drm/dp_mst: Add a helper to queue a topology probe

A follow up i915 patch will need to reprobe the MST topology after the
initial probing, add a helper for this.

Cc: Lyude Paul <lyude@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-3-imre.deak@intel.com

drivers/gpu/drm/display/drm_dp_mst_topology.c

@@ -3728,6 +3728,33 @@ drm_dp_mst_topology_mgr_invalidate_mstb(struct drm_dp_mst_branch *mstb)
 			drm_dp_mst_topology_mgr_invalidate_mstb(port->mstb);
 }
 
+/**
+ * drm_dp_mst_topology_queue_probe - Queue a topology probe
+ * @mgr: manager to probe
+ *
+ * Queue a work to probe the MST topology. Driver's should call this only to
+ * sync the topology's HW->SW state after the MST link's parameters have
+ * changed in a way the state could've become out-of-sync. This is the case
+ * for instance when the link rate between the source and first downstream
+ * branch device has switched between UHBR and non-UHBR rates. Except of those
+ * cases - for instance when a sink gets plugged/unplugged to a port - the SW
+ * state will get updated automatically via MST UP message notifications.
+ */
+void drm_dp_mst_topology_queue_probe(struct drm_dp_mst_topology_mgr *mgr)
+{
+	mutex_lock(&mgr->lock);
+
+	if (drm_WARN_ON(mgr->dev, !mgr->mst_state || !mgr->mst_primary))
+		goto out_unlock;
+
+	drm_dp_mst_topology_mgr_invalidate_mstb(mgr->mst_primary);
+	drm_dp_mst_queue_probe_work(mgr);
+
+out_unlock:
+	mutex_unlock(&mgr->lock);
+}
+EXPORT_SYMBOL(drm_dp_mst_topology_queue_probe);
+
 /**
  * drm_dp_mst_topology_mgr_suspend() - suspend the MST manager
  * @mgr: manager to suspend

include/drm/display/drm_dp_mst_helper.h

@@ -885,6 +885,8 @@ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr);
 void drm_dp_mst_dump_topology(struct seq_file *m,
 			      struct drm_dp_mst_topology_mgr *mgr);
 
+void drm_dp_mst_topology_queue_probe(struct drm_dp_mst_topology_mgr *mgr);
+
 void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr);
 int __must_check
 drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,