This will allow us to add some locking for port->* members, in
particular the PDT and ->connector, which can't be done from
drm_dp_destroy_port() since we don't know what locks the caller might be
holding.

Note that we already do this in delayed_destroy_work (renamed from
destroy_connector_work in this patch) for ports, we're just making it so
mstbs are also destroyed in this worker.

Changes since v2:
* Clarify commit message
Changes since v4:
* Clarify commit message more

Cc: Juston Li <juston...@intel.com>
Cc: Imre Deak <imre.d...@intel.com>
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Harry Wentland <hwent...@amd.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Reviewed-by: Sean Paul <s...@poorly.run>
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 40 +++++++++++----------------
 1 file changed, 16 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 66ff226d8c86..204d0c832c65 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1510,31 +1510,22 @@ static void drm_dp_destroy_port(struct kref *kref)
                container_of(kref, struct drm_dp_mst_port, topology_kref);
        struct drm_dp_mst_topology_mgr *mgr = port->mgr;
 
-       if (!port->input) {
-               kfree(port->cached_edid);
+       /* There's nothing that needs locking to destroy an input port yet */
+       if (port->input) {
+               drm_dp_mst_put_port_malloc(port);
+               return;
+       }
 
-               /*
-                * The only time we don't have a connector
-                * on an output port is if the connector init
-                * fails.
-                */
-               if (port->connector) {
-                       /* we can't destroy the connector here, as
-                        * we might be holding the mode_config.mutex
-                        * from an EDID retrieval */
+       kfree(port->cached_edid);
 
-                       mutex_lock(&mgr->delayed_destroy_lock);
-                       list_add(&port->next, &mgr->destroy_port_list);
-                       mutex_unlock(&mgr->delayed_destroy_lock);
-                       schedule_work(&mgr->delayed_destroy_work);
-                       return;
-               }
-               /* no need to clean up vcpi
-                * as if we have no connector we never setup a vcpi */
-               drm_dp_port_teardown_pdt(port, port->pdt);
-               port->pdt = DP_PEER_DEVICE_NONE;
-       }
-       drm_dp_mst_put_port_malloc(port);
+       /*
+        * we can't destroy the connector here, as we might be holding the
+        * mode_config.mutex from an EDID retrieval
+        */
+       mutex_lock(&mgr->delayed_destroy_lock);
+       list_add(&port->next, &mgr->destroy_port_list);
+       mutex_unlock(&mgr->delayed_destroy_lock);
+       schedule_work(&mgr->delayed_destroy_work);
 }
 
 /**
@@ -3981,7 +3972,8 @@ static void drm_dp_tx_work(struct work_struct *work)
 static inline void
 drm_dp_delayed_destroy_port(struct drm_dp_mst_port *port)
 {
-       port->mgr->cbs->destroy_connector(port->mgr, port->connector);
+       if (port->connector)
+               port->mgr->cbs->destroy_connector(port->mgr, port->connector);
 
        drm_dp_port_teardown_pdt(port, port->pdt);
        port->pdt = DP_PEER_DEVICE_NONE;
-- 
2.21.0

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