linux-kernel - Re: [PATCH 1/5] dt-bindings: arm: mediatek: mmsys: change compatible for MT8195

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Date:   Fri, 16 Sep 2022 09:08:47 +0800
From:   Jason-JH Lin <jason-jh.lin@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
CC:     CK Hu <ck.hu@...iatek.com>, Rex-BC Chen <rex-bc.chen@...iatek.com>,
        Singo Chang <singo.chang@...iatek.com>,
        Nancy Lin <nancy.lin@...iatek.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH 1/5] dt-bindings: arm: mediatek: mmsys: change
 compatible for MT8195

On Thu, 2022-09-15 at 18:20 +0200, Matthias Brugger wrote:
> Hi Jason,
> 
> On 15/09/2022 03:24, Jason-JH Lin wrote:
> > Hi Matthias,
> > 
> > Thanks for the reviews.
> > 
> > On Wed, 2022-09-14 at 23:24 +0200, Matthias Brugger wrote:
> > > 
> > > On 14/09/2022 20:23, Jason-JH.Lin wrote:
> > > > For previous MediaTek SoCs, such as MT8173, there are 2 display
> > > > HW
> > > > pipelines binding to 1 mmsys with the same power domain, the
> > > > same
> > > > clock driver and the same mediatek-drm driver.
> > > > 
> > > > For MT8195, VDOSYS0 and VDOSYS1 are 2 display HW pipelines
> > > > binding
> > > > to
> > > > 2 different power domains, different clock drivers and
> > > > different
> > > > mediatek-drm drivers.
> > > > 
> > > > Moreover, Hardware pipeline of VDOSYS0 has these components:
> > > > COLOR,
> > > > CCORR, AAL, GAMMA, DITHER. They are related to the PQ (Picture
> > > > Quality)
> > > > and they makes VDOSYS0 supports PQ function while they are not
> > > > including in VDOSYS1.
> > > > 
> > > > Hardware pipeline of VDOSYS1 has the component ETHDR (HDR
> > > > related
> > > > component). It makes VDOSYS1 supports the HDR function while
> > > > it's
> > > > not
> > > > including in VDOSYS0.
> > > > 
> > > > To summarize0:
> > > > Only VDOSYS0 can support PQ adjustment.
> > > > Only VDOSYS1 can support HDR adjustment.
> > > > 
> > > > Therefore, we need to separate these two different mmsys
> > > > hardwares
> > > > to
> > > > 2 different compatibles for MT8195.
> > > > 
> > > > Fixes: 81c5a41d10b9 ("dt-bindings: arm: mediatek: mmsys: add
> > > > mt8195
> > > > SoC binding")
> > > > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > > > Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> > > > Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > > 
> > > I'm not sure Krzysztof gave his Acked-by tag.
> > 
> > I'll remove this tag.
> > > 
> > > > ---
> > > >    .../devicetree/bindings/arm/mediatek/mediatek,mmsys.yaml    
> > > >     |
> > > > 2 ++
> > > >    1 file changed, 2 insertions(+)
> > > > 
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys
> > > > .yam
> > > > l
> > > > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys
> > > > .yam
> > > > l
> > > > index 6ad023eec193..a53b32c0a608 100644
> > > > ---
> > > > a/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys
> > > > .yam
> > > > l
> > > > +++
> > > > b/Documentation/devicetree/bindings/arm/mediatek/mediatek,mmsys
> > > > .yam
> > > > l
> > > > @@ -32,6 +32,8 @@ properties:
> > > >                  - mediatek,mt8186-mmsys
> > > >                  - mediatek,mt8192-mmsys
> > > >                  - mediatek,mt8195-mmsys
> > > > +              - mediatek,mt8195-vdosys0
> > > 
> > > As I said in the last submission, we should make mediatek,mt8195-
> > > mmsys as a
> > > fallback of vdosys0. Actually mediatek,mt8195-mmsys is only used
> > > for
> > > the
> > > fallback of vdosys0.
> > 
> > I think adding both vdosys0 and vdosys1 can make the description of
> > this patch clearer.
> > 
> > It's find to me to only add "mediatek,mt8195-vdosys0" in this
> > patch.
> > So I'll remove the "mediatek,mt8195-vdosys1" at the next version.
> > 
> 
> That's not what I wanted to suggest. Up to now in upstream kernel
> compatible 
> mediatek,mt8195-mmsys enables support fro vdosys0. The vdosys1 is not
> yet 
> upstream, so no support.
> If we change the compatible, we should keep mediatek,mt8195-mmsys as
> fallback of 
> "mediatek,mt8195-vdosys0" so that older device tree blobs won't break
> with a 
> newer kernel.
> For "mediatek,mt8195-vdosys1" we do not need a fallback compatible as
> the code 
> never reached upstream, so no breakage expected.
> 
> Hope I explain myself now.
> 
> Regards,
> Matthias
> 

I think I misunderstood your reply to the patch "dt-bindings: arm:
mediatek: mmsys: remove the unused compatible for mt8195", so I merge
it into this patch.

Thanks for your patient explanation.
I will keep the "mediatek,mt8195-
mmsys" in this patch.

Regards,
Jason-JH.Lin

> 
> > Regards,
> > Jason-JH.Lin
> > > 
> > > Regards,
> > > Matthias
> > > 
> > > > +              - mediatek,mt8195-vdosys1
> > > >                  - mediatek,mt8365-mmsys
> > > >              - const: syscon
> > > >          - items:
> > > 
> > > 
-- 
Jason-JH Lin <jason-jh.lin@...iatek.com>