drm/dp_mst: Skip CSN if topology probing is not done yet

[Why]
During resume, observe that we receive CSN event before we start topology
probing. Handling CSN at this moment based on uncertain topology is
unnecessary.

[How]
Add checking condition in drm_dp_mst_handle_up_req() to skip handling CSN
if the topology is yet to be probed.

Cc: Lyude Paul <[email protected]>
Cc: Harry Wentland <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Signed-off-by: Wayne Lin <[email protected]>
Reviewed-by: Lyude Paul <[email protected]>
Signed-off-by: Lyude Paul <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Wayne Lin

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -4069,6 +4069,7 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
 	if (up_req->msg.req_type == DP_CONNECTION_STATUS_NOTIFY) {
 		const struct drm_dp_connection_status_notify *conn_stat =
 			&up_req->msg.u.conn_stat;
+		bool handle_csn;
 
 		drm_dbg_kms(mgr->dev, "Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n",
 			    conn_stat->port_number,
@@ -4077,6 +4078,16 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
 			    conn_stat->message_capability_status,
 			    conn_stat->input_port,
 			    conn_stat->peer_device_type);
+
+		mutex_lock(&mgr->probe_lock);
+		handle_csn = mgr->mst_primary->link_address_sent;
+		mutex_unlock(&mgr->probe_lock);
+
+		if (!handle_csn) {
+			drm_dbg_kms(mgr->dev, "Got CSN before finish topology probing. Skip it.");
+			kfree(up_req);
+			goto out;
+		}
 	} else if (up_req->msg.req_type == DP_RESOURCE_STATUS_NOTIFY) {
 		const struct drm_dp_resource_status_notify *res_stat =
 			&up_req->msg.u.resource_stat;