drm/i915: Markup paired operations on display power domains

The majority of runtime-pm operations are bounded and scoped within a
function; these are easy to verify that the wakeref are handled
correctly. We can employ the compiler to help us, and reduce the number
of wakerefs tracked when debugging, by passing around cookies provided
by the various rpm_get functions to their rpm_put counterpart. This
makes the pairing explicit, and given the required wakeref cookie the
compiler can verify that we pass an initialised value to the rpm_put
(quite handy for double checking error paths).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190114142129.24398-16-chris@chris-wilson.co.uk

1 files changed, 46 insertions, 25 deletions

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index c29577d7a35a..6aeceab37000 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -1855,18 +1855,19 @@ __intel_display_power_get_domain(struct drm_i915_private *dev_priv,
  * Any power domain reference obtained by this function must have a symmetric
  * call to intel_display_power_put() to release the reference again.
  */
-void intel_display_power_get(struct drm_i915_private *dev_priv,
-			     enum intel_display_power_domain domain)
+intel_wakeref_t intel_display_power_get(struct drm_i915_private *dev_priv,
+					enum intel_display_power_domain domain)
 {
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
-
-	intel_runtime_pm_get(dev_priv);
+	intel_wakeref_t wakeref = intel_runtime_pm_get(dev_priv);
 
 	mutex_lock(&power_domains->lock);
 
 	__intel_display_power_get_domain(dev_priv, domain);
 
 	mutex_unlock(&power_domains->lock);
+
+	return wakeref;
 }
 
 /**
@@ -1881,13 +1882,16 @@ void intel_display_power_get(struct drm_i915_private *dev_priv,
  * Any power domain reference obtained by this function must have a symmetric
  * call to intel_display_power_put() to release the reference again.
  */
-bool intel_display_power_get_if_enabled(struct drm_i915_private *dev_priv,
-					enum intel_display_power_domain domain)
+intel_wakeref_t
+intel_display_power_get_if_enabled(struct drm_i915_private *dev_priv,
+				   enum intel_display_power_domain domain)
 {
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
+	intel_wakeref_t wakeref;
 	bool is_enabled;
 
-	if (!intel_runtime_pm_get_if_in_use(dev_priv))
+	wakeref = intel_runtime_pm_get_if_in_use(dev_priv);
+	if (!wakeref)
 		return false;
 
 	mutex_lock(&power_domains->lock);
@@ -1901,23 +1905,16 @@ bool intel_display_power_get_if_enabled(struct drm_i915_private *dev_priv,
 
 	mutex_unlock(&power_domains->lock);
 
-	if (!is_enabled)
-		intel_runtime_pm_put_unchecked(dev_priv);
+	if (!is_enabled) {
+		intel_runtime_pm_put(dev_priv, wakeref);
+		wakeref = 0;
+	}
 
-	return is_enabled;
+	return wakeref;
 }
 
-/**
- * intel_display_power_put - release a power domain reference
- * @dev_priv: i915 device instance
- * @domain: power domain to reference
- *
- * This function drops the power domain reference obtained by
- * intel_display_power_get() and might power down the corresponding hardware
- * block right away if this is the last reference.
- */
-void intel_display_power_put(struct drm_i915_private *dev_priv,
-			     enum intel_display_power_domain domain)
+static void __intel_display_power_put(struct drm_i915_private *dev_priv,
+				      enum intel_display_power_domain domain)
 {
 	struct i915_power_domains *power_domains;
 	struct i915_power_well *power_well;
@@ -1935,10 +1932,34 @@ void intel_display_power_put(struct drm_i915_private *dev_priv,
 		intel_power_well_put(dev_priv, power_well);
 
 	mutex_unlock(&power_domains->lock);
+}
 
+/**
+ * intel_display_power_put - release a power domain reference
+ * @dev_priv: i915 device instance
+ * @domain: power domain to reference
+ *
+ * This function drops the power domain reference obtained by
+ * intel_display_power_get() and might power down the corresponding hardware
+ * block right away if this is the last reference.
+ */
+void intel_display_power_put_unchecked(struct drm_i915_private *dev_priv,
+				       enum intel_display_power_domain domain)
+{
+	__intel_display_power_put(dev_priv, domain);
 	intel_runtime_pm_put_unchecked(dev_priv);
 }
 
+#if IS_ENABLED(CONFIG_DRM_I915_DEBUG_RUNTIME_PM)
+void intel_display_power_put(struct drm_i915_private *dev_priv,
+			     enum intel_display_power_domain domain,
+			     intel_wakeref_t wakeref)
+{
+	__intel_display_power_put(dev_priv, domain);
+	intel_runtime_pm_put(dev_priv, wakeref);
+}
+#endif
+
 #define I830_PIPES_POWER_DOMAINS (		\
 	BIT_ULL(POWER_DOMAIN_PIPE_A) |		\
 	BIT_ULL(POWER_DOMAIN_PIPE_B) |		\
@@ -4048,7 +4069,7 @@ void intel_power_domains_fini_hw(struct drm_i915_private *dev_priv)
 
 	/* Remove the refcount we took to keep power well support disabled. */
 	if (!i915_modparams.disable_power_well)
-		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
+		intel_display_power_put_unchecked(dev_priv, POWER_DOMAIN_INIT);
 
 	intel_power_domains_verify_state(dev_priv);
 }
@@ -4067,7 +4088,7 @@ void intel_power_domains_fini_hw(struct drm_i915_private *dev_priv)
  */
 void intel_power_domains_enable(struct drm_i915_private *dev_priv)
 {
-	intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
+	intel_display_power_put_unchecked(dev_priv, POWER_DOMAIN_INIT);
 
 	intel_power_domains_verify_state(dev_priv);
 }
@@ -4102,7 +4123,7 @@ void intel_power_domains_suspend(struct drm_i915_private *dev_priv,
 {
 	struct i915_power_domains *power_domains = &dev_priv->power_domains;
 
-	intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
+	intel_display_power_put_unchecked(dev_priv, POWER_DOMAIN_INIT);
 
 	/*
 	 * In case of suspend-to-idle (aka S0ix) on a DMC platform without DC9
@@ -4123,7 +4144,7 @@ void intel_power_domains_suspend(struct drm_i915_private *dev_priv,
 	 * power wells if power domains must be deinitialized for suspend.
 	 */
 	if (!i915_modparams.disable_power_well) {
-		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
+		intel_display_power_put_unchecked(dev_priv, POWER_DOMAIN_INIT);
 		intel_power_domains_verify_state(dev_priv);
 	}