drm/sun4i: Add support for plane alpha

Our backend supports a per-plane alpha property. Support it through our new
helper.
Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Acked-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/13e89f0d2f2b55752a22eb8c4f37f325246a3a9c.1523432341.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun4i_backend.c

@@ -295,6 +295,15 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 	DRM_DEBUG_DRIVER("Switching display backend interlaced mode %s\n",
 			 interlaced ? "on" : "off");
 
+	val = SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA(state->alpha >> 8);
+	if (state->alpha != DRM_BLEND_ALPHA_OPAQUE)
+		val |= SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN;
+	regmap_update_bits(backend->engine.regs,
+			   SUN4I_BACKEND_ATTCTL_REG0(layer),
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_MASK |
+			   SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN,
+			   val);
+
 	if (sun4i_backend_format_is_yuv(fb->format->format))
 		return sun4i_backend_update_yuv_format(backend, layer, plane);
 
@@ -490,7 +499,7 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 		DRM_DEBUG_DRIVER("Plane FB format is %s\n",
 				 drm_get_format_name(fb->format->format,
 						     &format_name));
-		if (fb->format->has_alpha)
+		if (fb->format->has_alpha || (plane_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
 			num_alpha_planes++;
 
 		if (sun4i_backend_format_is_yuv(fb->format->format)) {
@@ -548,7 +557,8 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 	}
 
 	/* We can't have an alpha plane at the lowest position */
-	if (plane_states[0]->fb->format->has_alpha)
+	if (plane_states[0]->fb->format->has_alpha ||
+	    (plane_states[0]->alpha != DRM_BLEND_ALPHA_OPAQUE))
 		return -EINVAL;
 
 	for (i = 1; i < num_planes; i++) {
@@ -560,7 +570,7 @@ static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
 		 * The only alpha position is the lowest plane of the
 		 * second pipe.
 		 */
-		if (fb->format->has_alpha)
+		if (fb->format->has_alpha || (p_state->alpha != DRM_BLEND_ALPHA_OPAQUE))
 			current_pipe++;
 
 		s_state->pipe = current_pipe;

drivers/gpu/drm/sun4i/sun4i_backend.h

@@ -68,12 +68,15 @@
 #define SUN4I_BACKEND_CKMIN_REG			0x884
 #define SUN4I_BACKEND_CKCFG_REG			0x888
 #define SUN4I_BACKEND_ATTCTL_REG0(l)		(0x890 + (0x4 * (l)))
+#define SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_MASK	GENMASK(31, 24)
+#define SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA(x)		((x) << 24)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL_MASK	BIT(15)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PIPESEL(x)		((x) << 15)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL_MASK	GENMASK(11, 10)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_PRISEL(x)			((x) << 10)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_YUVEN		BIT(2)
 #define SUN4I_BACKEND_ATTCTL_REG0_LAY_VDOEN		BIT(1)
+#define SUN4I_BACKEND_ATTCTL_REG0_LAY_GLBALPHA_EN	BIT(0)
 
 #define SUN4I_BACKEND_ATTCTL_REG1(l)		(0x8a0 + (0x4 * (l)))
 #define SUN4I_BACKEND_ATTCTL_REG1_LAY_HSCAFCT		GENMASK(15, 14)

drivers/gpu/drm/sun4i/sun4i_layer.c

@@ -37,6 +37,7 @@ static void sun4i_backend_layer_reset(struct drm_plane *plane)
 	if (state) {
 		plane->state = &state->state;
 		plane->state->plane = plane;
+		plane->state->alpha = DRM_BLEND_ALPHA_OPAQUE;
 		plane->state->zpos = layer->id;
 	}
 }
@@ -167,6 +168,7 @@ static struct sun4i_layer *sun4i_layer_init_one(struct drm_device *drm,
 			     &sun4i_backend_layer_helper_funcs);
 	layer->backend = backend;
 
+	drm_plane_create_alpha_property(&layer->plane);
 	drm_plane_create_zpos_property(&layer->plane, 0, 0,
 				       SUN4I_BACKEND_NUM_LAYERS - 1);