Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob,


On 17-06-29 03:40 PM, Rob Herring wrote:

On Tue, Jun 27, 2017 at 12:10 AM, Scott Branden
 wrote:

Hi Rob/Florian,

Thanks for input but still don't see any need for SoC specific
compatible stings.  IP revision specific yes.


On 17-06-22 06:04 PM, Florian Fainelli wrote:

On 06/22/2017 05:42 PM, Scott Branden wrote:


On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
 1 file changed, 13 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future
proof
against bugs/incompatibilities
between different versions of the hardware block due to integration
issues
or any other reason.
You can then compare in your driver because the strings were already
used in
the dtb.

That would make sense if you can't already differentiate what SoC you
are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

Then, if there is a workaround discovered in a particular SoC the driver
can be updated in the future without changing the dtb.

Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is
in uses the fallback compatible or machine_is_compatible string.

There is no difference in amount of code added to a driver when a new
SoC is introduced into the system that has bugs that need to be handled
by the driver.

The difference is in your recommendation we need to go through all the
drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.


Then, we have to modify all the devicetree documentation for all the
drivers.  Then, we have to ensure that all dts files populate this new
fallback string (even if it is unused).  We don't see the benefit in
doing any of that.  Using machine_is_compatible and having less
compatibility strings to deal appears much cleaner and more foolproof
for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.

In this particular case, the IP is integrated within and outside a family of
SoCs
(the exact same block is in Capri for example).
The only fallback compatablity string that makes sense is "brcm,
dte-ptp-v1".
When we integrate a new version of this IP we would add "brcm, dte-ptp-v2".

Unless you 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob,


On 17-06-29 03:40 PM, Rob Herring wrote:

On Tue, Jun 27, 2017 at 12:10 AM, Scott Branden
 wrote:

Hi Rob/Florian,

Thanks for input but still don't see any need for SoC specific
compatible stings.  IP revision specific yes.


On 17-06-22 06:04 PM, Florian Fainelli wrote:

On 06/22/2017 05:42 PM, Scott Branden wrote:


On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
 1 file changed, 13 insertions(+)
 create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future
proof
against bugs/incompatibilities
between different versions of the hardware block due to integration
issues
or any other reason.
You can then compare in your driver because the strings were already
used in
the dtb.

That would make sense if you can't already differentiate what SoC you
are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

Then, if there is a workaround discovered in a particular SoC the driver
can be updated in the future without changing the dtb.

Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is
in uses the fallback compatible or machine_is_compatible string.

There is no difference in amount of code added to a driver when a new
SoC is introduced into the system that has bugs that need to be handled
by the driver.

The difference is in your recommendation we need to go through all the
drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.


Then, we have to modify all the devicetree documentation for all the
drivers.  Then, we have to ensure that all dts files populate this new
fallback string (even if it is unused).  We don't see the benefit in
doing any of that.  Using machine_is_compatible and having less
compatibility strings to deal appears much cleaner and more foolproof
for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.

In this particular case, the IP is integrated within and outside a family of
SoCs
(the exact same block is in Capri for example).
The only fallback compatablity string that makes sense is "brcm,
dte-ptp-v1".
When we integrate a new version of this IP we would add "brcm, dte-ptp-v2".

Unless you have strong version control of IP versions, version numbers
aren't generally reliable. 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Tue, Jun 27, 2017 at 12:10 AM, Scott Branden
 wrote:
> Hi Rob/Florian,
>
> Thanks for input but still don't see any need for SoC specific
> compatible stings.  IP revision specific yes.
>
>
> On 17-06-22 06:04 PM, Florian Fainelli wrote:
>>
>> On 06/22/2017 05:42 PM, Scott Branden wrote:
>>>
>>>
>>> On 17-06-21 08:19 PM, Rob Herring wrote:

 On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
  wrote:
>
> Hi Rob,
>
>
> On 17-06-18 07:04 AM, Rob Herring wrote:
>>
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>>
>>> Add device tree binding documentation for the Broadcom DTE
>>> PTP clock driver.
>>>
>>> Signed-off-by: Arun Parameswaran 
>>> ---
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
>>> +
>>> 1 file changed, 13 insertions(+)
>>> create mode 100644
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> new file mode 100644
>>> index 000..07590bc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> @@ -0,0 +1,13 @@
>>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
>>
>> Bindings describe h/w, not drivers.
>>
>>> +
>>> +Required properties:
>>> +- compatible: should be "brcm,ptp-dte"
>>
>> Looks too generic. You need SoC specific compatible strings.
>
> Rob, could you please help me understand the use of adding SoC specific
> compatible strings.
> I still don't get it.
>
> It's my understanding that the SoC compatibility string is to future
> proof
> against bugs/incompatibilities
> between different versions of the hardware block due to integration
> issues
> or any other reason.
> You can then compare in your driver because the strings were already
> used in
> the dtb.
>
> That would make sense if you can't already differentiate what SoC you
> are
> running on.
> But the SoC is already specified in the root of the device tree in the
> compatible string?
> Why can't you just use of_machine_is_compatible inside your driver when
> needed?

