[Intel-gfx] [PATCH 3/4] drm/i915: make assert_device_not_suspended more precise

[Imre Deak]

Atm, we assert that the device is not suspended after the point when the
HW is truly put to a suspended state. This is fine, but we can catch
more problems if we check the RPM refcount. After that one drops to zero
we shouldn't access the HW any more, although the actual suspend may be
delayed. The only complication is that we want to avoid asserts while
the suspend handler itself is running, so add a flag to handle this
case.

This caught additional WARNs from the atomic path, those will be fixed
as a follow-up.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.c         |  5 +++++
 drivers/gpu/drm/i915/i915_drv.h         |  5 +++++
 drivers/gpu/drm/i915/intel_runtime_pm.c | 14 ++++++++++++--
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 77d183d..caeb218 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1494,6 +1494,9 @@ static int intel_runtime_suspend(struct device *device)
 
 		return -EAGAIN;
 	}
+
+	dev_priv->pm.disable_suspended_assert = true;
+
 	/*
 	 * We are safe here against re-faults, since the fault handler takes
 	 * an RPM reference.
@@ -1518,6 +1521,8 @@ static int intel_runtime_suspend(struct device *device)
 	intel_uncore_forcewake_reset(dev, false);
 	dev_priv->pm.suspended = true;
 
+	dev_priv->pm.disable_suspended_assert = false;
+
 	/*
 	 * FIXME: We really should find a document that references the arguments
 	 * used below!
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5628c5a..43fd341 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1599,6 +1599,11 @@ struct skl_wm_level {
  * For more, read the Documentation/power/runtime_pm.txt.
  */
 struct i915_runtime_pm {
+	/*
+	 * Used for the duration of runtime suspend to avoid false device
+	 * suspended asserts.
+	 */
+	bool disable_suspended_assert;
 	bool suspended;
 	bool irqs_enabled;
 };
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 4d39b3c..2e2083c 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -2120,8 +2120,18 @@ void intel_power_domains_init_hw(struct drm_i915_private *dev_priv, bool resume)
 
 void assert_device_not_suspended(struct drm_i915_private *dev_priv)
 {
-	WARN_ONCE(HAS_RUNTIME_PM(dev_priv->dev) && dev_priv->pm.suspended,
-		  "Device suspended\n");
+	int rpm_usage;
+
+	if (!HAS_RUNTIME_PM(dev_priv) || dev_priv->pm.disable_suspended_assert)
+		return;
+
+#ifdef CONFIG_PM
+	rpm_usage = atomic_read(&dev_priv->dev->dev->power.usage_count);
+#else
+	rpm_usage = 1;
+#endif
+
+	WARN_ONCE(dev_priv->pm.suspended || !rpm_usage, "Device suspended\n");
 }
 
 /**
-- 
2.5.0