[PATCH 1/6] dt-bindings: display: add Unisoc's drm master bindings

[Kevin Tang]

Hi Rob

Rob Herring <robh+dt at kernel.org> 于2020年12月1日周二 上午4:29写道：
>
> On Mon, Nov 30, 2020 at 7:28 AM Kevin Tang <kevin3.tang at gmail.com> wrote:
> >
> > From: Kevin Tang <kevin.tang at unisoc.com>
>
> Once again, DT patches must Cc the DT list if you want them reviewed.
Ok, i will add DT list to my Cc list.
>
> >
> > The Unisoc DRM master device is a virtual device needed to list all
> > DPU devices or other display interface nodes that comprise the
> > graphics subsystem
> >
> > Cc: Orson Zhai <orsonzhai at gmail.com>
> > Cc: Chunyan Zhang <zhang.lyra at gmail.com>
> > Signed-off-by: Kevin Tang <kevin.tang at unisoc.com>
> > ---
> >  .../display/sprd/sprd,display-subsystem.yaml       | 39
++++++++++++++++++++++
> >  1 file changed, 39 insertions(+)
> >  create mode 100644
Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> >
> > diff --git
a/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
b/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> > new file mode 100644
> > index 0000000..9487a39
> > --- /dev/null
> > +++
b/Documentation/devicetree/bindings/display/sprd/sprd,display-subsystem.yaml
> > @@ -0,0 +1,39 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id:
http://devicetree.org/schemas/display/sprd/sprd,display-subsystem.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Unisoc DRM master device
> > +
> > +maintainers:
> > +  - Kevin Tang <kevin.tang at unisoc.com>
> > +
> > +description: |
> > +  The Unisoc DRM master device is a virtual device needed to list all
> > +  DPU devices or other display interface nodes that comprise the
> > +  graphics subsystem.
> > +
> > +properties:
> > +  compatible:
> > +    const: sprd,display-subsystem
>
> As I said before, we try to avoid these virtual nodes. Make the DRM
> driver bind to the DPU node.
>
> The case where this might be needed is if you have h/w that's a
> mixture of shared and discrete blocks. I don't see anything here
> matching that.

This is how I understand this sentence: "h/w that's a mixture of shared and
discrete blocks"
We have multiple display controllers and corresponding physical interfaces,
typical dual-screen display scenario
E.g:
1. dpu0 and dpu1 both binding to DSI for dual mipi-dsi display;
2. dpu0 binding to DSI for primary display, and dpu1 binding to DP for
external display;

It looks like this:
dpu0------>MIPI-DSI------>DPHY/CPHY Combo------>Panel0
                        ^
    ----------------|
    |
dpu1------>DisplayPort------>PHY------>Panel1

For DTS like this:
display-subsystem {
compatible = "sprd,display-subsystem";
ports = <&dpu0_out>, <&dpu1_out>;
};

But this is our first time submitting code to the community, following the
suggestions of other reviewers, we only submitted a basic version. Other
virtual nodes and corresponding drivers will be submitted later.
>
> Rob
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