, but I don't know if it's wise to modify it.
What do you think?
Regards
-- Pantelis
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On 11/05/2012 08:34 AM, Grant Likely wrote: On Mon, Nov 5, 2012 at 1:25 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: On Nov 5, 2012, at 1:22 AM, Grant Likely wrote: On Fri, Nov 2, 2012 at 8:43 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. This is actually exactly the direction I want to go with DT, which the ability to load supplemental DT data blobs from either a kernel module or userspace using the firmware loading infrastructure. g. Hi Grant, That's pretty much our use case. Regards Good. I'm about 80% though putting together a project plan of what is required to implement this. I'll post it for RFC shortly. I would appreciate feedback and help on flushing out the design. The FPGA folks are also interested in dynamic DT configuration. There's been some discussion and postings on the DT list in the last few months you may have missed. It's maybe not completely the same use case, but there is some overlap here. Rob -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Mon, Nov 5, 2012 at 3:37 PM, Pantelis Antoniou
pa...@antoniou-consulting.com wrote:
Hi Grant,
On Nov 5, 2012, at 1:37 AM, Grant Likely wrote:
On Fri, Nov 2, 2012 at 12:32 PM, Pantelis Antoniou
pa...@antoniou-consulting.com wrote:
The i2c2 alias cannot be resolved at compile time; there has to be
a) A DT object format where unresolved aliases (symbols) are tracked
b) A runtime DT linker that will resolve the alias, and will insert the
i2c2-devices child nodes as children in the i2c2 node.
c) A method to trigger platform device creation for the child nodes just
inserted.
DT core changes aren't bound to be easily accepted, so without having a
clear
signal from the DT maintainers that they would consider such a method people
are just hesitant to go down this road.
I do agree and will accept such a method.
g.
Understood.
I'll think about the issues and come up with a design for the format, but
let's talk about this in the open for a while.
Agreed. I'm planning to post my first draft/RFC tonight.
I don't want to modify the DTB format, in order to avoid impacting any other
DT users.
Ditto. It should be a direct extension.
So would something like this work for you?
[...]
The dt-resolution node, can be appended to the dt fragment contents and
can be generated by the compiler.
Upon injection of the DT fragment the in-kernel loader can perform
symbol resolution and replace the phandles with the in-kernel values.
I know there's an aliases node, but I don't know if it's wise to modify it.
What do you think?
If I'm reading your intent correctly, your primary worry is the
problem of matching up phandles from the base dt with (potentially
different) phandle values in the overlay. This solution solves it by
encoding all of the phandle locations as offsets from the start of the
file into the dt-resolution node. Correct? My concern with this
approach is that it is fragile. Any changes to the fragment file, such
as to add extra properties or nodes, or even to repack the tree will
break all the offsets; probably silently.
It would be less fragile if each property containing phandles had some
kind of .prop-phandle-offsets companion property that listed the
phandles that need to be fixed up as an offset to the beginning of
only that properties' data. Better, in that modifying the tree won't
break the links, but I still worry that it is fragile and possibly too
complex.
However, the problem is based on the assumption that phandles are
effectively random and could change ever time the tree is recompiled.
Well, what if they weren't? What if dtc generated phandles using a
hash of the node full name so that the value changed rarely? Also,
what if the format was oriented around detecting if the phandles don't
match instead of fixing things up? The solution becomes a lot simpler
if the parser only has to verify that the referenced phandles already
exist at the right path in the tree.
Something like this:
/include/ base-file.dts /* include might not be the right syntax here */
i2c0 { /* i2c0 resolved by label */
touchpad@10 {
compatible = acme,touchpad;
reg = 0x10;
interrupt-parent = intc;
interrupts = 100;
};
};
And the generated overlay dtb may look like this:
/ {
.readonly;
interrupt-controller@0x10005000 {
.readonly;
phandle = 0x1234;
};
peripheral-bus {
.readonly;
i2c@20001000 {
touchpad@10 {
compatible = acme,touchpad;
reg = 0x10;
interrupt-parent = 0x1234;
interrupts = 100;
};
};
};
};
Which is obviously missing a bunch of information for the rest of the
system, but contains enough data to ensure that the path to the touchpad
node is valid and that the phandle has not changed.
This handles many of the use cases, but it assumes that an overlay is
board specific. If it ever is required to support multiple base boards
with a single overlay file then there is a problem. The .dtb overlays
generated in this manor cannot handle different phandles or nodes that
are in a different place. On the other hand, the overlay source files
should have no problem being compiled for multiple targets, so maybe
it isn't an issue. Plus if dtc is installed on the target, then the
live tree from /proc can be used as the reference when compiling the
overlay.
g.
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Mon, Nov 5, 2012 at 3:56 PM, Rob Herring robherri...@gmail.com wrote: On 11/05/2012 08:34 AM, Grant Likely wrote: Good. I'm about 80% though putting together a project plan of what is required to implement this. I'll post it for RFC shortly. I would appreciate feedback and help on flushing out the design. The FPGA folks are also interested in dynamic DT configuration. There's been some discussion and postings on the DT list in the last few months you may have missed. It's maybe not completely the same use case, but there is some overlap here. It should be very similar. I'll see if I can dig up those conversations. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Grant,
On Nov 5, 2012, at 8:10 PM, Grant Likely wrote:
On Mon, Nov 5, 2012 at 3:37 PM, Pantelis Antoniou
pa...@antoniou-consulting.com wrote:
Hi Grant,
On Nov 5, 2012, at 1:37 AM, Grant Likely wrote:
On Fri, Nov 2, 2012 at 12:32 PM, Pantelis Antoniou
pa...@antoniou-consulting.com wrote:
The i2c2 alias cannot be resolved at compile time; there has to be
a) A DT object format where unresolved aliases (symbols) are tracked
b) A runtime DT linker that will resolve the alias, and will insert the
i2c2-devices child nodes as children in the i2c2 node.
c) A method to trigger platform device creation for the child nodes just
inserted.
DT core changes aren't bound to be easily accepted, so without having a
clear
signal from the DT maintainers that they would consider such a method
people
are just hesitant to go down this road.
I do agree and will accept such a method.
g.
Understood.
I'll think about the issues and come up with a design for the format, but
let's talk about this in the open for a while.
Agreed. I'm planning to post my first draft/RFC tonight.
I don't want to modify the DTB format, in order to avoid impacting any other
DT users.
Ditto. It should be a direct extension.
Avoiding mobs of angry users with broken bootloader/kernel combos is a good
thing...
So would something like this work for you?
[...]
The dt-resolution node, can be appended to the dt fragment contents and
can be generated by the compiler.
Upon injection of the DT fragment the in-kernel loader can perform
symbol resolution and replace the phandles with the in-kernel values.
I know there's an aliases node, but I don't know if it's wise to modify it.
What do you think?
If I'm reading your intent correctly, your primary worry is the
problem of matching up phandles from the base dt with (potentially
different) phandle values in the overlay. This solution solves it by
encoding all of the phandle locations as offsets from the start of the
file into the dt-resolution node. Correct? My concern with this
approach is that it is fragile. Any changes to the fragment file, such
as to add extra properties or nodes, or even to repack the tree will
break all the offsets; probably silently.
Yes, this will not survive modification of the fragment file.
For the use case I'm targeting the DT fragment is going to be quite
minimal, a few tens of nodes at the most. Modification of a single
fragment file is not expected.
Modifications to the base tree, those would work just fine. The base
tree by definition will not have external references.
It would be less fragile if each property containing phandles had some
kind of .prop-phandle-offsets companion property that listed the
phandles that need to be fixed up as an offset to the beginning of
only that properties' data. Better, in that modifying the tree won't
break the links, but I still worry that it is fragile and possibly too
complex.
I believe this is considerably more complex, without fixing the
fragility problem.
However, the problem is based on the assumption that phandles are
effectively random and could change ever time the tree is recompiled.
Well, what if they weren't? What if dtc generated phandles using a
hash of the node full name so that the value changed rarely? Also,
what if the format was oriented around detecting if the phandles don't
match instead of fixing things up? The solution becomes a lot simpler
if the parser only has to verify that the referenced phandles already
exist at the right path in the tree.
Something like this:
/include/ base-file.dts /* include might not be the right syntax here */
i2c0 { /* i2c0 resolved by label */
touchpad@10 {
compatible = acme,touchpad;
reg = 0x10;
interrupt-parent = intc;
interrupts = 100;
};
};
And the generated overlay dtb may look like this:
/ {
.readonly;
interrupt-controller@0x10005000 {
.readonly;
phandle = 0x1234;
};
peripheral-bus {
.readonly;
i2c@20001000 {
touchpad@10 {
compatible = acme,touchpad;
reg = 0x10;
interrupt-parent = 0x1234;
interrupts = 100;
};
};
};
};
Which is obviously missing a bunch of information for the rest of the
system, but contains enough data to ensure that the path to the touchpad
node is valid and that the phandle has not changed.
I see what you mean. It will work, provided you 'link' (I don't know what
the proper terminology is) against the correct board dts file.
