Re: [PATCH 2/5] dt-bindings: soc: loongson,ls2k-pmc: Add missing compatible for Loongson-2K2000

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 29/08/2023 05:21, Binbin Zhou wrote:
> HI Conor:
> 
> Thanks for your reply.
> 
> On Mon, Aug 28, 2023 at 11:49 PM Conor Dooley <conor@kernel.org> wrote:
>>
>> On Mon, Aug 28, 2023 at 08:38:32PM +0800, Binbin Zhou wrote:
>>> Document the Power Management Unit system controller compatible for
>>> Loongson-2K2000.
>>>
>>> This is a missing compatible, now we add it.
>>>
>>> Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
>>> ---
>>>  .../devicetree/bindings/soc/loongson/loongson,ls2k-pmc.yaml      | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/soc/loongson/loongson,ls2k-pmc.yaml b/Documentation/devicetree/bindings/soc/loongson/loongson,ls2k-pmc.yaml
>>> index da2dcfeebf12..7473c5659929 100644
>>> --- a/Documentation/devicetree/bindings/soc/loongson/loongson,ls2k-pmc.yaml
>>> +++ b/Documentation/devicetree/bindings/soc/loongson/loongson,ls2k-pmc.yaml
>>> @@ -15,6 +15,7 @@ properties:
>>>        - enum:
>>>            - loongson,ls2k0500-pmc
>>>            - loongson,ls2k1000-pmc
>>> +          - loongson,ls2k2000-pmc
>>
>> Same thing here as the driver patch, the pmc on this newly added SoC
>> appears to use the same codepaths as the existing ones. Does it share a
>> programming model & should there be a fallback compatible here?
> 
> I noticed the guideline about fallback compatible:
> 
> "DO use fallback compatibles when devices are the same as or a subset
> of prior implementations."
> 
> But in fact, ls2k0500/ls2k1000/ls2k2000 are independent, there is no subset.

We do not consider here ls2k0500/ls2k1000/ls2k2000, but PMC in each of
them. If they are independent, why would they use the same interface?

> Can we define a "loongson,ls2k-pmc" superset for each ls2k SoC
> compatible fallback.
> 
> Such as:
> 
>   compatible:
>     oneOf:
>       - enum:
>           - loongson,ls2k0500-pmc
>           - loongson,ls2k1000-pmc
>           - loongson,ls2k2000-pmc
>       - const: loongson,ls2k-pmc

This is discouraged. Use 0500 as fallback.



Best regards,
Krzysztof