From: Wayne Lin <Wayne.Lin@amd.com>
Date: Wed, 5 Nov 2025 02:36:31 +0000 (+0800)
Subject: drm/amd/display: Enable mst when it's detected but yet to be initialized
X-Git-Tag: v6.18-rc5~12^2~2^2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3c6a743c6961cc2cab453b343bb157d6bbbf8120;p=thirdparty%2Flinux.git

drm/amd/display: Enable mst when it's detected but yet to be initialized

[Why]
drm_dp_mst_topology_queue_probe() is used under the assumption that
mst is already initialized. If we connect system with SST first
then switch to the mst branch during suspend, we will fail probing
topology by calling the wrong API since the mst manager is yet to
be initialized.

[How]
At dm_resume(), once it's detected as mst branc connected, check if
the mst is initialized already. If not, call
dm_helpers_dp_mst_start_top_mgr() instead to initialize mst

V2: Adjust the commit msg a bit

Fixes: bc068194f548 ("drm/amd/display: Don't write DP_MSTM_CTRL after LT")
Cc: Fangzhi Zuo <jerry.zuo@amd.com>
Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 62320fb8d91a0bddc44a228203cfa9bfbb5395bd)
Cc: stable@vger.kernel.org
---

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 2fe6520207d6..91c0188a29b2 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3563,6 +3563,7 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
 	/* Do mst topology probing after resuming cached state*/
 	drm_connector_list_iter_begin(ddev, &iter);
 	drm_for_each_connector_iter(connector, &iter) {
+		bool init = false;
 
 		if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
 			continue;
@@ -3572,7 +3573,14 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
 		    aconnector->mst_root)
 			continue;
 
-		drm_dp_mst_topology_queue_probe(&aconnector->mst_mgr);
+		scoped_guard(mutex, &aconnector->mst_mgr.lock) {
+			init = !aconnector->mst_mgr.mst_primary;
+		}
+		if (init)
+			dm_helpers_dp_mst_start_top_mgr(aconnector->dc_link->ctx,
+				aconnector->dc_link, false);
+		else
+			drm_dp_mst_topology_queue_probe(&aconnector->mst_mgr);
 	}
 	drm_connector_list_iter_end(&iter);