drm: rcar-du: Add support for external pixel clock

The DU uses the module functional clock as the default pixel clock, but
supports using an externally supplied pixel clock instead. Support this
by adding the external pixel clock to the DT bindings, and selecting the
clock automatically at runtime based on the requested mode pixel
frequency.

The input clock pins to DU channels routing is configurable, but
currently hardcoded to connect input clock i to channel i.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/video/renesas,du.txt b/Documentation/devicetree/bindings/video/renesas,du.txt
index 5102830f2760..c902323928f7 100644
--- a/Documentation/devicetree/bindings/video/renesas,du.txt
+++ b/Documentation/devicetree/bindings/video/renesas,du.txt
@@ -26,6 +26,10 @@ Required Properties:
       per LVDS encoder. The functional clocks must be named "du.x" with "x"
       being the channel numerical index. The LVDS clocks must be named
       "lvds.x" with "x" being the LVDS encoder numerical index.
+    - In addition to the functional and encoder clocks, all DU versions also
+      support externally supplied pixel clocks. Those clocks are optional.
+      When supplied they must be named "dclkin.x" with "x" being the input
+      clock numerical index.
 
 Required nodes: