drm/amd/display: Don't write DP_MSTM_CTRL after LT

commit bc06819 upstream.

[Why]
Observe after suspend/resme, we can't light up mst monitors under specific
mst hub. The reason is that driver still writes DPCD DP_MSTM_CTRL after LT.
It's forbidden even we write the same value for that dpcd register.

[How]
We already resume the mst branch device dpcd settings during
resume_mst_branch_status(). Leverage drm_dp_mst_topology_queue_probe() to
only probe the topology, not calling drm_dp_mst_topology_mgr_resume() which
will set DP_MSTM_CTRL as well.

Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[cascardo: adjust context in local declarations]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Wayne Lin

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2825,8 +2825,7 @@ static int dm_resume(void *handle)
 	struct dm_atomic_state *dm_state = to_dm_atomic_state(dm->atomic_obj.state);
 	enum dc_connection_type new_connection_type = dc_connection_none;
 	struct dc_state *dc_state;
-	int i, r, j, ret;
-	bool need_hotplug = false;
+	int i, r, j;
 
 	if (amdgpu_in_reset(adev)) {
 		dc_state = dm->cached_dc_state;
@@ -3003,23 +3002,16 @@ static int dm_resume(void *handle)
 		    aconnector->mst_root)
 			continue;
 
-		ret = drm_dp_mst_topology_mgr_resume(&aconnector->mst_mgr, true);
-
-		if (ret < 0) {
-			dm_helpers_dp_mst_stop_top_mgr(aconnector->dc_link->ctx,
-					aconnector->dc_link);
-			need_hotplug = true;
-		}
+		drm_dp_mst_topology_queue_probe(&aconnector->mst_mgr);
 	}
 	drm_connector_list_iter_end(&iter);
 
-	if (need_hotplug)
-		drm_kms_helper_hotplug_event(ddev);
-
 	amdgpu_dm_irq_resume_late(adev);
 
 	amdgpu_dm_smu_write_watermarks_table(adev);
 
+	drm_kms_helper_hotplug_event(ddev);
+
 	return 0;
 }