[PATCH 3/3] drm/amd/display: Solve mst monitors blank out problem after resume

[Wayne Lin <Wayne.Lin@amd.com>]

[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 the 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.

Fixes: 202dc359adda ("drm/amd/display: Defer handling mst up request in resume")
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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 c64cc2378a94..b01452eb0981 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2569,6 +2569,7 @@ 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");
@@ -3171,7 +3172,7 @@ 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);
 		}
 
-- 
2.37.3