This handles many of the use cases, but it assumes that an overlay is
board specific. If it ever is required to support multiple base boards
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Mon, Nov 5, 2012 at 7:54 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: This handles many of the use cases, but it assumes that an overlay is board specific. If it ever is required to support multiple base boards with a single overlay file then there is a problem. The .dtb overlays generated in this manor cannot handle different phandles or nodes that are in a different place. On the other hand, the overlay source files should have no problem being compiled for multiple targets, so maybe it isn't an issue. Plus if dtc is installed on the target, then the live tree from /proc can be used as the reference when compiling the overlay. My worry is that this format is dependent on linking against the board DTS file. One of the ideas thrown around here was that it might make sense to store the DTB fragment in the EEPROM of the device. Right, that wouldn't work well if the base DT changed, or if a BeagleBone2 is released that has the same header configuration, but different backing devices. It would be nice to have a solution for that. In that case you have a OS independent hardware description, which can be even used even by the bootloader to access devices it knows not about at compile time. Other than that, I have no other objections. I'm open to suggestions if anyone has any. I have not objections to a fixup approach, but I'm not comfortable with anything that is fragile to modifications to the fragment. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Grant, On Mon, Nov 5, 2012 at 2:14 PM, Grant Likely grant.lik...@secretlab.ca wrote: On Mon, Nov 5, 2012 at 7:54 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: This handles many of the use cases, but it assumes that an overlay is board specific. If it ever is required to support multiple base boards with a single overlay file then there is a problem. The .dtb overlays generated in this manor cannot handle different phandles or nodes that are in a different place. On the other hand, the overlay source files should have no problem being compiled for multiple targets, so maybe it isn't an issue. Plus if dtc is installed on the target, then the live tree from /proc can be used as the reference when compiling the overlay. My worry is that this format is dependent on linking against the board DTS file. One of the ideas thrown around here was that it might make sense to store the DTB fragment in the EEPROM of the device. Right, that wouldn't work well if the base DT changed, or if a BeagleBone2 is released that has the same header configuration, but different backing devices. It would be nice to have a solution for that. In that case you have a OS independent hardware description, which can be even used even by the bootloader to access devices it knows not about at compile time. Other than that, I have no other objections. I'm open to suggestions if anyone has any. I have not objections to a fixup approach, but I'm not comfortable with anything that is fragile to modifications to the fragment. I am fairly new to the DT world so please bear with me, but how about a method that resolves symbols the same way that the linux dynamic linker does when shared libraries are loaded? A separate table (similar to .PLT/GOT sections in the ELF object format) could be created when the fragment is loaded, and the phandle references could be fixed to point to the table offsets during compile time. This table would be a second level indirection and the kernel would populate this table with the in-kernel values of the phandles that the dt fragment refers to. This might involve changes to the DT core, but as such, this method wouldn't suffer from the fragility problem of either base or fragment DT trees being modified. The table itself could be added to the tree by the compiler, and the phandles could point to it (fixed). such phandles could be marked for special handling to facilitate the 1-level indirection. What do you think about this? Regards, Joel -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Joel A Fernandes agnel.j...@gmail.com wrote: Hi Grant, On Mon, Nov 5, 2012 at 2:14 PM, Grant Likely grant.lik...@secretlab.ca wrote: I'm open to suggestions if anyone has any. I have not objections to a fixup approach, but I'm not comfortable with anything that is fragile to modifications to the fragment. I am fairly new to the DT world so please bear with me, but how about a method that resolves symbols the same way that the linux dynamic linker does when shared libraries are loaded? A separate table (similar to .PLT/GOT sections in the ELF object format) could be created when the fragment is loaded, and the phandle references could be fixed to point to the table offsets during compile time. This table would be a second level indirection and the kernel would populate this table with the in-kernel values of the phandles that the dt fragment refers to. That's an interesting idea that is worth exploring. That would make it possible to avoid a fixup stage, but it also means that any parsing code must know how to handle the got-like table. It won't be backwards compatible with existing tools. It also wouldn't easily support the case of firmware applying the overlay and passing the resulting tree to the kernel. Hmmm Not being backwards compatible at the data level is a big problem. I really want a method that can resolve back to the current data format or is a compatible extension of it. This might involve changes to the DT core, but as such, this method wouldn't suffer from the fragility problem of either base or fragment DT trees being modified. The table itself could be added to the tree by the compiler, and the phandles could point to it (fixed). such phandles could be marked for special handling to facilitate the 1-level indirection. That's part of the problem. Property values are essentially anaonymous data. There is no mechanism currently for marking data such as indicate which data values are phandles. If there were then it would be a simple matter to find all the phandles and fix them up. We could possibly add data type suppplementary properties to the tree to solve that problem. They would have to be optional for the base tree to retain backwards compatibility, but could be required on overlays. g. -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Grant, On Mon, Nov 5, 2012 at 5:58 PM, Grant Likely grant.lik...@secretlab.ca wrote: Joel A Fernandes agnel.j...@gmail.com wrote: Hi Grant, On Mon, Nov 5, 2012 at 2:14 PM, Grant Likely grant.lik...@secretlab.ca wrote: I'm open to suggestions if anyone has any. I have not objections to a fixup approach, but I'm not comfortable with anything that is fragile to modifications to the fragment. I am fairly new to the DT world so please bear with me, but how about a method that resolves symbols the same way that the linux dynamic linker does when shared libraries are loaded? A separate table (similar to .PLT/GOT sections in the ELF object format) could be created when the fragment is loaded, and the phandle references could be fixed to point to the table offsets during compile time. This table would be a second level indirection and the kernel would populate this table with the in-kernel values of the phandles that the dt fragment refers to. That's an interesting idea that is worth exploring. That would make it possible to avoid a fixup stage, but it also means that any parsing code must know how to handle the got-like table. It won't be backwards compatible with existing tools. It also wouldn't easily support the case of firmware applying the overlay and passing the resulting tree to the kernel. Hmmm Not being backwards compatible at the data level is a big problem. I really want a method that can resolve back to the current data format or is a compatible extension of it. Is it meaningful or feasible to make the table a part of the tree structure itself? the table would initially be empty. If I'm right, this is how the GOT tables in ELF objects that refer to unresolved symbols in shared libraries are implemented as well, they are a part of the object and are loaded into memory and fixed up. If the table is a part of the DT data, the tools would then be able to parse such a tree. We could enforce that the got-like tree would strictly follow a predefined format. Something along these lines would also avoid the need for a tree fix up. Do you think this reduces the difficulty of backward compatibility with the parsing tools and firmware loading? This might involve changes to the DT core, but as such, this method wouldn't suffer from the fragility problem of either base or fragment DT trees being modified. The table itself could be added to the tree by the compiler, and the phandles could point to it (fixed). such phandles could be marked for special handling to facilitate the 1-level indirection. That's part of the problem. Property values are essentially anaonymous data. There is no mechanism currently for marking data such as indicate which data values are phandles. If there were then it would be a simple matter to find all the phandles and fix them up. We could possibly add data type suppplementary properties to the tree to solve that problem. They would have to be optional for the base tree to retain backwards compatibility, but could be required on overlays. Sure, so if we add data type supplementary properties to the tree to indicate the data type as indirect phandle, then kernel could refer to the index in the got-like table to fetch the actual phandle address (1-level of indirection), instead of directly using the address in the data field. Thanks and Regards, Joel -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 8:43 AM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. This is actually exactly the direction I want to go with DT, which the ability to load supplemental DT data blobs from either a kernel module or userspace using the firmware loading infrastructure. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 10:19 AM, Koen Kooi k...@dominion.thruhere.net wrote:
button@1 {
debounce_interval = 50;
linux,code = 105;
label = left;
gpios = gpio2 16 0x0;
gpio-key,wakeup;
autorepeat;
};
Is the linux,code pure hardware or have there already been exceptions to
that rule?
I generally push back on linux,blah bindings since they have the
tendency to change over time when someone changes the driver. However,
since the keycodes are part of the Linux userspace ABI, and are
therefore pretty much set it stone, I didn't object to the
linux,keycode binding. There are already drivers using it.
g.
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 12:32 PM, Pantelis Antoniou pa...@antoniou-consulting.com wrote: The i2c2 alias cannot be resolved at compile time; there has to be a) A DT object format where unresolved aliases (symbols) are tracked b) A runtime DT linker that will resolve the alias, and will insert the i2c2-devices child nodes as children in the i2c2 node. c) A method to trigger platform device creation for the child nodes just inserted. DT core changes aren't bound to be easily accepted, so without having a clear signal from the DT maintainers that they would consider such a method people are just hesitant to go down this road. I do agree and will accept such a method. g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 4:07 PM, Jason Kridner jkrid...@beagleboard.org wrote: Take a look at arch/x86/platform/mrst/mrst.c. It's a specific example of a platform which parses tables and attaches devices to the right physical bus in a manner they can be reliably probed even when the device has no sane autodetect. I know I *am* the slow person in the room, but doesn't this approach require the code to be compiled into the kernel to support the devices ahead of time? While I think it might be reasonable to have hardware developers provide DT fragments in their EEPROMs, there's no way to get them to submit code patches in order to get their hardware to work. They need to ship hardware that works with pre-existing software, since there will be hundreds of boards created by people with little to no previous Linux experience (akin to Arduino). I seem to be missing how that approach would get us there. If it is truly new hardware, then there really is no way around them either a) submitting new kernel drivers or b) driving them from userspace. If it is devices with existing drivers populated onto new custom cape boards, then the DT fragment approach should be sufficient for populating them into the Linux driver model. (assuming of course those drivers are already compiled into the kernel) g. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On 11/02/2012 09:43 AM, Pantelis Antoniou wrote: [...] And then use the standard DT support to create later the platform_device that does represent the new super-cape devices. We know this is the ideal case. In fact that's the long term goal and we had internal discussions about it. Since you already had internal discussions about this, it would have been a great help in avoiding lots of this discussion if you would've summarized this ideal case from the beginning, then describe the weaknesses and limitations of DT for handling hotplug/dynamic devices and thus the reasoning behind creating capebus. Now it's taken this long thread for others to try to convince you about something you already knew to be the ideal case. Seems a bit wasteful. Kernel development typically works by building/extending infrastructure that is already there. Only when it's obvious that the current infrastructure cannot be extended for a new kind of usage do we build new infrastruture. In this case, DT is the obvious infrastructure that needs extending. At least we can all agree on that, for starters. DT is nowhere near being able to do it. That would require the introduction of a DT object file format with aliases being capable to be resolved dynamically. We're talking about major changes here in the way DT files are being compiled and used in practice. So yes, in an ideal world that would be great. We're nowhere near close today unfortunately. Assuming that we do work on a DT object format, and that the runtime resolution mechanism is approved, then I agree that this part of the capebus patches can be dropped and the functionality assumed by generic DT core. The question is that this will take time, with no guarantees that this would be acceptable from the device tree maintainers. So I am putting them in the CC list, to see what they think about it. Since this thread has already ventured into the weeds a few times, I would suggest that you summarize the DT limitations (focusing on they dynamic/hotplug needs) and start a thread on devicetree-discuss, so that the DT maintainers can be helpful without having to follow this thread. IMO, the path forward is clear (though probably longer than you would like): Let's first try and extend DT infrastructure. If that is obviously going nowhere, and DT maintainers are against it. Then, let's revisit capebus. Kevin -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On 11/1/2012 1:00 PM, Koen Kooi wrote: tl;dr: please suggest an actual solution that allows plugplay when plugging in multiple capes and applying power after that. Preferably one that doesn't pass the buck to u-boot. Op 1 nov. 2012, om 12:26 heeft Cousson, Benoit b-cous...