[Intel-gfx] [PATCH 2/4] drm/i915: Remove delay for idle_work

[Chris Wilson]

The original intent for the delay before running the idle_work was to
provide a hysteresis to avoid ping-ponging the device runtime-pm. Since
then we have also pulled in some memory management and general device
management for parking. But with the inversion of the wakeref handling,
GEM is no longer responsible for the wakeref and by the time we call the
idle_work, the device is asleep. It seems appropriate now to drop the
delay and just run the worker immediately to flush the cached GEM state
before sleeping.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c           |  2 +-
 drivers/gpu/drm/i915/i915_drv.h               |  2 +-
 drivers/gpu/drm/i915/i915_gem_pm.c            | 21 +++++++------------
 .../gpu/drm/i915/selftests/i915_gem_object.c  |  2 +-
 .../gpu/drm/i915/selftests/mock_gem_device.c  |  4 ++--
 5 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index f60aed7747e5..fc6e60d82477 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -3949,8 +3949,8 @@ i915_drop_caches_set(void *data, u64 val)
 	if (val & DROP_IDLE) {
 		do {
 			flush_delayed_work(&i915->gem.retire_work);
-			drain_delayed_work(&i915->gem.idle_work);
 		} while (READ_ONCE(i915->gt.awake));
+		flush_work(&i915->gem.idle_work);
 	}
 
 	if (val & DROP_FREED)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 64fa353a62bb..2bf518fea36e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2031,7 +2031,7 @@ struct drm_i915_private {
 		 * arrive within a small period of time, we fire
 		 * off the idle_work.
 		 */
-		struct delayed_work idle_work;
+		struct work_struct idle_work;
 	} gem;
 
 	/* For i945gm vblank irq vs. C3 workaround */
diff --git a/drivers/gpu/drm/i915/i915_gem_pm.c b/drivers/gpu/drm/i915/i915_gem_pm.c
index 49b0ce594f20..ae91ad7cb31e 100644
--- a/drivers/gpu/drm/i915/i915_gem_pm.c
+++ b/drivers/gpu/drm/i915/i915_gem_pm.c
@@ -29,12 +29,12 @@ static void i915_gem_park(struct drm_i915_private *i915)
 static void idle_work_handler(struct work_struct *work)
 {
 	struct drm_i915_private *i915 =
-		container_of(work, typeof(*i915), gem.idle_work.work);
+		container_of(work, typeof(*i915), gem.idle_work);
 
 	mutex_lock(&i915->drm.struct_mutex);
 
 	intel_wakeref_lock(&i915->gt.wakeref);
-	if (!intel_wakeref_active(&i915->gt.wakeref))
+	if (!intel_wakeref_active(&i915->gt.wakeref) && !work_pending(work))
 		i915_gem_park(i915);
 	intel_wakeref_unlock(&i915->gt.wakeref);
 
@@ -74,9 +74,7 @@ static int pm_notifier(struct notifier_block *nb,
 		break;
 
 	case INTEL_GT_PARK:
-		mod_delayed_work(i915->wq,
-				 &i915->gem.idle_work,
-				 msecs_to_jiffies(100));
+		queue_work(i915->wq, &i915->gem.idle_work);
 		break;
 	}
 
@@ -142,16 +140,11 @@ void i915_gem_suspend(struct drm_i915_private *i915)
 	 * Assert that we successfully flushed all the work and
 	 * reset the GPU back to its idle, low power state.
 	 */
-	GEM_BUG_ON(i915->gt.awake);
-	cancel_delayed_work_sync(&i915->gpu_error.hangcheck_work);
-
 	drain_delayed_work(&i915->gem.retire_work);
+	GEM_BUG_ON(i915->gt.awake);
+	flush_work(&i915->gem.idle_work);
 
-	/*
-	 * As the idle_work is rearming if it detects a race, play safe and
-	 * repeat the flush until it is definitely idle.
-	 */
-	drain_delayed_work(&i915->gem.idle_work);
+	cancel_delayed_work_sync(&i915->gpu_error.hangcheck_work);
 
 	i915_gem_drain_freed_objects(i915);
 
@@ -242,7 +235,7 @@ void i915_gem_resume(struct drm_i915_private *i915)
 
 void i915_gem_init__pm(struct drm_i915_private *i915)
 {
-	INIT_DELAYED_WORK(&i915->gem.idle_work, idle_work_handler);
+	INIT_WORK(&i915->gem.idle_work, idle_work_handler);
 	INIT_DELAYED_WORK(&i915->gem.retire_work, retire_work_handler);
 
 	i915->gem.pm_notifier.notifier_call = pm_notifier;
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_object.c b/drivers/gpu/drm/i915/selftests/i915_gem_object.c
index 088b2aa05dcd..b926d1cd165d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_object.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_object.c
@@ -509,7 +509,7 @@ static void disable_retire_worker(struct drm_i915_private *i915)
 	intel_gt_pm_get(i915);
 
 	cancel_delayed_work_sync(&i915->gem.retire_work);
-	cancel_delayed_work_sync(&i915->gem.idle_work);
+	flush_work(&i915->gem.idle_work);
 }
 
 static void restore_retire_worker(struct drm_i915_private *i915)
diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
index e4033d0576c4..d919f512042c 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
@@ -59,7 +59,7 @@ static void mock_device_release(struct drm_device *dev)
 	mutex_unlock(&i915->drm.struct_mutex);
 
 	drain_delayed_work(&i915->gem.retire_work);
-	drain_delayed_work(&i915->gem.idle_work);
+	flush_work(&i915->gem.idle_work);
 	i915_gem_drain_workqueue(i915);
 
 	mutex_lock(&i915->drm.struct_mutex);
@@ -195,7 +195,7 @@ struct drm_i915_private *mock_gem_device(void)
 	mock_init_contexts(i915);
 
 	INIT_DELAYED_WORK(&i915->gem.retire_work, mock_retire_work_handler);
-	INIT_DELAYED_WORK(&i915->gem.idle_work, mock_idle_work_handler);
+	INIT_WORK(&i915->gem.idle_work, mock_idle_work_handler);
 
 	i915->gt.awake = true;
 
-- 
2.20.1