Hi Simon,
Thanks again for taking the time to check my comments.
On 6/3/20 10:17, Simon Glass wrote:
Hi Walter,
On Thu, 5 Mar 2020 at 06:54, Walter Lozano <[email protected]> wrote:
Hi Simon,
Thanks for taking the time to check for my comments
On 4/3/20 20:11, Simon Glass wrote:
Hi Walter,
On Wed, 4 Mar 2020 at 12:40, Walter Lozano <[email protected]> wrote:
When OF_PLATDATA is enabled DT information is parsed and platdata
structures are populated. In this context the links between DT nodes are
represented as pointers to platdata structures, and there is no clear way
to access to the device which owns the structure.
This patch implements a set of functions:
- device_find_by_platdata
- uclass_find_device_by_platdata
to access to the device.
Signed-off-by: Walter Lozano <[email protected]>
---
drivers/core/device.c | 19 +++++++++++++++++++
drivers/core/uclass.c | 34 ++++++++++++++++++++++++++++++++++
include/dm/device.h | 2 ++
include/dm/uclass-internal.h | 3 +++
include/dm/uclass.h | 2 ++
5 files changed, 60 insertions(+)
This is interesting. Could you also add the motivation for this? It's
not clear to me who would call this function.
I have been reviewing the OF_PLATDATA support as an R&D project, in this
context, in order to have
a better understanding on the possibilities and limitations I decided to add
its support to iMX6,
more particularly to the MMC drivers. The link issue arises when I tried to
setup the GPIO for
Card Detection, which is trivial when DT is available. However, when
OF_PLATDATA is enabled
this seems, at least for me, not straightforward.
In order to overcome this limitation I think that having a set of functions to
find/get devices
based on platdata could be useful. Of course, there might be a better
approach/idea, so that is
the motivation for this RFC.
An example of the usage could be
#if CONFIG_IS_ENABLED(DM_GPIO)
struct udevice *gpiodev;
ret = uclass_get_device_by_platdata(UCLASS_GPIO, (void
*)dtplat->cd_gpios->node, &gpiodev);
if (ret)
return ret;
ret = gpio_dev_request_index(gpiodev, gpiodev->name, "cd-gpios",
dtplat->cd_gpios->arg[0], GPIOD_IS_IN,
dtplat->cd_gpios->arg[1],
&priv->cd_gpio);
if (ret)
return ret;
#endif
This is part of my current work, a series of patches to add OF_PLATDATA support
as explained.
Does this make sense to you?
Not yet :-)
What is the context of this call? Typically dtplat is only available
in the driver that includes it.
Sorry for not being clear enough. I'm working in a patchset that needs
some clean up, that is the reason I didn't send it yet. I'll try to
clarify, but if you think it could be useful to share it, please let me
know.
What driver is the above code in? Is it for MMC that needs a GPIO to
function? I'll assume it is for now.
The driver on which I'm working in is drivers/mmc/fsl_esdhc_imx.c, I'm
adding support for OF_PLATDATA to it, and in this sense trying to get
the GPIOs used for CD to be requested.
Then the weird thing is that we are accessing the dtplat of another
device. It's a clever technique but I wonder if we can find another
way.
If you see drivers/mmc/rockchip_sdhci.c it has:
ret = clk_get_by_index_platdata(dev, 0, dtplat->clocks, &clk);
So I wonder if we need gpio_dev_request_by_platdata()?
Thanks for pointing to this example, as I saw it before starting to work
on these functions and had some doubts. I'll use it in the next
paragraph to share my thoughts and the motivation of my work.
From my understanding, clk_get_by_index_platdata in this context can
only get a UCLASS_CLK device with id == 0. Is this correct?
If it is so, this will only allow us to use this function if we know in
advance that the UCLASS_CLK device has index 0.
How can we get the correct UCLASS_CLK device in case of multiple instances?
I understand that we need a way to use the link information present in
platdata. However I could not find a way to get the actual index of the
UCLASS_CLK device. In this context, I thought that the simplest but
still valid approach could be to find the right device based on the
struct platdata pointer it owns.
So in my understanding, your code could be more generic in this way
diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
index 71878474eb..61041bb3b8 100644
--- a/drivers/clk/clk-uclass.c
+++ b/drivers/clk/clk-uclass.c
@@ -25,14 +25,12 @@ static inline const struct clk_ops *clk_dev_ops(struct
udevice *dev)
#if CONFIG_IS_ENABLED(OF_CONTROL)
# if CONFIG_IS_ENABLED(OF_PLATDATA)
-int clk_get_by_index_platdata(struct udevice *dev, int index,
- struct phandle_1_arg *cells, struct clk *clk)
+int clk_get_by_platdata(struct udevice *dev, struct phandle_1_arg *cells,
+ struct clk *clk)
{
int ret;
- if (index != 0)
- return -ENOSYS;
- ret = uclass_get_device(UCLASS_CLK, 0, &clk->dev);
+ ret = uclass_get_device_by_platdata(UCLASS_CLK (void *)cells->node,
&clk->dev);
if (ret)
return ret;
clk->id = cells[0].arg[0];
I understand there could be a more elegant way, which I still don't see,
that is the motivation of this RFC.
What do you think?
Also it relates to another thing I've been thinking about for a while,
which is to validate that all the structs pointed to are correct.
E.g. if every struct had a magic number like:
struct tpm_platdata {
DM_STRUCT(UCLASS_TPM, DM_STRUCT_PLATDATA, ...)
fields here
};
then we could check the structure pointers are correct.
DM_STRUCT() would define to nothing if we were not building with
CONFIG_DM_DEBUG or similar.
Interesting, I think it could be useful and save us from headaches while
debugging.
Thanks for sharing this idea.
Anyway, I wonder whether you could expand your definition a bit so you
have an enum for the different types of struct you can request:
enum dm_struct_t {
DM_STRUCT_PLATDATA,
...
DM_STRUCT_COUNT,
};
and modify the function so it can request it via the enum?
Let me check if I understand correctly, your suggestion is to do
something like diff --git a/include/dm/uclass.h b/include/dm/uclass.h
index 92c07f8426..bf09dadf3f 100644 --- a/include/dm/uclass.h +++
b/include/dm/uclass.h
@@ -167,8 +167,8 @@ int uclass_get_device(enum uclass_id id, int index,
struct udevice **devp);
int uclass_get_device_by_name(enum uclass_id id, const char *name,
struct udevice **devp); -int
uclass_get_device_by_platdata(enum uclass_id id, void *platdata,
- struct udevice **devp);
+int uclass_get_device_by_struct(enum uclass_id id, enum dm_struct_t
struct_id, + void *struct_pointer, struct
udevice **devp); /** * uclass_get_device_by_seq() - Get a uclass
device based on an ID and sequence *
If that is the case, I would be happy to help.
Also, if my understanding is correct, could you elaborate which cases
are you trying to cover with this approach? Regards,
This is just so that in dev_get_priv(), for example, we can write a
check that dev->privdata is actually the expected struct. We can check
the uclass and the dm_struct_t.
It is really just a run-time assert to help with getting these things mixed up.
So if I understand correctly I think that if that the approach that I
have in mind is really useful, which I intend to validate with this RFC,
your suggestion is to add some run-time checks, to make sure that in the
above example cells->node is a valid platdata? Is my understanding is
correct?
Regards,
Simon
