diff options
| author | Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com> | 2026-05-28 10:10:48 +0300 |
|---|---|---|
| committer | Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com> | 2026-06-08 09:48:42 +0300 |
| commit | cd0d23939b8775482c30ca7ab207f185aecd6555 (patch) | |
| tree | 0601c9ae1cffe47942f28ad09b86231b1740add1 | |
| parent | ce73a5db44e3d5f9c0c061f0868ae209b59605f1 (diff) | |
| download | linux-cd0d23939b8775482c30ca7ab207f185aecd6555.tar.gz linux-cd0d23939b8775482c30ca7ab207f185aecd6555.zip | |
drm/bridge: split hpd_mutex into two mutexes
Currently almost all bridge drivers which implement hpd_enable /
hpd_disable callbacks simply toggle the hardware registers generating
the interrupt. However, as pointed out by Jonas Karlman and Sashiko bot,
using those callbacks for enable_irq() / disable_irq() calls or
scheduling and cancelling the work can cause a AB-BA deadlock (between
hpd_mutex lock and the corresponding lock).
Split the hpd_mutex into two locks: one simply making sure that hpd_cb /
hpd_data are consistent and another one, hpd_state_mutex, making sure
that concurrent drm_bridge_hpd_enable() / drm_bridge_hpd_disable() calls
can't end up with inconsistency between hpd_cb/_data and bridge's
internal state.
Link: https://lore.kernel.org/dri-devel/9aa4bd35-bff6-4009-a959-ce31010c7b35@kwiboo.se
Link: https://sashiko.dev/#/patchset/20260513-dp-connector-hpd-v2-0-42f757bfcbf9%40oss.qualcomm.com
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patch.msgid.link/20260528-dp-connector-hpd-v3-1-d656eb1079b7@oss.qualcomm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
| -rw-r--r-- | drivers/gpu/drm/drm_bridge.c | 16 | ||||
| -rw-r--r-- | include/drm/drm_bridge.h | 4 |
2 files changed, 17 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 687b36eea0c7..9a185032a3bd 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -417,6 +417,7 @@ void drm_bridge_add(struct drm_bridge *bridge) if (!list_empty(&bridge->list)) list_del_init(&bridge->list); + mutex_init(&bridge->hpd_state_mutex); mutex_init(&bridge->hpd_mutex); if (bridge->ops & DRM_BRIDGE_OP_HDMI) @@ -469,6 +470,7 @@ void drm_bridge_remove(struct drm_bridge *bridge) mutex_unlock(&bridge_lock); mutex_destroy(&bridge->hpd_mutex); + mutex_destroy(&bridge->hpd_state_mutex); drm_bridge_put(bridge); } @@ -1451,19 +1453,25 @@ void drm_bridge_hpd_enable(struct drm_bridge *bridge, if (!(bridge->ops & DRM_BRIDGE_OP_HPD)) return; + mutex_lock(&bridge->hpd_state_mutex); + mutex_lock(&bridge->hpd_mutex); - if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n")) + if (WARN(bridge->hpd_cb, "Hot plug detection already enabled\n")) { + mutex_unlock(&bridge->hpd_mutex); goto unlock; + } bridge->hpd_cb = cb; bridge->hpd_data = data; + mutex_unlock(&bridge->hpd_mutex); + if (bridge->funcs->hpd_enable) bridge->funcs->hpd_enable(bridge); unlock: - mutex_unlock(&bridge->hpd_mutex); + mutex_unlock(&bridge->hpd_state_mutex); } EXPORT_SYMBOL_GPL(drm_bridge_hpd_enable); @@ -1484,13 +1492,15 @@ void drm_bridge_hpd_disable(struct drm_bridge *bridge) if (!(bridge->ops & DRM_BRIDGE_OP_HPD)) return; - mutex_lock(&bridge->hpd_mutex); + mutex_lock(&bridge->hpd_state_mutex); if (bridge->funcs->hpd_disable) bridge->funcs->hpd_disable(bridge); + mutex_lock(&bridge->hpd_mutex); bridge->hpd_cb = NULL; bridge->hpd_data = NULL; mutex_unlock(&bridge->hpd_mutex); + mutex_unlock(&bridge->hpd_state_mutex); } EXPORT_SYMBOL_GPL(drm_bridge_hpd_disable); diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 4ba3a5deef9a..00a95f927e34 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -1257,6 +1257,10 @@ struct drm_bridge { */ struct mutex hpd_mutex; /** + * @hpd_state_mutex: Protects the HPD en/disablement state for the bridge. + */ + struct mutex hpd_state_mutex; + /** * @hpd_cb: Hot plug detection callback, registered with * drm_bridge_hpd_enable(). */ |