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

[Chun-Kuang Hu]

Hi, Rob:

Rob Herring <robh@xxxxxxxxxx> 於 2021年8月30日 週一 下午11:06寫道：
>
> On Mon, Aug 30, 2021 at 2:58 AM moudy ho <moudy.ho@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> > > > ---
> > > >  .../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@xxxxxxxxxxxx>
> > > > +  - Moudy Ho <moudy.ho@xxxxxxxxxxxx>
> > > > +
> > > > +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.

Because mediatek drm driver has the same problem with mdp driver, and
it has already use the aliases [1]. No matter what is the conclusion
for mdp driver, I think mediatek drm driver should align to this
conclusion. If the conclusion is to remove aliases, should I modify
the dts which has already upstreamed? Should mediatek drm driver be
backward-compatible with down stream dts which use aliases?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/mediatek/mt8173.dtsi?h=v5.14

Regards,
Chun-Kuang.

>
> > 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
>
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