[RFC v2 2/2] dt-bindings: mipi-dsi: Add dual-channel DSI related info

[Philippe CORNU]

Hi Archit,

Many thanks for this documentation add-on.

I wonder if an extra example of "2 DSI hosts driving a dual-channel DSI 
peripheral controlled by the mipi bus" could be useful? well, I am not 
really convinced it is necessary and maybe this extra example could be 
added later when someone will meet the case... and I should have sent 
this comment on v1 (sorry for the delay).

Reviewed-by: Philippe Cornu <philippe.cornu at st.com>

Philippe :-)

On 01/18/2018 05:53 AM, Archit Taneja wrote:
> Add binding info for peripherals that support dual-channel DSI. Add
> corresponding optional bindings for DSI host controllers that may
> be configured in this mode. Add an example of an I2C controlled
> device operating in dual-channel DSI mode.
> 
> Signed-off-by: Archit Taneja <architt at codeaurora.org>
> ---
> v2:
> - Specify that clock-master is a boolean property.
> - Drop/add unit-address and #*-cells where applicable.
> 
>   .../devicetree/bindings/display/mipi-dsi-bus.txt   | 80 ++++++++++++++++++++++
>   1 file changed, 80 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt b/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt
> index 94fb72cb916f..7a3abbedb3fa 100644
> --- a/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt
> +++ b/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt
> @@ -29,6 +29,13 @@ Required properties:
>   - #size-cells: Should be 0. There are cases where it makes sense to use a
>     different value here. See below.
>   
> +Optional properties:
> +- clock-master: boolean. Should be enabled if the host is being used in
> +  conjunction with another DSI host to drive the same peripheral. Hardware
> +  supporting such a configuration generally requires the data on both the busses
> +  to be driven by the same clock. Only the DSI host instance controlling this
> +  clock should contain this property.
> +
>   DSI peripheral
>   ==============
>   
> @@ -62,6 +69,16 @@ primary control bus, but are also connected to a DSI bus (mostly for the data
>   path). Connections between such peripherals and a DSI host can be represented
>   using the graph bindings [1], [2].
>   
> +Peripherals that support dual channel DSI
> +-----------------------------------------
> +
> +Peripherals with higher bandwidth requirements can be connected to 2 DSI
> +busses. Each DSI bus/channel drives some portion of the pixel data (generally
> +left/right half of each line of the display, or even/odd lines of the display).
> +The graph bindings should be used to represent the multiple DSI busses that are
> +connected to this peripheral. Each DSI host's output endpoint can be linked to
> +an input endpoint of the DSI peripheral.
> +
>   [1] Documentation/devicetree/bindings/graph.txt
>   [2] Documentation/devicetree/bindings/media/video-interfaces.txt
>   
> @@ -71,6 +88,8 @@ Examples
>     with different virtual channel configurations.
>   - (4) is an example of a peripheral on a I2C control bus connected with to
>     a DSI host using of-graph bindings.
> +- (5) is an example of 2 DSI hosts driving a dual-channel DSI peripheral,
> +  which uses I2C as its primary control bus.
>   
>   1)
>   	dsi-host {
> @@ -153,3 +172,64 @@ Examples
>   			};
>   		};
>   	};
> +
> +5)
> +	i2c-host {
> +		dsi-bridge at 35 {
> +			compatible = "...";
> +			reg = <0x35>;
> +
> +			ports {
> +				#address-cells = <1>;
> +				#size-cells = <0>;
> +
> +				port at 0 {
> +					reg = <0>;
> +					dsi0_in: endpoint {
> +						remote-endpoint = <&dsi0_out>;
> +					};
> +				};
> +
> +				port at 1 {
> +					reg = <1>;
> +					dsi1_in: endpoint {
> +						remote-endpoint = <&dsi1_out>;
> +					};
> +				};
> +			};
> +		};
> +	};
> +
> +	dsi0-host {
> +		...
> +
> +		/*
> +		 * this DSI instance drives the clock for both the host
> +		 * controllers
> +		 */
> +		clock-master;
> +
> +		ports {
> +			...
> +
> +			port {
> +				dsi0_out: endpoint {
> +					remote-endpoint = <&dsi0_in>;
> +				};
> +			};
> +		};
> +	};
> +
> +	dsi1-host {
> +		...
> +
> +		ports {
> +			...
> +
> +			port {
> +				dsi1_out: endpoint {
> +					remote-endpoint = <&dsi1_in>;
> +				};
> +			};
> +		};
> +	};
>