Hi, On Thu, Jul 06, 2017 at 09:24:47PM +0200, Hans de Goede wrote: > 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. > > Reported-by: FKr <bugs-freedesktop@xxxxxxxxxxx> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > --- > Changes in v2: > -Rebase on current (July 6th 2017) drm-next > --- > drivers/gpu/drm/i915/intel_uncore.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c > index 9882724bc2b6..168b28a87f76 100644 > --- a/drivers/gpu/drm/i915/intel_uncore.c > +++ b/drivers/gpu/drm/i915/intel_uncore.c > @@ -1171,8 +1171,15 @@ static int i915_pmic_bus_access_notifier(struct notifier_block *nb, > * bus, which will be busy after this notification, leading to: > * "render: timed out waiting for forcewake ack request." > * errors. > + * > + * This notifier may get called between intel_runtime_pm_put() > + * doing atomic_dec(wakeref_count) and intel_runtime_resume() > + * unregistering this notifier, which leads to false-positive > + * assert_rpm_wakelock_held() triggering. the following would describe better the reason for disabling wakeref asserts. That is we access the HW without holding a runtime PM reference, but it's ok here since it's handled as a special case during runtime suspend: * The notifier is unregistered during intel_runtime_suspend(), * so it's ok to access the HW here without holding an RPM * wake reference -> disable wakeref asserts for the time of * the access. With that this looks ok: Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx> > */ > + disable_rpm_wakeref_asserts(dev_priv); > intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL); > + enable_rpm_wakeref_asserts(dev_priv); > break; > case MBI_PMIC_BUS_ACCESS_END: > intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL); > -- > 2.13.0 > _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
