[Why]
Observe that we have several problems while releasing remote dc_sink
under mst cases.

- When unplug mst branch device from the source, we now try to free all
  remote dc_sinks in dm_helpers_dp_mst_stop_top_mgr(). However, there are
  bugs while we're releasing dc_sinks here. First of all,
  link->remote_sinks[] array get shuffled within
  dc_link_remove_remote_sink(). As the result, increasing the array index
  within the releasing loop is wrong. Secondly, it tries to call
  dc_sink_release() to release the dc_sink of the same aconnector every
  time in the loop. Which can't release dc_sink of all aconnector in the
  mst topology.
- There is no code path for us to release remote dc_sink for disconnected
  sst monitor which unplug event is notified by CSN sideband message. Which
  means we'll use stale dc_sink data to represent later on connected
  monitor. Also, has chance to break the maximum remote dc_sink number
  constraint.

[How]
Distinguish unplug event of mst scenario into 2 cases.

* Unplug sst/legacy stream sink off the mst topology
- Release related remote dc_sink in detec_ctx().

* Unplug mst branch device off the mst topology
- Release related remote dc_sink in early_unregister()

Signed-off-by: Wayne Lin <wayne....@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  5 ++-
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 18 +--------
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 39 +++++++++++++++++--
 3 files changed, 39 insertions(+), 23 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 d81b9ef11dba..f53f8962e6da 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -2191,7 +2191,8 @@ static void s3_handle_mst(struct drm_device *dev, bool 
suspend)
                } else {
                        ret = drm_dp_mst_topology_mgr_resume(mgr, true);
                        if (ret < 0) {
-                               drm_dp_mst_topology_mgr_set_mst(mgr, false);
+                               
dm_helpers_dp_mst_stop_top_mgr(aconnector->dc_link->ctx,
+                                       aconnector->dc_link);
                                need_hotplug = true;
                        }
                }
@@ -10359,7 +10360,7 @@ static int dm_update_crtc_state(struct 
amdgpu_display_manager *dm,
                 * added MST connectors not found in existing crtc_state in the 
chained mode
                 * TODO: need to dig out the root cause of that
                 */
-               if (!aconnector || (!aconnector->dc_sink && 
aconnector->mst_port))
+               if (!aconnector)
                        goto skip_modeset;
 
                if (modereset_required(new_crtc_state))
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index 28cf24f6ab32..e4fb19a68ccd 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -451,7 +451,6 @@ bool dm_helpers_dp_mst_stop_top_mgr(
                struct dc_link *link)
 {
        struct amdgpu_dm_connector *aconnector = link->priv;
-       uint8_t i;
 
        if (!aconnector) {
                DRM_ERROR("Failed to find connector for link!");
@@ -463,22 +462,7 @@ bool dm_helpers_dp_mst_stop_top_mgr(
 
        if (aconnector->mst_mgr.mst_state == true) {
                drm_dp_mst_topology_mgr_set_mst(&aconnector->mst_mgr, false);
-
-               for (i = 0; i < MAX_SINKS_PER_LINK; i++) {
-                       if (link->remote_sinks[i] == NULL)
-                               continue;
-
-                       if (link->remote_sinks[i]->sink_signal ==
-                           SIGNAL_TYPE_DISPLAY_PORT_MST) {
-                               dc_link_remove_remote_sink(link, 
link->remote_sinks[i]);
-
-                               if (aconnector->dc_sink) {
-                                       dc_sink_release(aconnector->dc_sink);
-                                       aconnector->dc_sink = NULL;
-                                       
aconnector->dc_link->cur_link_settings.lane_count = 0;
-                               }
-                       }
-               }
+               link->cur_link_settings.lane_count = 0;
        }
 
        return false;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 0542034530b1..e0531a569a14 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -142,11 +142,28 @@ amdgpu_dm_mst_connector_late_register(struct 
drm_connector *connector)
 static void
 amdgpu_dm_mst_connector_early_unregister(struct drm_connector *connector)
 {
-       struct amdgpu_dm_connector *amdgpu_dm_connector =
+       struct amdgpu_dm_connector *aconnector =
                to_amdgpu_dm_connector(connector);
-       struct drm_dp_mst_port *port = amdgpu_dm_connector->port;
+       struct drm_dp_mst_port *port = aconnector->port;
+       struct amdgpu_dm_connector *root = aconnector->mst_port;
+       struct dc_link *dc_link = aconnector->dc_link;
+       struct dc_sink *dc_sink = aconnector->dc_sink;
 
        drm_dp_mst_connector_early_unregister(connector, port);
+
+       /*
+        * Release dc_sink for connector which its attached port is
+        * no longer in the mst topology
+        */
+       drm_modeset_lock(&root->mst_mgr.base.lock, NULL);
+       if (dc_sink) {
+               if (dc_link->sink_count)
+                       dc_link_remove_remote_sink(dc_link, dc_sink);
+
+               dc_sink_release(dc_sink);
+               aconnector->dc_sink = NULL;
+       }
+       drm_modeset_unlock(&root->mst_mgr.base.lock);
 }
 
 static const struct drm_connector_funcs dm_dp_mst_connector_funcs = {
@@ -346,12 +363,26 @@ dm_dp_mst_detect(struct drm_connector *connector,
 {
        struct amdgpu_dm_connector *aconnector = 
to_amdgpu_dm_connector(connector);
        struct amdgpu_dm_connector *master = aconnector->mst_port;
+       int connection_status;
 
        if (drm_connector_is_unregistered(connector))
                return connector_status_disconnected;
 
-       return drm_dp_mst_detect_port(connector, ctx, &master->mst_mgr,
-                                     aconnector->port);
+       connection_status = drm_dp_mst_detect_port(connector, ctx, 
&master->mst_mgr,
+                                                       aconnector->port);
+
+       /*
+        * Release dc_sink for connector which unplug event is notified by CSN 
msg
+        */
+       if (connection_status == connector_status_disconnected && 
aconnector->dc_sink) {
+               if (aconnector->dc_link->sink_count)
+                       dc_link_remove_remote_sink(aconnector->dc_link, 
aconnector->dc_sink);
+
+               dc_sink_release(aconnector->dc_sink);
+               aconnector->dc_sink = NULL;
+       }
+
+       return connection_status;
 }
 
 static int dm_dp_mst_atomic_check(struct drm_connector *connector,
-- 
2.36.1

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