A regression in output polling was introduced by commit
4ad8d57d902fbc7c82507cfc1b031f3a07c3de6e
("drm: Check output polling initialized before disabling") in the 6.1.y stable
tree.
As a result, when the i915 driver detects an HPD IRQ storm and attempts to
switch
from IRQ-based hotplug detection to polling, output polling fails to resume.
The root cause is the use of dev->mode_config.poll_running. Once poll_running
is set
(during the first connector detection) the calls to
drm_kms_helper_poll_enable(), such as
intel_hpd_irq_storm_switch_to_polling() fails to schedule output_poll_work as
expected.
Therefore, after an IRQ storm disables HPD IRQs, polling does not start,
breaking hotplug detection.
The fix is to remove the dev->mode_config.poll_running in the check condition,
ensuring polling
is always scheduled as requested.
Notes:
Initial analysis, assumptions, device testing details, the correct fix and
detailed rationale
were discussed here https://lore.kernel.org/stable/aI32HUzrT95nS_H9@ideak-desk/
Cc: sta...@vger.kernel.org # 6.1.y
Cc: Imre Deak <imre.d...@intel.com>
Cc: Shradha Gupta <shradhagu...@linux.microsoft.com>
Suggested-by: Imre Deak <imre.d...@intel.com>
Signed-off-by: Nicusor Huhulea <nicusor.huhu...@siemens.com>
---
drivers/gpu/drm/drm_probe_helper.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_probe_helper.c
b/drivers/gpu/drm/drm_probe_helper.c
index 0e5eadc6d44d..a515b78f839e 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -250,7 +250,7 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
unsigned long delay = DRM_OUTPUT_POLL_PERIOD;
if (drm_WARN_ON_ONCE(dev, !dev->mode_config.poll_enabled) ||
- !drm_kms_helper_poll || dev->mode_config.poll_running)
+ !drm_kms_helper_poll)
return;
drm_connector_list_iter_begin(dev, &conn_iter);
--
2.39.2
