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

[Ahmad Fatoum]

Hello,

On 15.03.21 15:29, Marek Vasut wrote:
> On 3/15/21 1:05 PM, Ahmad Fatoum wrote:
>> On 15.03.21 12:41, Christoph Niedermaier wrote:
>>>> 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.
>>>
>>> In our case, we cannot mux the GPIO pins in the carrier board DTS
>>> to another functions, because then we break our SOM standard (DHCOM).
>>> So in the case we relabel a GPIO in the carrier board e.g. "DHCOM-I"
>>> becomes "LED1" the mux function have to be GPIO.
>>
>> For standards like SMARC, where the interface is predefined, I think it makes
>> much sense to have the SoM dtsi contain not only the line-names, but also
>> ready-to-use, pinmuxing settings.
>>
>> Base boards can then either enable peripherals with just a status = "okay"
>> if they follow the standard or just override it if they choose to do
>> stuff differently.
> 
> Sadly, I think I have to remind you of the discussion around pinctrl groups we have in stm32mp15-pinctrl.dtsi and how that does not scale. This is a very similar situation here, since the SoM is rather universal.

I don't think this is directly comparable. A SoC has _lots_ of possible way to mux and
conf pads. A SMARC, AFAIU, has exactly one official pinout. That one you can add into
the dtsi and the bast board either extends that or overrides it if it diverges.

> And the other thing I would like to point out here are the discussions around DT connector. What you described above is exactly that, except the implementation is still not finished. Let's CC Frank.
Thanks for the pointer. I'll check it out.

Cheers,
Ahmad

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