Date:   Mon, 15 May 2017 15:44:57 -0500
From:   Rob Herring <robh@...nel.org>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org,
        Thierry Reding <thierry.reding@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] dt-bindings: Document the Raspberry Pi Touchscreen
 nodes.

On Thu, May 11, 2017 at 04:56:23PM -0700, Eric Anholt wrote:
> The Raspberry Pi 7" Touchscreen is a DPI touchscreen panel with
> DSI->DPI bridge and touchscreen controller integrated, that connects
> to the Raspberry Pi through its 15-pin "DSI" connector (some lines are
> DSI, some lines are I2C).
> 
> This device is represented in the DT as three nodes (DSI device, I2C
> device, panel).  Input will be left to a separate binding later, as it
> will be a basic I2C client device.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>  .../raspberrypi,7inch-touchscreen-bridge.txt       | 68 ++++++++++++++++++++++
>  .../panel/raspberrypi,7inch-touchscreen-panel.txt  |  7 +++
>  2 files changed, 75 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/raspberrypi,7inch-touchscreen-bridge.txt
>  create mode 100644 Documentation/devicetree/bindings/display/panel/raspberrypi,7inch-touchscreen-panel.txt
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/raspberrypi,7inch-touchscreen-bridge.txt b/Documentation/devicetree/bindings/display/bridge/raspberrypi,7inch-touchscreen-bridge.txt
> new file mode 100644
> index 000000000000..a5669beaf68f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/bridge/raspberrypi,7inch-touchscreen-bridge.txt
> @@ -0,0 +1,68 @@
> +Official 7" (800x480) Raspberry Pi touchscreen panel's bridge.
> +
> +This DSI panel contains:
> +
> +- TC358762 DSI->DPI bridge
> +- Atmel microcontroller on I2C for power sequencing the DSI bridge and
> +  controlling backlight
> +- Touchscreen controller on I2C for touch input

This is 1 uC or 2?

> +
> +and this covers the TC358762 bridge and Atmel microcontroller, while
> +../panel/raspberrypi,7inch-touchscreen-panel.txt covers the panel.
> +
> +Required properties:
> +- compatible:	Must be "raspberrypi,7inch-touchscreen-bridge"
> +- raspberrypi,touchscreen-bridge:
> +		Handle to the I2C device for Atmel microcontroller
> +
> +Example:
> +
> +dsi1: dsi@...00000 {
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	<...>
> +
> +	lcd-bridge@0 {
> +		compatible = "raspberrypi,7inch-touchscreen-bridge";
> +		reg = <0>;
> +
> +		raspberrypi,touchscreen-bridge = <&pitouchscreen_bridge>;

I think this should be a port with a graph connection from the DSI 
node to the i2c bridge device (and then to the panel).

It's also how other DSI bridges like the tc358767 are done.

> +		ports {
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +			port@0 {
> +				reg = <0>;

BTW, you don't need this when there is only 1.

> +				pitouchscreen_bridge_port: endpoint {
> +					remote-endpoint = <&pitouchscreen_panel_port>;
> +				};
> +			};
> +		};
> +	};
> +};
> +
> +i2c_dsi: i2c {
> +	compatible = "i2c-gpio";
> +	#address-cells = <1>;
> +	#size-cells = <0>;
> +	gpios = <&gpio 28 0
> +		 &gpio 29 0>;
> +
> +	pitouchscreen_bridge: bridge@45 {
> +		compatible = "raspberrypi,touchscreen-bridge-i2c";
> +		reg = <0x45>;
> +	};
> +};
> +
> +lcd {
> +	compatible = "raspberrypi,7inch-touchscreen-panel";
> +	ports {
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		port@0 {
> +			reg = <0>;
> +			pitouchscreen_panel_port: endpoint {
> +				remote-endpoint = <&pitouchscreen_bridge_port>;
> +			};
> +		};
> +	};
> +};
> diff --git a/Documentation/devicetree/bindings/display/panel/raspberrypi,7inch-touchscreen-panel.txt b/Documentation/devicetree/bindings/display/panel/raspberrypi,7inch-touchscreen-panel.txt
> new file mode 100644
> index 000000000000..1e84f97b3b20
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/raspberrypi,7inch-touchscreen-panel.txt
> @@ -0,0 +1,7 @@
> +Official 7" (800x480) Raspberry Pi touchscreen panel's panel.
> +
> +This binding is compatible with the simple-panel binding, which is specified
> +in simple-panel.txt in this directory.
> +
> +Required properties:
> +- compatible:	Must be "raspberrypi,7inch-touchscreen-panel"
> -- 
> 2.11.0
> 
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