drm/sun4i: sun6i-drc: Support DRC on A31 and A31s

The A31 and A31s also have the DRC as part of the display pipeline.
As we know virtually nothing about them, just add compatible strings
for both SoCs to the stub driver.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
index b95696d..5368961 100644
--- a/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
+++ b/Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
@@ -64,6 +64,8 @@
 
 Required properties:
   - compatible: value must be one of:
+    * allwinner,sun6i-a31-drc
+    * allwinner,sun6i-a31s-drc
     * allwinner,sun8i-a33-drc
   - reg: base address and size of the memory-mapped region.
   - interrupts: interrupt associated to this IP
diff --git a/drivers/gpu/drm/sun4i/sun6i_drc.c b/drivers/gpu/drm/sun4i/sun6i_drc.c
index bf6d846..6ef707c 100644
--- a/drivers/gpu/drm/sun4i/sun6i_drc.c
+++ b/drivers/gpu/drm/sun4i/sun6i_drc.c
@@ -98,6 +98,8 @@
 }
 
 static const struct of_device_id sun6i_drc_of_table[] = {
+	{ .compatible = "allwinner,sun6i-a31-drc" },
+	{ .compatible = "allwinner,sun6i-a31s-drc" },
 	{ .compatible = "allwinner,sun8i-a33-drc" },
 	{ }
 };