 Use of of_machine_is_compatible in drivers will result in the same
 mess we had with machine_is_X defines pre-DT. It practically
 guarantees that you must update the driver for a new SoC (with
 fallback compatibles you don't). Plus the matching logic for
 of_machine_is_compatible is open coded logic in every driver which is
 worse IMO than having a standard match table.
>>>
>>> I don't understand what you mean by fallback compatible then.
>>>
>>> Let's say I have 3 SoCs that each contain the same ip block.
>>> You want us to add a fallback compatibility per SoC, is that correct?
>>
>> I think Rob meant a fallback compatibility for the particular block.
>> E.g: brcm,iproc-ptp is the fallback compatible string, but in your
>> SoC-specific DTS, you would have at least:
>>
>> compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";
>>
>> Where cygnus-ptp is more specific than iproc-ptp
>>>
>>> Then, if there is a workaround discovered in a particular SoC the driver
>>> can be updated in the future without changing the dtb.
>>>
>>> Then, the block gets added to a 4th SoC.
>>> You want us to another new compatibility string for the new SoC?
>>> If the new SoC has a bug then the driver has to be updated whether it is
>>> in uses the fallback compatible or machine_is_compatible string.
>>>
>>> There is no difference in amount of code added to a driver when a new
>>> SoC is introduced into the system that has bugs that need to be handled
>>> by the driver.
>>>
>>> The difference is in your recommendation we need to go through all the
>>> drivers used by the new SoC and add fallback compatibility strings.
>>
>> Not really, the fallback is what the driver should be matching by
>> default (hence the name fallback) and if and only if you need to have a
>> SoC-specific behavior in your driver (because of bugs, or slight
>> differences) would you be matching this SoC-specific compatible string
>> to capture that and key the driver behavior based off that.
>>
>>> Then, we have to modify all the devicetree documentation for all the
>>> drivers.  Then, we have to ensure that all dts files populate this new
>>> fallback string (even if it is unused).  We don't see the benefit in
>>> doing any of that.  Using machine_is_compatible and having less
>>> compatibility strings to deal appears much cleaner and more foolproof
>>> for all situations.
>>
>> When you introduce a new SoC, you would update all the bindings for the
>> devices (not drivers) that are susceptible to be used by this 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Tue, Jun 27, 2017 at 12:10 AM, Scott Branden
 wrote:
> Hi Rob/Florian,
>
> Thanks for input but still don't see any need for SoC specific
> compatible stings.  IP revision specific yes.
>
>
> On 17-06-22 06:04 PM, Florian Fainelli wrote:
>>
>> On 06/22/2017 05:42 PM, Scott Branden wrote:
>>>
>>>
>>> On 17-06-21 08:19 PM, Rob Herring wrote:

 On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
  wrote:
>
> Hi Rob,
>
>
> On 17-06-18 07:04 AM, Rob Herring wrote:
>>
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>>
>>> Add device tree binding documentation for the Broadcom DTE
>>> PTP clock driver.
>>>
>>> Signed-off-by: Arun Parameswaran 
>>> ---
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
>>> +
>>> 1 file changed, 13 insertions(+)
>>> create mode 100644
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> new file mode 100644
>>> index 000..07590bc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> @@ -0,0 +1,13 @@
>>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
>>
>> Bindings describe h/w, not drivers.
>>
>>> +
>>> +Required properties:
>>> +- compatible: should be "brcm,ptp-dte"
>>
>> Looks too generic. You need SoC specific compatible strings.
>
> Rob, could you please help me understand the use of adding SoC specific
> compatible strings.
> I still don't get it.
>
> It's my understanding that the SoC compatibility string is to future
> proof
> against bugs/incompatibilities
> between different versions of the hardware block due to integration
> issues
> or any other reason.
> You can then compare in your driver because the strings were already
> used in
> the dtb.
>
> That would make sense if you can't already differentiate what SoC you
> are
> running on.
> But the SoC is already specified in the root of the device tree in the
> compatible string?
> Why can't you just use of_machine_is_compatible inside your driver when
> needed?

 Use of of_machine_is_compatible in drivers will result in the same
 mess we had with machine_is_X defines pre-DT. It practically
 guarantees that you must update the driver for a new SoC (with
 fallback compatibles you don't). Plus the matching logic for
 of_machine_is_compatible is open coded logic in every driver which is
 worse IMO than having a standard match table.
>>>
>>> I don't understand what you mean by fallback compatible then.
>>>
>>> Let's say I have 3 SoCs that each contain the same ip block.
>>> You want us to add a fallback compatibility per SoC, is that correct?
>>
>> I think Rob meant a fallback compatibility for the particular block.
>> E.g: brcm,iproc-ptp is the fallback compatible string, but in your
>> SoC-specific DTS, you would have at least:
>>
>> compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";
>>
>> Where cygnus-ptp is more specific than iproc-ptp
>>>
>>> Then, if there is a workaround discovered in a particular SoC the driver
>>> can be updated in the future without changing the dtb.
>>>
>>> Then, the block gets added to a 4th SoC.
>>> You want us to another new compatibility string for the new SoC?
>>> If the new SoC has a bug then the driver has to be updated whether it is
>>> in uses the fallback compatible or machine_is_compatible string.
>>>
>>> There is no difference in amount of code added to a driver when a new
>>> SoC is introduced into the system that has bugs that need to be handled
>>> by the driver.
>>>
>>> The difference is in your recommendation we need to go through all the
>>> drivers used by the new SoC and add fallback compatibility strings.
>>
>> Not really, the fallback is what the driver should be matching by
>> default (hence the name fallback) and if and only if you need to have a
>> SoC-specific behavior in your driver (because of bugs, or slight
>> differences) would you be matching this SoC-specific compatible string
>> to capture that and key the driver behavior based off that.
>>
>>> Then, we have to modify all the devicetree documentation for all the
>>> drivers.  Then, we have to ensure that all dts files populate this new
>>> fallback string (even if it is unused).  We don't see the benefit in
>>> doing any of that.  Using machine_is_compatible and having less
>>> compatibility strings to deal appears much cleaner and more foolproof
>>> for all situations.
>>
>> When you introduce a new SoC, you would update all the bindings for the
>> devices (not drivers) that are susceptible to be used by this SoC. If
>> all goes well, your SoC has little bugs, and your drivers don't even
>> need to 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob/Florian,

Thanks for input but still don't see any need for SoC specific
compatible stings.  IP revision specific yes.

