linux-kernel - Re: [PATCH] dt-bindings: display: panel-simple: Add Arm virtual platforms display

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Message-ID: <CAL_JsqJmkp=LUa+TmFo=3dZAKPhPNMGFWj5jyHq_Q9RxZqz4qw@mail.gmail.com>
Date:   Fri, 10 Jun 2022 15:25:05 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Andre Przywara <andre.przywara@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Robin Murphy <robin.murphy@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dt-bindings: display: panel-simple: Add Arm virtual
 platforms display

On Fri, Jun 10, 2022 at 2:55 PM Sam Ravnborg <sam@...nborg.org> wrote:
>
> Hi Rob,
>
> On Fri, Jun 10, 2022 at 02:38:18PM -0600, Rob Herring wrote:
> > 'arm,rtsm-display' is a panel for Arm, Ltd. virtual platforms (e.g. FVP).
> > The binding has been in use for a long time, but was never documented.
> >
> > Some users and an example have a 'panel-dpi' compatible, but that's not
> > needed without a 'panel-timing' node which none of the users have since
> > commit 928faf5e3e8d ("arm64: dts: fvp: Remove panel timings"). The
> > example does have a 'panel-timing' node, but it should not for the
> > same reasons the node was removed in the dts files. So update the
> > example in arm,pl11x.yaml to match the schema.
> >
> > Cc: Linus Walleij <linus.walleij@...aro.org>
> > Cc: Robin Murphy <robin.murphy@....com>
> > Cc: Andre Przywara <andre.przywara@....com>
> > Signed-off-by: Rob Herring <robh@...nel.org>
> > ---
> >  .../bindings/display/arm,pl11x.yaml           | 15 +-------------
> >  .../bindings/display/panel/panel-simple.yaml  | 20 +++++++++++++------
> >  2 files changed, 15 insertions(+), 20 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/display/arm,pl11x.yaml b/Documentation/devicetree/bindings/display/arm,pl11x.yaml
> > index b545c6d20325..6cc9045e5c68 100644
> > --- a/Documentation/devicetree/bindings/display/arm,pl11x.yaml
> > +++ b/Documentation/devicetree/bindings/display/arm,pl11x.yaml
> > @@ -159,25 +159,12 @@ examples:
> >      };
> >
> >      panel {
> > -        compatible = "arm,rtsm-display", "panel-dpi";
> > -        power-supply = <&vcc_supply>;
> > +        compatible = "arm,rtsm-display";
> >
> >          port {
> >              clcd_panel: endpoint {
> >                  remote-endpoint = <&clcd_pads>;
> >              };
> >          };
> > -
> > -        panel-timing {
> > -            clock-frequency = <25175000>;
> > -            hactive = <640>;
> > -            hback-porch = <40>;
> > -            hfront-porch = <24>;
> > -            hsync-len = <96>;
> > -            vactive = <480>;
> > -            vback-porch = <32>;
> > -            vfront-porch = <11>;
> > -            vsync-len = <2>;
> > -        };
> >      };
> >  ...
> > diff --git a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
> > index 21ba90c9fe33..97afd276c54a 100644
> > --- a/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
> > +++ b/Documentation/devicetree/bindings/display/panel/panel-simple.yaml
> > @@ -19,9 +19,6 @@ description: |
> >
> >    If the panel is more advanced a dedicated binding file is required.
> >
> > -allOf:
> > -  - $ref: panel-common.yaml#
> > -
> >  properties:
> >
> >    compatible:
> > @@ -35,6 +32,8 @@ properties:
> >        - ampire,am-480272h3tmqw-t01h
> >          # Ampire AM-800480R3TMQW-A1H 7.0" WVGA TFT LCD panel
> >        - ampire,am800480r3tmqwa1h
> > +        # Arm, Ltd. Virtual Platforms Display
> > +      - arm,rtsm-display
> >          # AU Optronics Corporation 10.1" WSVGA TFT LCD panel
> >        - auo,b101aw03
> >          # AU Optronics Corporation 10.1" WSVGA TFT LCD panel
> > @@ -340,9 +339,18 @@ properties:
> >
> >  additionalProperties: false
> >
> > -required:
> > -  - compatible
> > -  - power-supply
> > +allOf:
> > +  - $ref: panel-common.yaml#
> > +  - if:
> > +      # Most 'simple' panels must have a single supply, but a virtual display does not
> > +      not:
> > +        properties:
> > +          compatible:
> > +            contains:
> > +              const: arm,rtsm-display
> > +    then:
> > +      required:
> > +        - power-supply
>
> Sorry, but I do not like this change. The beauty of panel-simple is that
> this is a collection of simple display with identical bindings because
> the HW is more or less the same (in general - not in details like size
> etc).
>
> Any panels that requires more are pushed out to their own binding and
> for arm,rtsm-display that would be better.

But I require less...

> It is not this single exceptions that bothers me, it is the many
> exceptions we will have in a few years from now.

Fair enough, I'll make it a separate file.

Rob