(C) 2009-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
(C) 2010 Alan Stern <stern@rowland.harvard.edu>
+(C) 2014 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com>
1. Introduction
bool pm_runtime_status_suspended(struct device *dev);
- return true if the device's runtime PM status is 'suspended'
+ bool pm_runtime_suspended_if_enabled(struct device *dev);
+ - return true if the device's runtime PM status is 'suspended' and its
+ 'power.disable_depth' field is equal to 1
+
void pm_runtime_allow(struct device *dev);
- set the power.runtime_auto flag for the device and decrease its usage
counter (used by the /sys/devices/.../power/control interface to
be more efficient to leave the devices that had been suspended before the system
suspend began in the suspended state.
+To this end, the PM core provides a mechanism allowing some coordination between
+different levels of device hierarchy. Namely, if a system suspend .prepare()
+callback returns a positive number for a device, that indicates to the PM core
+that the device appears to be runtime-suspended and its state is fine, so it
+may be left in runtime suspend provided that all of its descendants are also
+left in runtime suspend. If that happens, the PM core will not execute any
+system suspend and resume callbacks for all of those devices, except for the
+complete callback, which is then entirely responsible for handling the device
+as appropriate. This only applies to system suspend transitions that are not
+related to hibernation (see Documentation/power/devices.txt for more
+information).
+
The PM core does its best to reduce the probability of race conditions between
the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
out the following operations:
- * During system suspend it calls pm_runtime_get_noresume() and
- pm_runtime_barrier() for every device right before executing the
- subsystem-level .suspend() callback for it. In addition to that it calls
- __pm_runtime_disable() with 'false' as the second argument for every device
- right before executing the subsystem-level .suspend_late() callback for it.
-
- * During system resume it calls pm_runtime_enable() and pm_runtime_put()
- for every device right after executing the subsystem-level .resume_early()
- callback and right after executing the subsystem-level .resume() callback
+ * During system suspend pm_runtime_get_noresume() is called for every device
+ right before executing the subsystem-level .prepare() callback for it and
+ pm_runtime_barrier() is called for every device right before executing the
+ subsystem-level .suspend() callback for it. In addition to that the PM core
+ calls __pm_runtime_disable() with 'false' as the second argument for every
+ device right before executing the subsystem-level .suspend_late() callback
+ for it.
+
+ * During system resume pm_runtime_enable() and pm_runtime_put() are called for
+ every device right after executing the subsystem-level .resume_early()
+ callback and right after executing the subsystem-level .complete() callback
for it, respectively.
7. Generic subsystem callbacks