backend-drm: schedule connector disable for detached head

Currently, if a head is detached, the entire state of the device is invalidated
to make sure that the connector is disabled on the next atomic commit. Side
effect of the invalid state is that all planes are disabled on the next commit.
This includes planes that are used with a different head that is not part of the
next atomic commit. Disabling the planes of unrelated outputs causes a blanking
of these outputs until output is repainted and the plane is reenabled.

Store the detached heads in a list on the output and disable the connectors for
all heads in this list in the next atomic commit.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
(cherry picked from commit bcacd9ec5a924317416eabb65a6cd6767d5bfb94)

libweston/backend-drm/drm-internal.h

@@ -519,6 +519,9 @@ struct drm_head {
 	drmModeModeInfo inherited_mode;	/**< Original mode on the connector */
 	uint32_t inherited_max_bpc;	/**< Original max_bpc on the connector */
 	uint32_t inherited_crtc_id;	/**< Original CRTC assignment */
+
+	/* drm_output::disable_head */
+	struct wl_list disable_head_link;
 };
 
 struct drm_crtc {
@@ -541,6 +544,9 @@ struct drm_output {
 	struct drm_device *device;
 	struct drm_crtc *crtc;
 
+	/* drm_head::disable_head_link */
+	struct wl_list disable_head;
+
 	bool page_flip_pending;
 	bool atomic_complete_pending;
 	bool destroy_pending;

libweston/backend-drm/drm.c

@@ -1299,10 +1299,14 @@ drm_output_attach_head(struct weston_output *output_base,
 {
 	struct drm_backend *b = to_drm_backend(output_base->compositor);
 	struct drm_device *device = b->drm;
+	struct drm_head *head = to_drm_head(head_base);
 
 	if (wl_list_length(&output_base->head_list) >= MAX_CLONED_CONNECTORS)
 		return -1;
 
+	wl_list_remove(&head->disable_head_link);
+	wl_list_init(&head->disable_head_link);
+
 	if (!output_base->enabled)
 		return 0;
 
@@ -1326,18 +1330,14 @@ static void
 drm_output_detach_head(struct weston_output *output_base,
 		       struct weston_head *head_base)
 {
-	struct drm_backend *b = to_drm_backend(output_base->compositor);
-	struct drm_device *device = b->drm;
+	struct drm_output *output = to_drm_output(output_base);
+	struct drm_head *head = to_drm_head(head_base);
 
 	if (!output_base->enabled)
 		return;
 
-	/* Need to go through modeset to drop connectors that should no longer
-	 * be driven. */
-	/* XXX: Ideally we'd do this per-output, not globally. */
-	device->state_invalid = true;
-
-	weston_output_schedule_repaint(output_base);
+	/* Drop connectors that should no longer be driven on next repaint. */
+	wl_list_insert(&output->disable_head, &head->disable_head_link);
 }
 
 int
@@ -2249,6 +2249,8 @@ drm_head_create(struct drm_device *device, drmModeConnector *conn,
 
 	head->base.backend_id = drm_head_destroy;
 
+	wl_list_init(&head->disable_head_link);
+
 	ret = drm_head_update_info(head, conn);
 	if (ret < 0)
 		goto err_update;
@@ -2322,6 +2324,8 @@ drm_output_create(struct weston_compositor *compositor, const char *name)
 	output->device = device;
 	output->crtc = NULL;
 
+	wl_list_init(&output->disable_head);
+
 	output->max_bpc = 16;
 	output->gbm_format = DRM_FORMAT_INVALID;
 #ifdef BUILD_DRM_GBM

libweston/backend-drm/kms.c

@@ -951,6 +951,7 @@ drm_output_apply_state_atomic(struct drm_output_state *state,
 	struct drm_plane_state *plane_state;
 	struct drm_mode *current_mode = to_drm_mode(output->base.current_mode);
 	struct drm_head *head;
+	struct drm_head *tmp;
 	int ret = 0;
 
 	drm_debug(b, "\t\t[atomic] %s output %lu (%s) state\n",
@@ -987,6 +988,14 @@ drm_output_apply_state_atomic(struct drm_output_state *state,
 		wl_list_for_each(head, &output->base.head_list, base.output_link)
 			ret |= connector_add_prop(req, &head->connector,
 						  WDRM_CONNECTOR_CRTC_ID, 0);
+
+		wl_list_for_each_safe(head, tmp, &output->disable_head,
+				      disable_head_link) {
+			ret |= connector_add_prop(req, &head->connector,
+						  WDRM_CONNECTOR_CRTC_ID, 0);
+			wl_list_remove(&head->disable_head_link);
+			wl_list_init(&head->disable_head_link);
+		}
 	}
 
 	wl_list_for_each(head, &output->base.head_list, base.output_link) {