backend-drm: Construct a zpos candidate list of planes

In order to better optimize view assignment to HW planes, we construct
an intermediary zpos candidate list which is used aggregate all suitable
planes for handling scan-out capable client buffers.

We go over it twice: once to construct it and once to pick-and-choose a
suitable plane based its highest zpos position.

In order to maintain the view order correctly we track current zpos
value being applied to the plane state and use it when trying to place
a view into a plane.

Pass the computed zpos value to be applied to the plane state.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Suggested-by: Daniel Stone <daniel.stone@collabora.com>

libweston/backend-drm/drm-internal.h

@@ -369,6 +369,16 @@ struct drm_output_state {
 	struct wl_list plane_list;
 };
 
+/**
+ * An instance of this class is created each time we believe we have a plane
+ * suitable to be used by a view as a direct scan-out. The list is initalized
+ * and populated locally.
+ */
+struct drm_plane_zpos {
+	struct drm_plane *plane;
+	struct wl_list link;	/**< :candidate_plane_zpos_list */
+};
+
 /**
  * Plane state holds the dynamic state for a plane: where it is positioned,
  * and which buffer it is currently displaying.
@@ -727,7 +737,7 @@ void
 drm_plane_state_put_back(struct drm_plane_state *state);
 bool
 drm_plane_state_coords_for_view(struct drm_plane_state *state,
-				struct weston_view *ev);
+				struct weston_view *ev, uint64_t zpos);
 
 void
 drm_assign_planes(struct weston_output *output_base, void *repaint_data);

libweston/backend-drm/state-helpers.c

@@ -165,7 +165,7 @@ drm_plane_state_put_back(struct drm_plane_state *state)
  */
 bool
 drm_plane_state_coords_for_view(struct drm_plane_state *state,
-				struct weston_view *ev)
+				struct weston_view *ev, uint64_t zpos)
 {
 	struct drm_output *output = state->output;
 	struct weston_buffer *buffer = ev->surface->buffer_ref.buffer;
@@ -245,6 +245,9 @@ drm_plane_state_coords_for_view(struct drm_plane_state *state,
 	if (state->src_h > (uint32_t) ((buffer->height << 16) - state->src_y))
 		state->src_h = (buffer->height << 16) - state->src_y;
 
+	/* apply zpos if available */
+	state->zpos = zpos;
+
 	return true;
 }
 

libweston/backend-drm/state-propose.c

@@ -62,10 +62,72 @@ drm_propose_state_mode_to_string(enum drm_output_propose_state_mode mode)
 	return drm_output_propose_state_mode_as_string[mode];
 }
 
+static void
+drm_output_add_zpos_plane(struct drm_plane *plane, struct wl_list *planes)
+{
+	struct drm_backend *b = plane->backend;
+	struct drm_plane_zpos *h_plane;
+	struct drm_plane_zpos *plane_zpos;
+
+	plane_zpos = zalloc(sizeof(*plane_zpos));
+	if (!plane_zpos)
+		return;
+
+	plane_zpos->plane = plane;
+
+	drm_debug(b, "\t\t\t\t[plane] plane %d added to candidate list\n",
+		      plane->plane_id);
+
+	if (wl_list_empty(planes)) {
+		wl_list_insert(planes, &plane_zpos->link);
+		return;
+	}
+
+	h_plane = wl_container_of(planes->next, h_plane, link);
+	if (h_plane->plane->zpos_max >= plane->zpos_max) {
+		wl_list_insert(planes->prev, &plane_zpos->link);
+	} else {
+		struct drm_plane_zpos *p_zpos = NULL;
+
+		if (wl_list_length(planes) == 1) {
+			wl_list_insert(planes->prev, &plane_zpos->link);
+			return;
+		}
+
+		wl_list_for_each(p_zpos, planes, link) {
+			if (p_zpos->plane->zpos_max >
+			    plane_zpos->plane->zpos_max)
+				break;
+		}
+
+		wl_list_insert(p_zpos->link.prev, &plane_zpos->link);
+	}
+}
+
+static void
+drm_output_destroy_zpos_plane(struct drm_plane_zpos *plane_zpos)
+{
+	wl_list_remove(&plane_zpos->link);
+	free(plane_zpos);
+}
+
+static bool
+drm_output_check_plane_has_view_assigned(struct drm_plane *plane,
+                                        struct drm_output_state *output_state)
+{
+	struct drm_plane_state *ps;
+	wl_list_for_each(ps, &output_state->plane_list, link) {
+		if (ps->plane == plane && ps->fb)
+			return true;
+	}
+	return false;
+}
+
 static struct drm_plane_state *
 drm_output_prepare_overlay_view(struct drm_output_state *output_state,
 				struct weston_view *ev,
-				enum drm_output_propose_state_mode mode)
+				enum drm_output_propose_state_mode mode,
+				uint64_t zpos)
 {
 	struct drm_output *output = output_state->output;
 	struct weston_compositor *ec = output->base.compositor;
@@ -136,7 +198,7 @@ drm_output_prepare_overlay_view(struct drm_output_state *output_state,
 
