From f4359cedfb43b934f38c50d1604db21333abe57b Mon Sep 17 00:00:00 2001
From: Hans de Goede <j.w.r.degoede@gmail.com>
Date: Fri, 10 Nov 2017 16:03:01 +0100
Subject: [PATCH] drm/i915: Fix false-positive assert_rpm_wakelock_held in i915_pmic_bus_access_notifier v2
Git-commit: f4359cedfb43b934f38c50d1604db21333abe57b
Patch-mainline: v4.15-rc2
References: FATE#322643 bsc#1055900
No-fix: ce30560c80dead91e98a03d90fb8791e57a9b69d
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
(cherry picked from commit ce30560c80dead91e98a03d90fb8791e57a9b69d)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/intel_uncore.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1240,8 +1240,15 @@ static int i915_pmic_bus_access_notifier
* bus, which will be busy after this notification, leading to:
* "render: timed out waiting for forcewake ack request."
* errors.
+ *
+ * The notifier is unregistered during intel_runtime_suspend(),
+ * so it's ok to access the HW here without holding a RPM
+ * wake reference -> disable wakeref asserts for the time of
+ * the access.
*/
+ 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);