Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Medium] drm/bridge: analogix_dp: race on dp->connection_notified in analogix_dp_bridge_notify() --
commit e243ae0110d3bc583be1aa034e4af8955ad61137 Author: Damon Ding <[email protected]> drm/bridge: analogix_dp: Handle HPD notification from downstream bridge This commit handles hotplug notifications from a downstream bridge that supports HPD events (DRM_BRIDGE_OP_HPD) when no downstream bridge provides detection (DRM_BRIDGE_OP_DETECT). It caches the status passed to the bridge's .hpd_notify callback and uses it in analogix_dp_get_plug_in_status() while muting and skipping native HPD initialization. Link: https://lore.kernel.org/all/5609825.iZASKD2KPV@diego/ > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c > b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c > index df898f3142549..90245d55d1d2c 100644 > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c [ ... ] > @@ -1260,6 +1276,14 @@ static void > analogix_dp_bridge_atomic_post_disable(struct drm_bridge *bridge, > DRM_ERROR("Failed to enable psr (%d)\n", ret); > } > > +static void analogix_dp_bridge_notify(struct drm_bridge *bridge, struct > drm_connector *connector, > + enum drm_connector_status status) > +{ > + struct analogix_dp_device *dp = to_dp(bridge); > + > + dp->connection_notified = (status == connector_status_connected); > +} [Severity: Medium] Can a concurrent connector probe overwrite a downstream HPD notification here and cause the hotplug transition to be lost? When dp->hpd_notify_mode is enabled, drm_bridge_connector_init() sets bridge_connector->bridge_detect to the Analogix DP bridge and bridge_connector->bridge_hpd to the downstream bridge. In the connector detection path (for example via drm_mode_getconnector(), drm_client_modeset_probe(), or status_store()), drm_bridge_connector_detect_ctx() holds dev->mode_config.mutex, calls detect->funcs->detect() which reads dp->connection_notified via: analogix_dp_bridge_detect() -> analogix_dp_detect_hpd() -> analogix_dp_get_plug_in_status() and then feeds that return value back into drm_bridge_connector_hpd_notify(): drivers/gpu/drm/display/drm_bridge_connector.c:drm_bridge_connector_detect_ctx() { ... if (detect) status = detect->funcs->detect(detect, connector); ... drm_bridge_connector_hpd_notify(connector, status); } Meanwhile, when a downstream HPD event arrives via drm_bridge_hpd_notify(), drm_bridge_connector_handle_hpd() releases dev->mode_config.mutex before calling drm_bridge_connector_hpd_notify(): drivers/gpu/drm/display/drm_bridge_connector.c:drm_bridge_connector_handle_hpd() { ... mutex_lock(&dev->mode_config.mutex); connector->status = status; mutex_unlock(&dev->mode_config.mutex); drm_bridge_connector_hpd_notify(connector, status); drm_kms_helper_connector_hotplug_event(connector); } If these two paths interleave: 1. drm_bridge_connector_handle_hpd() updates connector->status and unlocks dev->mode_config.mutex. 2. A concurrent probe enters drm_bridge_connector_detect_ctx() under dev->mode_config.mutex and calls analogix_dp_bridge_detect(), reading the stale dp->connection_notified value. 3. drm_bridge_connector_handle_hpd() calls drm_bridge_connector_hpd_notify() -> analogix_dp_bridge_notify(), setting dp->connection_notified to the new status, and then waits on dev->mode_config.mutex inside drm_kms_helper_connector_hotplug_event(). 4. drm_bridge_connector_detect_ctx() finishes and calls drm_bridge_connector_hpd_notify() -> analogix_dp_bridge_notify() with the stale status it read in step 2, clobbering dp->connection_notified. When drm_kms_helper_connector_hotplug_event() (or userspace handling the hotplug event) subsequently probes the connector, analogix_dp_get_plug_in_status() will see the stale dp->connection_notified value and the hotplug state change is lost. [ ... ] -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=13
