drm/i915: Fix false-positive assert_rpm_wakelock_held in i915_pmic_bus_access_notifier v2
authorHans de Goede <j.w.r.degoede@gmail.com>
Fri, 10 Nov 2017 15:03:01 +0000 (16:03 +0100)
committerHans de Goede <hdegoede@redhat.com>
Wed, 15 Nov 2017 08:54:53 +0000 (09:54 +0100)
commitce30560c80dead91e98a03d90fb8791e57a9b69d
tree10ae1afd6632a69adc03c50d3409ef07f4498041
parent6e1281412ab9e6772d8f6c26e592181fcdd2ae0c
drm/i915: Fix false-positive assert_rpm_wakelock_held in i915_pmic_bus_access_notifier v2

assert_rpm_wakelock_held is triggered from i915_pmic_bus_access_notifier
even though it gets unregistered on (runtime) suspend, this is caused
by a race happening under the following circumstances:

intel_runtime_pm_put does:

   atomic_dec(&dev_priv->pm.wakeref_count);

   pm_runtime_mark_last_busy(kdev);
   pm_runtime_put_autosuspend(kdev);

And pm_runtime_put_autosuspend calls intel_runtime_suspend from
a workqueue, so there is ample of time between the atomic_dec() and
intel_runtime_suspend() unregistering the notifier. If the notifier
gets called in this windowd assert_rpm_wakelock_held falsely triggers
(at this point we're not runtime-suspended yet).

This commit adds disable_rpm_wakeref_asserts and
enable_rpm_wakeref_asserts calls around the
intel_uncore_forcewake_get(FORCEWAKE_ALL) call in
i915_pmic_bus_access_notifier fixing the false-positive WARN_ON.

Changes in v2:
-Reword comment explaining why disabling the wakeref asserts is
 ok and necessary

Cc: stable@vger.kernel.org
Reported-by: FKr <bugs-freedesktop@ubermail.me>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171110150301.9601-2-hdegoede@redhat.com
drivers/gpu/drm/i915/intel_uncore.c