PM: runtime: Convert pm_runtime_blocked() to static inline

The comment in pm_runtime_blocked() is acutally wrong: power.last_status
is not a bit field.  Its data type is an enum and so one can reasonably
assume that partial updates of it will not be observed.

Accordingly, pm_runtime_blocked() can be converted to a static inline
function and the related locking overhead can be eliminated, so long
as it is only used in system suspend/resume code paths because
power.last_status is not expected to be updated concurrently while
that code is running.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/1923449.tdWV9SEqCh@rjwysocki.net

Author: rafaeljw

drivers/base/power/runtime.c

@@ -1560,23 +1560,6 @@ void pm_runtime_enable(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_runtime_enable);
 
-bool pm_runtime_blocked(struct device *dev)
-{
-	bool ret;
-
-	/*
-	 * dev->power.last_status is a bit field, so in case it is updated via
-	 * RMW, read it under the spin lock.
-	 */
-	spin_lock_irq(&dev->power.lock);
-
-	ret = dev->power.last_status == RPM_BLOCKED;
-
-	spin_unlock_irq(&dev->power.lock);
-
-	return ret;
-}
-
 static void pm_runtime_disable_action(void *data)
 {
 	pm_runtime_dont_use_autosuspend(data);

include/linux/pm_runtime.h

@@ -82,7 +82,6 @@ extern bool pm_runtime_block_if_disabled(struct device *dev);
 extern void pm_runtime_unblock(struct device *dev);
 extern void pm_runtime_enable(struct device *dev);
 extern void __pm_runtime_disable(struct device *dev, bool check_resume);
-extern bool pm_runtime_blocked(struct device *dev);
 extern void pm_runtime_allow(struct device *dev);
 extern void pm_runtime_forbid(struct device *dev);
 extern void pm_runtime_no_callbacks(struct device *dev);
@@ -200,6 +199,17 @@ static inline bool pm_runtime_enabled(struct device *dev)
 	return !dev->power.disable_depth;
 }
 
+/**
+ * pm_runtime_blocked - Check if runtime PM enabling is blocked.
+ * @dev: Target device.
+ *
+ * Do not call this function outside system suspend/resume code paths.
+ */
+static inline bool pm_runtime_blocked(struct device *dev)
+{
+	return dev->power.last_status == RPM_BLOCKED;
+}
+
 /**
  * pm_runtime_has_no_callbacks - Check if runtime PM callbacks may be present.
  * @dev: Target device.