drm/amd/display: Release remote dc_sink under mst scenario

[Why]
Observe that we have several problems while releasing remote dc_sink
under mst cases.

- When unplug mst branch device from the source, we now try to free all
  remote dc_sinks in dm_helpers_dp_mst_stop_top_mgr(). However, there are
  bugs while we're releasing dc_sinks here. First of all,
  link->remote_sinks[] array get shuffled within
  dc_link_remove_remote_sink(). As the result, increasing the array index
  within the releasing loop is wrong. Secondly, it tries to call
  dc_sink_release() to release the dc_sink of the same aconnector every
  time in the loop. Which can't release dc_sink of all aconnector in the
  mst topology.
- There is no code path for us to release remote dc_sink for disconnected
  sst monitor which unplug event is notified by CSN sideband message. Which
  means we'll use stale dc_sink data to represent later on connected
  monitor. Also, has chance to break the maximum remote dc_sink number
  constraint.

[How]
Distinguish unplug event of mst scenario into 2 cases.

* Unplug sst/legacy stream sink off the mst topology
- Release related remote dc_sink in detec_ctx().

* Unplug mst branch device off the mst topology
- Release related remote dc_sink in early_unregister()
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Reviewed-by: Aurabindo Jayamohanan Pillai <Aurabindo.Pillai@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2201,7 +2201,8 @@ static void s3_handle_mst(struct drm_device *dev, bool suspend)
 		} else {
 			ret = drm_dp_mst_topology_mgr_resume(mgr, true);
 			if (ret < 0) {
-				drm_dp_mst_topology_mgr_set_mst(mgr, false);
+				dm_helpers_dp_mst_stop_top_mgr(aconnector->dc_link->ctx,
+					aconnector->dc_link);
 				need_hotplug = true;
 			}
 		}
@@ -10606,7 +10607,7 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
 		 * added MST connectors not found in existing crtc_state in the chained mode
 		 * TODO: need to dig out the root cause of that
 		 */
-		if (!aconnector || (!aconnector->dc_sink && aconnector->mst_port))
+		if (!aconnector)
 			goto skip_modeset;
 
 		if (modereset_required(new_crtc_state))

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c

@@ -451,7 +451,6 @@ bool dm_helpers_dp_mst_stop_top_mgr(
 		struct dc_link *link)
 {
 	struct amdgpu_dm_connector *aconnector = link->priv;
-	uint8_t i;
 
 	if (!aconnector) {
 		DRM_ERROR("Failed to find connector for link!");
@@ -463,22 +462,7 @@ bool dm_helpers_dp_mst_stop_top_mgr(
 
 	if (aconnector->mst_mgr.mst_state == true) {
 		drm_dp_mst_topology_mgr_set_mst(&aconnector->mst_mgr, false);
-
-		for (i = 0; i < MAX_SINKS_PER_LINK; i++) {
-			if (link->remote_sinks[i] == NULL)
-				continue;
-
-			if (link->remote_sinks[i]->sink_signal ==
-			    SIGNAL_TYPE_DISPLAY_PORT_MST) {
-				dc_link_remove_remote_sink(link, link->remote_sinks[i]);
-
-				if (aconnector->dc_sink) {
-					dc_sink_release(aconnector->dc_sink);
-					aconnector->dc_sink = NULL;
-					aconnector->dc_link->cur_link_settings.lane_count = 0;
-				}
-			}
-		}
+		link->cur_link_settings.lane_count = 0;
 	}
 
 	return false;

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c

@@ -140,11 +140,28 @@ amdgpu_dm_mst_connector_late_register(struct drm_connector *connector)
 static void
 amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 {
-	struct amdgpu_dm_connector *amdgpu_dm_connector =
+	struct amdgpu_dm_connector *aconnector =
 		to_amdgpu_dm_connector(connector);
-	struct drm_dp_mst_port *port = amdgpu_dm_connector->port;
+	struct drm_dp_mst_port *port = aconnector->port;
+	struct amdgpu_dm_connector *root = aconnector->mst_port;
+	struct dc_link *dc_link = aconnector->dc_link;
+	struct dc_sink *dc_sink = aconnector->dc_sink;
 
 	drm_dp_mst_connector_early_unregister(connector, port);
+
+	/*
+	 * Release dc_sink for connector which its attached port is
+	 * no longer in the mst topology
+	 */
+	drm_modeset_lock(&root->mst_mgr.base.lock, NULL);
+	if (dc_sink) {
+		if (dc_link->sink_count)
+			dc_link_remove_remote_sink(dc_link, dc_sink);
+
+		dc_sink_release(dc_sink);
+		aconnector->dc_sink = NULL;
+	}
+	drm_modeset_unlock(&root->mst_mgr.base.lock);
 }
 
 static const struct drm_connector_funcs dm_dp_mst_connector_funcs = {
@@ -351,7 +368,7 @@ dm_dp_mst_detect(struct drm_connector *connector,
 		return connector_status_disconnected;
 
 	connection_status = drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr,
-				      aconnector->port);
+							aconnector->port);
 
 	if (port->pdt != DP_PEER_DEVICE_NONE && !port->dpcd_rev) {
 		uint8_t dpcd_rev;
@@ -385,6 +402,17 @@ dm_dp_mst_detect(struct drm_connector *connector,
 		port->dpcd_rev = 0;
 	}
 
+	/*
+	 * Release dc_sink for connector which unplug event is notified by CSN msg
+	 */
+	if (connection_status == connector_status_disconnected && aconnector->dc_sink) {
+		if (aconnector->dc_link->sink_count)
+			dc_link_remove_remote_sink(aconnector->dc_link, aconnector->dc_sink);
+
+		dc_sink_release(aconnector->dc_sink);
+		aconnector->dc_sink = NULL;
+	}
+
 	return connection_status;
 }