PM / Runtime: Add new helper function: pm_runtime_active()

This boolean function simply returns whether or not the runtime
status of the device is 'active'. The typical scenario is driver
calls pm_runtime_get firstly, then check pm_runtime_active in
atomic environment.

Also add entry to Documentation/power/runtime.txt

Signed-off-by: Yanmin Zhang <yanmin.zhang@intel.com>
Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/power/runtime_pm.txt

@@ -426,6 +426,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
       'power.runtime_error' is set or 'power.disable_depth' is greater than
       zero)
 
+  bool pm_runtime_active(struct device *dev);
+    - return true if the device's runtime PM status is 'active' or its
+      'power.disable_depth' field is not equal to zero, or false otherwise
+
   bool pm_runtime_suspended(struct device *dev);
     - return true if the device's runtime PM status is 'suspended' and its
       'power.disable_depth' field is equal to zero, or false otherwise

include/linux/pm_runtime.h

@@ -80,6 +80,12 @@ static inline bool pm_runtime_suspended(struct device *dev)
 		&& !dev->power.disable_depth;
 }
 
+static inline bool pm_runtime_active(struct device *dev)
+{
+	return dev->power.runtime_status == RPM_ACTIVE
+		|| dev->power.disable_depth;
+}
+
 static inline bool pm_runtime_status_suspended(struct device *dev)
 {
 	return dev->power.runtime_status == RPM_SUSPENDED;
@@ -132,6 +138,7 @@ static inline void pm_runtime_put_noidle(struct device *dev) {}
 static inline bool device_run_wake(struct device *dev) { return false; }
 static inline void device_set_run_wake(struct device *dev, bool enable) {}
 static inline bool pm_runtime_suspended(struct device *dev) { return false; }
+static inline bool pm_runtime_active(struct device *dev) { return true; }
 static inline bool pm_runtime_status_suspended(struct device *dev) { return false; }
 static inline bool pm_runtime_enabled(struct device *dev) { return false; }