 		state->ev = ev;
 		state->output = output;
-		if (!drm_plane_state_coords_for_view(state, ev)) {
+		if (!drm_plane_state_coords_for_view(state, ev, zpos)) {
 			drm_debug(b, "\t\t\t\t[overlay] not placing view %p on overlay: "
 				     "unsuitable transform\n", ev);
 			drm_plane_state_put_back(state);
@@ -254,7 +316,7 @@ cursor_bo_update(struct drm_plane_state *plane_state, struct weston_view *ev)
 
 static struct drm_plane_state *
 drm_output_prepare_cursor_view(struct drm_output_state *output_state,
-			       struct weston_view *ev)
+			       struct weston_view *ev, uint64_t zpos)
 {
 	struct drm_output *output = output_state->output;
 	struct drm_backend *b = to_drm_backend(output->base.compositor);
@@ -278,11 +340,6 @@ drm_output_prepare_cursor_view(struct drm_output_state *output_state,
 	if (b->gbm == NULL)
 		return NULL;
 
-	if (!weston_view_has_valid_buffer(ev)) {
-		drm_debug(b, "\t\t\t\t[cursor] not assigning view %p to cursor plane "
-			     "(no buffer available)\n", ev);
-		return NULL;
-	}
 	shmbuf = wl_shm_buffer_get(ev->surface->buffer_ref.buffer->resource);
 	if (!shmbuf) {
 		drm_debug(b, "\t\t\t\t[cursor] not assigning view %p to cursor plane "
@@ -305,7 +362,7 @@ drm_output_prepare_cursor_view(struct drm_output_state *output_state,
 	/* We can't scale with the legacy API, and we don't try to account for
 	 * simple cropping/translation in cursor_bo_update. */
 	plane_state->output = output;
-	if (!drm_plane_state_coords_for_view(plane_state, ev))
+	if (!drm_plane_state_coords_for_view(plane_state, ev, zpos))
 		goto err;
 
 	if (plane_state->src_x != 0 || plane_state->src_y != 0 ||
@@ -365,7 +422,7 @@ err:
 #else
 static struct drm_plane_state *
 drm_output_prepare_cursor_view(struct drm_output_state *output_state,
-			       struct weston_view *ev)
+			       struct weston_view *ev, uint64_t zpos)
 {
 	return NULL;
 }
@@ -374,7 +431,8 @@ drm_output_prepare_cursor_view(struct drm_output_state *output_state,
 static struct drm_plane_state *
 drm_output_prepare_scanout_view(struct drm_output_state *output_state,
 				struct weston_view *ev,
-				enum drm_output_propose_state_mode mode)
+				enum drm_output_propose_state_mode mode,
+				uint64_t zpos)
 {
 	struct drm_output *output = output_state->output;
 	struct drm_backend *b = to_drm_backend(output->base.compositor);
@@ -415,7 +473,7 @@ drm_output_prepare_scanout_view(struct drm_output_state *output_state,
 	state->fb = fb;
 	state->ev = ev;
 	state->output = output;
-	if (!drm_plane_state_coords_for_view(state, ev))
+	if (!drm_plane_state_coords_for_view(state, ev, zpos))
 		goto err;
 
 	if (state->dest_x != 0 || state->dest_y != 0 ||
@@ -434,6 +492,184 @@ err:
 	return NULL;
 }
 
