linux-kernel - Re: [PATCH v2] arm64: dts: mt8192: Add vcodec lat and core nodes

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Date:   Wed, 28 Sep 2022 19:26:16 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Allen-KH Cheng (程冠勳) 
        <Allen-KH.Cheng@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2] arm64: dts: mt8192: Add vcodec lat and core nodes

On 28/09/2022 09:58, AngeloGioacchino Del Regno wrote:
> Il 28/09/22 09:04, Krzysztof Kozlowski ha scritto:
>> On 27/09/2022 12:17, AngeloGioacchino Del Regno wrote:
>>>>>
>>>>
>>>> Sorry, my bad. I alsways run `make dtbs_check` to confirm dtb with
>>>> bindings. I just think we didn't limit node names in mtk-vodec
>>>> bindings. I will pay attention next time.
>>>>
>>>>
>>>> Since currently the vcodec lat and core nodes are absent from the mtk
>>>> dts, do you think the child node name should be changed to something
>>>> more general (ex: video-codec) in mediatek,vcodec-subdev-decoder
>>>> bindings?
>>>
>>> The video codec is mt8192-vcodec-dec, while the other nodes are describing
>>> the VPU instances (and/or vpu cores)... I'm not sure.
>>>
>>> Krzysztof, please, can you give your opinion on that?
>>>
>>
>> What's the difference between them? I understand parent device is entire
>> block of consisting of multiple processing units? If so, video-codec
>> actually could fit in both places. But feel free to call it a bit
>> different (video-codec-core, video-codec-lat, processing-unit, even
>> something less generic). Sometimes it's tricky to find nice name, so I
>> wouldn't worry too much in that case. Just not "mt8192-vcodec" :)
>>
> 
> The parent device is the entire block consisting of multiple processing units
> and has "global" control registers; children are LAT(s) and processing cores.
> 
>  From my understanding, the processing cores are physical cores of one big VPU
> and, depending on the actual (current gen) SoC, the VPU may have one or two
> cores.
> 
> Right now, the bindings want vcodec-latX@...r, vcodec-coreX@...r (where X is
> a number, like vcodec-core0, vcodec-core1) but, in my opinion, changing that
> to video-codec-lat@...r and video-codec-core@...r would be more descriptive.
> 
> ...Or should we simply leave the bindings as they are and just go with the
> abbreviated "vcodec-(hwtype)" names?

video-codec-lat sounds better, but I am not sure if it is worth the
churn, so I am fine with both.

Best regards,
Krzysztof