drm/omap: Add 'alpha' and 'pixel blend mode' plane properties

Add the following properties for planes:
* alpha
* pixel blend mode. Only "Pre-multiplied" and "Coverage" are supported
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190711135219.23402-1-jjhiblot@ti.com

drivers/gpu/drm/omapdrm/omap_plane.c

@@ -53,8 +53,12 @@ static void omap_plane_atomic_update(struct drm_plane *plane,
 	memset(&info, 0, sizeof(info));
 	info.rotation_type = OMAP_DSS_ROT_NONE;
 	info.rotation = DRM_MODE_ROTATE_0;
-	info.global_alpha = 0xff;
+	info.global_alpha = state->alpha >> 8;
 	info.zorder = state->normalized_zpos;
+	if (state->pixel_blend_mode == DRM_MODE_BLEND_PREMULTI)
+		info.pre_mult_alpha = 1;
+	else
+		info.pre_mult_alpha = 0;
 
 	/* update scanout: */
 	omap_framebuffer_update_scanout(state->fb, state, &info);
@@ -285,6 +289,9 @@ struct drm_plane *omap_plane_init(struct drm_device *dev,
 
 	omap_plane_install_properties(plane, &plane->base);
 	drm_plane_create_zpos_property(plane, 0, 0, num_planes - 1);
+	drm_plane_create_alpha_property(plane);
+	drm_plane_create_blend_mode_property(plane, BIT(DRM_MODE_BLEND_PREMULTI) |
+					     BIT(DRM_MODE_BLEND_COVERAGE));
 
 	return plane;