+static struct drm_plane_state *
+drm_output_try_view_on_plane(struct drm_plane *plane,
+			     struct drm_output_state *state,
+			     struct weston_view *ev,
+			     enum drm_output_propose_state_mode mode,
+			     uint64_t zpos)
+{
+	struct drm_backend *b = state->pending_state->backend;
+	struct weston_output *wet_output = &state->output->base;
+	bool view_matches_entire_output, scanout_has_view_assigned;
+	struct drm_plane *scanout_plane = state->output->scanout_plane;
+
+	/* sanity checks in case we over/underflow zpos or pass incorrect
+	 * values */
+	assert(zpos <= plane->zpos_max ||
+	       zpos != DRM_PLANE_ZPOS_INVALID_PLANE);
+
+	switch (plane->type) {
+	case WDRM_PLANE_TYPE_CURSOR:
+		if (b->cursors_are_broken) {
+			drm_debug(b, "\t\t\t\t[plane] plane %d refusing to "
+				     "place view %p in cursor\n",
+				     plane->plane_id, ev);
+			return NULL;
+		}
+		return drm_output_prepare_cursor_view(state, ev, zpos);
+	case WDRM_PLANE_TYPE_OVERLAY:
+		/* do not attempt to place it in the overlay if we don't have
+		 * anything in the scanout/primary and the view doesn't cover
+		 * the entire output  */
+		view_matches_entire_output =
+			weston_view_matches_output_entirely(ev, wet_output);
+		scanout_has_view_assigned =
+			drm_output_check_plane_has_view_assigned(scanout_plane,
+								 state);
+
+		if (view_matches_entire_output && !scanout_has_view_assigned) {
+			drm_debug(b, "\t\t\t\t[plane] plane %d refusing to "
+				     "place view %p in overlay\n",
+				     plane->plane_id, ev);
+			return NULL;
+		}
+		return drm_output_prepare_overlay_view(state, ev, mode, zpos);
+	case WDRM_PLANE_TYPE_PRIMARY:
+		if (mode != DRM_OUTPUT_PROPOSE_STATE_PLANES_ONLY) {
+			drm_debug(b, "\t\t\t\t[plane] plane %d refusing to "
+				     "place view %p in scanout\n",
+				     plane->plane_id, ev);
+			return NULL;
+		}
+		return drm_output_prepare_scanout_view(state, ev, mode, zpos);
+	default:
+		assert(0);
+		break;
+	}
+}
+
+static int
+drm_output_check_zpos_plane_states(struct drm_output_state *state)
+{
+	struct drm_backend *b = state->pending_state->backend;
+	struct drm_plane_state *ps;
+	int ret = 0;
+
+	wl_list_for_each(ps, &state->plane_list, link) {
+		struct wl_list *next_node = ps->link.next;
+		bool found_dup = false;
+
+		/* find another plane with the same zpos value */
+		if (next_node == &state->plane_list)
+			break;
+
+		while (next_node && next_node != &state->plane_list) {
+			struct drm_plane_state *ps_next;
+
+			ps_next = container_of(next_node,
+					       struct drm_plane_state,
+					       link);
+
+			if (ps->zpos == ps_next->zpos) {
+				found_dup = true;
+				break;
+			}
+			next_node = next_node->next;
+		}
+
+		if (found_dup) {
+			ret = 1;
+			drm_debug(b, "\t\t\t[plane] found duplicate zpos values\n");
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static struct drm_plane_state *
+drm_output_prepare_plane_view(struct drm_output_state *state,
+			      struct weston_view *ev,
+			      enum drm_output_propose_state_mode mode,
+			      uint64_t current_lowest_zpos)
+{