@ti.com het volgende geschreven: Hi Panto, On 11/1/2012 11:39 AM, Pantelis Antoniou wrote: Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Benoit, On Nov 2, 2012, at 10:15 AM, Cousson, Benoit wrote: On 11/1/2012 1:00 PM, Koen Kooi wrote: tl;dr: please suggest an actual solution that allows plugplay when plugging in multiple capes and applying power after that. Preferably one that doesn't pass the buck to u-boot. Op 1 nov. 2012, om 12:26 heeft Cousson, Benoit b-cous...@ti.com het volgende geschreven: Hi Panto, On 11/1/2012 11:39 AM, Pantelis Antoniou wrote: Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi, On Thu, Nov 01, 2012 at 04:49:23PM -0700, Russ Dill wrote: On Thu, Nov 1, 2012 at 3:05 PM, Felipe Balbi ba...@ti.com wrote: HI, On Thu, Nov 01, 2012 at 03:59:50PM +0200, Pantelis Antoniou wrote: Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat flexible. One devices read may be another devices write. A detect look at what other drivers do. You can read a revision register, you can write a command and see if the device responds as expected, it doesn't matter. method that only performs reads could easily toggle a gpio that resets the board, rewrite and eeprom, or set the printer on fire. If you how ? It's just a read. browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) it doesn't mean it can't be done. On top of all this the detect routine does not tell you if the alert pin is connected to some IRQ, or in the case of a GPIO expander, what those GPIOs are connected to, etc, etc. so what ? All you want to do with detect is figure out if the far end is who you think it is, not what it's doing. -- balbi signature.asc Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Jason, On 11/1/2012 7:50 PM, Jason Kridner wrote: My apologies for starting a new thread, but I don't have this thread in my Inbox. http://www.spinics.net/lists/linux-omap/msg81034.html Tony Lindgren wrote: * Pantelis Antoniou panto@xxx [121031 15:02]: So when device's node is 'disabled' of_platform_device_create_pdata() will not create the device. Now, of course it is possible to re-trigger the platform's probe method to be called, and in fact I do so in the capebus patches. You should fix this in generic way then rather than working around it in capebus. The same problem exists changing between different functionality for the shared pins, let's say between USB pins and UART pins if you want a serial debug console on some phone. The current capebus solution goes a long way to fixing a huge issue for BeagleBone users and I don't understand what seems to be a push-back on principle. On BeagleBone capes, these conflicts cannot be resolved early. I don't think there is any push-back on the principle. It is a very valid problem that does not have any solution today. The comments are more on the implementation. Do you have suggestions on some more generic method? It seems to me the proposed capebus approach strikes a good balance. Well, yeah, that's a generic DT issue, not a beagle-cape issue. We should not necessarily handle it by introducing some fake bus and some new binding like spi-dt / i2c-dt that does not mean anything in term of HW. DT is about pure HW representation. Introducing some fake hierarchy to make SW life easier is not necessarily the good approach. Adding the version information in the nodes is potentially a good idea, but should clearly be well thought and part of the DT core. Regards, Benoit -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 1:57 AM, Felipe Balbi ba...@ti.com wrote: Hi, On Thu, Nov 01, 2012 at 04:49:23PM -0700, Russ Dill wrote: On Thu, Nov 1, 2012 at 3:05 PM, Felipe Balbi ba...@ti.com wrote: HI, On Thu, Nov 01, 2012 at 03:59:50PM +0200, Pantelis Antoniou wrote: Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat flexible. One devices read may be another devices write. A detect look at what other drivers do. You can read a revision register, you can write a command and see if the device responds as expected, it doesn't matter. Since a revision register isn't required by the I²C spec, it isn't implemented on a huge number of chips. Also, having a few dozen probe routines come though and write to random address of every single I²C device can a) take a really long time, and b) have quite a few unintended side effects. method that only performs reads could easily toggle a gpio that resets the board, rewrite and eeprom, or set the printer on fire. If you how ? It's just a read. Because the I²C spec is incredibly flexible. For a lot of devices, reading from a register is done by writing the register address, and then reading the contents. For devices that don't implement registers in that way (such as many eeproms), this is just a write. browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) it doesn't mean it can't be done. Really? Please, do tell how you would write a detect function for a PCA9534. It has 4 registers, an input port registers, an output port register, a polarity inversion register, and a configuration register. And don't forget, since we are probing, every detect routine for every I²C driver will have to run with every I²C address on every bus, possibly with both address formats. On top of all this the detect routine does not tell you if the alert pin is connected to some IRQ, or in the case of a GPIO expander, what those GPIOs are connected to, etc, etc. so what ? All you want to do with detect is figure out if the far end is who you think it is, not what it's doing. If we already knew who was there, we wouldn't need a detect routine. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Op 2 nov. 2012, om 10:26 heeft Cousson, Benoit b-cous...@ti.com het
volgende geschreven:
Hi Jason,
On 11/1/2012 7:50 PM, Jason Kridner wrote:
My apologies for starting a new thread, but I don't have this thread
in my Inbox.
http://www.spinics.net/lists/linux-omap/msg81034.html
Tony Lindgren wrote:
* Pantelis Antoniou panto@xxx [121031 15:02]:
So when device's node is 'disabled' of_platform_device_create_pdata()
will not create the device.
Now, of course it is possible to re-trigger the platform's probe method
to be called, and in fact I do so in the capebus patches.
You should fix this in generic way then rather than working
around it in capebus. The same problem exists changing
between different functionality for the shared pins,
let's say between USB pins and UART pins if you want a
serial debug console on some phone.
The current capebus solution goes a long way to fixing a huge issue
for BeagleBone users and I don't understand what seems to be a
push-back on principle. On BeagleBone capes, these conflicts cannot be
resolved early.
I don't think there is any push-back on the principle. It is a very valid
problem that does not have any solution today.
The comments are more on the implementation.
Do you have suggestions on some more generic method? It seems to me
the proposed capebus approach strikes a good balance.
Well, yeah, that's a generic DT issue, not a beagle-cape issue.
We should not necessarily handle it by introducing some fake bus and some new
binding like spi-dt / i2c-dt that does not mean anything in term of HW.
DT is about pure HW representation. Introducing some fake hierarchy to make
SW life easier is not necessarily the good approach.
I see, pure HW. Let's look at this:
gpio_keys {
compatible = gpio-keys;
pinctrl-names = default;
pinctrl-0 = bone_lcd3_cape_keys_00A0_pins;
#address-cells = 1;
#size-cells = 0;
button@1 {
debounce_interval = 50;
linux,code = 105;
label = left;
gpios = gpio2 16 0x0;
gpio-key,wakeup;
autorepeat;
};
Is the linux,code pure hardware or have there already been exceptions to that
rule?
regards,
Koen--
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Op 2 nov. 2012, om 10:42 heeft Russ Dill russ.d...@ti.com het volgende geschreven: On Fri, Nov 2, 2012 at 1:57 AM, Felipe Balbi ba...@ti.com wrote: Hi, On Thu, Nov 01, 2012 at 04:49:23PM -0700, Russ Dill wrote: On Thu, Nov 1, 2012 at 3:05 PM, Felipe Balbi ba...@ti.com wrote: HI, On Thu, Nov 01, 2012 at 03:59:50PM +0200, Pantelis Antoniou wrote: Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat flexible. One devices read may be another devices write. A detect look at what other drivers do. You can read a revision register, you can write a command and see if the device responds as expected, it doesn't matter. Since a revision register isn't required by the I²C spec, it isn't implemented on a huge number of chips. Also, having a few dozen probe routines come though and write to random address of every single I²C device can a) take a really long time, and b) have quite a few unintended side effects. method that only performs reads could easily toggle a gpio that resets the board, rewrite and eeprom, or set the printer on fire. If you how ? It's just a read. Because the I²C spec is incredibly flexible. For a lot of devices, reading from a register is done by writing the register address, and then reading the contents. For devices that don't implement registers in that way (such as many eeproms), this is just a write. browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) it doesn't mean it can't be done. Really? Please, do tell how you would write a detect function for a PCA9534. It has 4 registers, an input port registers, an output port register, a polarity inversion register, and a configuration register. And don't forget, since we are probing, every detect routine for every I²C driver will have to run with every I²C address on every bus, possibly with both address formats. Worse, things like early revisions of the picoDLP projector will erase their firmware if you do a linear scan through all addresses. regards, Koen-- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi, On Fri, Nov 02, 2012 at 02:42:51AM -0700, Russ Dill wrote: browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) it doesn't mean it can't be done. Really? Please, do tell how you would write a detect function for a PCA9534. It has 4 registers, an input port registers, an output port register, a polarity inversion register, and a configuration register. read them and match to their reset values, perhaps ? And don't forget, since we are probing, every detect routine for every I²C driver will have to run with every I²C address on every bus, possibly with both address formats. not *every* I2C address. What you say is wrong, a -detect() method will only run for those addresses which the device can actually assume. On top of all this the detect routine does not tell you if the alert pin is connected to some IRQ, or in the case of a GPIO expander, what those GPIOs are connected to, etc, etc. so what ? All you want to do with detect is figure out if the far end is who you think it is, not what it's doing. If we already knew who was there, we wouldn't need a detect routine. of course not :-) But the whole discussion has been about not knowing which capes (and thus which devices) are attached to the bone. -- balbi signature.asc Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. A bus is the wrong construct. You need something to add devices onto the busses. You can do that. The Intel SFI layer on phones for example enumerates devices through a firmware table set and creates them on the right actual physical bus not on their own fake one. It's not hotplug in the sense that the phone happens be a fixed configuration but it does support hotplug behaviour because the order of the drivers and enumeration is undefined (and both orders work). I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat It doesn't matter. What you are basically talking about is cape layer - wtf is this - how do I plumb it - create device nodes with correct name for binding, address etc on the right bus i2c layer - ooh a new i2c device - probe as indicated by device name - attach correct driver Architecturally its possible you want to make some caps MFDs if they have their own bus heirarchies etc but generally I doubt it. Take a look at arch/x86/platform/mrst/mrst.c. It's a specific example of a platform which parses tables and attaches devices to the right physical bus in a manner they can be reliably probed even when the device has no sane autodetect. Alan -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Alan,
On Nov 2, 2012, at 1:21 PM, Alan Cox wrote:
Fair enough. But there's no such thing a 'hotplug enumeration
construct' in Linux yet, and a bus is the closest thing to it. It does
take advantage of the nice way device code matches drivers and devices
though.
A bus is the wrong construct. You need something to add devices onto the
busses. You can do that. The Intel SFI layer on phones for example
enumerates devices through a firmware table set and creates them on the
right actual physical bus not on their own fake one.
It's not hotplug in the sense that the phone happens be a fixed
configuration but it does support hotplug behaviour because the order of
the drivers and enumeration is undefined (and both orders work).
I see. The firmware table format is similar to our case where we use DT.
We don't have to come up with another firmware table format, like SFI here.
The problem is that we have to inject DT fragments to the kernel's runtime
device tree, at some arbitrary point in time, after the cape probing is
complete.
Not only that, the DT fragment for each device is not self contained; it
contains
references to other nodes which have to be resolved in runtime.
Let me demonstrate what the problem is - take for example the very simple
example of a (non-versioned) cape, with a single I2C device.
--8---8--
Kernel's boot DT:
i2c2: i2c@4819c000 {
compatible = ti,omap4-i2c;
#address-cells = 1;
#size-cells = 0;
ti,hwmods = i2c3; /* TODO: Fix hwmod */
reg = 0x4819c000 0x1000;
interrupt-parent = intc;
interrupts = 30;
status = on-demand; /* there's no on-demand status property defined
yet */
/* means that it will be set to okay when a
i2c */
/* device node turn it to okay
*/
/* we can't enable it at boot because of
possible */
/* conflicts with other peripherals
*/
pinctrl-names = default;
pinctrl-0 = i2c2_pins;
clock-frequency = 10;
};
--8---8--
A cape DT fragment (probable syntax) :
i2c2-devices {
parent = i2c2;
/* Ambient light sensor */
tsl2550@39 {
compatible = tsl,tsl2550;
reg = 0x39;
};
};
--8---8--
The i2c2 alias cannot be resolved at compile time; there has to be
a) A DT object format where unresolved aliases (symbols) are tracked
b) A runtime DT linker that will resolve the alias, and will insert the
i2c2-devices child nodes as children in the i2c2 node.
c) A method to trigger platform device creation for the child nodes just
inserted.
