drm/amd/display: Add Debug Log for MST and PCON

Add log for MST/PCON specific use case:
1. If DP1.2 hub where gives reduced link bw and no dsc support.
2. If less than 4-lane configuration where gives reduced bw.
3. If FRL PCON enabled for asic.
4. Track MST sink count.
Reviewed-by: Hersen Wu <Hersenxs.Wu@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1622,6 +1622,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	/* TODO: Remove after DP2 receiver gets proper support of Cable ID feature */
 	adev->dm.dc->debug.ignore_cable_id = true;
 
+	if (adev->dm.dc->caps.dp_hdmi21_pcon_support)
+		DRM_INFO("DP-HDMI FRL PCON supported\n");
+
 	r = dm_dmub_hw_init(adev);
 	if (r) {
 		DRM_ERROR("DMUB interface failed to initialize: status=%d\n", r);

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

@@ -403,6 +403,7 @@ bool dm_helpers_dp_mst_start_top_mgr(
 		bool boot)
 {
 	struct amdgpu_dm_connector *aconnector = link->priv;
+	int ret;
 
 	if (!aconnector) {
 		DRM_ERROR("Failed to find connector for link!");
@@ -418,7 +419,16 @@ bool dm_helpers_dp_mst_start_top_mgr(
 	DRM_INFO("DM_MST: starting TM on aconnector: %p [id: %d]\n",
 			aconnector, aconnector->base.base.id);
 
-	return (drm_dp_mst_topology_mgr_set_mst(&aconnector->mst_mgr, true) == 0);
+	ret = drm_dp_mst_topology_mgr_set_mst(&aconnector->mst_mgr, true);
+	if (ret < 0) {
+		DRM_ERROR("DM_MST: Failed to set the device into MST mode!");
+		return false;
+	}
+
+	DRM_INFO("DM_MST: DP%x, %d-lane link detected\n", aconnector->mst_mgr.dpcd[0],
+		aconnector->mst_mgr.dpcd[2] & DP_MAX_LANE_COUNT_MASK);
+
+	return true;
 }
 
 bool dm_helpers_dp_mst_stop_top_mgr(

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

@@ -177,6 +177,9 @@ amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 		if (dc_link->sink_count)
 			dc_link_remove_remote_sink(dc_link, dc_sink);
 
+		DC_LOG_MST("DM_MST: remove remote sink 0x%p, %d remaining\n",
+			dc_sink, dc_link->sink_count);
+
 		dc_sink_release(dc_sink);
 		aconnector->dc_sink = NULL;
 		aconnector->edid = NULL;
@@ -308,6 +311,9 @@ static int dm_dp_mst_get_modes(struct drm_connector *connector)
 					return 0;
 				}
 
+				DC_LOG_MST("DM_MST: add remote sink 0x%p, %d remaining\n",
+					dc_sink, aconnector->dc_link->sink_count);
+
 				dc_sink->priv = aconnector;
 				aconnector->dc_sink = dc_sink;
 			}
@@ -341,6 +347,9 @@ static int dm_dp_mst_get_modes(struct drm_connector *connector)
 			return 0;
 		}
 
+		DC_LOG_MST("DM_MST: add remote sink 0x%p, %d remaining\n",
+			dc_sink, aconnector->dc_link->sink_count);
+
 		dc_sink->priv = aconnector;
 		/* dc_link_add_remote_sink returns a new reference */
 		aconnector->dc_sink = dc_sink;
@@ -458,6 +467,9 @@ dm_dp_mst_detect(struct drm_connector *connector,
 		if (aconnector->dc_link->sink_count)
 			dc_link_remove_remote_sink(aconnector->dc_link, aconnector->dc_sink);
 
+		DC_LOG_MST("DM_MST: remove remote sink 0x%p, %d remaining\n",
+			aconnector->dc_link, aconnector->dc_link->sink_count);
+
 		dc_sink_release(aconnector->dc_sink);
 		aconnector->dc_sink = NULL;
 		aconnector->edid = NULL;