+	struct drm_output *output = state->output;
+	struct drm_backend *b = to_drm_backend(output->base.compositor);
+
+	struct drm_plane_state *ps = NULL;
+	struct drm_plane *plane;
+	struct drm_plane_zpos *p_zpos, *p_zpos_next;
+	struct wl_list zpos_candidate_list;
+
+	wl_list_init(&zpos_candidate_list);
+
+	/* check view for valid buffer, doesn't make sense to even try */
+	if (!weston_view_has_valid_buffer(ev))
+		return ps;
+
+	/* assemble a list with possible candidates */
+	wl_list_for_each(plane, &b->plane_list, link) {
+		if (!drm_plane_is_available(plane, output))
+			continue;
+
+		if (drm_output_check_plane_has_view_assigned(plane, state)) {
+			drm_debug(b, "\t\t\t\t[plane] not adding plane %d to"
+				     " candidate list: view already assigned "
+				     "to a plane\n", plane->plane_id);
+			continue;
+		}
+
+		if (plane->zpos_min >= current_lowest_zpos) {
+			drm_debug(b, "\t\t\t\t[plane] not adding plane %d to "
+				     "candidate list: minium zpos (%"PRIu64") "
+				     "plane's above current lowest zpos "
+				     "(%"PRIu64")\n", plane->plane_id,
+				     plane->zpos_min, current_lowest_zpos);
+			continue;
+		}
+
+		drm_output_add_zpos_plane(plane, &zpos_candidate_list);
+	}
+
+	/* go over the potential candidate list and try to find a possible
+	 * plane suitable for \c ev; start with the highest zpos value of a
+	 * plane to maximize our chances, but do note we pass the zpos value
+	 * based on current tracked value by \c current_lowest_zpos_in_use */
+	while (!wl_list_empty(&zpos_candidate_list)) {
+		struct drm_plane_zpos *head_p_zpos =
+			wl_container_of(zpos_candidate_list.next,
+					head_p_zpos, link);
+		struct drm_plane *plane = head_p_zpos->plane;
+		const char *p_name = drm_output_get_plane_type_name(plane);
+		uint64_t zpos;
+
+		if (current_lowest_zpos == DRM_PLANE_ZPOS_INVALID_PLANE)
+			zpos = plane->zpos_max;
+		else
+			zpos = MIN(current_lowest_zpos - 1, plane->zpos_max);
+
+		drm_debug(b, "\t\t\t\t[plane] plane %d picked "
+			     "from candidate list, type: %s\n",
+			     plane->plane_id, p_name);
+
+		ps = drm_output_try_view_on_plane(plane, state, ev, mode, zpos);
+		drm_output_destroy_zpos_plane(head_p_zpos);
+
+		if (ps) {
+			drm_debug(b, "\t\t\t\t[view] view %p has been placed to "
+				     "%s plane with computed zpos %"PRIu64"\n",
+				     ev, p_name, zpos);
+			break;
+		}
+	}
+
+	wl_list_for_each_safe(p_zpos, p_zpos_next, &zpos_candidate_list, link)
+		drm_output_destroy_zpos_plane(p_zpos);
+
+	return ps;
+}
+
 static struct drm_output_state *
 drm_output_propose_state(struct weston_output *output_base,
 			 struct drm_pending_state *pending_state,
@@ -445,9 +681,9 @@ drm_output_propose_state(struct weston_output *output_base,
 	struct drm_plane_state *scanout_state = NULL;
 	struct weston_view *ev;
 	pixman_region32_t surface_overlap, renderer_region, occluded_region;
-	bool planes_ok = (mode != DRM_OUTPUT_PROPOSE_STATE_RENDERER_ONLY);
 	bool renderer_ok = (mode != DRM_OUTPUT_PROPOSE_STATE_PLANES_ONLY);
 	int ret;
+	uint64_t current_lowest_zpos = DRM_PLANE_ZPOS_INVALID_PLANE;
 