On 17-06-22 06:04 PM, Florian Fainelli wrote:

On 06/22/2017 05:42 PM, Scott Branden wrote:


On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
1 file changed, 13 insertions(+)
create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future
proof
against bugs/incompatibilities
between different versions of the hardware block due to integration
issues
or any other reason.
You can then compare in your driver because the strings were already
used in
the dtb.

That would make sense if you can't already differentiate what SoC you
are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

Then, if there is a workaround discovered in a particular SoC the driver
can be updated in the future without changing the dtb.

Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is
in uses the fallback compatible or machine_is_compatible string.

There is no difference in amount of code added to a driver when a new
SoC is introduced into the system that has bugs that need to be handled
by the driver.

The difference is in your recommendation we need to go through all the
drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.


Then, we have to modify all the devicetree documentation for all the
drivers.  Then, we have to ensure that all dts files populate this new
fallback string (even if it is unused).  We don't see the benefit in
doing any of that.  Using machine_is_compatible and having less
compatibility strings to deal appears much cleaner and more foolproof
for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.
In this particular case, the IP is integrated within and outside a 
family of SoCs

(the exact same block is in Capri for example).
The only fallback compatablity string that makes sense is "brcm, 
dte-ptp-v1".

When we integrate a new version of this IP we would add "brcm, dte-ptp-v2".

Rob, I still see no need to define any other compatablity strings.

Everything else can be handled with machine_is_compatible
with the exact same 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob/Florian,

Thanks for input but still don't see any need for SoC specific
compatible stings.  IP revision specific yes.

On 17-06-22 06:04 PM, Florian Fainelli wrote:

On 06/22/2017 05:42 PM, Scott Branden wrote:


On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
1 file changed, 13 insertions(+)
create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future
proof
against bugs/incompatibilities
between different versions of the hardware block due to integration
issues
or any other reason.
You can then compare in your driver because the strings were already
used in
the dtb.

That would make sense if you can't already differentiate what SoC you
are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

Then, if there is a workaround discovered in a particular SoC the driver
can be updated in the future without changing the dtb.

Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is
in uses the fallback compatible or machine_is_compatible string.

There is no difference in amount of code added to a driver when a new
SoC is introduced into the system that has bugs that need to be handled
by the driver.

The difference is in your recommendation we need to go through all the
drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.


Then, we have to modify all the devicetree documentation for all the
drivers.  Then, we have to ensure that all dts files populate this new
fallback string (even if it is unused).  We don't see the benefit in
doing any of that.  Using machine_is_compatible and having less
compatibility strings to deal appears much cleaner and more foolproof
for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.
In this particular case, the IP is integrated within and outside a 
family of SoCs

(the exact same block is in Capri for example).
The only fallback compatablity string that makes sense is "brcm, 
dte-ptp-v1".

When we integrate a new version of this IP we would add "brcm, dte-ptp-v2".

Rob, I still see no need to define any other compatablity strings.

Everything else can be handled with machine_is_compatible
with the exact same amount of code change to the driver?
Adding the additional 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Florian Fainelli]

On 06/22/2017 05:42 PM, Scott Branden wrote:
> 
> 
> On 17-06-21 08:19 PM, Rob Herring wrote:
>> On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
>>  wrote:
>>> Hi Rob,
>>>
>>>
>>> On 17-06-18 07:04 AM, Rob Herring wrote:
 On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> Add device tree binding documentation for the Broadcom DTE
> PTP clock driver.
>
> Signed-off-by: Arun Parameswaran 
> ---
>Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
> +
>1 file changed, 13 insertions(+)
>create mode 100644
> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>
> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> new file mode 100644
> index 000..07590bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> @@ -0,0 +1,13 @@
> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
 Bindings describe h/w, not drivers.

> +
> +Required properties:
> +- compatible: should be "brcm,ptp-dte"
 Looks too generic. You need SoC specific compatible strings.
>>>
>>> Rob, could you please help me understand the use of adding SoC specific
>>> compatible strings.
>>> I still don't get it.
>>>
>>> It's my understanding that the SoC compatibility string is to future
>>> proof
>>> against bugs/incompatibilities
>>> between different versions of the hardware block due to integration
>>> issues
>>> or any other reason.
>>> You can then compare in your driver because the strings were already
>>> used in
>>> the dtb.
>>>
>>> That would make sense if you can't already differentiate what SoC you
>>> are
>>> running on.
>>> But the SoC is already specified in the root of the device tree in the
>>> compatible string?
>>> Why can't you just use of_machine_is_compatible inside your driver when
>>> needed?
>> Use of of_machine_is_compatible in drivers will result in the same
>> mess we had with machine_is_X defines pre-DT. It practically
>> guarantees that you must update the driver for a new SoC (with
>> fallback compatibles you don't). Plus the matching logic for
>> of_machine_is_compatible is open coded logic in every driver which is
>> worse IMO than having a standard match table.
> I don't understand what you mean by fallback compatible then.
> 
> Let's say I have 3 SoCs that each contain the same ip block.
> You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

> 
> Then, if there is a workaround discovered in a particular SoC the driver
> can be updated in the future without changing the dtb.
> 
> Then, the block gets added to a 4th SoC.
> You want us to another new compatibility string for the new SoC?
> If the new SoC has a bug then the driver has to be updated whether it is
> in uses the fallback compatible or machine_is_compatible string.
> 
> There is no difference in amount of code added to a driver when a new
> SoC is introduced into the system that has bugs that need to be handled
> by the driver.
> 
> The difference is in your recommendation we need to go through all the
> drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.

