[Intel-gfx] [PATCH 1/2] drm/i915: Schedule the HPD poll init work on an unbound workqueue

[Imre Deak]

Disabling HPD polling from i915_hpd_poll_init_work() involves probing
all display connectors explicitly to account for lost hotplug
interrupts. On some platforms (mostly pre-ICL) with HDMI connectors the
I2C EDID bit-banging using udelay() triggers in turn the

 workqueue: i915_hpd_poll_init_work [i915] hogged CPU for >10000us 4 times, consider switching to WQ_UNBOUND

warning.

Fix the above by scheduling i915_hpd_poll_init_work() on a WQ_UNBOUND
workqueue. It's ok to use a system WQ, since i915_hpd_poll_init_work()
is properly flushed in intel_hpd_cancel_work().

The connector probing from drm_mode_config::output_poll_work resulting
in the same warning is fixed by the next patch.

Cc: Tejun Heo <tj at kernel.org>
Cc: Heiner Kallweit <hkallweit1 at gmail.com>
CC: stable at vger.kernel.org # 6.5
Suggested-by: Tejun Heo <tj at kernel.org>
Suggested-by: Heiner Kallweit <hkallweit1 at gmail.com>
Reported-by: Heiner Kallweit <hkallweit1 at gmail.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9245
Link: https://lore.kernel.org/all/f7e21caa-e98d-e5b5-932a-fe12d27fde9b@gmail.com
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hotplug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
index e8562f6f8bb44..accc2fec562a0 100644
--- a/drivers/gpu/drm/i915/display/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
@@ -774,7 +774,7 @@ void intel_hpd_poll_enable(struct drm_i915_private *dev_priv)
 	 * As well, there's no issue if we race here since we always reschedule
 	 * this worker anyway
 	 */
-	queue_work(dev_priv->unordered_wq,
+	queue_work(system_unbound_wq,
 		   &dev_priv->display.hotplug.poll_init_work);
 }
 
@@ -803,7 +803,7 @@ void intel_hpd_poll_disable(struct drm_i915_private *dev_priv)
 		return;
 
 	WRITE_ONCE(dev_priv->display.hotplug.poll_enabled, false);
-	queue_work(dev_priv->unordered_wq,
+	queue_work(system_unbound_wq,
 		   &dev_priv->display.hotplug.poll_init_work);
 }
 
-- 
2.37.2