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

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Date:   Wed, 28 Sep 2022 09:58:18 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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

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?

Regards,
Angelo