> Then, we have to modify all the devicetree documentation for all the
> drivers.  Then, we have to ensure that all dts files populate this new
> fallback string (even if it is unused).  We don't see the benefit in
> doing any of that.  Using machine_is_compatible and having less
> compatibility strings to deal appears much cleaner and more foolproof
> for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.
-- 
Florian

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Florian Fainelli]

On 06/22/2017 05:42 PM, Scott Branden wrote:
> 
> 
> On 17-06-21 08:19 PM, Rob Herring wrote:
>> On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
>>  wrote:
>>> Hi Rob,
>>>
>>>
>>> On 17-06-18 07:04 AM, Rob Herring wrote:
 On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> Add device tree binding documentation for the Broadcom DTE
> PTP clock driver.
>
> Signed-off-by: Arun Parameswaran 
> ---
>Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
> +
>1 file changed, 13 insertions(+)
>create mode 100644
> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>
> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> new file mode 100644
> index 000..07590bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> @@ -0,0 +1,13 @@
> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
 Bindings describe h/w, not drivers.

> +
> +Required properties:
> +- compatible: should be "brcm,ptp-dte"
 Looks too generic. You need SoC specific compatible strings.
>>>
>>> Rob, could you please help me understand the use of adding SoC specific
>>> compatible strings.
>>> I still don't get it.
>>>
>>> It's my understanding that the SoC compatibility string is to future
>>> proof
>>> against bugs/incompatibilities
>>> between different versions of the hardware block due to integration
>>> issues
>>> or any other reason.
>>> You can then compare in your driver because the strings were already
>>> used in
>>> the dtb.
>>>
>>> That would make sense if you can't already differentiate what SoC you
>>> are
>>> running on.
>>> But the SoC is already specified in the root of the device tree in the
>>> compatible string?
>>> Why can't you just use of_machine_is_compatible inside your driver when
>>> needed?
>> Use of of_machine_is_compatible in drivers will result in the same
>> mess we had with machine_is_X defines pre-DT. It practically
>> guarantees that you must update the driver for a new SoC (with
>> fallback compatibles you don't). Plus the matching logic for
>> of_machine_is_compatible is open coded logic in every driver which is
>> worse IMO than having a standard match table.
> I don't understand what you mean by fallback compatible then.
> 
> Let's say I have 3 SoCs that each contain the same ip block.
> You want us to add a fallback compatibility per SoC, is that correct?

I think Rob meant a fallback compatibility for the particular block.
E.g: brcm,iproc-ptp is the fallback compatible string, but in your
SoC-specific DTS, you would have at least:

compatible = "brcm,cygnus-ptp", "brcm,iproc-ptp";

Where cygnus-ptp is more specific than iproc-ptp

> 
> Then, if there is a workaround discovered in a particular SoC the driver
> can be updated in the future without changing the dtb.
> 
> Then, the block gets added to a 4th SoC.
> You want us to another new compatibility string for the new SoC?
> If the new SoC has a bug then the driver has to be updated whether it is
> in uses the fallback compatible or machine_is_compatible string.
> 
> There is no difference in amount of code added to a driver when a new
> SoC is introduced into the system that has bugs that need to be handled
> by the driver.
> 
> The difference is in your recommendation we need to go through all the
> drivers used by the new SoC and add fallback compatibility strings.

Not really, the fallback is what the driver should be matching by
default (hence the name fallback) and if and only if you need to have a
SoC-specific behavior in your driver (because of bugs, or slight
differences) would you be matching this SoC-specific compatible string
to capture that and key the driver behavior based off that.

> Then, we have to modify all the devicetree documentation for all the
> drivers.  Then, we have to ensure that all dts files populate this new
> fallback string (even if it is unused).  We don't see the benefit in
> doing any of that.  Using machine_is_compatible and having less
> compatibility strings to deal appears much cleaner and more foolproof
> for all situations.

When you introduce a new SoC, you would update all the bindings for the
devices (not drivers) that are susceptible to be used by this SoC. If
all goes well, your SoC has little bugs, and your drivers don't even
need to see an update because they are already matching the fallback
compatible string.

That's what I understand from the suggestion but I may be totally off
rails here.
-- 
Florian

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
   Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
   1 file changed, 13 insertions(+)
   create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.


Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future proof
against bugs/incompatibilities
between different versions of the hardware block due to integration issues
or any other reason.
You can then compare in your driver because the strings were already used in
the dtb.

That would make sense if you can't already differentiate what SoC you are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

Then, if there is a workaround discovered in a particular SoC the driver 
can be updated in the future without changing the dtb.


Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is 
in uses the fallback compatible or machine_is_compatible string.


There is no difference in amount of code added to a driver when a new 
SoC is introduced into the system that has bugs that need to be handled 
by the driver.


