Hi Simon,
On 8/4/20 00:14, Simon Glass wrote:
Hi Walter,
On Tue, 7 Apr 2020 at 14:05, Walter Lozano<walter.loz...@collabora.com> wrote:
Hi Simon,
On 6/4/20 00:43, Simon Glass wrote:
Hi Walter,
On Mon, 9 Mar 2020 at 12:27, Walter Lozano<walter.loz...@collabora.com> wrote:
Hi Simon
On 6/3/20 17:32, Simon Glass wrote:
Hi Walter,
On Fri, 6 Mar 2020 at 09:10, Walter Lozano<walter.loz...@collabora.com> wrote:
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<walter.loz...@collabora.com> 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<walter.loz...@collabora.com> 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<walter.loz...@collabora.com>
---
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?
We actually can't support that at present. I think we would need to
change the property to be an array, like:
clocks = [
[&clk1, CLK_ID_SPI],
[&clk1, CLK_ID_I2C, 23],
]
which would need a fancier dtoc. Perhaps we should start by
upstreaming that tool.
In this case, are you suggesting to replace CLK_ID_SPI and CLK_ID_I2C
with a integer calculated by dtoc based on the clocks entries available?
If I understand correctly, what we need is to get the index parameter to
feed the function uclass_find_device. Is this correct?
No, I was thinking that it would be the same CLK_ID_SPI value from the binding.
We currently have (see the 'rock' board):
struct dtd_rockchip_rk3188_uart {
fdt32_t clock_frequency;
struct phandle_1_arg clocks[2];
fdt32_t interrupts[3];
fdt32_t reg[2];
fdt32_t reg_io_width;
fdt32_t reg_shift;
};
So the phandle_1_arg is similar to what you want. It could use phandle_2_arg.
Since the array has two elements, there is room for two clocks.
Now is clear, thanks.
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.
The index should be the first value after the phandle. If you check
the output of dtoc you should see it.
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?
Yes I see, but I think it is better to enhance dtoc if needed, to give
us the info we need.
I understand. When I first reviewed the work to be done and dtoc tool
source code I asked myself some questions. Let me share my thoughts
using rock_defconfig as reference.
The link information regarding phandles is processed by dtoc tool. By
default the phandle_id is converted to fdt32_t, but in case of clocks
the function
get_phandle_argc(self, prop, node_name)
resolves the link and generates a pointer to the dt_struct of the linked
node.
So without the special treatment for clocks a dt_struct looks like
static const struct dtd_rockchip_rk3188_dmc dtv_dmc_at_20020000 = {
.clocks = {0x2, 0x160, 0x2, 0x161},
And with the special treatment the phandle_id gets converted to a pointer
static const struct dtd_rockchip_rk3188_dmc dtv_dmc_at_20020000 = {
.clocks = {
{&dtv_clock_controller_at_20000000, {352}},
{&dtv_clock_controller_at_20000000, {353}},},
This approach was what encouraged me to try to find the device which
owns dtv_clock_controller_at_20000000 pointer or something similar.
I think at present it is very simple. E.g. see
clk_get_by_index_platdata() which only supports a 1-arg phandle and
always uses the first available clock device.
However, I was also thinking that other possibility is to keep dtoc
simple and don't process this information at all, leaving the
phandle_id, and also adding the phandle_id in each node dt_struct, in
order to be able to get/find the device by phandle_id.
I understand that this approach is NOT what you thought it was the best
for some reason I am not aware of.
Well you don't have the device tree with of-platdata, so you cannot
look up a phandle. I suppose we could add the phandle into the
structures but we would need to know how to find it generically.
So in my mind there should be a generic way to get/find a device based
on some information in the dt_struct, valid for clocks, gpios and any
other type of device/node as the phandle_id. In the specific case I'm
working on, the cd-gpios property should allow us to get/find the gpio
device to check for the status of the input gpio.
OK I see.
DM_GET_DRIVER() is a compile-time way to find a driver. I wonder if we
could have a compile-time way to find a device?
It should be possible since each U_BOOT_DEVICE() get s a symbol and
the symbols are named methodically. So we can actually find the device
at compile time.
So how about we have DM_GET_DEVICE(name) in that field. That way you
have the device pointer available, with no lookup needed.
I found this approach very interesting. Let me investigate it and I'll
get back to you. I really appreciate this suggestion, I hope to come
with something useful.
Yes me too...
But sadly I don't think it is enough. It points to the driver data,
the data *used* to create the device, but not the device itself, which
is dynamically allocated with malloc().
The good news is that it is a compile-time check, so there is some
value in the idea. Good to avoid runtime failure if possible.
One option would be to add a pointer at run-time from the driver data
to the device, for of-platdata. That way we could follow a pointer and
find the device. It would be easy enough to do.
Thank you so much for sharing all these ideas. I hope to make good use
of these suggestions. I think I'm following your idea, however this will
be clearer when I start to work on this, hopefully next week, and
probably will come back to you with some silly questions.
At this point what I see
- I like the compile-time check, you have showed me that benefits with
several of your previous patches, thanks for that.
- If we need to add a pointer from driver data to the device, why not
add this pointer to struct platdata instead?
Before you suggested me to add more information to dtoc, but it is not
clear to me what info to add to have a generic solution related to
linked nodes and phandles.
It isn't clear to me either. It needs some thought. But hopefully what
I said above puts you on the right track?
Yes, indeed. Please let me investigate your suggestion about
DM_GET_DEVICE(name), and then we can discuss further.
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?
Yes, the purpose of the checks is completely different from your goal.
It just happens that your function is something that would help there.
Thanks for clarifying, now I get a better understanding of you comments.
OK.
Regards,
Simon
Regards,
Walter
