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

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Message-ID: <6b8a0f42ae7f868bc09039af07f165bf2e640e05.camel@mediatek.com>
Date:   Thu, 29 Sep 2022 11:25:49 +0000
From:   Allen-KH Cheng (程冠勳) 
        <Allen-KH.Cheng@...iatek.com>
To:     "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.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 Thu, 2022-09-29 at 10:30 +0200, AngeloGioacchino Del Regno wrote:
> Il 28/09/22 19:26, Krzysztof Kozlowski ha scritto:
> > 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.
> > 
> 
> Thank you Krzysztof!
> 
> Allen, can you please change the binding to use "video-codec-lat" and
> "video-codec-core" (so change "vcodec" to "video-codec") and then use
> these names for this commit?
> 
> Doing the change right now won't break the ABI, as there's no
> devicetree
> using that binding yet (with this commit adding the first user), so
> you
> can safely go for the rename without any complication.
> 
> Regards,
> Angelo
> 
> 
> 

Hi Angelo,

No problem, I will update in the following version.

Thanks,
Allen