linux-kernel - Re: [PATCH 1/5] dt-bindings: media: venus: Add qcm2290 dt schema

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Message-ID: <c7aef6cd-e07d-4422-a34a-ce04c37ad2e8@kernel.org>
Date: Tue, 17 Jun 2025 08:14:23 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Jorge Ramirez <jorge.ramirez@....qualcomm.com>
Cc: quic_vgarodia@...cinc.com, quic_dikshita@...cinc.com,
 bryan.odonoghue@...aro.org, mchehab@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, stanimir.varbanov@...aro.org,
 linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] dt-bindings: media: venus: Add qcm2290 dt schema

On 16/06/2025 18:59, Jorge Ramirez wrote:
> On 16/06/25 18:23:18, Krzysztof Kozlowski wrote:
>> On 16/06/2025 18:18, Jorge Ramirez wrote:
>>> On 16/06/25 16:41:44, Krzysztof Kozlowski wrote:
>>>> On 16/06/2025 14:52, Jorge Ramirez wrote:
>>>>>>
>>>>>>> +  The Venus AR50_LITE IP is a video encode and decode accelerator present
>>>>>>> +  on Qualcomm platforms
>>>>>>> +
>>>>>>> +allOf:
>>>>>>> +  - $ref: qcom,venus-common.yaml#
>>>>>>> +
>>>>>>> +properties:
>>>>>>> +  compatible:
>>>>>>> +    const: qcom,qcm2290-venus
>>>>>>> +
>>>>>>> +  power-domains:
>>>>>>> +    minItems: 2
>>>>>>> +    maxItems: 3
>>>>>>> +
>>>>>>> +  power-domain-names:
>>>>>>> +    minItems: 2
>>>>>>
>>>>>> Why is this flexible? Either you have two or three. Not mixed.
>>>>>
>>>>> please check 5b380f242f360256c96e96adabeb7ce9ec784306
>>>>
>>>> This does not explain why this is optional HERE. You cannot use for a
>>>> new platform an argument that some existing platform was changed in
>>>> ABI-preserving way.
>>>
>>> thanks for quick the follow up.
>>>
>>> but bear with me please because I dont follow - why can the same logic
>>> be used - it being applicable - and therefore result in a definition
>>> similar to those other platforms?
>>
>> Because this platform either has 2 or 3, not both. Unless that's not
>> true, but then please share some arguments.
> 
> as with every other venus schema with more than 1 power domain, the
> argument is the same one that I have shared with you a couple of
> messages back (DVFS).
> 
> verbatim:
>     Venus needs to vote for the performance state of a power domain (cx)
>     to be able to support DVFS. This 'cx' power domain is controlled by
>     rpm and is a common power domain (scalable) not specific to
>     venus alone. This is optional in the sense that, leaving this power
>     domain out does not really impact the functionality but just makes
>     the platform a little less power efficient.

That's not definition of optional. The domain is needed for this device,
the device is one way or another having its rails routed to that domain.
It is not optional.

> 
> Seeing all these venus schemas follow the same pattern, it seems to me
> that this is the correct way of implementing the above.

No for the reason I mentioned earlier.

> 
> You seem to disagree. please could you explain?

I already explained. You add new device, so argument to preserve ABI,
which was accepted THAT TIME, is not valid. You do not have ABI.


Best regards,
Krzysztof