drm/dp/mst: fixup handling hotplug on port removal.

output ports should always have a connector, unless
in the rare case connector allocation fails in the
driver.

In this case we only need to teardown the pdt,
and free the struct, and there is no need to
send a hotplug msg.

In the case were we add the port to the destroy
list we need to send a hotplug if we destroy
any connectors, so userspace knows to reprobe
stuff.

this patch also handles port->connector allocation
failing which should be a rare event, but makes
the code consistent.
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_dp_mst_topology.c

@@ -863,29 +863,33 @@ static void drm_dp_destroy_port(struct kref *kref)
 {
 	struct drm_dp_mst_port *port = container_of(kref, struct drm_dp_mst_port, kref);
 	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
+
 	if (!port->input) {
 		port->vcpi.num_slots = 0;
 
 		kfree(port->cached_edid);
 
-		/* we can't destroy the connector here, as
-		   we might be holding the mode_config.mutex
-		   from an EDID retrieval */
+		/*
+		 * The only time we don't have a connector
+		 * on an output port is if the connector init
+		 * fails.
+		 */
 		if (port->connector) {
+			/* we can't destroy the connector here, as
+			 * we might be holding the mode_config.mutex
+			 * from an EDID retrieval */
+
 			mutex_lock(&mgr->destroy_connector_lock);
 			list_add(&port->next, &mgr->destroy_connector_list);
 			mutex_unlock(&mgr->destroy_connector_lock);
 			schedule_work(&mgr->destroy_connector_work);
 			return;
 		}
+		/* no need to clean up vcpi
+		 * as if we have no connector we never setup a vcpi */
 		drm_dp_port_teardown_pdt(port, port->pdt);
-
-		if (!port->input && port->vcpi.vcpi > 0)
-			drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
 	}
 	kfree(port);
-
-	(*mgr->cbs->hotplug)(mgr);
 }
 
 static void drm_dp_put_port(struct drm_dp_mst_port *port)
@@ -1116,12 +1120,21 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 
 		build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath));
 		port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, port, proppath);
-
+		if (!port->connector) {
+			/* remove it from the port list */
+			mutex_lock(&mstb->mgr->lock);
+			list_del(&port->next);
+			mutex_unlock(&mstb->mgr->lock);
+			/* drop port list reference */
+			drm_dp_put_port(port);
+			goto out;
+		}
 		if (port->port_num >= 8) {
 			port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
 		}
 	}
 
+out:
 	/* put reference to this port */
 	drm_dp_put_port(port);
 }
@@ -2672,7 +2685,7 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
 {
 	struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work);
 	struct drm_dp_mst_port *port;
-
+	bool send_hotplug = false;
 	/*
 	 * Not a regular list traverse as we have to drop the destroy
 	 * connector lock before destroying the connector, to avoid AB->BA
@@ -2695,7 +2708,10 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
 		if (!port->input && port->vcpi.vcpi > 0)
 			drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
 		kfree(port);
+		send_hotplug = true;
 	}
+	if (send_hotplug)
+		(*mgr->cbs->hotplug)(mgr);
 }
 
 /**