diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e78c73e975ed..4104f15f4594 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3447,6 +3447,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 	int ret = 0;
 	struct drm_dp_mst_branch *mstb = NULL;
 
+	mutex_lock(&mgr->payload_lock);
 	mutex_lock(&mgr->lock);
 	if (mst_state == mgr->mst_state)
 		goto out_unlock;
@@ -3505,7 +3506,10 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 		/* this can fail if the device is gone */
 		drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
 		ret = 0;
-		memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload));
+		memset(mgr->payloads, 0,
+		       mgr->max_payloads * sizeof(mgr->payloads[0]));
+		memset(mgr->proposed_vcpis, 0,
+		       mgr->max_payloads * sizeof(mgr->proposed_vcpis[0]));
 		mgr->payload_mask = 0;
 		set_bit(0, &mgr->payload_mask);
 		mgr->vcpi_mask = 0;
@@ -3514,6 +3518,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
 
 out_unlock:
 	mutex_unlock(&mgr->lock);
+	mutex_unlock(&mgr->payload_lock);
 	if (mstb)
 		drm_dp_mst_topology_put_mstb(mstb);
 	return ret;