linux-kernel - Re: [PATCH 1/9] dt-bindings: media: mtk-vcodec: Add binding for MT8195 two venc cores

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Date:   Wed, 25 Aug 2021 00:49:41 -0300
From:   Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:     Irui Wang (王瑞) <Irui.Wang@...iatek.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Longfei Wang (王龙飞) 
        <Longfei.Wang@...iatek.com>,
        Tiffany Lin (林慧珊) 
        <tiffany.lin@...iatek.com>,
        "frkoenig@...omium.org" <frkoenig@...omium.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        Maoguang Meng (孟毛广) 
        <Maoguang.Meng@...iatek.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "tzungbi@...omium.org" <tzungbi@...omium.org>,
        Yunfei Dong (董云飞) 
        <Yunfei.Dong@...iatek.com>,
        Yong Wu (吴勇) <Yong.Wu@...iatek.com>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        "tfiga@...gle.com" <tfiga@...gle.com>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
        "hsinyi@...omium.org" <hsinyi@...omium.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        Andrew-CT Chen (陳智迪) 
        <Andrew-CT.Chen@...iatek.com>,
        "acourbot@...omium.org" <acourbot@...omium.org>
Subject: Re: [PATCH 1/9] dt-bindings: media: mtk-vcodec: Add binding for
 MT8195 two venc cores

On Tue, 24 Aug 2021 at 23:04, Irui Wang (王瑞) <Irui.Wang@...iatek.com> wrote:
>
> Hi,Ezequiel,
>
> Thanks for your reviewing.
>
> On Tue, 2021-08-24 at 08:02 -0300, Ezequiel Garcia wrote:
> > Hi Irui,
> >
> > On Mon, 16 Aug 2021 at 08:00, Irui Wang <irui.wang@...iatek.com>
> > wrote:
> > >
> > > Enable MT8195 two H.264 venc cores, updates vcodec binding
> > > document.
> > >
> > > Signed-off-by: Irui Wang <irui.wang@...iatek.com>
> > > ---
> > >  Documentation/devicetree/bindings/media/mediatek-vcodec.txt | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/media/mediatek-
> > > vcodec.txt b/Documentation/devicetree/bindings/media/mediatek-
> > > vcodec.txt
> > > index de961699ba0a..eb2e24c32426 100644
> > > --- a/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> > > +++ b/Documentation/devicetree/bindings/media/mediatek-vcodec.txt
> > > @@ -11,6 +11,8 @@ Required properties:
> > >    "mediatek,mt8173-vcodec-dec" for MT8173 decoder.
> > >    "mediatek,mt8192-vcodec-enc" for MT8192 encoder.
> > >    "mediatek,mt8195-vcodec-enc" for MT8195 encoder.
> > > +  "mediatek,mtk-venc-core0" for MT8195 avc core0 device.
> > > +  "mediatek,mtk-venc-core1" for MT8195 avc core1 device.
> >
> > What is the difference between core0 and core1?
> >
> > Thanks,
> > Ezequiel
>
> Both core0 and core1 are H264 encoder hardware, they have their own
> hardware register base, used power-domains/clocks/irqs. We can use any
> of them for H.264 encoding, but the two cores can work together for
> higher performance, it's called "frame racing", a hardware encoding
> mode, control flow just like in the commit messages:
>
> core0 frame#0.frame#2.frame#4...
> core1    frame#1.frame#3.frame#5...
>

If they are two encoder cores, why do you need different compatible strings?

It would be interesting to see a device tree which shows how this should
be used in the real world, but from the looks of it, it seems you don't
need a separate compatible.

It seems this series is somewhat related to Yunfei's "[PATCH v5,
00/15] Using component framework to support multi hardware decode",
but I don't see a device tree patch either in that series.

Given this is a complex architecture, I don't know if it
makes sense to discuss decoder and encoder independently.

If you guys unify the two series, and add the device tree patches for it,
or at least for the most complex cases, maybe that will surface the
architecture more clearly and come up with an easier solution that
doesn't involve
an async framework to pull in the parts together.

Thanks,
Ezequiel