DT core changes aren't bound to be easily accepted, so without having a clear
signal from the DT maintainers that they would consider such a method people
are just hesitant to go down this road.
I'm afraid that having the I2C/SPI drivers doing the detection won't
work. The capes can have arbitrary I2C/SPI devices (and even more
weird components). There is no way to assure for example that the I2C
device responding to address 'foo' in cape A is the same I2C device
responding to the same address in cape B.
your -detect() method should take care of that.
There isn't some magical serial number in I²C devices that a
-detect() method can read and the implementation of I²C is somewhat
It doesn't matter.
What you are basically talking about is
cape layer
- wtf is this
- how do I plumb it
- create device nodes with correct name for
binding, address etc on the right bus
i2c layer
- ooh a new i2c device
- probe as indicated by device name
- attach correct driver
Architecturally its possible you want to make some caps MFDs if they have
their own bus heirarchies etc but generally I doubt it.
Take a look at arch/x86/platform/mrst/mrst.c. It's a specific example of
a platform which parses tables and attaches devices to the right physical
bus in a manner they can be reliably probed even when the device has no
sane autodetect.
Alan
Regards
-- Pantelis
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 7:21 AM, Alan Cox a...@lxorguk.ukuu.org.uk wrote: Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. A bus is the wrong construct. You need something to add devices onto the busses. You can do that. The Intel SFI layer on phones for example enumerates devices through a firmware table set and creates them on the right actual physical bus not on their own fake one. Physically, it is a bus, though it is made up of several other busses. While I could certainly see people using the mechanism for enumerating soldered-down devices over the fixed busses, there is a physical connector that deserves some abstraction/identification. Further, it is critical to enable hardware vendors to avoid writing any code for which there are existing drivers. It's not hotplug in the sense that the phone happens be a fixed configuration but it does support hotplug behaviour because the order of the drivers and enumeration is undefined (and both orders work). I think SFI is interesting, but certainly lacks all of the interfaces. It seems reasonable to me to extend the specification to add the missing interfaces, but what doesn't seem to map is the fact that the SFI structures are initially processed in the bootloader and passed statically to the kernel, rather than enabling run-time operation. Users may make run-time trade-offs and also need mechanisms for performing initial debug on products like proto capes. Capebus seems to me to provide this solution fairly well. I don't believe the SFI approach covers the most critical aspects of hotplug behaviour. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat It doesn't matter. What you are basically talking about is cape layer - wtf is this - how do I plumb it - create device nodes with correct name for binding, address etc on the right bus i2c layer - ooh a new i2c device - probe as indicated by device name - attach correct driver Many of the devices cannot be probed. Architecturally its possible you want to make some caps MFDs if they have their own bus heirarchies etc but generally I doubt it. Take a look at arch/x86/platform/mrst/mrst.c. It's a specific example of a platform which parses tables and attaches devices to the right physical bus in a manner they can be reliably probed even when the device has no sane autodetect. I know I *am* the slow person in the room, but doesn't this approach require the code to be compiled into the kernel to support the devices ahead of time? While I think it might be reasonable to have hardware developers provide DT fragments in their EEPROMs, there's no way to get them to submit code patches in order to get their hardware to work. They need to ship hardware that works with pre-existing software, since there will be hundreds of boards created by people with little to no previous Linux experience (akin to Arduino). I seem to be missing how that approach would get us there. Alan -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Further, it is critical to enable hardware vendors to avoid writing any code for which there are existing drivers. Which is why you don't want to create a new bus type for it. Capebus seems to me to provide this solution fairly well. I don't believe the SFI approach covers the most critical aspects of hotplug behaviour. I think you missed the point - it just an example of doing this not one I'd suggest using directly. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat It doesn't matter. What you are basically talking about is cape layer - wtf is this - how do I plumb it - create device nodes with correct name for binding, address etc on the right bus i2c layer - ooh a new i2c device - probe as indicated by device name - attach correct driver Many of the devices cannot be probed. Look more closely at the code I pointed you at. I wonder if have a differing understanding of the word probe in this situation. In the Linux space the driver bindings call the matching probe function based upon the device structure. In Linux the probe method does not mean scan the bus and enumerate/detect the devices If an i²c bus is thrown a device which has an address and a matching name the only thing it will attempt to do is to call the probe method of the device driver matching that name on the given i²c address. In other words its a probe in the sense of I've been told there is one of your widgets here, please take a look not a probe in the sense of scan 255 i²c addresses and poke randomly at them SFI for example creates entries for things like type foo pressure sensor at 0x68 on bus 3 and the core kernel i²c code will only call the foo drivers probe method and only on bus 3 and only for address 0x68. In your case you want to use your DT fragments or any other descriptor format to do exactly the same. Not create a new bus but add a bunch of devices to the existing busses. It's like hot plugging a PCI card - you don't create a new PCI bus, you add a device to the existing bus. In the PCI case the device has properties that uniquely identify it from hardware level. In the i²c case the properties come from your DT fragment or similar. The rest is the same. I know I *am* the slow person in the room, but doesn't this approach require the code to be compiled into the kernel to support the devices ahead of time? While I think it might be reasonable to have hardware The specific implementation in SFI does but thats a property of SFI. I'm not trying to push SFI itself anywhere except over the edge of a very tall cliff. The point is that you can take a description of things like i²c devices and have then properly identified on the existing busses using the existing bus architecture just fine. developers provide DT fragments in their EEPROMs, there's no way to get them to submit code patches in order to get their hardware to work. They need to ship hardware that works with pre-existing software, since there will be hundreds of boards created by people with little to no previous Linux experience (akin to Arduino). I seem to be missing how that approach would get us there. That is what I assume and what I believe can be provided without inventing imaginary bus types. Alan -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Fri, Nov 2, 2012 at 4:00 AM, Felipe Balbi ba...@ti.com wrote: Hi, On Fri, Nov 02, 2012 at 02:42:51AM -0700, Russ Dill wrote: browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) it doesn't mean it can't be done. Really? Please, do tell how you would write a detect function for a PCA9534. It has 4 registers, an input port registers, an output port register, a polarity inversion register, and a configuration register. read them and match to their reset values, perhaps ? So its ok for it to not work on warm reset? Also, I'm pretty sure [ random, 0xff, 0x00, 0xff ] describes quite a few chips. And don't forget, since we are probing, every detect routine for every I²C driver will have to run with every I²C address on every bus, possibly with both address formats. not *every* I2C address. What you say is wrong, a -detect() method will only run for those addresses which the device can actually assume. OK, that's still a potentially large number of addresses. On top of all this the detect routine does not tell you if the alert pin is connected to some IRQ, or in the case of a GPIO expander, what those GPIOs are connected to, etc, etc. so what ? All you want to do with detect is figure out if the far end is who you think it is, not what it's doing. If we already knew who was there, we wouldn't need a detect routine. of course not :-) But the whole discussion has been about not knowing which capes (and thus which devices) are attached to the bone. Eh? Finding out which bone is connected is pretty easy, they all have an EEPROM with identifying information. That isn't the problem that capebus is solving, capebus is solving the problem of enumerating that hardware. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some generic-cape bits (like gpios, pwms, keys what-ever). But it will put them to use in the custom in-kernel driver in it's own way. You can't put that task to user-space, if it's ever slightly complex. So for really simple capes, after considerable pain you might, just might, dump the problem to user-space and try to make it work. People have tried that and it's a total pain. There is no way that
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some generic-cape bits (like gpios, pwms, keys what-ever). But it will put them to use in the custom in-kernel driver in it's own way. You can't put that task to user-space, if it's ever slightly complex. So for really simple capes, after considerable pain you might, just might, dump the problem to user-space and try to make it work. People have tried that and it's a total pain. There is no way that this will work with anything more complex than a
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some generic-cape bits (like gpios, pwms, keys what-ever). But it will put them to use in the custom in-kernel driver in it's own way. You can't put that task to user-space, if it's ever slightly complex. So for really simple capes, after considerable pain you might, just
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi,
On Thu, Nov 01, 2012 at 12:39:30PM +0200, Pantelis Antoniou wrote:
lcd@0 {
compatible = adafruit,tft-lcd-1.8-red,
sitronix,st7735;
spi-max-frequency = 800;
reg = 0;
spi-cpol;
spi-cpha;
pinctrl-names = default;
pinctrl-0 = lcd_pins;
st7735-rst = gpio4 19 0;
st7735-dc = gpio4 21 0;
};
};
};
I guess there is no easy solution for that, but it looks to me that
what you have to do is to make the DT creation dynamic in your case.
Assuming you do not want to do that in the bootloader, you must do
that pretty early during the boot process to end up with a full
description of your DT tree before creating the devices.
Do it pretty early in the boot processes ended up with the am335xevm board
file in the PSP tree.
The whole set of possible cape designs cannot be controlled, nor do we want
to.
We want to empower users to come up with their own designs without having to
do any kernel/boot loader
hacking.
that's impossible since you will have to provide the capebus driver
anyway.
Each cape will have their own DTS and based on some board id you
will fix the DT dynamically.
My point is that the issue you are facing is a real limitation of
DT, so you should fix the DT core and not workaround it by creating
artificial bindings / drivers.
You still haven't described any mechanism to deal with all the use
cases I described.
DT can't and will not deal with the complexity that we're facing right
now.
and DT-itself shouldn't. I agree with Benoit that this should be built
at bootloader level, perhaps. Whatever you're doing in capebus, you
could do at kernel space, build your DT bindings in runtime, and pass
that DT blob to kernel.
One question though, what do you mean by some capes are full blown
devices with their own drivers ? Do you mean you have capes running
some other (RT)OS and communicating with linux somehow ? How does it
communicate to the bone ?
cheers
--
balbi
signature.asc
Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Panto, On 11/1/2012 11:39 AM, Pantelis Antoniou wrote: Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some generic-cape bits (like gpios, pwms, keys what-ever). But it will put them to use in the custom in-kernel driver in it's own way. You can't put that task to user-space, if it's ever slightly complex. So for really simple capes, after considerable pain you might, just might, dump the problem to user-space and try to make
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi
On Nov 1, 2012, at 1:04 PM, Felipe Balbi wrote:
Hi,
On Thu, Nov 01, 2012 at 12:39:30PM +0200, Pantelis Antoniou wrote:
lcd@0 {
compatible = adafruit,tft-lcd-1.8-red,
sitronix,st7735;
spi-max-frequency = 800;
reg = 0;
spi-cpol;
spi-cpha;
pinctrl-names = default;
pinctrl-0 = lcd_pins;
st7735-rst = gpio4 19 0;
st7735-dc = gpio4 21 0;
};
};
};
I guess there is no easy solution for that, but it looks to me that
what you have to do is to make the DT creation dynamic in your case.
Assuming you do not want to do that in the bootloader, you must do
that pretty early during the boot process to end up with a full
description of your DT tree before creating the devices.
