[PATCH] drm/i915: Use lockdep to prove runtime_pm correctness

[Chris Wilson]

Include a lockmap into our runtime_pm so that we can check lock
ordering wrt runtime suspend.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c         |  7 ++++++
 drivers/gpu/drm/i915/i915_drv.h         |  3 +++
 drivers/gpu/drm/i915/intel_runtime_pm.c | 29 ++++++++++++++++++++++---
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 0db3c83cce29..47df8480e741 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -873,6 +873,7 @@ static void intel_detect_preproduction_hw(struct drm_i915_private *dev_priv)
 static int i915_driver_init_early(struct drm_i915_private *dev_priv,
 				  const struct pci_device_id *ent)
 {
+	static struct lock_class_key rpm_key;
 	const struct intel_device_info *match_info =
 		(struct intel_device_info *)ent->driver_data;
 	struct intel_device_info *device_info;
@@ -900,6 +901,10 @@ static int i915_driver_init_early(struct drm_i915_private *dev_priv,
 	mutex_init(&dev_priv->wm.wm_mutex);
 	mutex_init(&dev_priv->pps_mutex);
 
+	spin_lock_init(&dev_priv->runtime_pm.lock);
+	lockdep_init_map(&dev_priv->runtime_pm.lockmap,
+			 "i915.runtime_pm", &rpm_key, 0);
+
 	i915_memcpy_init_early(dev_priv);
 
 	ret = i915_workqueues_init(dev_priv);
@@ -2594,6 +2599,7 @@ static int intel_runtime_suspend(struct device *kdev)
 	DRM_DEBUG_KMS("Suspending device\n");
 
 	disable_rpm_wakeref_asserts(dev_priv);
+	lock_map_acquire(&dev_priv->runtime_pm.lockmap);
 
 	/*
 	 * We are safe here against re-faults, since the fault handler takes
@@ -2728,6 +2734,7 @@ static int intel_runtime_resume(struct device *kdev)
 
 	intel_enable_ipc(dev_priv);
 
+	lock_map_release(&dev_priv->runtime_pm.lockmap);
 	enable_rpm_wakeref_asserts(dev_priv);
 
 	if (ret)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 6f08ab310118..9e82fd279da3 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1267,6 +1267,9 @@ struct i915_runtime_pm {
 	atomic_t wakeref_count;
 	bool suspended;
 	bool irqs_enabled;
+
+	struct lockdep_map lockmap;
+	spinlock_t lock;
 };
 
 enum intel_pipe_crc_source {
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index de3a81034f77..8c0ddd04a3f4 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -3361,6 +3361,26 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv)
 	mutex_unlock(&power_domains->lock);
 }
 
+static void rpm_acquire(struct i915_runtime_pm *rpm)
+{
+	if (atomic_inc_not_zero(&rpm->wakeref_count))
+		return;
+
+	spin_lock(&rpm->lock);
+	if (!atomic_fetch_inc(&rpm->wakeref_count))
+		lock_map_acquire_read(&rpm->lockmap);
+	spin_unlock(&rpm->lock);
+}
+
+static void rpm_release(struct i915_runtime_pm *rpm)
+{
+	if (atomic_dec_and_lock(&rpm->wakeref_count, &rpm->lock))
+		return;
+
+	lock_map_release(&rpm->lockmap);
+	spin_unlock(&rpm->lock);
+}
+
 /**
  * intel_runtime_pm_get - grab a runtime pm reference
  * @dev_priv: i915 device instance
@@ -3380,7 +3400,7 @@ void intel_runtime_pm_get(struct drm_i915_private *dev_priv)
 	ret = pm_runtime_get_sync(kdev);
 	WARN_ONCE(ret < 0, "pm_runtime_get_sync() failed: %d\n", ret);
 
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
+	rpm_acquire(&dev_priv->runtime_pm);
 	assert_rpm_wakelock_held(dev_priv);
 }
 
@@ -3413,7 +3433,7 @@ bool intel_runtime_pm_get_if_in_use(struct drm_i915_private *dev_priv)
 			return false;
 	}
 
-	atomic_inc(&dev_priv->runtime_pm.wakeref_count);
+	rpm_acquire(&dev_priv->runtime_pm);
 	assert_rpm_wakelock_held(dev_priv);
 
 	return true;
@@ -3441,6 +3461,9 @@ void intel_runtime_pm_get_noresume(struct drm_i915_private *dev_priv)
 	struct pci_dev *pdev = dev_priv->drm.pdev;
 	struct device *kdev = &pdev->dev;
 
+	WARN_ON(IS_ENABLED(CONFIG_LOCKDEP) &&
+		!lock_is_held(&dev_priv->runtime_pm.lockmap));
+
 	assert_rpm_wakelock_held(dev_priv);
 	pm_runtime_get_noresume(kdev);
 
@@ -3461,7 +3484,7 @@ void intel_runtime_pm_put(struct drm_i915_private *dev_priv)
 	struct device *kdev = &pdev->dev;
 
 	assert_rpm_wakelock_held(dev_priv);
-	atomic_dec(&dev_priv->runtime_pm.wakeref_count);
+	rpm_release(&dev_priv->runtime_pm);
 
 	pm_runtime_mark_last_busy(kdev);
 	pm_runtime_put_autosuspend(kdev);
-- 
2.18.0.rc2