On Mon, 31 Mar 2025, Thadeu Lima de Souza Cascardo cascardo@igalia.com wrote:

From: Wayne Lin Wayne.Lin@amd.com

[ Upstream commit bc068194f548ef1f230d96c4398046bf59165992 ]

[Why] Observe after suspend/resme, we can't light up mst monitors under specific mst hub.

This is already at stable backport stage, but it would really be helpful to log *which* specific mst hub we're talking about here. Now the information is lost in time, at least to outsiders.

BR, Jani.

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 Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@igalia.com

---

.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-)

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 d9a3917d207e..c4c6538eabae 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -3231,8 +3231,7 @@ 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; struct dc_commit_streams_params commit_params = {};

if (dm->dc->caps.ips_support) { @@ -3427,23 +3426,16 @@ 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;

}