 	assert(!output->state_last);
 	state = drm_output_state_duplicate(output->state_cur,
@@ -518,7 +754,6 @@ drm_output_propose_state(struct weston_output *output_base,
 		bool force_renderer = false;
 		pixman_region32_t clipped_view;
 		bool totally_occluded = false;
-		bool overlay_occluded = false;
 
 		drm_debug(b, "\t\t\t[view] evaluating view %p for "
 		             "output %s (%lu)\n",
@@ -575,6 +810,7 @@ drm_output_propose_state(struct weston_output *output_base,
 			             "(occluded by renderer views)\n", ev);
 			force_renderer = true;
 		}
+		pixman_region32_fini(&surface_overlap);
 
 		/* In case of enforced mode of content-protection do not
 		 * assign planes for a protected surface on an unsecured output.
@@ -586,51 +822,18 @@ drm_output_propose_state(struct weston_output *output_base,
 			force_renderer = true;
 		}
 
-		/* We do not control the stacking order of overlay planes;
+		if (!force_renderer) {
-		 * the scanout plane is strictly stacked bottom and the cursor
+			drm_debug(b, "\t\t\t[plane] started with zpos %"PRIu64"\n",
-		 * plane top, but the ordering of overlay planes with respect
+				      current_lowest_zpos);
-		 * to each other is undefined. Make sure we do not have two
+			ps = drm_output_prepare_plane_view(state, ev, mode,
-		 * planes overlapping each other. */
+							   current_lowest_zpos);
-		pixman_region32_intersect(&surface_overlap, &occluded_region,
-					  &clipped_view);
-		if (pixman_region32_not_empty(&surface_overlap)) {
-			drm_debug(b, "\t\t\t\t[view] not assigning view %p to plane "
-			             "(occluded by other overlay planes)\n", ev);
-			overlay_occluded = true;
 		}
-		pixman_region32_fini(&surface_overlap);
-
-		/* The cursor plane is 'special' in the sense that we can still
-		 * place it in the legacy API, and we gate that with a separate
-		 * cursors_are_broken flag. */
-		if (!force_renderer && !overlay_occluded && !b->cursors_are_broken)
-			ps = drm_output_prepare_cursor_view(state, ev);
-
-		/* If sprites are disabled or the view is not fully opaque, we
-		 * must put the view into the renderer - unless it has already
-		 * been placed in the cursor plane, which can handle alpha. */
-		if (!ps && !planes_ok) {
-			drm_debug(b, "\t\t\t\t[view] not assigning view %p to plane "
-			             "(precluded by mode)\n", ev);
-			force_renderer = true;
-		}
-		if (!ps && !weston_view_is_opaque(ev, &clipped_view)) {
-			drm_debug(b, "\t\t\t\t[view] not assigning view %p to plane "
-			             "(view not fully opaque)\n", ev);
-			force_renderer = true;
-		}
-
-		/* Only try to place scanout surfaces in planes-only mode; in
-		 * mixed mode, we have already failed to place a view on the
-		 * scanout surface, forcing usage of the renderer on the
-		 * scanout plane. */
-		if (!ps && !force_renderer && !renderer_ok)
-			ps = drm_output_prepare_scanout_view(state, ev, mode);
-
-		if (!ps && !overlay_occluded && !force_renderer)
-			ps = drm_output_prepare_overlay_view(state, ev, mode);
 
 		if (ps) {
+			current_lowest_zpos = ps->zpos;
+			drm_debug(b, "\t\t\t[plane] next zpos to use %"PRIu64"\n",
+				      current_lowest_zpos);
+
 			/* If we have been assigned to an overlay or scanout
 			 * plane, add this area to the occluded region, so
 			 * other views are known to be behind it. The cursor
@@ -671,6 +874,14 @@ drm_output_propose_state(struct weston_output *output_base,
 	if (mode == DRM_OUTPUT_PROPOSE_STATE_RENDERER_ONLY)
 		return state;
 
+	/* check if we have invalid zpos values, like duplicate(s) */
+	ret = drm_output_check_zpos_plane_states(state);
+	if (ret != 0) {
+		drm_debug(b, "\t\t[view] failing state generation: "
+			     "zpos values are in-consistent\n");
+		goto err;
+	}
+
 	/* Check to see if this state will actually work. */
 	ret = drm_pending_state_test(state->pending_state);
 	if (ret != 0) {