[PATCH 2/5] drm/bridge_connector: preserve connector status for IRQ-only HPD events

[Yongxing Mou]

The bridge connector HPD handling path currently updates
connector->status for every hpd_notify() invocation.

This does not work well for IRQ-only notifications where the event being
reported is carried by extra_status and no connector status transition is
associated with it.

One example is DP MST. HPD IRQs are propagated through
drm_bridge_hpd_notify_*() so that bridge drivers can process the
notification. During MST operation, however, the SST connector attached
to the bridge connector is intentionally kept disconnected while the MST
topology manager handles all connector creation, removal and hotplug
processing.

Updating connector->status for an IRQ-only MST notification may cause
the SST connector state to oscillate between connected and disconnected
depending on the notification path. These artificial state transitions
can later be detected by the polling logic and result in unnecessary
hotplug events being generated. Userspace then re-probes connector
status, potentially triggering the same sequence again.

Treat notifications with status == connector_status_unknown and a valid
extra_status as IRQ-only events. Forward the notification to bridge
drivers without modifying connector->status.

This keeps IRQ delivery working while leaving connector state management
to the component that actually owns it, such as the DP MST topology
framework.

Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/display/drm_bridge_connector.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
index 5edca47a025f..7334d6677604 100644
--- a/drivers/gpu/drm/display/drm_bridge_connector.c
+++ b/drivers/gpu/drm/display/drm_bridge_connector.c
@@ -163,6 +163,18 @@ static void drm_bridge_connector_handle_hpd(struct drm_bridge_connector *drm_bri
 	struct drm_connector *connector = &drm_bridge_connector->base;
 	struct drm_device *dev = connector->dev;
 
+	/*
+	 * IRQ-only notification: extra_status carries the event but
+	 * status is unknown — do not overwrite connector->status.
+	 */
+	if (status == connector_status_unknown &&
+	    extra_status != DRM_CONNECTOR_NO_EXTRA_STATUS) {
+		drm_bridge_connector_hpd_notify(connector,
+						connector->status,
+						extra_status, NULL);
+		return;
+	}
+
 	mutex_lock(&dev->mode_config.mutex);
 	connector->status = status;
 	mutex_unlock(&dev->mode_config.mutex);

-- 
2.43.0