The difference is in your recommendation we need to go through all the 
drivers used by the new SoC and add fallback compatibility strings.
Then, we have to modify all the devicetree documentation for all the 
drivers.  Then, we have to ensure that all dts files populate this new 
fallback string (even if it is unused).  We don't see the benefit in 
doing any of that.  Using machine_is_compatible and having less 
compatibility strings to deal appears much cleaner and more foolproof 
for all situations.

Please explain what I'm missing.  I see other drivers already following the
of_machine_is_compatible
approach and it makes more sense to me than adding SoC specific compatible
strings into every
driver.

If the IP blocks are all the same, you don't have to add them to any
drivers, just add fallback compatibles.



Rob

Regards,
Scott

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

On 17-06-21 08:19 PM, Rob Herring wrote:

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
   Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
+
   1 file changed, 13 insertions(+)
   create mode 100644
Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.


Rob, could you please help me understand the use of adding SoC specific
compatible strings.
I still don't get it.

It's my understanding that the SoC compatibility string is to future proof
against bugs/incompatibilities
between different versions of the hardware block due to integration issues
or any other reason.
You can then compare in your driver because the strings were already used in
the dtb.

That would make sense if you can't already differentiate what SoC you are
running on.
But the SoC is already specified in the root of the device tree in the
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when
needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

I don't understand what you mean by fallback compatible then.

Let's say I have 3 SoCs that each contain the same ip block.
You want us to add a fallback compatibility per SoC, is that correct?

Then, if there is a workaround discovered in a particular SoC the driver 
can be updated in the future without changing the dtb.


Then, the block gets added to a 4th SoC.
You want us to another new compatibility string for the new SoC?
If the new SoC has a bug then the driver has to be updated whether it is 
in uses the fallback compatible or machine_is_compatible string.


There is no difference in amount of code added to a driver when a new 
SoC is introduced into the system that has bugs that need to be handled 
by the driver.


The difference is in your recommendation we need to go through all the 
drivers used by the new SoC and add fallback compatibility strings.
Then, we have to modify all the devicetree documentation for all the 
drivers.  Then, we have to ensure that all dts files populate this new 
fallback string (even if it is unused).  We don't see the benefit in 
doing any of that.  Using machine_is_compatible and having less 
compatibility strings to deal appears much cleaner and more foolproof 
for all situations.

Please explain what I'm missing.  I see other drivers already following the
of_machine_is_compatible
approach and it makes more sense to me than adding SoC specific compatible
strings into every
driver.

If the IP blocks are all the same, you don't have to add them to any
drivers, just add fallback compatibles.



Rob

Regards,
Scott

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:
> Hi Rob,
>
>
> On 17-06-18 07:04 AM, Rob Herring wrote:
>>
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>>
>>> Add device tree binding documentation for the Broadcom DTE
>>> PTP clock driver.
>>>
>>> Signed-off-by: Arun Parameswaran 
>>> ---
>>>   Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
>>> +
>>>   1 file changed, 13 insertions(+)
>>>   create mode 100644
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> new file mode 100644
>>> index 000..07590bc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> @@ -0,0 +1,13 @@
>>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
>>
>> Bindings describe h/w, not drivers.
>>
>>> +
>>> +Required properties:
>>> +- compatible: should be "brcm,ptp-dte"
>>
>> Looks too generic. You need SoC specific compatible strings.
>
>
> Rob, could you please help me understand the use of adding SoC specific
> compatible strings.
> I still don't get it.
>
> It's my understanding that the SoC compatibility string is to future proof
> against bugs/incompatibilities
> between different versions of the hardware block due to integration issues
> or any other reason.
> You can then compare in your driver because the strings were already used in
> the dtb.
>
> That would make sense if you can't already differentiate what SoC you are
> running on.
> But the SoC is already specified in the root of the device tree in the
> compatible string?
> Why can't you just use of_machine_is_compatible inside your driver when
> needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

>
> Please explain what I'm missing.  I see other drivers already following the
> of_machine_is_compatible
> approach and it makes more sense to me than adding SoC specific compatible
> strings into every
> driver.

If the IP blocks are all the same, you don't have to add them to any
drivers, just add fallback compatibles.

Rob

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Tue, Jun 20, 2017 at 3:48 PM, Scott Branden
 wrote:
> Hi Rob,
>
>
> On 17-06-18 07:04 AM, Rob Herring wrote:
>>
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>>
>>> Add device tree binding documentation for the Broadcom DTE
>>> PTP clock driver.
>>>
>>> Signed-off-by: Arun Parameswaran 
>>> ---
>>>   Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13
>>> +
>>>   1 file changed, 13 insertions(+)
>>>   create mode 100644
>>> Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> new file mode 100644
>>> index 000..07590bc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>> @@ -0,0 +1,13 @@
>>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
>>
>> Bindings describe h/w, not drivers.
>>
>>> +
>>> +Required properties:
>>> +- compatible: should be "brcm,ptp-dte"
>>
>> Looks too generic. You need SoC specific compatible strings.
>
>
> Rob, could you please help me understand the use of adding SoC specific
> compatible strings.
> I still don't get it.
>
> It's my understanding that the SoC compatibility string is to future proof
> against bugs/incompatibilities
> between different versions of the hardware block due to integration issues
> or any other reason.
> You can then compare in your driver because the strings were already used in
> the dtb.
>
> That would make sense if you can't already differentiate what SoC you are
> running on.
> But the SoC is already specified in the root of the device tree in the
> compatible string?
> Why can't you just use of_machine_is_compatible inside your driver when
> needed?

