drm/bridge: split hpd_mutex into two mutexes

Browse source

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>

...

This commit is contained in:

Dmitry Baryshkov 2026-05-28 10:10:48 +03:00

parent ce73a5db44

commit cd0d23939b

2 changed files with 17 additions and 3 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

16

drivers/gpu/drm/drm_bridge.c

View file

4

include/drm/drm_bridge.h

View file