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Date:   Sun, 8 Dec 2019 10:39:48 +0100
From:   Sam Ravnborg <sam@ravnborg.org>
To:     Rob Clark <robdclark@gmail.com>
Cc:     dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
        aarch64-laptops@lists.linaro.org,
        Rob Clark <robdclark@chromium.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, Jeffrey Hugo <jhugo@codeaurora.org>,
        open list <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Vasily Khoruzhick <anarsoul@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Thierry Reding <thierry.reding@gmail.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Subject: Re: [PATCH 1/4] dt-bindings: display: panel: document panel-id
Message-ID: <20191208093948.GB21141@ravnborg.org>
References: <20191207203553.286017-1-robdclark@gmail.com>
 <20191207203553.286017-2-robdclark@gmail.com>
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Hi Rob.

The panel-id can be used to help in several usecase.
With a few nits pointed out below fixed:
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>

	Sam

On Sat, Dec 07, 2019 at 12:35:50PM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> For devices that have one of several possible panels installed, the
> panel-id property gives firmware a generic way to locate and enable the
> panel node corresponding to the installed panel.  Example of how to use
> this property:
> 
>     ivo_panel {
>         compatible = "ivo,m133nwf4-r0";
>         panel-id = <0xc5>;
>         status = "disabled";
> 
>         ports {
>             port {
>                 ivo_panel_in_edp: endpoint {
>                     remote-endpoint = <&sn65dsi86_out_ivo>;
>                 };
>             };
>         };
>     };
> 
>     boe_panel {
>         compatible = "boe,nv133fhm-n61";
>         panel-id = <0xc4>;
>         status = "disabled";
> 
>         ports {
>             port {
>                 boe_panel_in_edp: endpoint {
>                     remote-endpoint = <&sn65dsi86_out_boe>;
>                 };
>             };
>         };
>     };
> 
>     sn65dsi86: bridge@2c {
>         compatible = "ti,sn65dsi86";
> 
>         ports {
>             #address-cells = <1>;
>             #size-cells = <0>;
> 
>             port@0 {
>                 reg = <0>;
>                 sn65dsi86_in_a: endpoint {
>                     remote-endpoint = <&dsi0_out>;
>                 };
>             };
> 
>             port@1 {
>                 reg = <1>;
> 
>                 sn65dsi86_out_boe: endpoint@c4 {
>                     remote-endpoint = <&boe_panel_in_edp>;
>                 };
> 
>                 sn65dsi86_out_ivo: endpoint@c5 {
>                     remote-endpoint = <&ivo_panel_in_edp>;
>                 };
>             };
>         };
>     };
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  .../bindings/display/panel/panel-common.yaml  | 26 +++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-common.yaml b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> index ef8d8cdfcede..6113319b91dd 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> +++ b/Documentation/devicetree/bindings/display/panel/panel-common.yaml
> @@ -75,6 +75,32 @@ properties:
>        in the device graph bindings defined in
>        Documentation/devicetree/bindings/graph.txt.
>  
> +  panel-id:
> +    description:
> +      To support the case where one of several different panels can be installed
> +      on a device, the panel-id property can be used by the firmware to identify
> +      which panel should have it's status changed to "ok".  This property is not
Use "okay" as this is waht is specified in the CT files.

> +      used by the HLOS itself.
Spell out HLOS - it is not obvious for all what it is.

> +
> +      For a device with multiple potential panels, a node for each potential
> +      should be defined with status = "disabled", and an appropriate panel-id
"potential panel should"

> +      property.  The video data producer should be setup with endpoints going to
> +      each possible panel.  The firmware will find the dt node with a panel-id
> +      matching the actual panel installed, and change it's status to "ok".
> +
> +      The exact method the firmware uses to determine the panel-id of the installed
> +      panel is outside the scope of this binding, but a few examples are
> +
> +      1) u-boot module reading a value from a u-boot env var
> +      2) EFI driver module reading a value from an EFI variable
> +      3) device specific firmware reading some device specific GPIOs or
> +         e-fuse
> +
> +      The panel-id values are an opaque integer.  They can be sparse.  The only
> +      important thing is that each possible panel in the system has a unique
> +      panel-id, and that the values configured in the device's DTB match the
> +      values that the firmware is looking for.
> +
>    ddc-i2c-bus:
>      $ref: /schemas/types.yaml#/definitions/phandle
>      description:
> -- 
> 2.23.0
> 
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