drm/amd/display: Drop reusing drm connector for MST

[why]
It is not safe to keep existing connector while entire topology
has been removed. Could lead potential impact to uapi.
Entirely unregister all the connectors on the topology,
and use a new set of connectors when the topology is plugged back
on.

[How]
Remove the drm connector entirely each time when the
corresponding MST topology is gone.
When hotunplug a connector (e.g., DP2)
1. Remove connector from userspace.
2. Drop it's reference.
When hotplug back on:
1. Detect new topology, and create new connectors.
2. Notify userspace with sysfs hotplug event.
3. Reprobe new connectors, and reassign CRTC from old (e.g., DP2)
to new (e.g., DP3) connector.

Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -160,8 +160,6 @@ struct amdgpu_dm_connector {
 	struct mutex hpd_lock;
 
 	bool fake_enable;
-
-	bool mst_connected;
 };
 
 #define to_amdgpu_dm_connector(x) container_of(x, struct amdgpu_dm_connector, base)

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

@@ -320,25 +320,6 @@ dm_dp_add_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 	struct amdgpu_device *adev = dev->dev_private;
 	struct amdgpu_dm_connector *aconnector;
 	struct drm_connector *connector;
-	struct drm_connector_list_iter conn_iter;
-
-	drm_connector_list_iter_begin(dev, &conn_iter);
-	drm_for_each_connector_iter(connector, &conn_iter) {
-		aconnector = to_amdgpu_dm_connector(connector);
-		if (aconnector->mst_port == master
-				&& !aconnector->port) {
-			DRM_INFO("DM_MST: reusing connector: %p [id: %d] [master: %p]\n",
-						aconnector, connector->base.id, aconnector->mst_port);
-
-			aconnector->port = port;
-			drm_connector_set_path_property(connector, pathprop);
-
-			drm_connector_list_iter_end(&conn_iter);
-			aconnector->mst_connected = true;
-			return &aconnector->base;
-		}
-	}
-	drm_connector_list_iter_end(&conn_iter);
 
 	aconnector = kzalloc(sizeof(*aconnector), GFP_KERNEL);
 	if (!aconnector)
@@ -387,8 +368,6 @@ dm_dp_add_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 	 */
 	amdgpu_dm_connector_funcs_reset(connector);
 
-	aconnector->mst_connected = true;
-
 	DRM_INFO("DM_MST: added connector: %p [id: %d] [master: %p]\n",
 			aconnector, connector->base.id, aconnector->mst_port);
 
@@ -400,6 +379,9 @@ dm_dp_add_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 static void dm_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 					struct drm_connector *connector)
 {
+	struct amdgpu_dm_connector *master = container_of(mgr, struct amdgpu_dm_connector, mst_mgr);
+	struct drm_device *dev = master->base.dev;
+	struct amdgpu_device *adev = dev->dev_private;
 	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 
 	DRM_INFO("DM_MST: Disabling connector: %p [id: %d] [master: %p]\n",
@@ -413,7 +395,10 @@ static void dm_dp_destroy_mst_connector(struct drm_dp_mst_topology_mgr *mgr,
 		aconnector->dc_sink = NULL;
 	}
 
-	aconnector->mst_connected = false;
+	drm_connector_unregister(connector);
+	if (adev->mode_info.rfbdev)
+		drm_fb_helper_remove_one_connector(&adev->mode_info.rfbdev->helper, connector);
+	drm_connector_put(connector);
 }
 
 static void dm_dp_mst_hotplug(struct drm_dp_mst_topology_mgr *mgr)
@@ -424,18 +409,10 @@ static void dm_dp_mst_hotplug(struct drm_dp_mst_topology_mgr *mgr)
 	drm_kms_helper_hotplug_event(dev);
 }
 
-static void dm_dp_mst_link_status_reset(struct drm_connector *connector)
-{
-	mutex_lock(&connector->dev->mode_config.mutex);
-	drm_connector_set_link_status_property(connector, DRM_MODE_LINK_STATUS_BAD);
-	mutex_unlock(&connector->dev->mode_config.mutex);
-}
-
 static void dm_dp_mst_register_connector(struct drm_connector *connector)
 {
 	struct drm_device *dev = connector->dev;
 	struct amdgpu_device *adev = dev->dev_private;
-	struct amdgpu_dm_connector *aconnector = to_amdgpu_dm_connector(connector);
 
 	if (adev->mode_info.rfbdev)
 		drm_fb_helper_add_one_connector(&adev->mode_info.rfbdev->helper, connector);
@@ -443,9 +420,6 @@ static void dm_dp_mst_register_connector(struct drm_connector *connector)
 		DRM_ERROR("adev->mode_info.rfbdev is NULL\n");
 
 	drm_connector_register(connector);
-
-	if (aconnector->mst_connected)
-		dm_dp_mst_link_status_reset(connector);
 }
 
 static const struct drm_dp_mst_topology_cbs dm_mst_cbs = {