Do it pretty early in the boot processes ended up with the am335xevm board
file in the PSP tree.
The whole set of possible cape designs cannot be controlled, nor do we want
to.
We want to empower users to come up with their own designs without having to
do any kernel/boot loader
hacking.
that's impossible since you will have to provide the capebus driver
anyway.
The generic cape bus driver can handle the easy stuff. More complex
stuff can be supported with per-cape drivers.
Each cape will have their own DTS and based on some board id you
will fix the DT dynamically.
My point is that the issue you are facing is a real limitation of
DT, so you should fix the DT core and not workaround it by creating
artificial bindings / drivers.
You still haven't described any mechanism to deal with all the use
cases I described.
DT can't and will not deal with the complexity that we're facing right
now.
and DT-itself shouldn't. I agree with Benoit that this should be built
at bootloader level, perhaps. Whatever you're doing in capebus, you
could do at kernel space, build your DT bindings in runtime, and pass
that DT blob to kernel.
We're just passing the buck someplace else. We're not fixing the problem.
What makes you think that dealing with this in the bootloader is going
to be simpler?
One question though, what do you mean by some capes are full blown
devices with their own drivers ? Do you mean you have capes running
some other (RT)OS and communicating with linux somehow ? How does it
communicate to the bone ?
Some have FPGAs.
https://specialcomp.com/beaglebone/BeagleBone_FPGA.html
Some capes have their own MCUs.
A recent one has an 6502 communicating with uio_pruss.
https://github.com/ohporter/b6502
What I'm saying is that there are simple capes, that are just DT devices
which can be handled via cape-generic. The complex ones need their own
drivers which need a place to live.
Capebus handles both.
cheers
--
balbi
Regards
-- Pantelis
--
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Benoit, On Nov 1, 2012, at 1:26 PM, Cousson, Benoit wrote: Hi Panto, On 11/1/2012 11:39 AM, Pantelis Antoniou wrote: Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards you will need a specific driver. That driver will probably use some generic-cape bits (like gpios, pwms, keys what-ever). But it will put them to use in the custom in-kernel driver in it's own way. You can't
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
tl;dr: please suggest an actual solution that allows plugplay when plugging in multiple capes and applying power after that. Preferably one that doesn't pass the buck to u-boot. Op 1 nov. 2012, om 12:26 heeft Cousson, Benoit b-cous...@ti.com het volgende geschreven: Hi Panto, On 11/1/2012 11:39 AM, Pantelis Antoniou wrote: Hi Benoit, On Nov 1, 2012, at 12:23 PM, Cousson, Benoit wrote: On 11/1/2012 8:02 AM, Pantelis Antoniou wrote: Hi Felibe, On Nov 1, 2012, at 12:14 AM, Felipe Balbi wrote: Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. What do you think capebus is? It is an actual bus that allows you to do so. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. The I2C/SPI devices are not a problem at all. Let me try to explain what the problem is, and why it all this is needed. First of all, capes may be relatively simple boards, which may function as a generic device - like the generic capes. They might not necessarily be simple. Some capes, for example the geiger cape have a number of components that perform a specific task; in this instance the driving circuit of the geiger tube and the event detector input. Other capes that are being designed now are even more complex, i.e. there's a radar cape, an fpga cape and so on. So for these kind of boards
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi,
On Thu, Nov 01, 2012 at 01:26:10PM +0200, Pantelis Antoniou wrote:
Hi
On Nov 1, 2012, at 1:04 PM, Felipe Balbi wrote:
Hi,
On Thu, Nov 01, 2012 at 12:39:30PM +0200, Pantelis Antoniou wrote:
lcd@0 {
compatible = adafruit,tft-lcd-1.8-red,
sitronix,st7735;
spi-max-frequency = 800;
reg = 0;
spi-cpol;
spi-cpha;
pinctrl-names = default;
pinctrl-0 = lcd_pins;
st7735-rst = gpio4 19 0;
st7735-dc = gpio4 21 0;
};
};
};
I guess there is no easy solution for that, but it looks to me that
what you have to do is to make the DT creation dynamic in your case.
Assuming you do not want to do that in the bootloader, you must do
that pretty early during the boot process to end up with a full
description of your DT tree before creating the devices.
Do it pretty early in the boot processes ended up with the am335xevm board
file in the PSP tree.
The whole set of possible cape designs cannot be controlled, nor do we
want to.
We want to empower users to come up with their own designs without having
to do any kernel/boot loader
hacking.
that's impossible since you will have to provide the capebus driver
anyway.
The generic cape bus driver can handle the easy stuff. More complex
stuff can be supported with per-cape drivers.
likewise:
the generic stuff can be handled by FDT easily, the more complex stuff
can be supported by dynamically changing FDT blob, no ?
Each cape will have their own DTS and based on some board id you
will fix the DT dynamically.
My point is that the issue you are facing is a real limitation of
DT, so you should fix the DT core and not workaround it by creating
artificial bindings / drivers.
You still haven't described any mechanism to deal with all the use
cases I described.
DT can't and will not deal with the complexity that we're facing right
now.
and DT-itself shouldn't. I agree with Benoit that this should be built
at bootloader level, perhaps. Whatever you're doing in capebus, you
could do at kernel space, build your DT bindings in runtime, and pass
that DT blob to kernel.
We're just passing the buck someplace else. We're not fixing the problem.
What makes you think that dealing with this in the bootloader is going
to be simpler?
I never said it was supposed to be simpler, it just doesn't sound like
something the kernel should care about. Kernel cares about the
One question though, what do you mean by some capes are full blown
devices with their own drivers ? Do you mean you have capes running
some other (RT)OS and communicating with linux somehow ? How does it
communicate to the bone ?
Some have FPGAs.
https://specialcomp.com/beaglebone/BeagleBone_FPGA.html
how does linux communicate with those ? What they are matters very
little ;-) All we need is an interface to load binaries to the FPGA.
Some capes have their own MCUs.
A recent one has an 6502 communicating with uio_pruss.
https://github.com/ohporter/b6502
that uses remoteproc, so I assume it's using OMAP's mailbox ?
Again I say that this is not a 'capebus', it's just another device
which we use another interface to talk to.
i2c devices will be children of the omap i2c controller, spi devices
will be children of the omap mcspi, GPMC devices will need the GPMC
controller and so on, but none of this looks like argument to introduce
a fake bus into the kernel.
--
balbi
signature.asc
Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi,
On Nov 1, 2012, at 2:40 PM, Felipe Balbi wrote:
Hi,
On Thu, Nov 01, 2012 at 01:26:10PM +0200, Pantelis Antoniou wrote:
Hi
On Nov 1, 2012, at 1:04 PM, Felipe Balbi wrote:
Hi,
On Thu, Nov 01, 2012 at 12:39:30PM +0200, Pantelis Antoniou wrote:
lcd@0 {
compatible = adafruit,tft-lcd-1.8-red,
sitronix,st7735;
spi-max-frequency = 800;
reg = 0;
spi-cpol;
spi-cpha;
pinctrl-names = default;
pinctrl-0 = lcd_pins;
st7735-rst = gpio4 19 0;
st7735-dc = gpio4 21 0;
};
};
};
I guess there is no easy solution for that, but it looks to me that
what you have to do is to make the DT creation dynamic in your case.
Assuming you do not want to do that in the bootloader, you must do
that pretty early during the boot process to end up with a full
description of your DT tree before creating the devices.
Do it pretty early in the boot processes ended up with the am335xevm board
file in the PSP tree.
The whole set of possible cape designs cannot be controlled, nor do we
want to.
We want to empower users to come up with their own designs without having
to do any kernel/boot loader
hacking.
that's impossible since you will have to provide the capebus driver
anyway.
The generic cape bus driver can handle the easy stuff. More complex
stuff can be supported with per-cape drivers.
likewise:
the generic stuff can be handled by FDT easily, the more complex stuff
can be supported by dynamically changing FDT blob, no ?
No. You're missing the point. Up until we read the EEPROM we don't know
what to dynamically change in the device tree (not the blob). What you
will end up is something like capebus again. Only you're going to reinvent it
with a different name.
Each cape will have their own DTS and based on some board id you
will fix the DT dynamically.
My point is that the issue you are facing is a real limitation of
DT, so you should fix the DT core and not workaround it by creating
artificial bindings / drivers.
You still haven't described any mechanism to deal with all the use
cases I described.
DT can't and will not deal with the complexity that we're facing right
now.
and DT-itself shouldn't. I agree with Benoit that this should be built
at bootloader level, perhaps. Whatever you're doing in capebus, you
could do at kernel space, build your DT bindings in runtime, and pass
that DT blob to kernel.
We're just passing the buck someplace else. We're not fixing the problem.
What makes you think that dealing with this in the bootloader is going
to be simpler?
I never said it was supposed to be simpler, it just doesn't sound like
something the kernel should care about. Kernel cares about the
I just disagree here. The kernel should provide services that make the life
of users easier, not the lives of the kernel developers easier.
One question though, what do you mean by some capes are full blown
devices with their own drivers ? Do you mean you have capes running
some other (RT)OS and communicating with linux somehow ? How does it
communicate to the bone ?
Some have FPGAs.
https://specialcomp.com/beaglebone/BeagleBone_FPGA.html
how does linux communicate with those ? What they are matters very
little ;-) All we need is an interface to load binaries to the FPGA.
We can not know what people will come up with. It might have a few GPIOs
to load the bitfile to the FPGA, but after that, no-one can tell.
I might not interface to Linux at all; it might interface via I2C, or RS232.
Chances are, it won't fit in any kind of known drivers of linux.
Some guy is using an FPGA for SDR, another is making a radar cape.
These guys don't give a damn frankly about Linux. What they do care about
is having a cheap/easy to develop platform for their own little widget.
If you are going to ask from the to hunt down their own dts and assemble
from various dtsi's they'll just move to something else.
Which is a shame, cause we do have a nice platform here.
Some capes have their own MCUs.
A recent one has an 6502 communicating with uio_pruss.
https://github.com/ohporter/b6502
that uses remoteproc, so I assume it's using OMAP's mailbox ?
Again I say that this is not a 'capebus', it's just another device
which we use another interface to talk to.
i2c devices will be children of the omap i2c controller, spi devices
will be children of the omap mcspi, GPMC devices will need the GPMC
controller and so on, but none of this looks like argument to introduce
a fake bus into the kernel.
I'll let the users of said bus to do the talking. You're just flat out
wrong IMO.
