[PATCH] drm/amd/display: Solve mst monitors blank out problem after resume

[Wayne Lin <Wayne.Lin@xxxxxxx>]

[Why]
In dm resume, we firstly restore dc state and do the mst resume for topology
probing thereafter. If we change dpcd DP_MSTM_CTRL value after LT in mst reume,
it will cause light up problem on the hub.

[How]
Revert commit 202dc359adda ("drm/amd/display: Defer handling mst up request in resume").
And adjust the reason to trigger dc_link_detect by DETECT_REASON_RESUMEFROMS3S4.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 202dc359adda ("drm/amd/display: Defer handling mst up request in resume")
Signed-off-by: Wayne Lin <Wayne.Lin@xxxxxxx>
Reviewed-by: Fangzhi Zuo <jerry.zuo@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 98cf523a629e..29af22ddccc9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2583,6 +2583,7 @@ static void resume_mst_branch_status(struct drm_dp_mst_topology_mgr *mgr)
 
 	ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
 				 DP_MST_EN |
+				 DP_UP_REQ_EN |
 				 DP_UPSTREAM_IS_SRC);
 	if (ret < 0) {
 		drm_dbg_kms(mgr->dev, "mst write failed - undocked during suspend?\n");
@@ -3186,7 +3187,7 @@ static int dm_resume(void *handle)
 		} else {
 			mutex_lock(&dm->dc_lock);
 			dc_exit_ips_for_hw_access(dm->dc);
-			dc_link_detect(aconnector->dc_link, DETECT_REASON_HPD);
+			dc_link_detect(aconnector->dc_link, DETECT_REASON_RESUMEFROMS3S4);
 			mutex_unlock(&dm->dc_lock);
 		}