Use of of_machine_is_compatible in drivers will result in the same
mess we had with machine_is_X defines pre-DT. It practically
guarantees that you must update the driver for a new SoC (with
fallback compatibles you don't). Plus the matching logic for
of_machine_is_compatible is open coded logic in every driver which is
worse IMO than having a standard match table.

>
> Please explain what I'm missing.  I see other drivers already following the
> of_machine_is_compatible
> approach and it makes more sense to me than adding SoC specific compatible
> strings into every
> driver.

If the IP blocks are all the same, you don't have to add them to any
drivers, just add fallback compatibles.

Rob

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
  1 file changed, 13 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.


Rob, could you please help me understand the use of adding SoC specific 
compatible strings.

I still don't get it.

It's my understanding that the SoC compatibility string is to future 
proof against bugs/incompatibilities
between different versions of the hardware block due to integration 
issues or any other reason.
You can then compare in your driver because the strings were already 
used in the dtb.


That would make sense if you can't already differentiate what SoC you 
are running on.
But the SoC is already specified in the root of the device tree in the 
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when 
needed?


Please explain what I'm missing.  I see other drivers already following 
the of_machine_is_compatible
approach and it makes more sense to me than adding SoC specific 
compatible strings into every

driver.

Regards,
 Scott

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Scott Branden]

Hi Rob,


On 17-06-18 07:04 AM, Rob Herring wrote:

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
  1 file changed, 13 insertions(+)
  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.


+
+Required properties:
+- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.


Rob, could you please help me understand the use of adding SoC specific 
compatible strings.

I still don't get it.

It's my understanding that the SoC compatibility string is to future 
proof against bugs/incompatibilities
between different versions of the hardware block due to integration 
issues or any other reason.
You can then compare in your driver because the strings were already 
used in the dtb.


That would make sense if you can't already differentiate what SoC you 
are running on.
But the SoC is already specified in the root of the device tree in the 
compatible string?
Why can't you just use of_machine_is_compatible inside your driver when 
needed?


Please explain what I'm missing.  I see other drivers already following 
the of_machine_is_compatible
approach and it makes more sense to me than adding SoC specific 
compatible strings into every

driver.

Regards,
 Scott

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Hi David, Rob,
I will address all of Rob's comments below.

Since a part of the patch was applied to 'net-next', would you like me to
send a new patch (based on the applied one), or a 'V2' of this patch ?

Thanks
Arun

On 17-06-18 07:04 AM, Rob Herring wrote:
> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>> Add device tree binding documentation for the Broadcom DTE
>> PTP clock driver.
>>
>> Signed-off-by: Arun Parameswaran 
>> ---
>>  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
>>  1 file changed, 13 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>
>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>> new file mode 100644
>> index 000..07590bc
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>> @@ -0,0 +1,13 @@
>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
> 
> Bindings describe h/w, not drivers.
> 
>> +
>> +Required properties:
>> +- compatible: should be "brcm,ptp-dte"
> 
> Looks too generic. You need SoC specific compatible strings.
> 
>> +- reg: address and length of the DTE block's NCO registers
>> +
>> +Example:
>> +
>> +ptp_dte: ptp_dte@180af650 {
> 
> Don't use '_' in node names.
> 
>> +compatible = "brcm,ptp-dte";
>> +reg = <0x180af650 0x10>;
>> +status = "okay";
>> +};
>> -- 
>> 1.9.1
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Hi David, Rob,
I will address all of Rob's comments below.

Since a part of the patch was applied to 'net-next', would you like me to
send a new patch (based on the applied one), or a 'V2' of this patch ?

Thanks
Arun

On 17-06-18 07:04 AM, Rob Herring wrote:
> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>> Add device tree binding documentation for the Broadcom DTE
>> PTP clock driver.
>>
>> Signed-off-by: Arun Parameswaran 
>> ---
>>  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
>>  1 file changed, 13 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>>
>> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
>> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>> new file mode 100644
>> index 000..07590bc
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
>> @@ -0,0 +1,13 @@
>> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver
> 
> Bindings describe h/w, not drivers.
> 
>> +
>> +Required properties:
>> +- compatible: should be "brcm,ptp-dte"
> 
> Looks too generic. You need SoC specific compatible strings.
> 
>> +- reg: address and length of the DTE block's NCO registers
>> +
>> +Example:
>> +
>> +ptp_dte: ptp_dte@180af650 {
> 
> Don't use '_' in node names.
> 
>> +compatible = "brcm,ptp-dte";
>> +reg = <0x180af650 0x10>;
>> +status = "okay";
>> +};
>> -- 
>> 1.9.1
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> Add device tree binding documentation for the Broadcom DTE
> PTP clock driver.
> 
> Signed-off-by: Arun Parameswaran 
> ---
>  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
>  1 file changed, 13 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> 
> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> new file mode 100644
> index 000..07590bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> @@ -0,0 +1,13 @@
> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.

> +
> +Required properties:
> +- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

> +- reg: address and length of the DTE block's NCO registers
> +
> +Example:
> +
> +ptp_dte: ptp_dte@180af650 {

Don't use '_' in node names.

> + compatible = "brcm,ptp-dte";
> + reg = <0x180af650 0x10>;
> + status = "okay";
> +};
> -- 
> 1.9.1
> 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Rob Herring]

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> Add device tree binding documentation for the Broadcom DTE
> PTP clock driver.
> 
> Signed-off-by: Arun Parameswaran 
> ---
>  Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
>  1 file changed, 13 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> 
> diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
> b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> new file mode 100644
> index 000..07590bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
> @@ -0,0 +1,13 @@
> +* Broadcom Digital Timing Engine(DTE) based PTP clock driver

Bindings describe h/w, not drivers.

