drm/sun4i: backend: Assign the pipes automatically

Since we now have a way to enforce the zpos, check for the number of alpha
planes, the only missing part is to assign our pipe automatically instead
of hardcoding it.

The algorithm is quite simple, but requires two iterations over the list of
planes.

In the first one (which is the same one that we've had to check for alpha,
the frontend usage, and so on), we order the planes by their zpos.

We can then do a second iteration over that array by ascending zpos
starting with the pipe 0. When and if we encounter our alpha plane, we put
it and all the other subsequent planes in the second pipe.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/e9caf21d831438d36a3ccc7cef229c9a7ea7f69f.1518802627.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun4i_backend.c

@@ -275,12 +275,16 @@ int sun4i_backend_update_layer_zpos(struct sun4i_backend *backend, int layer,
 				    struct drm_plane *plane)
 {
 	struct drm_plane_state *state = plane->state;
+	struct sun4i_layer_state *p_state = state_to_sun4i_layer_state(state);
 	unsigned int priority = state->normalized_zpos;
+	unsigned int pipe = p_state->pipe;
 
-	DRM_DEBUG_DRIVER("Setting layer %d's priority to %d\n", layer, priority);
-
+	DRM_DEBUG_DRIVER("Setting layer %d's priority to %d and pipe %d\n",
+			 layer, priority, pipe);
 	regmap_update_bits(backend->engine.regs, SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL_MASK |
 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK,
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(p_state->pipe) |
 			   SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(priority));
 
 	return 0;
@@ -325,12 +329,15 @@ static void sun4i_backend_atomic_begin(struct sunxi_engine *engine,
 static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 				      struct drm_crtc_state *crtc_state)
 {
+	struct drm_plane_state *plane_states[SUN4I_BACKEND_NUM_LAYERS] = { 0 };
 	struct drm_atomic_state *state = crtc_state->state;
 	struct drm_device *drm = state->dev;
 	struct drm_plane *plane;
 	unsigned int num_planes = 0;
 	unsigned int num_alpha_planes = 0;
 	unsigned int num_frontend_planes = 0;
+	unsigned int current_pipe = 0;
+	unsigned int i;
 
 	DRM_DEBUG_DRIVER("Starting checking our planes\n");
 
@@ -361,9 +368,19 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 		if (fb->format->has_alpha)
 			num_alpha_planes++;
 
+		DRM_DEBUG_DRIVER("Plane zpos is %d\n",
+				 plane_state->normalized_zpos);
+
+		/* Sort our planes by Zpos */
+		plane_states[plane_state->normalized_zpos] = plane_state;
+
 		num_planes++;
 	}
 
+	/* All our planes were disabled, bail out */
+	if (!num_planes)
+		return 0;
+
 	/*
 	 * The hardware is a bit unusual here.
 	 *
@@ -400,6 +417,25 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 		return -EINVAL;
 	}
 
+	/* We can't have an alpha plane at the lowest position */
+	if (plane_states[0]->fb->format->has_alpha)
+		return -EINVAL;
+
+	for (i = 1; i < num_planes; i++) {
+		struct drm_plane_state *p_state = plane_states[i];
+		struct drm_framebuffer *fb = p_state->fb;
+		struct sun4i_layer_state *s_state = state_to_sun4i_layer_state(p_state);
+
+		/*
+		 * The only alpha position is the lowest plane of the
+		 * second pipe.
+		 */
+		if (fb->format->has_alpha)
+			current_pipe++;
+
+		s_state->pipe = current_pipe;
+	}
+
 	if (num_frontend_planes > SUN4I_BACKEND_NUM_FRONTEND_LAYERS) {
 		DRM_DEBUG_DRIVER("Too many planes going through the frontend, rejecting\n");
 		return -EINVAL;

drivers/gpu/drm/sun4i/sun4i_layer.c

@@ -220,12 +220,6 @@ struct drm_plane **sun4i_layers_init(struct drm_device *drm,
 
 		drm_plane_create_zpos_immutable_property(&layer->plane, i);
 
-		DRM_DEBUG_DRIVER("Assigning %s plane to pipe %d\n",
-				 i ? "overlay" : "primary", plane->pipe);
-		regmap_update_bits(engine->regs, SUN4I_BACKEND_ATTCTL_REG0(i),
-				   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL_MASK,
-				   SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(plane->pipe));
-
 		layer->id = i;
 		planes[i] = &layer->plane;
 	};

drivers/gpu/drm/sun4i/sun4i_layer.h

@@ -24,6 +24,7 @@ struct sun4i_layer {
 
 struct sun4i_layer_state {
 	struct drm_plane_state	state;
+	unsigned int		pipe;
 	bool			uses_frontend;
 };