--
balbi
Regards
-- Pantelis
--
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Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi, On Thu, Nov 01, 2012 at 01:00:21PM +0100, Koen Kooi wrote: tl;dr: please suggest an actual solution that allows plugplay when plugging in multiple capes and applying power after that. Preferably one that doesn't pass the buck to u-boot. I can think of a few ways: 1) ship your distribution with all necessary drivers and let udev handle driver probing. clearly this will require constant updates for the distribution as new capes are developed. But IIUC, that's the same with Arduino where new libraries are added to the Arduino OS. 2) ship with drivers for EEPROMs only and setup a repository of drivers this would require every driver to be packaged separately, then you create a setup where bone's userland will use EEPROMs data to figure out which drivers it needs, pass that information to SDK via USB, then SDK downloads all necessary/missing packages, sends them to bone via USB and all packages are installed on the bone. Note that since packages would be 'installed', this would be a one-time-only thing. 3) realize that if your user can build an FPGA cape, s/he can most likely write code and adding/recompiling kernel shouldn't be the biggest of his/her worries (no comments to this one, I understand it's not feasible) in any case, capebus sounds like something which is hugely unnecessary. ps: at least for the I2C subsystem, i2c-core can detect for you if your driver provides -detect() method. Op 1 nov. 2012, om 12:26 heeft Cousson, Benoit b-cous...@ti.com het volgende geschreven: FWIW, we do have a similar, but simpler, problem with the beagle / beagle-xm and panda / panda-es. But for the moment we are just using a different DTS for each board. A different DTS for each board combination... There alot more capes for the bone that they are for the beagle the panda. And more are going to come, but not necessarily from people that have any connection to TI or CCO. Sure, but my point is that your solution will not solve our problem :-) This is a generic problem that you address with a very custom / specific approach. You still haven't described how I could solve the issue of conflicting capes using a single DTS. Well I don't have the solution otherwise I will have done it already :-) My point is that the solution has to be in the DT core if not in the bootloader. snarky commentSo when we at beagleboard.org handled the beagleboard and beagleboard xM expansionboards in the bootloader (detection, muxing, etc) we were told it was wrong and we should handle it in the kernel and if we waited a bit, DT would solve everything. And now that we actually handle it in the kernel you are saying that it is wrong and we should handle it in the bootloader and that DT won't solve everything. I guess someone will now tell us that uEFI will fix everything./snarky comment Apart from that, you and others still fail to tell us how you want to handle a user (or customer) that buys a beaglebone, an LCD cape, a weatherstation cape and a geiger counter cape and plugs those together and powers them on. With the evil TI vendor tree and extra patches the boardfile reads the eeproms and tries its best to instantiate all the platform data. One of the capes won't have working LEDs since appending to the leds-gpio struct is pretty much impossible in this couldn't you just instantiate multiple leds-gpio device ? situation. But it gets a picture on the screen, blinks LEDs and does largely what the user expects. With capebus we get: 1) da8xx-fb which lacks DT bindingsp[1] receives plaftorm data to match the LCD this is something which could be fixed at the driver level, right ? :-) 2) the i2c sensors on the weathercape are registered that will work with or without capebus. 3) the one-wire bus on the weathercape gets registered also should work with or without capebus. 4) the LEDs on the lcd cape get registered5 also works with or without capebus. 5) the LED on the geigercape gets registered and adds a custom trigger also works with or without capebus. 6) the ADC, which again, lacks DT bindings[2], receives plaftorm data and a custom IIO binding driver problem. 7) pinctrl sets the pinmuxes for the above also works with or without capebus. In other words: plug play, even for devices with drivers that are still lacking DT support. I _do_ agree with you that we could have a grace period where DT and non-DT would boot together, but apparently that's not something which isn't trivial to do. I guess Benoit might also be concerned that if we add such an infrastructure than conversion to DT will never finish heh. Now please explain to me why you think it's such an awesome idea that the users will need to find the right dtsi files (multiple revisions of the lcd cape exist), include them in the dts, run dtc, add a
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi, On Thu, Nov 01, 2012 at 02:57:26PM +0200, Pantelis Antoniou wrote: Each cape will have their own DTS and based on some board id you will fix the DT dynamically. My point is that the issue you are facing is a real limitation of DT, so you should fix the DT core and not workaround it by creating artificial bindings / drivers. You still haven't described any mechanism to deal with all the use cases I described. DT can't and will not deal with the complexity that we're facing right now. and DT-itself shouldn't. I agree with Benoit that this should be built at bootloader level, perhaps. Whatever you're doing in capebus, you could do at kernel space, build your DT bindings in runtime, and pass that DT blob to kernel. We're just passing the buck someplace else. We're not fixing the problem. What makes you think that dealing with this in the bootloader is going to be simpler? I never said it was supposed to be simpler, it just doesn't sound like something the kernel should care about. Kernel cares about the I just disagree here. The kernel should provide services that make the life of users easier, not the lives of the kernel developers easier. and it's already doing that isn't it ? we have i2c framework for i2c clients. From a userland point of view, you have input layer, iio, hwmon, chardev and a whole bunch of other interfaces which standardize device accesses. Look at your sentence again: kernel should make life of users easier, not that of kernel developers; IMHO capebus is just making it easier for the kernel developers who have to maintain a bunch of drivers for different devices on different capes ;-) At the end of the day, capebus will just be creating devices which will be handled by the same I2C framework, iio, input, hwmon, and so on. So what was the great benefit from capebus other than decreasing the amount of changes to .dts files ? One question though, what do you mean by some capes are full blown devices with their own drivers ? Do you mean you have capes running some other (RT)OS and communicating with linux somehow ? How does it communicate to the bone ? Some have FPGAs. https://specialcomp.com/beaglebone/BeagleBone_FPGA.html how does linux communicate with those ? What they are matters very little ;-) All we need is an interface to load binaries to the FPGA. We can not know what people will come up with. It might have a few GPIOs to load the bitfile to the FPGA, but after that, no-one can tell. I might not interface to Linux at all; it might interface via I2C, or RS232. which means that whoever writes RTL for the FPGA needs to do so with bone's I/O choices in mind. Let's assume the use UART to send bitfile to FPGA and bitfile is a model of an I2C Sensor, they'll have to use /dev/ttyOn to pass bitfile to FPGA and later an i2c-client driver (possibly using iio, since it's a sensor) will be loaded. Right ? Chances are, it won't fit in any kind of known drivers of linux. Some guy is using an FPGA for SDR, another is making a radar cape. awesome. That means we need to take care of those :-) Even with capebus, they will still have to write those drivers won't they ? So instead of writing some capebus driver, why can't the guy write a driver for his radar instead ? That way, if he ever turns that into an ASIC and decides to sell it as a chip, he doesn't have to write another driver just to strip the capebus away. These guys don't give a damn frankly about Linux. What they do care about is having a cheap/easy to develop platform for their own little widget. If you are going to ask from the to hunt down their own dts and assemble from various dtsi's they'll just move to something else. I never asked that :-) What I'm claiming is that capebus doesn't sound like the best solution for the problem exposed. Which is a shame, cause we do have a nice platform here. I agree with you, the bone is quite awesome ;-) Some capes have their own MCUs. A recent one has an 6502 communicating with uio_pruss. https://github.com/ohporter/b6502 that uses remoteproc, so I assume it's using OMAP's mailbox ? Again I say that this is not a 'capebus', it's just another device which we use another interface to talk to. i2c devices will be children of the omap i2c controller, spi devices will be children of the omap mcspi, GPMC devices will need the GPMC controller and so on, but none of this looks like argument to introduce a fake bus into the kernel. I'll let the users of said bus to do the talking. You're just flat out wrong IMO. fair enough, I feel the same way about your capebus ;-) -- balbi signature.asc Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Op 1 nov. 2012, om 14:06 heeft Felipe Balbi ba...@ti.com het volgende geschreven: Hi, On Thu, Nov 01, 2012 at 01:00:21PM +0100, Koen Kooi wrote: tl;dr: please suggest an actual solution that allows plugplay when plugging in multiple capes and applying power after that. Preferably one that doesn't pass the buck to u-boot. I can think of a few ways: 1) ship your distribution with all necessary drivers and let udev handle driver probing. clearly this will require constant updates for the distribution as new capes are developed. But IIUC, that's the same with Arduino where new libraries are added to the Arduino OS. And how are you going to handle pinmuxing and conflict resolution? You're basically saying that people should just use /dev/mem to write drivers, since you don't consider their use case valid. 2) ship with drivers for EEPROMs only and setup a repository of drivers this would require every driver to be packaged separately, then you create a setup where bone's userland will use EEPROMs data to figure out which drivers it needs, pass that information to SDK via USB, then SDK downloads all necessary/missing packages, sends them to bone via USB and all packages are installed on the bone. Note that since packages would be 'installed', this would be a one-time-only thing. I lack the words to describe my emotions after reading this. Let's leave it at that. 3) realize that if your user can build an FPGA cape, s/he can most likely write code and adding/recompiling kernel shouldn't be the biggest of his/her worries (no comments to this one, I understand it's not feasible) You'd be surprised. in any case, capebus sounds like something which is hugely unnecessary. On tablets and phones, yes. But TI chips are use for different use-cases, bone + capes being one of those. ps: at least for the I2C subsystem, i2c-core can detect for you if your driver provides -detect() method. So I just need to patch all i2c drivers and force people to use the standard address for the i2c chip when designing a board. Op 1 nov. 2012, om 12:26 heeft Cousson, Benoit b-cous...@ti.com het volgende geschreven: FWIW, we do have a similar, but simpler, problem with the beagle / beagle-xm and panda / panda-es. But for the moment we are just using a different DTS for each board. A different DTS for each board combination... There alot more capes for the bone that they are for the beagle the panda. And more are going to come, but not necessarily from people that have any connection to TI or CCO. Sure, but my point is that your solution will not solve our problem :-) This is a generic problem that you address with a very custom / specific approach. You still haven't described how I could solve the issue of conflicting capes using a single DTS. Well I don't have the solution otherwise I will have done it already :-) My point is that the solution has to be in the DT core if not in the bootloader. snarky commentSo when we at beagleboard.org handled the beagleboard and beagleboard xM expansionboards in the bootloader (detection, muxing, etc) we were told it was wrong and we should handle it in the kernel and if we waited a bit, DT would solve everything. And now that we actually handle it in the kernel you are saying that it is wrong and we should handle it in the bootloader and that DT won't solve everything. I guess someone will now tell us that uEFI will fix everything./snarky comment Apart from that, you and others still fail to tell us how you want to handle a user (or customer) that buys a beaglebone, an LCD cape, a weatherstation cape and a geiger counter cape and plugs those together and powers them on. With the evil TI vendor tree and extra patches the boardfile reads the eeproms and tries its best to instantiate all the platform data. One of the capes won't have working LEDs since appending to the leds-gpio struct is pretty much impossible in this couldn't you just instantiate multiple leds-gpio device ? No, and that is a problem in the driver core, see earlier discussions about similar problems. situation. But it gets a picture on the screen, blinks LEDs and does largely what the user expects. With capebus we get: 1) da8xx-fb which lacks DT bindingsp[1] receives plaftorm data to match the LCD this is something which could be fixed at the driver level, right ? :-) You'd have to tell your coworkers that. 2) the i2c sensors on the weathercape are registered that will work with or without capebus. Not in a plug and play way. 3) the one-wire bus on the weathercape gets registered also should work with or without capebus. Not in a plug and play way. 4) the LEDs on the lcd cape get registered5 also works with or without capebus. Not in a plug and play way. 5) the LED on the geigercape gets registered and adds