> +
> +Required properties:
> +- compatible: should be "brcm,ptp-dte"

Looks too generic. You need SoC specific compatible strings.

> +- reg: address and length of the DTE block's NCO registers
> +
> +Example:
> +
> +ptp_dte: ptp_dte@180af650 {

Don't use '_' in node names.

> + compatible = "brcm,ptp-dte";
> + reg = <0x180af650 0x10>;
> + status = "okay";
> +};
> -- 
> 1.9.1
> 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

On 17-06-14 11:18 AM, Ray Jui wrote:
> 
> 
> On 6/13/17 10:46 AM, Arun Parameswaran wrote:
>>
>> Hi Richard,
>>
>> On 17-06-12 10:09 PM, Richard Cochran wrote:
>>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
 +Example:
 +
 +ptp_dte: ptp_dte@180af650 {
 +  compatible = "brcm,ptp-dte";
 +  reg = <0x180af650 0x10>;
 +  status = "okay";
 +};
>>> This patch set looks okay, as far as it goes, but how does one
>>> actually use the clock?
>>>
>>> How does one connect this node to an Ethernet MAC, for example?
>> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
>> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
>> all the future SoC's synced this way (for Ethernet).
>>
> 
> So apparently you do not need any phandle based DT binding defined for
> the connection between the Ethernet device node and the PTP device node?
> 
Correct. This driver doesn't need any phandle.

The Ethernet driver, in SoC's where the hardware link is not available,
might need the phandle to this driver.

>> In other scenarios, we use an user-space app to perform the sync based on
>> time-stamps from external hardware sources like the Wi-Fi.
>>> Thanks,
>>> Richard
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

On 17-06-14 11:18 AM, Ray Jui wrote:
> 
> 
> On 6/13/17 10:46 AM, Arun Parameswaran wrote:
>>
>> Hi Richard,
>>
>> On 17-06-12 10:09 PM, Richard Cochran wrote:
>>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
 +Example:
 +
 +ptp_dte: ptp_dte@180af650 {
 +  compatible = "brcm,ptp-dte";
 +  reg = <0x180af650 0x10>;
 +  status = "okay";
 +};
>>> This patch set looks okay, as far as it goes, but how does one
>>> actually use the clock?
>>>
>>> How does one connect this node to an Ethernet MAC, for example?
>> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
>> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
>> all the future SoC's synced this way (for Ethernet).
>>
> 
> So apparently you do not need any phandle based DT binding defined for
> the connection between the Ethernet device node and the PTP device node?
> 
Correct. This driver doesn't need any phandle.

The Ethernet driver, in SoC's where the hardware link is not available,
might need the phandle to this driver.

>> In other scenarios, we use an user-space app to perform the sync based on
>> time-stamps from external hardware sources like the Wi-Fi.
>>> Thanks,
>>> Richard
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

On 17-06-14 11:18 AM, Ray Jui wrote:
> 
> 
> On 6/13/17 10:46 AM, Arun Parameswaran wrote:
>>
>> Hi Richard,
>>
>> On 17-06-12 10:09 PM, Richard Cochran wrote:
>>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
 +Example:
 +
 +ptp_dte: ptp_dte@180af650 {
 +  compatible = "brcm,ptp-dte";
 +  reg = <0x180af650 0x10>;
 +  status = "okay";
 +};
>>> This patch set looks okay, as far as it goes, but how does one
>>> actually use the clock?
>>>
>>> How does one connect this node to an Ethernet MAC, for example?
>> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
>> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
>> all the future SoC's synced this way (for Ethernet).
>>
> 
> So apparently you do not need any phandle based DT binding defined for
> the connection between the Ethernet device node and the PTP device node?
> 
Correct. This driver doesn't need any phandle.

The Ethernet/Switch driver, in the SoC's where the hardware link is not
available, might need the phandle to this driver.

>> In other scenarios, we use an user-space app to perform the sync based on
>> time-stamps from external hardware sources like the Wi-Fi.
>>> Thanks,
>>> Richard
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

On 17-06-14 11:18 AM, Ray Jui wrote:
> 
> 
> On 6/13/17 10:46 AM, Arun Parameswaran wrote:
>>
>> Hi Richard,
>>
>> On 17-06-12 10:09 PM, Richard Cochran wrote:
>>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
 +Example:
 +
 +ptp_dte: ptp_dte@180af650 {
 +  compatible = "brcm,ptp-dte";
 +  reg = <0x180af650 0x10>;
 +  status = "okay";
 +};
>>> This patch set looks okay, as far as it goes, but how does one
>>> actually use the clock?
>>>
>>> How does one connect this node to an Ethernet MAC, for example?
>> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
>> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
>> all the future SoC's synced this way (for Ethernet).
>>
> 
> So apparently you do not need any phandle based DT binding defined for
> the connection between the Ethernet device node and the PTP device node?
> 
Correct. This driver doesn't need any phandle.

The Ethernet/Switch driver, in the SoC's where the hardware link is not
available, might need the phandle to this driver.

