linux-kernel - Re: [PATCH 1/6] media: dt-bindings: Document SC8280XP/SM8350 Venus

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Date:   Mon, 7 Aug 2023 17:02:23 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Stanimir Varbanov <stanimir.k.varbanov@...il.com>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     Marijn Suijten <marijn.suijten@...ainline.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] media: dt-bindings: Document SC8280XP/SM8350 Venus

On 7.08.2023 16:04, Krzysztof Kozlowski wrote:
> On 07/08/2023 14:41, Konrad Dybcio wrote:
>> On 5.08.2023 21:29, Krzysztof Kozlowski wrote:
>>> On 04/08/2023 22:09, Konrad Dybcio wrote:
>>>> Both of these SoCs implement an IRIS2 block, with SC8280XP being able
>>>> to clock it a bit higher.
>>>>
>>>
>>> ...
>>>
>>>> +
>>>> +  iommus:
>>>> +    maxItems: 1
>>>> +
>>>> +  video-decoder:
>>>> +    type: object
>>>> +
>>>> +    properties:
>>>> +      compatible:
>>>> +        const: venus-decoder
>>>
>>> That's not how compatibles are constructed... missing vendor prefix, SoC
>>> or IP block name.
>>>
>>>> +
>>>> +    required:
>>>> +      - compatible
>>>> +
>>>> +    additionalProperties: false
>>>
>>> Why do you need this child node? Child nodes without properties are
>>> usually useless.
>> For both comments: I aligned with what was there..
>>
>> The driver abuses these compats to probe enc/dec submodules, even though
>> every Venus implementation (to my knowledge) is implicitly enc/dec capable..
> 
> Holy crap, I see...
> 
>>
>> Perhaps a bigger clean-up is due. I guess I could just create the venc/vdec
>> devices from the venus core probe and get rid of this fake stuff?
> 
> Few devices (qcom,msm8996-venus.yaml, sdm660, sdm845) have clocks there,
> so we actually could stay with these subnodes, just correct the
> compatibles to a list with correct prefixes:
> 
> qcom,sc8280xp-venus-decoder + qcom,venus-decoder
Hm.. looks like pre-845-v2 (with the v2 being "v2 binding" and not
"v2 chip" or "v2 hardware") these were used to look up clocks but
then they were moved to the root node.

I am not quite sure if it makes sense to distinguish e.g.
sc8280xp-venus-decoder within sc8280xp-venus..

Perhaps deprecating the "8916 way" (clocks under subnodes), adding
some boilerplate to look up clocks/pds in both places and converting
everybody to the "7180 way" way of doing things (clocks under venus),
and then getting rid of venus encoder/decoder completely (by calling
device creation from venus probe) would be better. WDYT?

Konrad