linux-kernel - Re: [PATCH v7 3/5] dt-binding: mt8183: Add Mediatek MDP3 dt-bindings

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Date:   Wed, 1 Sep 2021 18:16:16 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     moudy ho <moudy.ho@...iatek.com>
Cc:     Rob Herring <robh@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Maoguang Meng <maoguang.meng@...iatek.com>,
        daoyuan huang <daoyuan.huang@...iatek.com>,
        Ping-Hsun Wu <ping-hsun.wu@...iatek.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Rob Landley <rob@...dley.net>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Pi-Hsun Shih <pihsun@...omium.org>, menghui.lin@...iatek.com,
        Sj Huang <sj.huang@...iatek.com>, ben.lok@...iatek.com,
        Randy Wu <randy.wu@...iatek.com>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Hsin-Yi Wang <hsinyi@...gle.com>
Subject: Re: [PATCH v7 3/5] dt-binding: mt8183: Add Mediatek MDP3 dt-bindings

On Wed, Sep 1, 2021 at 5:04 PM moudy ho <moudy.ho@...iatek.com> wrote:
>
> On Mon, 2021-08-30 at 10:05 -0500, Rob Herring wrote:
> > On Mon, Aug 30, 2021 at 2:58 AM moudy ho <moudy.ho@...iatek.com>
> > wrote:
> > >
> > > On Tue, 2021-08-24 at 13:02 -0500, Rob Herring wrote:
> > > > On Tue, Aug 24, 2021 at 06:00:25PM +0800, Moudy Ho wrote:
> > > > > This patch adds DT binding document for Media Data Path 3
> > > > > (MDP3)
> > > > > a unit in multimedia system used for scaling and color format
> > > > > convert.
> > > > >
> > > > > Signed-off-by: Moudy Ho <moudy.ho@...iatek.com>
> > > > > ---
> > > > >  .../bindings/media/mediatek,mdp3-ccorr.yaml   |  57 +++++
> > > > >  .../bindings/media/mediatek,mdp3-rdma.yaml    | 207
> > > > > ++++++++++++++++++
> > > > >  .../bindings/media/mediatek,mdp3-rsz.yaml     |  65 ++++++
> > > > >  .../bindings/media/mediatek,mdp3-wdma.yaml    |  71 ++++++
> > > > >  .../bindings/media/mediatek,mdp3-wrot.yaml    |  71 ++++++
> > > > >  5 files changed, 471 insertions(+)
> > > > >  create mode 100644
> > > > > Documentation/devicetree/bindings/media/mediatek,mdp3-
> > > > > ccorr.yaml
> > > > >  create mode 100644
> > > > > Documentation/devicetree/bindings/media/mediatek,mdp3-rdma.yaml
> > > > >  create mode 100644
> > > > > Documentation/devicetree/bindings/media/mediatek,mdp3-rsz.yaml
> > > > >  create mode 100644
> > > > > Documentation/devicetree/bindings/media/mediatek,mdp3-wdma.yaml
> > > > >  create mode 100644
> > > > > Documentation/devicetree/bindings/media/mediatek,mdp3-wrot.yaml
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/media/mediatek,mdp3-
> > > > > ccorr.yaml
> > > > > b/Documentation/devicetree/bindings/media/mediatek,mdp3-
> > > > > ccorr.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..59fd68b46022
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/media/mediatek,mdp3-
> > > > > ccorr.yaml
> > > > > @@ -0,0 +1,57 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id:
> > > > >
> https://urldefense.com/v3/__http://devicetree.org/schemas/media/mediatek,mdp3-ccorr.yaml*__;Iw!!CTRNKA9wMg0ARbw!1C0ChLqzi7Zq8D2d4_S4IqCEei4GXdgy3_VCQg8MdsJP7n8TlxbGyajipusfH8hi$
> > > > >
> > > > > +$schema:
> > > > >
> https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!1C0ChLqzi7Zq8D2d4_S4IqCEei4GXdgy3_VCQg8MdsJP7n8TlxbGyajipi-OInix$
> > > > >
> > > > > +
> > > > > +title: Mediatek Media Data Path 3 CCORR Device Tree Bindings
> > > > > +
> > > > > +maintainers:
> > > > > +  - Daoyuan Huang <daoyuan.huang@...iatek.com>
> > > > > +  - Moudy Ho <moudy.ho@...iatek.com>
> > > > > +
> > > > > +description: |
> > > > > +  One of Media Data Path 3 (MDP3) components used to do color
> > > > > correction with 3X3 matrix.
> > > > > +
> > > > > +properties:
> > > > > +  compatible:
> > > > > +    items:
> > > > > +      - enum:
> > > > > +        - mediatek,mt8183-mdp3-ccorr
> > > > > +
> > > > > +  mediatek,mdp3-id:
> > > > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > > > +    maxItems: 1
> > > > > +    description: |
> > > > > +      HW index to distinguish same functionality modules.
> > > >
> > > > If we wanted h/w indexes in DT, we'd have a standard property.
> > > > Why
> > > > do
> > > > you need this?
> > > >
> > >
> > > I'm sorry not quite sure what HW indexes means (something like
> > > aliases?)
> >
> > It means whatever you said in your description.
> >
> > And no, I'm not suggesting you use aliases.
>
> Sorry for the inaccuracy described here, the comment i mentioned before
> should be "standard property" instead of "HW index".
>
> > > It was originally used to mark multiple identical modules in the
> > > MDP
> > > data path algorithm, so that appropriate paths can be dynamically
> > > dispatched.
> >
> > If they are identical, then why do you need to distinguish them in
> > DT?
> > If there's some difference you need to know about such as connections
> > to other blocks, then describe that. Another common example is
> > needing
> > to know what bits/registers to access in a syscon phandle. For that,
> > make the register offset or bits be args to the phandle property.
> >
> > Rob
>
> Integrating the previous discussion, maybe I can revise the description
> to the following:
>     description: |
>       There may be multiple blocks with the same function but different
>       addresses in MDP3. In order to distinguish the connection with
>       other blocks, a unique ID is needed to dynamically use one or
>       more identical blocks to implement multiple pipelines.

With display pipelines it is common to describe the pipeline with an OF
graph. With the pipeline drawn out, you also get ways to derive identifiers
for otherwise identical blocks, such as from port IDs.

See Documentation/devicetree/bindings/display/allwinner,sun4i-a10-display-engine.yaml
and arch/arm/boot/dts/sun9i-a80.dtsi for such an example.


ChenYu