[PATCH 4.4 204/342] drm/dp/mst: deallocate payload on port destruction

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mykola Lysenko <Mykola.Lysenko@xxxxxxx>

commit 91a25e463130c8e19bdb42f2d827836c7937992e upstream.

This is needed to properly deallocate port payload
after downstream branch get unplugged.

In order to do this unplugged MST topology should
be preserved, to find first alive port on path to
unplugged MST topology, and send payload deallocation
request to branch device of found port.

For this mstb and port kref's are used in reversed
order to track when port and branch memory could be
freed.

Added additional functions to find appropriate mstb
as described above.

Signed-off-by: Mykola Lysenko <Mykola.Lysenko@xxxxxxx>
Reviewed-by: Harry Wentland <Harry.Wentland@xxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/drm_dp_mst_topology.c |   91 +++++++++++++++++++++++++++++++---
 1 file changed, 83 insertions(+), 8 deletions(-)

--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -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)