dt-bindings: mipi-dsi: Add dual-channel DSI related info

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.

Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Philippe Cornu <philippe.cornu@st.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180709090751.10221-3-architt@codeaurora.org

diff --git a/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt b/Documentation/devicetree/bindings/display/mipi-dsi-bus.txt
index b7c5bf4..a336599 100644 (file)
--- 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 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@35 {
+                       compatible = "...";
+                       reg = <0x35>;
+
+                       ports {
+                               #address-cells = <1>;
+                               #size-cells = <0>;
+
+                               port@0 {
+                                       reg = <0>;
+                                       dsi0_in: endpoint {
+                                               remote-endpoint = <&dsi0_out>;
+                                       };
+                               };
+
+                               port@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>;
+                               };
+                       };
+               };
+       };