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi On Nov 1, 2012, at 3:16 PM, Felipe Balbi wrote: Hi, On Thu, Nov 01, 2012 at 02:57:26PM +0200, Pantelis Antoniou wrote: Each cape will have their own DTS and based on some board id you will fix the DT dynamically. My point is that the issue you are facing is a real limitation of DT, so you should fix the DT core and not workaround it by creating artificial bindings / drivers. You still haven't described any mechanism to deal with all the use cases I described. DT can't and will not deal with the complexity that we're facing right now. and DT-itself shouldn't. I agree with Benoit that this should be built at bootloader level, perhaps. Whatever you're doing in capebus, you could do at kernel space, build your DT bindings in runtime, and pass that DT blob to kernel. We're just passing the buck someplace else. We're not fixing the problem. What makes you think that dealing with this in the bootloader is going to be simpler? I never said it was supposed to be simpler, it just doesn't sound like something the kernel should care about. Kernel cares about the I just disagree here. The kernel should provide services that make the life of users easier, not the lives of the kernel developers easier. and it's already doing that isn't it ? we have i2c framework for i2c clients. From a userland point of view, you have input layer, iio, hwmon, chardev and a whole bunch of other interfaces which standardize device accesses. Look at your sentence again: kernel should make life of users easier, not that of kernel developers; IMHO capebus is just making it easier for the kernel developers who have to maintain a bunch of drivers for different devices on different capes ;-) At the end of the day, capebus will just be creating devices which will be handled by the same I2C framework, iio, input, hwmon, and so on. So what was the great benefit from capebus other than decreasing the amount of changes to .dts files ? How about true plug and play, conflict resolution real easy development of new cape designs. I fail to see how your convoluted method(s) fixes any of the above. And no passing the buck to someone else (be it u-boot, u-dev, user-space) won't cut it. What you are proposing will just stop dead all cape development besides the ones that dedicated teams at TI do. In fact the whole project, of a cheap Linux based, hackable community board will fail. One question though, what do you mean by some capes are full blown devices with their own drivers ? Do you mean you have capes running some other (RT)OS and communicating with linux somehow ? How does it communicate to the bone ? Some have FPGAs. https://specialcomp.com/beaglebone/BeagleBone_FPGA.html how does linux communicate with those ? What they are matters very little ;-) All we need is an interface to load binaries to the FPGA. We can not know what people will come up with. It might have a few GPIOs to load the bitfile to the FPGA, but after that, no-one can tell. I might not interface to Linux at all; it might interface via I2C, or RS232. which means that whoever writes RTL for the FPGA needs to do so with bone's I/O choices in mind. Let's assume the use UART to send bitfile to FPGA and bitfile is a model of an I2C Sensor, they'll have to use /dev/ttyOn to pass bitfile to FPGA and later an i2c-client driver (possibly using iio, since it's a sensor) will be loaded. Right ? No. I don't know details about what the actual cape design is, but they certainly don't want to deal with the piece-meal method, of loading one driver, and then creating a bunch of I2C devices, and then activating an RS232 tty, and then using that to burn the bitfile and so on. What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. Chances are, it won't fit in any kind of known drivers of linux. Some guy is using an FPGA for SDR, another is making a radar cape. awesome. That means we need to take care of those :-) Even with capebus, they will still have to write those drivers won't they ? So instead of writing some capebus driver, why can't the guy write a driver for his radar instead ? That way, if he ever turns that into an ASIC and decides to sell it as a chip, he doesn't have to write another driver just to strip the capebus away. You have to build something working first, before you move on to make a custom board based to it. FWIW, after a design gets to work as a cape, chances are the hardware redesign will just end up with the same h/w connections as a cape, and just use an override to avoid putting the EEPROM in there. These guys don't give a damn frankly about Linux. What they do care about is having a cheap/easy to develop platform for their own little widget. If you are
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. In a nutshell, no, I'm not writing any custom drivers for the stuff that exists already. There is no extra layer after the device is created and operates as it was located in the proper place in the DTS. The custom drivers are only needed for complex capes where you can't have the device simply work by creating the devices. Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
My apologies for starting a new thread, but I don't have this thread in my Inbox. http://www.spinics.net/lists/linux-omap/msg81034.html Tony Lindgren wrote: * Pantelis Antoniou panto@xxx [121031 15:02]: So when device's node is 'disabled' of_platform_device_create_pdata() will not create the device. Now, of course it is possible to re-trigger the platform's probe method to be called, and in fact I do so in the capebus patches. You should fix this in generic way then rather than working around it in capebus. The same problem exists changing between different functionality for the shared pins, let's say between USB pins and UART pins if you want a serial debug console on some phone. The current capebus solution goes a long way to fixing a huge issue for BeagleBone users and I don't understand what seems to be a push-back on principle. On BeagleBone capes, these conflicts cannot be resolved early. Do you have suggestions on some more generic method? It seems to me the proposed capebus approach strikes a good balance. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Jason Kridner jkrid...@beagleboard.org [121101 11:52]: My apologies for starting a new thread, but I don't have this thread in my Inbox. http://www.spinics.net/lists/linux-omap/msg81034.html Tony Lindgren wrote: * Pantelis Antoniou panto@xxx [121031 15:02]: So when device's node is 'disabled' of_platform_device_create_pdata() will not create the device. Now, of course it is possible to re-trigger the platform's probe method to be called, and in fact I do so in the capebus patches. You should fix this in generic way then rather than working around it in capebus. The same problem exists changing between different functionality for the shared pins, let's say between USB pins and UART pins if you want a serial debug console on some phone. The current capebus solution goes a long way to fixing a huge issue for BeagleBone users and I don't understand what seems to be a push-back on principle. On BeagleBone capes, these conflicts cannot be resolved early. Do you have suggestions on some more generic method? It seems to me the proposed capebus approach strikes a good balance. Having it all behave like a hotpluggable bus makes sense. But the way to sort it out is to have all the omap internal devices defined in a .dts file and have them set initially with status = disabled in the .dts. Then you just need a function dynamically change the kernel internal device tree to enable and disable devices dynamically so the dev entries get created and driver probe can happen. Sure that means that some hwmod and omap_device functions can't be __init any longer, but there should not be any need to call hwmod and omap_device functions directly from capebus. If you want to take it one step further, you can also add new capes to the kernel internal device tree dynamically as you may have different pinmux and omap internal device configurations on the capes. Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
HI, On Thu, Nov 01, 2012 at 03:59:50PM +0200, Pantelis Antoniou wrote: Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. -- balbi signature.asc Description: Digital signature
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Thu, Nov 1, 2012 at 3:05 PM, Felipe Balbi ba...@ti.com wrote: HI, On Thu, Nov 01, 2012 at 03:59:50PM +0200, Pantelis Antoniou wrote: Hi Alan, On Nov 1, 2012, at 3:51 PM, Alan Cox wrote: What they want, and what every user wants, is I plug this board in, and the driver make sure everything is loaded and ready. No, the end users don't want to see any of the implementation details of how the bitfile is transported; the driver can handle it. That doesn't necessarily make it a bus merely some kind of hotplug enumeration of devices. That should all work properly both for devices and busses with spi and i²c as the final bits needed for it got fixed some time ago. In an ideal world you don't want to be writing custom drivers for stuff. If your cape routes an i²c serial device to the existing system i²c busses then you want to just create an instance of any existing driver on the existing i²c bus not create a whole new layer of goop. It does need to do the plumbing and resource management for the plumbing but thats not the same as being a bus. Alan Fair enough. But there's no such thing a 'hotplug enumeration construct' in Linux yet, and a bus is the closest thing to it. It does take advantage of the nice way device code matches drivers and devices though. I'm afraid that having the I2C/SPI drivers doing the detection won't work. The capes can have arbitrary I2C/SPI devices (and even more weird components). There is no way to assure for example that the I2C device responding to address 'foo' in cape A is the same I2C device responding to the same address in cape B. your -detect() method should take care of that. There isn't some magical serial number in I²C devices that a -detect() method can read and the implementation of I²C is somewhat flexible. One devices read may be another devices write. A detect method that only performs reads could easily toggle a gpio that resets the board, rewrite and eeprom, or set the printer on fire. If you browse through various detect functions, yes, some of them key off an ID, but a lot of them just check various registers to see if certain bits are zero, or certain bits are one. A lot of I²C devices I've dealt with have no good way of probing them, especially GPIO chips (you'll notice none of the I²C GPIO expanders have detect functions) On top of all this the detect routine does not tell you if the alert pin is connected to some IRQ, or in the case of a GPIO expander, what those GPIOs are connected to, etc, etc. -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 0/3] capebus moving omap_devices to mach-omap2
It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Pantelis Antoniou (3): omap-device: Remove __init from omap_device_build family functions da8xx-dt: Create da8xx DT adapter device ti-tscadc-dt: Create ti-tscadc-dt DT adapter device arch/arm/mach-omap2/Makefile | 4 + arch/arm/mach-omap2/da8xx-dt.c | 197 + arch/arm/mach-omap2/ti-tscadc-dt.c | 155 + arch/arm/plat-omap/omap_device.c | 4 +- 4 files changed, 358 insertions(+), 2 deletions(-) create mode 100644 arch/arm/mach-omap2/da8xx-dt.c create mode 100644 arch/arm/mach-omap2/ti-tscadc-dt.c -- 1.7.12 -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Tony, On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 10:26]: It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Hmm I think you misunderstood me. You only need to create the platform_device under arch/arm/mach-omap2. The device creation happens only at __init, so omap_build_device can stay as __init. The driver itself should be under drivers. But is this bus on non-device-tree omaps? If not, just make it device tree only. I'm afraid that's not the case. The whole notion of capebus is that instantiation of the devices doesn't just happen early at the boot sequence. It is perfectly valid for a cape to be instantiated via loading a module, or by making an override by writing a sysfs file. When having the __init there, the function has been long removed and you get a crash by calling into the weeds. So the sequence is: early boot Register the adapter driver. user insmod bone-geiger-cape cape-is-matched call omap_build_device Please look into the capebus patches for the details. Regards, Tony Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Pantelis Antoniou pa...@antoniou-consulting.com [121031 11:05]: Hi Tony, On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 10:26]: It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Hmm I think you misunderstood me. You only need to create the platform_device under arch/arm/mach-omap2. The device creation happens only at __init, so omap_build_device can stay as __init. The driver itself should be under drivers. But is this bus on non-device-tree omaps? If not, just make it device tree only. I'm afraid that's not the case. The whole notion of capebus is that instantiation of the devices doesn't just happen early at the boot sequence. It is perfectly valid for a cape to be instantiated via loading a module, or by making an override by writing a sysfs file. When having the __init there, the function has been long removed and you get a crash by calling into the weeds. So the sequence is: early boot Register the adapter driver. OK this is always there for the hardware, and done during the __init and this one should have an omap_device.. user insmod bone-geiger-cape cape-is-matched call omap_build_device Please look into the capebus patches for the details. ..but it seems that the devices connected to capebus should not have anything to do with omap_device and hwmod? They should only need to use capebus, just like USB devices use the USB bus and are registered as USB devices. Anyways, please sort it out with Benoit, Kevin and Paul, I've added them to cc. Maybe I'm missing something here. Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
