Re: [PATCH v4 1/5] dt-bindings: arm: renesas: Document Renesas RZ/G2UL SMARC EVK

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On 02/04/2022 21:05, Biju Das wrote:
> Hi Krzysztof Kozlowski,
> 
> Thanks for the feedback.
> 
>> Subject: Re: [PATCH v4 1/5] dt-bindings: arm: renesas: Document Renesas
>> RZ/G2UL SMARC EVK
>>
>> On 02/04/2022 09:32, Biju Das wrote:
>>> Document the Renesas SMARC EVK board which is based on the Renesas
>>> RZ/G2UL Type-1 (R9A07G043U11) SoC.  The SMARC EVK consists of an
>>> RZ/G2UL Type-1 SoM module and a SMARC carrier board.  The SoM module
>>> sits on top of the carrier board.
>>>
>>> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
>>> ---
>>> V4:
>>> * new patch
>>> ---
>>>  Documentation/devicetree/bindings/arm/renesas.yaml | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/arm/renesas.yaml
>>> b/Documentation/devicetree/bindings/arm/renesas.yaml
>>> index fa435d6fda77..f61807103867 100644
>>> --- a/Documentation/devicetree/bindings/arm/renesas.yaml
>>> +++ b/Documentation/devicetree/bindings/arm/renesas.yaml
>>> @@ -405,6 +405,8 @@ properties:
>>>
>>>        - description: RZ/G2UL (R9A07G043)
>>>          items:
>>> +          - enum:
>>> +              - renesas,smarc-evk # SMARC EVK
>>
>> I see you are using same compatible for different configurations. I think
>> it should be rather a specific compatible (e.g.
>> renesas,smarc-evk-r9a07g043). It's the most detailed compatible, so the
>> user is expected to check it and have the answer about specific board.
>> Here it won't work - you have three different configurations with the
>> same, most specific compatible.
> 
> SMARC-EVK is common to RZ/G2L(R9A07G044L), RZ/G2LC(R9A07G044C) , RZ/V2L(R9A07G054L),
> RZ/G2UL Type-1(r9a07g043u11) and RZ/Five(r9a07g043f) SoC's.
> 
> For consistency I have made similar change. So you recommend to change
> Other SoC's as well?
> 
> SMARC-EVK is common carrier board and We have a SoM module which contains SoC.
> 
> R9A07G043 is generic compatible for RZ/G2UL arm based SoC and RZ/Five RISC
> Based SoC.
> 
> Do I miss any thing compared to other existing  renesas SoC's, please let me know.

I understand that carrier board is the same, so the SoM differs. In your
model to figure out what type of hardware is it, your choice is to
compare two compatibles:
renesas,smarc-evk + renesas,r9a07g043u11

If user-space compares only last compatible, it get's only SMARC, so it
does not know on what hardware it runs.

Maybe I am wrong, but the combination of compatibles should not be used
as a specific description. IOW, only one, final compatible should
determine the type of hardware.

Therefore in your case it should be:
renesas,smarc-evk-r9a07g043u11 + renesas,r9a07g043u11 + renesas,r9a07g043

That's my understanding of compatibles from Devicetree spec.

Such approach is used in other boards, you can check for example Toradex
and Variscite boards in arm/fsl.yaml.

For example VAR-SOM-MX8MM is a SoM and it's boards are:
 - const: variscite,var-som-mx8mm-symphony

 - const: variscite,var-som-mx8mm
 - const: fsl,imx8mm


The first const could be an enum, but there are no other boards, except
Symphony kit. Symphony can be used with other modules as well, so there is:
variscite,var-som-mx8mn-symphony
(notice 8mm -> 8mn)

Best regards,
Krzysztof



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