PM-runtime: Add new interface to get accounted time

Some drivers (like i915/drm) needs to get the accounted suspended time.
pm_runtime_suspended_time() will return the suspended accounted time
in ns unit.
Reviewed-by: NUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: NVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/runtime.c

@@ -88,6 +88,21 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status)
 	dev->power.runtime_status = status;
 }
 
+u64 pm_runtime_suspended_time(struct device *dev)
+{
+	unsigned long flags, time;
+
+	spin_lock_irqsave(&dev->power.lock, flags);
+
+	update_pm_runtime_accounting(dev);
+	time = dev->power.suspended_jiffies;
+
+	spin_unlock_irqrestore(&dev->power.lock, flags);
+
+	return jiffies_to_nsecs(time);
+}
+EXPORT_SYMBOL_GPL(pm_runtime_suspended_time);
+
 /**
  * pm_runtime_deactivate_timer - Deactivate given device's suspend timer.
  * @dev: Device to handle.

include/linux/pm_runtime.h

@@ -113,6 +113,8 @@ static inline bool pm_runtime_is_irq_safe(struct device *dev)
 	return dev->power.irq_safe;
 }
 
+extern u64 pm_runtime_suspended_time(struct device *dev);
+
 #else /* !CONFIG_PM */
 
 static inline bool queue_pm_work(struct work_struct *work) { return false; }