linux-kernel - Re: [PATCH v6 12/16] dt-bindings: display: mediatek: color: add compatible for MT8195

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Message-ID: <20230928-keep-attractor-1e7cd0df03b2@spud>
Date:   Thu, 28 Sep 2023 17:49:01 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Moudy Ho (何宗原) <Moudy.Ho@...iatek.com>
Cc:     "conor.dooley@...rochip.com" <conor.dooley@...rochip.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>,
        "airlied@...il.com" <airlied@...il.com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v6 12/16] dt-bindings: display: mediatek: color: add
 compatible for MT8195

On Thu, Sep 28, 2023 at 02:52:23AM +0000, Moudy Ho (何宗原) wrote:
> On Wed, 2023-09-27 at 10:47 +0100, Conor Dooley wrote:
> > On Wed, Sep 27, 2023 at 07:19:28AM +0000, Moudy Ho (何宗原) wrote:
> > > On Fri, 2023-09-22 at 16:51 +0100, Conor Dooley wrote:
> > > > On Fri, Sep 22, 2023 at 04:49:14PM +0100, Conor Dooley wrote:
> > > > > On Fri, Sep 22, 2023 at 03:21:12PM +0800, Moudy Ho wrote:
> > > > > > Add a compatible string for the COLOR block in MediaTek
> > > > > > MT8195
> > > > > > that
> > > > > > is controlled by MDP3.
> > > > > > 
> > > > > > Signed-off-by: Moudy Ho <moudy.ho@...iatek.com>
> > > > > > ---
> > > > > >  .../devicetree/bindings/display/mediatek/mediatek,color.yaml
> > > > > >     
> > > > > >  | 1 +
> > > > > >  1 file changed, 1 insertion(+)
> > > > > > 
> > > > > > diff --git
> > > > > > a/Documentation/devicetree/bindings/display/mediatek/mediatek
> > > > > > ,col
> > > > > > or.yaml
> > > > > > b/Documentation/devicetree/bindings/display/mediatek/mediatek
> > > > > > ,col
> > > > > > or.yaml
> > > > > > index f21e44092043..b886ca0d89ea 100644
> > > > > > ---
> > > > > > a/Documentation/devicetree/bindings/display/mediatek/mediatek
> > > > > > ,col
> > > > > > or.yaml
> > > > > > +++
> > > > > > b/Documentation/devicetree/bindings/display/mediatek/mediatek
> > > > > > ,col
> > > > > > or.yaml
> > > > > > @@ -26,6 +26,7 @@ properties:
> > > > > >            - mediatek,mt2701-disp-color
> > > > > >            - mediatek,mt8167-disp-color
> > > > > >            - mediatek,mt8173-disp-color
> > > > > > +          - mediatek,mt8195-mdp3-color
> > > > > 
> > > > > How come this one is a "mdp3" not a "disp"?
> > > > 
> > > > I don't know what mdp3 means & googling gives me no answers.
> > > > What's
> > > > the
> > > > "disp" one controlled by, since it isn't controlled by mdp3?
> > > > 

> > > Mediatek's Media Data Path ver.3 (MDP3) is associated with MMSYS
> > > and
> > > acts as an independent driver that operates between VDEC and DISP.
> > > By controlling multiple components, it carries out tasks like
> > > converting color formats, resizing, and applying specific Picture
> > > Quality (PQ) effects.
> > > The driver can be found at "driver/media/platform/mediatek/mdp3".
> > > Since the same hardware components are configured in both MDP3 and
> > > DISP, considering previous discussions, I attemped to integrate
> > > into a
> > > single binding, named after the controlling user.
> > 
> > I'm still kinda struggling to understand this. Do you mean that the
> > hardware can be controlled by either of the disp and mdp3 drivers,
> > and
> > a compatible containing "disp" would use one driver, and one
> > containing
> > "mdp3" would use another?
> > 

> Sorry for any confusion caused by the software information. In the
> video pipeline, after decoding, the data flows sequentially through two
> subsystems: MDP and DISP. Each subsystems has multiple IPs, with some
> serving the same functionality as COLOR mentioned here. However, these
> IPs cannot be controlled by different subsystems. Therefore, I included
> the name of the subsystem after SoC to identify the configuration's
> location. Is this approach feasible?

I'll have to leave things to the likes of Laurent to comment here I
think. I don't understand this hardware well enough to have a useful
opinion. It would seem like a different part of the datapath is a
different device that should be documented separately, but I don't know
enough to say for sure, sorry.

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