[6.6,2/3] drm/dp_mst: Add a helper to queue a topology probe

Commit Message

Thadeu Lima de Souza Cascardo March 31, 2025, 7:42 p.m. UTC

From: Imre Deak <[e-mail]>

[ Upstream commit dbaeef363ea54f4c18112874b77503c72ba60fec ]

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

Cc: Lyude Paul <[e-mail]>
Cc: [e-mail]
Reviewed-by: Lyude Paul <[e-mail]>
Signed-off-by: Imre Deak <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Thadeu Lima de Souza Cascardo <[e-mail]>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 27 +++++++++++++++++++
 include/drm/display/drm_dp_mst_helper.h       |  2 ++
 2 files changed, 29 insertions(+)

Patch

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 2a6feb83f786..71a30387ca12 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3685,6 +3685,33 @@  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
diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
index ab1d73f93408..46705dacdd08 100644
--- a/include/drm/display/drm_dp_mst_helper.h
+++ b/include/drm/display/drm_dp_mst_helper.h
@@ -859,6 +859,8 @@  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,