On Oct 31, 2012, at 8:09 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 11:05]: Hi Tony, On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 10:26]: It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Hmm I think you misunderstood me. You only need to create the platform_device under arch/arm/mach-omap2. The device creation happens only at __init, so omap_build_device can stay as __init. The driver itself should be under drivers. But is this bus on non-device-tree omaps? If not, just make it device tree only. I'm afraid that's not the case. The whole notion of capebus is that instantiation of the devices doesn't just happen early at the boot sequence. It is perfectly valid for a cape to be instantiated via loading a module, or by making an override by writing a sysfs file. When having the __init there, the function has been long removed and you get a crash by calling into the weeds. So the sequence is: early boot Register the adapter driver. OK this is always there for the hardware, and done during the __init and this one should have an omap_device.. It is there at this point in time. The __init section will go away after the boot is complete. So you have this (as an example da8xx-dt): 1. During the boot sequence (postcore_initcall) da8xx_dt_init() is called. It registers the platform device driver (da8xx_dt_driver). The probe method is _not_ called yet since a matching device is _not_ yet in the DT. The matching device is found in a number of cape definitions but none have been activated. 2. capebus probes the capes and enumerates using the EEPROM header (for the beaglebone case). But a matching cape driver is not yet been loaded. 3. At this point booting ends, and the __init sections are discarded. 4. User space starts and insmod's the cape driver. 5. Capebus now has match and calls the cape driver's probe method. 6. Cape driver, locates matching da8xx_dt in the cape DT definition, and eventuall will call device_add. device_add will eventually call da8xx-dt's probe method. 7. da8xx-dt probe method will retrieve the hwmod (all OK) and it will call omap_device_build (which it is in an __init section) and is now freed. 8. Crash. user insmod bone-geiger-cape cape-is-matched call omap_build_device Please look into the capebus patches for the details. ..but it seems that the devices connected to capebus should not have anything to do with omap_device and hwmod? They should only need to use capebus, just like USB devices use the USB bus and are registered as USB devices. Anyways, please sort it out with Benoit, Kevin and Paul, I've added them to cc. Maybe I'm missing something here. Regards, Tony Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Panto, On 10/31/2012 07:09 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 11:05]: Hi Tony, On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 10:26]: It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Hmm I think you misunderstood me. You only need to create the platform_device under arch/arm/mach-omap2. The device creation happens only at __init, so omap_build_device can stay as __init. The driver itself should be under drivers. But is this bus on non-device-tree omaps? If not, just make it device tree only. I'm afraid that's not the case. The whole notion of capebus is that instantiation of the devices doesn't just happen early at the boot sequence. It is perfectly valid for a cape to be instantiated via loading a module, or by making an override by writing a sysfs file. When having the __init there, the function has been long removed and you get a crash by calling into the weeds. So the sequence is: early boot Register the adapter driver. OK this is always there for the hardware, and done during the __init and this one should have an omap_device.. user insmod bone-geiger-cape cape-is-matched call omap_build_device Please look into the capebus patches for the details. ..but it seems that the devices connected to capebus should not have anything to do with omap_device and hwmod? Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? Regards, Benoit -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Benoit, On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Hi Panto, On 10/31/2012 07:09 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 11:05]: Hi Tony, On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 10:26]: It is painless to move the adapter DT devices to arch/arm/mach-omap2 However I got bit by the __init at omap_build_device family functions. If you don't remove it, crashes every time you instantiate a device at runtime, or you load the cape driver as a module. Hmm I think you misunderstood me. You only need to create the platform_device under arch/arm/mach-omap2. The device creation happens only at __init, so omap_build_device can stay as __init. The driver itself should be under drivers. But is this bus on non-device-tree omaps? If not, just make it device tree only. I'm afraid that's not the case. The whole notion of capebus is that instantiation of the devices doesn't just happen early at the boot sequence. It is perfectly valid for a cape to be instantiated via loading a module, or by making an override by writing a sysfs file. When having the __init there, the function has been long removed and you get a crash by calling into the weeds. So the sequence is: early boot Register the adapter driver. OK this is always there for the hardware, and done during the __init and this one should have an omap_device.. user insmod bone-geiger-cape cape-is-matched call omap_build_device Please look into the capebus patches for the details. ..but it seems that the devices connected to capebus should not have anything to do with omap_device and hwmod? Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. In the da8xx case it contains only the minimum hardware required for interfacing to the required display type, be it an LCD or a DVI or something other. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. So this is a use case that hasn't been encountered yet I'm afraid, but it is a valid use case. I don't see what the big deal is about to be honest. The omap device is safely created in the da8xx-dt adapter's probe method, and everything seems to work. If there are any gotcha's or problems with this approach I think can be overcome. Regards, Benoit Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Tony, On Oct 31, 2012, at 11:26 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. We don't have a board file anymore where to do i. This is all on board-generic, getting ready for the one kernel fits all for ARM. Everything is local to arch/arm/mach-omap2, the only problem is that __init modifier that's keeping us from loading the cape drivers as modules. If you take some time and scan the full patchset you will understand why this is the way it is. Regards, Tony Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Pantelis Antoniou pa...@antoniou-consulting.com [121031 14:38]: There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. You don't need to instantiate the capes during __init, you need to just instantiate the omap internal devices which are always there in the hardware. These internal devices just need to be set to state = disabled until they are used. The capes themselves should not have anything to do with omap_hwmod or omap_device, they just contain external connectors, regulators, LCD panels etc. To your capebus the omap internal devices should look like just regular struct device entries. Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi Tony, On Oct 31, 2012, at 11:43 PM, Tony Lindgren wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 14:38]: There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. You don't need to instantiate the capes during __init, you need to just instantiate the omap internal devices which are always there in the hardware. These internal devices just need to be set to state = disabled until they are used. If you set the device's node state to disable the device doesn't get registered; i.e. the device's probe method will not be called. The devices are instantiated by the call to of_platform_populate(NULL, omap_dt_match_table, NULL, NULL); in omap_generic_init() (arch/arm/mach-omap2/board-generic.c) Which for each child of the root node will call of_platform_bus_create which in turn will call of_platform_device_create_pdata. First check in there is if (!of_device_is_available(np)) return NULL; of_device_is_available() will return 0 in any case status is neither okay or ok. So when device's node is 'disabled' of_platform_device_create_pdata() will not create the device. Now, of course it is possible to re-trigger the platform's probe method to be called, and in fact I do so in the capebus patches. Since the bus drives of things like i2c spi must be disabled if not used by any cape, they are disabled by default, and are activated when referenced by a cape. In the file drivers/capebus/capebus-driver.c, there are two functions. The first, capebus_of_platform_device_enable() will check if the referenced device node is disabled, and after enabling it (with capebus_of_device_node_enable()) will call of_platform_device_create(), but now this time the instantiation will be successful. The problem is that now, we're way past the point in the boot sequence that omap_build_device has been freed; calling the probe method will now lead to a crash. The capes themselves should not have anything to do with omap_hwmod or omap_device, they just contain external connectors, regulators, LCD panels etc. To your capebus the omap internal devices should look like just regular struct device entries. Regards, Tony Regards -- Pantelis -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
* Pantelis Antoniou pa...@antoniou-consulting.com [121031 15:02]: So when device's node is 'disabled' of_platform_device_create_pdata() will not create the device. Now, of course it is possible to re-trigger the platform's probe method to be called, and in fact I do so in the capebus patches. You should fix this in generic way then rather than working around it in capebus. The same problem exists changing between different functionality for the shared pins, let's say between USB pins and UART pins if you want a serial debug console on some phone. Regards, Tony -- To unsubscribe from this list: send the line unsubscribe linux-omap in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2
Hi, On Wed, Oct 31, 2012 at 11:36:25PM +0200, Pantelis Antoniou wrote: * Pantelis Antoniou pa...@antoniou-consulting.com [121031 13:14]: On Oct 31, 2012, at 9:55 PM, Benoit Cousson wrote: Yeah, I do agree. I'm confused as well. Only OMAP IPs under PRCM control could have an hwmod and thus must be handled by an omap_device. Any devices that is created later cannot be omap_device. The DT core will create regular platform_device for them. Since cape is an external board, it should have nothing to do with omap_device. Looking at your patch: da8xx-dt: Create da8xx DT adapter device I understand why you do that, but in fact that patch does not make sense to me :-( Why do you have to create an omap_device from the driver probe? The problem is that capes are not external boards in the normal sense as a PCI board is. In the PCI case the hardware that implements the desired functionality is on the PCI board, while in the cape case the hardware module is in the SoC. The cape most of the times is quite simple and contains passive components, leds or some kind of I2C/SPI devices. Ah now I see, you're talking about the beaglebone extension boards :) The way to deal with those properly is to just edit the board .dts entry to include omap-beaglebone-cape-xyz.dtsi whatever. That is what is being done... This is the fallout. You can't instantiate the omap_device early in the boot process like it was done up to now in the board file. You can only do that later in the boot process (for built-in cape drivers), or even after user-space has booted and the matching cape driver module has been loaded. Yes you can, just edit the .dts file for the extension board you have connected. This stuff should be DT only for sure, let's not even start adding platform_data entries for that. The omap_device entries for the omap internal devices will be created automatically during startup based on the .dts. Note that you can set status = disabled for the omap internal devices in the .dts file, the devices are there in the hardware. If you are sure the extension boards are safely hot pluggable, then all you need is some interface to enable and disable devices after booting. But that should be done in Linux generic way. So we should not export any omap_hwmod or omap_device things, and want to keep it __init only, and local to arch/arm/mach-omap2. I disagree. This is not something that is handled by just editing the dts. The way it is handled, is in the Linux generic way, we have a proper bus, and the drivers as compiled as standalone file. when you have an actual bus, that'd be correct. We're hitting a use case that wasn't there in omap until now. There a a whole bunch of conflicting capes. There's no way to instantiate them together. They must be instantiated only after their EEPROMs are read and they are matched to their corresponding cape drivers. why this requirement of instantiating them only after reading EEPROMs ? It's unnecessary to add that requirement, just do what Tony said (include my-awesome-cape.dtsi to bone.dts) and all i2c/spi devices should be created automatically. The thing is that there is no such thing as a cape-device. The cape is just a collection of I2C, 1-wire and SPI devices anyway. What we should instantiate is bmp085, tls2550, sht21, instead of instantiating beagle-bone-weather-cape. What's the problem in just instantiating all of those from bone.dts ? Expose the EEPROMs to userland so whatever SW you guys have running on the bone can figure out what features to expose to the SDK which the user sees, but the kernel doesn't need to know that there is a weather-cape attached to the bone. -- balbi signature.asc Description: Digital signature
