linux-kernel - Re: [PATCH 1/3] dt-bindings: display: mediatek: Correct disp

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Date:   Thu, 7 Apr 2022 16:38:50 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <chunkuang.hu@...nel.org>, <robh+dt@...nel.org>,
        <krzk+dt@...nel.org>
CC:     <matthias.bgg@...il.com>, <p.zabel@...gutronix.de>,
        <airlied@...ux.ie>, <yongqiang.niu@...iatek.com>,
        <jason-jh.lin@...iatek.com>, <nancy.lin@...iatek.com>,
        <allen-kh.cheng@...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 1/3] dt-bindings: display: mediatek: Correct disp_aal
 binding for MT8183

On Thu, 2022-04-07 at 08:49 +0200, Krzysztof Kozlowski wrote:
> On 07/04/2022 08:22, Rex-BC Chen wrote:
> > On Wed, 2022-04-06 at 16:44 +0200, Krzysztof Kozlowski wrote:
> > > On 06/04/2022 11:46, Rex-BC Chen wrote:
> > > > The driver data of MT8183 and MT8173 are different.
> > > > The value of has_gamma for MT8173 is true while the value of
> > > > MT8183
> > > > is
> > > > false. Therefore, the compatible of disp_aal for MT8183 is not
> > > > suitable
> > > > for the compatible for MT8173.
> > > 
> > > Just because one feature is not supported, it does not mean they
> > > are
> > > incompatible, which you claim in the patch below. Are you sure
> > > they
> > > are
> > > really incompatible and MT8173 fallback cannot be used?
> > > 
> > > 
> > > Best regards,
> > > Krzysztof
> > 
> > Hello Krzysztof,
> > 
> > Thanks for your review.
> > 
> > The difference of disp_aal for each MediaTek SoCs is "has_gamma".
> > And we only control this variable for different MediaTek SoCs.
> > 
> > The value of has_gamma for MT8173 is true.
> > The value of has_gamma for MT8183 is false. (Moreover, the driver
> > data
> > is null for MT8183)
> > 
> > From this situation, I think it's not compatible between MT8173 and
> > MT8183.
> 
> You repeated the commit msg without bringing any new information...
> but
> let it be, I assume setting gamma on MTT8183 is incorrect or produces
> wrong results.
> 
> 
> Best regards,
> Krzysztof

Hello Krzysztof,

Sorry for this.
I can explain more detailed.

For MT8173, the gamma module is inside disp_aal. When we need to adjust
gamma value, we need to use "has_gamma" to control gamma function
inside disp_aal to adjust gamma value.

Since MT8183 (MT8192/MT8195/MT8186), display gamma is seperated from
disp_aal. We just need to control disp_gamma directly and we don't need
to control gamma function inside disp_aal.

I will add these comments to commit message in next version to explain
it.

BRs,
Rex