[PATCH] ARM: dts: stm32: Fill GPIO line names on AV96

[Marek Vasut]

On 3/12/21 6:38 PM, Christoph Niedermaier wrote:
> From: Marek Vasut [mailto:marex at denx.de]
> Sent: Friday, March 12, 2021 5:17 PM
>> To: Christoph Niedermaier <cniedermaier at dh-electronics.com>; linux-arm-
>> kernel at lists.infradead.org; linus.walleij at linaro.org
>> Cc: Alexandre Torgue <alexandre.torgue at st.com>; Patrice Chotard
>> <patrice.chotard at st.com>; Patrick Delaunay <patrick.delaunay at st.com>;
>> Maxime Coquelin <mcoquelin.stm32 at gmail.com>; linux-stm32 at st-md-
>> mailman.stormreply.com
>> Subject: Re: [PATCH] ARM: dts: stm32: Fill GPIO line names on AV96
>>
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>>
>>
>> On 3/12/21 4:17 PM, Christoph Niedermaier wrote:
>>> From: Marek Vasut [mailto:marex at denx.de]
>>> Sent: Thursday, August 6, 2020 9:30 AM
>>>
>>>> On 8/6/20 9:09 AM, Christoph Niedermaier wrote:
>>>>> From: Marek Vasut <marex at denx.de>
>>>>> Sent: Friday, July 24, 2020 12:16 PM
>>>>>>
>>>>>> Fill in the custom GPIO line names used by DH.
>>>>>>
>>>>> [...]
>>>>>> +&gpioa {
>>>>>> +       gpio-line-names = "", "", "", "",
>>>>>> +                         "", "", "", "",
>>>>>> +                         "", "", "", "DH-GPIO-K",
>>>>>> +                         "DH-GPIO-I", "", "DH-GPIO-A", "";
>>>>>> +};
>>>>>> +
>>>>> [...]
>>>>>
>>>>> We have been using the GPIO names at DH electronics for some time and also
>>>>> on other SOMs, but have not yet streamed them. We started with the naming
>>>>> only with a capital letter "A-W" since then without problems. To avoid a
>>>>> hard cut or patching for us and our customers it would be good if we could
>>>>> use the same naming in the mainline kernel as well. Marek, we would be
>>>>> happy if you would adopt our valued GPIO naming in your patch.
>>>>
>>>> My counter-argument to this is that the naming should be unique and
>>>> provide a hint where those GPIO lines come from, so maybe even DH-GPIO-n
>>>> should rather be DHCOM-n . I can't say I'm particularly fond of the
>>>> plain 'n' naming of GPIO lines, because then the GPIO label (and e.g.
>>>> listing in libgpiod tools) does not give any hint what the GPIO is or
>>>> where it comes from. Also, I worry a plain 'n' naming might clash with
>>>> other GPIO IPs easily, while a more unique name can not.
>>>
>>> Hello Marek,
>>>
>>> after an internal discussion, we decided the following:
>>>
>>> Could you update the patch for the Avenger96 to the GPIO naming "AV96-n".
>>>
>>> Moreover for the SOM layer (stm32mp15xx-dhcom-som.dtsi) we would prefer
>>> "DHCOM-n". It would be nice if you could create a patch for it.
>>
>> I don't think we should have any SoM-side gpio-line-names, because once
>> you plug the SoM into new carrier board, the gpio-lane-names will no
>> longer make sense. So, I think all the gpio-line-names should be
>> implemented in the carrier board DTS.
> 
> The idea is to define the GPIO names on the SOM layer and then
> overwrite them on the carrier board DTS if needed. If there is no
> naming on the carrier board, at least you have access via the DHCOM
> GPIO names. The DHCOM GPIO names are standardized, so that you can
> be sure that the assignment to a pin always fits.

So I'll pose another question here to the GPIO maintainers.

Is it OK to define gpio-line-names in SoM DTSI even for pins which will 
not be used as GPIOs e.g. because they are muxed differently in the 
carrier board DTS ?

If that is OK, then the above approach is then also OK.