[PATCH] drm/i915: cancel delayed_resume_work when suspending

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

It is possible that, by the time we run i915_drm_freeze(),
delayed_resume_work was already queued but did not run yet. If it
still didn't run after intel_runtime_pm_disable_interrupts(), by the
time it runs it will try to change the interrupt registers with the
interrupts already disabled, which will trigger a WARN. We can
reliably reproduce this with the pm_rpm system-suspend test case.

In order to avoid the probelm, we flush the work and put the necessary
resources in case the work was already scheduled.

Another thing I tried was to move the intel_suspend_gt_powersave()
call to before intel_runtime_pm_disable_interrupts(), but since that
function needs to be called after the interrupts are already disabled,
due to dev_priv->rps.work, this strategy didn't work.

Testcase: igt/pm_rpm/system-suspend
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80517
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c  | 2 ++
 drivers/gpu/drm/i915/intel_drv.h | 1 +
 drivers/gpu/drm/i915/intel_pm.c  | 8 ++++++++
 3 files changed, 11 insertions(+)

Now the maintainers and reviewers can choose if they prefer the "cancel" or the
"flush" version of the patch.

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 6eb45ac..dad7e8b 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -520,6 +520,8 @@ static int i915_drm_freeze(struct drm_device *dev)
 			return error;
 		}
 
+		intel_cancel_rps_resume_work(dev_priv);
+
 		intel_runtime_pm_disable_interrupts(dev);
 		dev_priv->enable_hotplug_processing = false;
 
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 5f7c7bd..b122b12 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -993,6 +993,7 @@ void intel_enable_gt_powersave(struct drm_device *dev);
 void intel_disable_gt_powersave(struct drm_device *dev);
 void intel_suspend_gt_powersave(struct drm_device *dev);
 void intel_reset_gt_powersave(struct drm_device *dev);
+void intel_cancel_rps_resume_work(struct drm_i915_private *dev_priv);
 void ironlake_teardown_rc6(struct drm_device *dev);
 void gen6_update_ring_freq(struct drm_device *dev);
 void gen6_rps_idle(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a90fdbd..664099f 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4911,6 +4911,14 @@ void intel_disable_gt_powersave(struct drm_device *dev)
 	}
 }
 
+/* This function needs to put/clear any resources that the
+ * rps.delayed_resume_work function puts/clears. */
+void intel_cancel_rps_resume_work(struct drm_i915_private *dev_priv)
+{
+	if (cancel_delayed_work_sync(&dev_priv->rps.delayed_resume_work))
+		intel_runtime_pm_put(dev_priv);
+}
+
 static void intel_gen6_powersave_work(struct work_struct *work)
 {
 	struct drm_i915_private *dev_priv =
-- 
2.0.0