Patch "drm/dp/mst: deallocate payload on port destruction" has been added to the 4.4-stable tree

@@ -798,6 +798,18 @@ static struct drm_dp_mst_branch *drm_dp_
 	return mstb;
 }
 
+static void drm_dp_free_mst_port(struct kref *kref);
+
+static void drm_dp_free_mst_branch_device(struct kref *kref)
+{
+	struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, kref);
+	if (mstb->port_parent) {
+		if (list_empty(&mstb->port_parent->next))
+			kref_put(&mstb->port_parent->kref, drm_dp_free_mst_port);
+	}
+	kfree(mstb);
+}
+
 static void drm_dp_destroy_mst_branch_device(struct kref *kref)
 {
 	struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, kref);

@@ -805,6 +817,15 @@ static void drm_dp_destroy_mst_branch_de
 	bool wake_tx = false;
 
 	/*
+	 * init kref again to be used by ports to remove mst branch when it is
+	 * not needed anymore
+	 */
+	kref_init(kref);
+
+	if (mstb->port_parent && list_empty(&mstb->port_parent->next))
+		kref_get(&mstb->port_parent->kref);
+
+	/*
 	 * destroy all ports - don't need lock
 	 * as there are no more references to the mst branch
 	 * device at this point.

@@ -830,7 +851,8 @@ static void drm_dp_destroy_mst_branch_de
 
 	if (wake_tx)
 		wake_up(&mstb->mgr->tx_waitq);
-	kfree(mstb);
+
+	kref_put(kref, drm_dp_free_mst_branch_device);
 }
 
 static void drm_dp_put_mst_branch_device(struct drm_dp_mst_branch *mstb)

@@ -878,6 +900,7 @@ static void drm_dp_destroy_port(struct k
 			 * from an EDID retrieval */
 
 			mutex_lock(&mgr->destroy_connector_lock);
+			kref_get(&port->parent->kref);
 			list_add(&port->next, &mgr->destroy_connector_list);
 			mutex_unlock(&mgr->destroy_connector_lock);
 			schedule_work(&mgr->destroy_connector_work);

@@ -1602,6 +1625,37 @@ static int drm_dp_send_enum_path_resourc
 	return 0;
 }
 
+static struct drm_dp_mst_port *drm_dp_get_last_connected_port_to_mstb(struct drm_dp_mst_branch *mstb)
+{
+	if (!mstb->port_parent)
+		return NULL;
+
+	if (mstb->port_parent->mstb != mstb)
+		return mstb->port_parent;
+
+	return drm_dp_get_last_connected_port_to_mstb(mstb->port_parent->parent);
+}
+
+static struct drm_dp_mst_branch *drm_dp_get_last_connected_port_and_mstb(struct drm_dp_mst_topology_mgr *mgr,
+									 struct drm_dp_mst_branch *mstb,
+									 int *port_num)
+{
+	struct drm_dp_mst_branch *rmstb = NULL;
+	struct drm_dp_mst_port *found_port;
+	mutex_lock(&mgr->lock);
+	if (mgr->mst_primary) {
+		found_port = drm_dp_get_last_connected_port_to_mstb(mstb);
+
+		if (found_port) {
+			rmstb = found_port->parent;
+			kref_get(&rmstb->kref);
+			*port_num = found_port->port_num;
+		}
+	}
+	mutex_unlock(&mgr->lock);
+	return rmstb;
+}
+
 static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 				   struct drm_dp_mst_port *port,
 				   int id,

@@ -1609,11 +1663,16 @@ static int drm_dp_payload_send_msg(struc
 {
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
-	int len, ret;
+	int len, ret, port_num;
 
+	port_num = port->port_num;
 	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
-	if (!mstb)
-		return -EINVAL;
+	if (!mstb) {
+		mstb = drm_dp_get_last_connected_port_and_mstb(mgr, port->parent, &port_num);
+
+		if (!mstb)
+			return -EINVAL;
+	}
 
 	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
 	if (!txmsg) {

@@ -1622,7 +1681,7 @@ static int drm_dp_payload_send_msg(struc
 	}
 
 	txmsg->dst = mstb;
-	len = build_allocate_payload(txmsg, port->port_num,
+	len = build_allocate_payload(txmsg, port_num,
 				     id,
 				     pbn);
 

@@ -2752,6 +2811,13 @@ static void drm_dp_tx_work(struct work_s
 	mutex_unlock(&mgr->qlock);
 }
 
+static void drm_dp_free_mst_port(struct kref *kref)
+{
+	struct drm_dp_mst_port *port = container_of(kref, struct drm_dp_mst_port, kref);
+	kref_put(&port->parent->kref, drm_dp_free_mst_branch_device);
+	kfree(port);
+}
+
 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);

@@ -2772,13 +2838,22 @@ static void drm_dp_destroy_connector_wor
 		list_del(&port->next);
 		mutex_unlock(&mgr->destroy_connector_lock);
 
+		kref_init(&port->kref);
+		INIT_LIST_HEAD(&port->next);
+
 		mgr->cbs->destroy_connector(mgr, port->connector);
 
 		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);
+		if (!port->input && port->vcpi.vcpi > 0) {
+			if (mgr->mst_state) {
+				drm_dp_mst_reset_vcpi_slots(mgr, port);
+				drm_dp_update_payload_part1(mgr);
+				drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
+			}
+		}
+
+		kref_put(&port->kref, drm_dp_free_mst_port);
 		send_hotplug = true;
 	}
 	if (send_hotplug)