linux-kernel - Re: [PATCH 2/5] dt-bindings: display/panel: Expand rotation documentation

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Date:   Tue, 11 Jun 2019 09:25:37 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Derek Basehore <dbasehore@...omium.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        CK Hu <ck.hu@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree@...r.kernel.org,
        Intel Graphics <intel-gfx@...ts.freedesktop.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH 2/5] dt-bindings: display/panel: Expand rotation documentation

On Mon, Jun 10, 2019 at 10:03 PM Derek Basehore <dbasehore@...omium.org> wrote:
>
> This adds to the rotation documentation to explain how drivers should
> use the property and gives an example of the property in a devicetree
> node.
>
> Signed-off-by: Derek Basehore <dbasehore@...omium.org>
> ---
>  .../bindings/display/panel/panel.txt          | 32 +++++++++++++++++++
>  1 file changed, 32 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/panel/panel.txt b/Documentation/devicetree/bindings/display/panel/panel.txt
> index e2e6867852b8..f35d62d933fc 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel.txt
> +++ b/Documentation/devicetree/bindings/display/panel/panel.txt
> @@ -2,3 +2,35 @@ Common display properties
>  -------------------------
>
>  - rotation:    Display rotation in degrees counter clockwise (0,90,180,270)
> +
> +Property read from the device tree using of of_drm_get_panel_orientation

Don't put kernel specifics into bindings.

> +
> +The panel driver may apply the rotation at the TCON level, which will

What's TCON? Something Mediatek specific IIRC.

> +make the panel look like it isn't rotated to the kernel and any other
> +software.
> +
> +If not, a panel orientation property should be added through the SoC
> +vendor DRM code using the drm_connector_init_panel_orientation_property
> +function.

The 'rotation' property should be defined purely based on how the
panel is mounted relative to a device's orientation. If the display
pipeline has some ability to handle rotation, that's a feature of the
display pipeline and not the panel.

> +
> +Example:

This file is a collection of common properties. It shouldn't have an
example especially as this example is mostly non-common properties.

> +       panel: panel@0 {
> +               compatible = "boe,himax8279d8p";
> +               reg = <0>;
> +               enable-gpios = <&pio 45 0>;

> +               pp33-gpios = <&pio 35 0>;
> +               pp18-gpios = <&pio 36 0>;

BTW, are these upstream because they look like GPIO controlled
supplies which we model with gpio-regulator binding typically.

> +               pinctrl-names = "default", "state_3300mv", "state_1800mv";
> +               pinctrl-0 = <&panel_pins_default>;
> +               pinctrl-1 = <&panel_pins_3300mv>;
> +               pinctrl-2 = <&panel_pins_1800mv>;
> +               backlight = <&backlight_lcd0>;
> +               rotation = <180>;
> +               status = "okay";
> +
> +               port {
> +                       panel_in: endpoint {
> +                               remote-endpoint = <&dsi_out>;
> +                       };
> +               };
> +       };
> --
> 2.22.0.rc2.383.gf4fbbf30c2-goog
>