drm/sun4i: Add compatible string for A31/A31s TCON (timing controller)

The A31 TCON has mux controls for how TCON outputs are routed to the
HDMI and MIPI DSI blocks.

Since the A31s does not have MIPI DSI, it only has a mux for the HDMI
controller input.

This patch only adds support for the compatible strings. Actual support
for the mux controls should be added with HDMI and MIPI DSI support.

Signed-off-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>

Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt

···
 Required properties:
  - compatible: value must be either:
    * allwinner,sun5i-a13-tcon
+   * allwinner,sun6i-a31-tcon
+   * allwinner,sun6i-a31s-tcon
    * allwinner,sun8i-a33-tcon
  - reg: base address and size of memory-mapped region
  - interrupts: interrupt associated to this IP
···
   second the block connected to the TCON channel 1 (usually the TV
   encoder)
 
-On the A13, there is one more clock required:
+On SoCs other than the A33, there is one more clock required:
    - 'tcon-ch1': The clock driving the TCON channel 1
 
 DRC

drivers/gpu/drm/sun4i/sun4i_drv.c

···
 static bool sun4i_drv_node_is_tcon(struct device_node *node)
 {
 	return of_device_is_compatible(node, "allwinner,sun5i-a13-tcon") ||
+		of_device_is_compatible(node, "allwinner,sun6i-a31-tcon") ||
+		of_device_is_compatible(node, "allwinner,sun6i-a31s-tcon") ||
 		of_device_is_compatible(node, "allwinner,sun8i-a33-tcon");
 }
 

drivers/gpu/drm/sun4i/sun4i_tcon.c

···
 	.has_channel_1	= true,
 };
 
+static const struct sun4i_tcon_quirks sun6i_a31_quirks = {
+	.has_channel_1	= true,
+};
+
+static const struct sun4i_tcon_quirks sun6i_a31s_quirks = {
+	.has_channel_1	= true,
+};
+
 static const struct sun4i_tcon_quirks sun8i_a33_quirks = {
 	/* nothing is supported */
 };
 
 static const struct of_device_id sun4i_tcon_of_table[] = {
 	{ .compatible = "allwinner,sun5i-a13-tcon", .data = &sun5i_a13_quirks },
+	{ .compatible = "allwinner,sun6i-a31-tcon", .data = &sun6i_a31_quirks },
+	{ .compatible = "allwinner,sun6i-a31s-tcon", .data = &sun6i_a31s_quirks },
 	{ .compatible = "allwinner,sun8i-a33-tcon", .data = &sun8i_a33_quirks },
 	{ }
 };