drm/sun4i: abstract a engine type

As we are going to add support for the Allwinner DE2 engine in sun4i-drm
driver, we will finally have two types of display engines -- the DE1
backend and the DE2 mixer. They both do some display blending and feed
graphics data to TCON, and is part of the "Display Engine" called by
Allwinner, so I choose to call them both "engine" here.

Abstract the engine type to a new struct with an ops struct, which contains
functions that should be called outside the engine-specified code (in
TCON, CRTC or TV Encoder code).

In order to preserve bisectability, we also switch the backend and layer
code in its own module.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.h b/drivers/gpu/drm/sun4i/sun4i_backend.h
index 6327a29..21945af 100644
--- a/drivers/gpu/drm/sun4i/sun4i_backend.h
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.h
@@ -19,6 +19,8 @@
 #include <linux/regmap.h>
 #include <linux/reset.h>
 
+#include "sunxi_engine.h"
+
 #define SUN4I_BACKEND_MODCTL_REG		0x800
 #define SUN4I_BACKEND_MODCTL_LINE_SEL			BIT(29)
 #define SUN4I_BACKEND_MODCTL_ITLMOD_EN			BIT(28)
@@ -141,8 +143,7 @@
 #define SUN4I_BACKEND_PIPE_OFF(p)		(0x5000 + (0x400 * (p)))
 
 struct sun4i_backend {
-	struct device_node	*node;
-	struct regmap		*regs;
+	struct sunxi_engine	engine;
 
 	struct reset_control	*reset;
 
@@ -152,17 +153,13 @@ struct sun4i_backend {
 
 	struct clk		*sat_clk;
 	struct reset_control	*sat_reset;
-
-	int			id;
-
-	/* Backend list management */
-	struct list_head	list;
 };
 
-void sun4i_backend_apply_color_correction(struct sun4i_backend *backend);
-void sun4i_backend_disable_color_correction(struct sun4i_backend *backend);
-
-void sun4i_backend_commit(struct sun4i_backend *backend);
+static inline struct sun4i_backend *
+engine_to_sun4i_backend(struct sunxi_engine *engine)
+{
+	return container_of(engine, struct sun4i_backend, engine);
+}
 
 void sun4i_backend_layer_enable(struct sun4i_backend *backend,
 				int layer, bool enable);