>> In other scenarios, we use an user-space app to perform the sync based on
>> time-stamps from external hardware sources like the Wi-Fi.
>>> Thanks,
>>> Richard
>>

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Ray Jui]

On 6/13/17 10:46 AM, Arun Parameswaran wrote:
> 
> Hi Richard,
> 
> On 17-06-12 10:09 PM, Richard Cochran wrote:
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>> +Example:
>>> +
>>> +ptp_dte: ptp_dte@180af650 {
>>> +   compatible = "brcm,ptp-dte";
>>> +   reg = <0x180af650 0x10>;
>>> +   status = "okay";
>>> +};
>> This patch set looks okay, as far as it goes, but how does one
>> actually use the clock?
>>
>> How does one connect this node to an Ethernet MAC, for example?
> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
> all the future SoC's synced this way (for Ethernet).
> 

So apparently you do not need any phandle based DT binding defined for
the connection between the Ethernet device node and the PTP device node?

> In other scenarios, we use an user-space app to perform the sync based on
> time-stamps from external hardware sources like the Wi-Fi.
>> Thanks,
>> Richard
> 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Ray Jui]

On 6/13/17 10:46 AM, Arun Parameswaran wrote:
> 
> Hi Richard,
> 
> On 17-06-12 10:09 PM, Richard Cochran wrote:
>> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>>> +Example:
>>> +
>>> +ptp_dte: ptp_dte@180af650 {
>>> +   compatible = "brcm,ptp-dte";
>>> +   reg = <0x180af650 0x10>;
>>> +   status = "okay";
>>> +};
>> This patch set looks okay, as far as it goes, but how does one
>> actually use the clock?
>>
>> How does one connect this node to an Ethernet MAC, for example?
> In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
> 1588 Shim NCO (used for time-stamping the packets). We are working on getting
> all the future SoC's synced this way (for Ethernet).
> 

So apparently you do not need any phandle based DT binding defined for
the connection between the Ethernet device node and the PTP device node?

> In other scenarios, we use an user-space app to perform the sync based on
> time-stamps from external hardware sources like the Wi-Fi.
>> Thanks,
>> Richard
> 

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Hi Richard,

On 17-06-12 10:09 PM, Richard Cochran wrote:
> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>> +Example:
>> +
>> +ptp_dte: ptp_dte@180af650 {
>> +compatible = "brcm,ptp-dte";
>> +reg = <0x180af650 0x10>;
>> +status = "okay";
>> +};
> This patch set looks okay, as far as it goes, but how does one
> actually use the clock?
>
> How does one connect this node to an Ethernet MAC, for example?
In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
1588 Shim NCO (used for time-stamping the packets). We are working on getting
all the future SoC's synced this way (for Ethernet).

In other scenarios, we use an user-space app to perform the sync based on
time-stamps from external hardware sources like the Wi-Fi.
> Thanks,
> Richard

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Hi Richard,

On 17-06-12 10:09 PM, Richard Cochran wrote:
> On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
>> +Example:
>> +
>> +ptp_dte: ptp_dte@180af650 {
>> +compatible = "brcm,ptp-dte";
>> +reg = <0x180af650 0x10>;
>> +status = "okay";
>> +};
> This patch set looks okay, as far as it goes, but how does one
> actually use the clock?
>
> How does one connect this node to an Ethernet MAC, for example?
In some of the SoC's, the DTE's NCO is synced in hardware with the Ethernet's
1588 Shim NCO (used for time-stamping the packets). We are working on getting
all the future SoC's synced this way (for Ethernet).

In other scenarios, we use an user-space app to perform the sync based on
time-stamps from external hardware sources like the Wi-Fi.
> Thanks,
> Richard

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Richard Cochran]

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> +Example:
> +
> +ptp_dte: ptp_dte@180af650 {
> + compatible = "brcm,ptp-dte";
> + reg = <0x180af650 0x10>;
> + status = "okay";
> +};

This patch set looks okay, as far as it goes, but how does one
actually use the clock?

How does one connect this node to an Ethernet MAC, for example?

Thanks,
Richard

Re: [PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Richard Cochran]

On Mon, Jun 12, 2017 at 01:26:00PM -0700, Arun Parameswaran wrote:
> +Example:
> +
> +ptp_dte: ptp_dte@180af650 {
> + compatible = "brcm,ptp-dte";
> + reg = <0x180af650 0x10>;
> + status = "okay";
> +};

This patch set looks okay, as far as it goes, but how does one
actually use the clock?

How does one connect this node to an Ethernet MAC, for example?

Thanks,
Richard

[PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
 1 file changed, 13 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver
+
+Required properties:
+- compatible: should be "brcm,ptp-dte"
+- reg: address and length of the DTE block's NCO registers
+
+Example:
+
+ptp_dte: ptp_dte@180af650 {
+   compatible = "brcm,ptp-dte";
+   reg = <0x180af650 0x10>;
+   status = "okay";
+};
-- 
1.9.1

[PATCH v1 1/2] dt-binding: ptp: add bindings document for dte based ptp clock

[Arun Parameswaran]

Add device tree binding documentation for the Broadcom DTE
PTP clock driver.

Signed-off-by: Arun Parameswaran 
---
 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt | 13 +
 1 file changed, 13 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt

diff --git a/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt 
b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
new file mode 100644
index 000..07590bc
--- /dev/null
+++ b/Documentation/devicetree/bindings/ptp/brcm,ptp-dte.txt
@@ -0,0 +1,13 @@
+* Broadcom Digital Timing Engine(DTE) based PTP clock driver
+
+Required properties:
+- compatible: should be "brcm,ptp-dte"
+- reg: address and length of the DTE block's NCO registers
+
+Example:
+
+ptp_dte: ptp_dte@180af650 {
+   compatible = "brcm,ptp-dte";
+   reg = <0x180af650 0x10>;
+   status = "okay";
+};
-- 
1.9.1