Lines Matching +full:pm +full:- +full:bus
5 (C) 2009-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
14 Support for runtime power management (runtime PM) of I/O devices is provided
15 at the power management core (PM core) level by means of:
17 * The power management workqueue pm_wq in which bus types and device drivers can
18 put their PM-related work items. It is strongly recommended that pm_wq be
19 used for queuing all work items related to runtime PM, because this allows
20 them to be synchronized with system-wide power transitions (suspend to RAM,
24 * A number of runtime PM fields in the 'power' member of 'struct device' (which
25 is of the type 'struct dev_pm_info', defined in include/linux/pm.h) that can
26 be used for synchronizing runtime PM operations with one another.
28 * Three device runtime PM callbacks in 'struct dev_pm_ops' (defined in
29 include/linux/pm.h).
32 used for carrying out runtime PM operations in such a way that the
33 synchronization between them is taken care of by the PM core. Bus types and
36 The runtime PM callbacks present in 'struct dev_pm_ops', the device runtime PM
38 runtime PM are described below.
40 2. Device Runtime PM Callbacks
43 There are three device runtime PM callbacks defined in 'struct dev_pm_ops'::
53 The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks
54 are executed by the PM core for the device's subsystem that may be either of
57 1. PM domain of the device, if the device's PM domain object, dev->pm_domain,
60 2. Device type of the device, if both dev->type and dev->type->pm are present.
62 3. Device class of the device, if both dev->class and dev->class->pm are
65 4. Bus type of the device, if both dev->bus and dev->bus->pm are present.
68 callback, the PM core will invoke the corresponding driver callback stored in
69 dev->driver->pm directly (if present).
71 The PM core always checks which callback to use in the order given above, so the
72 priority order of callbacks from high to low is: PM domain, device type, class
73 and bus type. Moreover, the high-priority one will always take precedence over
74 a low-priority one. The PM domain, bus type, device type and class callbacks
75 are referred to as subsystem-level callbacks in what follows.
79 the PM core that it is safe to run the ->runtime_suspend(), ->runtime_resume()
80 and ->runtime_idle() callbacks for the given device in atomic context with
86 The subsystem-level suspend callback, if present, is _entirely_ _responsible_
88 include executing the device driver's own ->runtime_suspend() callback (from the
89 PM core's point of view it is not necessary to implement a ->runtime_suspend()
90 callback in a device driver as long as the subsystem-level suspend callback
93 * Once the subsystem-level suspend callback (or the driver suspend callback,
94 if invoked directly) has completed successfully for the given device, the PM
99 PM status of a device after successful execution of the suspend callback is
102 * If the suspend callback returns -EBUSY or -EAGAIN, the device's runtime PM
106 * If the suspend callback returns an error code different from -EBUSY and
107 -EAGAIN, the PM core regards this as a fatal error and will refuse to run
109 is directly set to either 'active', or 'suspended' (the PM core provides
115 device, then ->runtime_suspend() should return -EBUSY. On the other hand, if
117 low-power state during the execution of the suspend callback, it is expected
119 should be enabled for all input devices put into low-power states at run time.
121 The subsystem-level resume callback, if present, is **entirely responsible** for
123 include executing the device driver's own ->runtime_resume() callback (from the
124 PM core's point of view it is not necessary to implement a ->runtime_resume()
125 callback in a device driver as long as the subsystem-level resume callback knows
128 * Once the subsystem-level resume callback (or the driver resume callback, if
129 invoked directly) has completed successfully, the PM core regards the device
131 I/O operations as needed. The runtime PM status of the device is then
134 * If the resume callback returns an error code, the PM core regards this as a
137 'suspended' (by means of special helper functions provided by the PM core
140 The idle callback (a subsystem-level one, if present, or the driver one) is
141 executed by the PM core whenever the device appears to be idle, which is
142 indicated to the PM core by two counters, the device's usage counter and the
146 the PM core and it turns out to be equal to zero, the other counter is
147 checked. If that counter also is equal to zero, the PM core executes the
155 0, then the PM core will attempt to carry out a runtime suspend of the device,
160 started a delayed suspend), the routine must return a non-zero value. Negative
161 error return codes are ignored by the PM core.
163 The helper functions provided by the PM core, described in Section 4, guarantee
164 that the following constraints are met with respect to runtime PM callbacks for
168 ->runtime_suspend() in parallel with ->runtime_resume() or with another
169 instance of ->runtime_suspend() for the same device) with the exception that
170 ->runtime_suspend() or ->runtime_resume() can be executed in parallel with
171 ->runtime_idle() (although ->runtime_idle() will not be started while any
174 (2) ->runtime_idle() and ->runtime_suspend() can only be executed for 'active'
175 devices (i.e. the PM core will only execute ->runtime_idle() or
176 ->runtime_suspend() for the devices the runtime PM status of which is
179 (3) ->runtime_idle() and ->runtime_suspend() can only be executed for a device
184 (4) ->runtime_resume() can only be executed for 'suspended' devices (i.e. the
185 PM core will only execute ->runtime_resume() for the devices the runtime
186 PM status of which is 'suspended').
188 Additionally, the helper functions provided by the PM core obey the following
191 * If ->runtime_suspend() is about to be executed or there's a pending request
192 to execute it, ->runtime_idle() will not be executed for the same device.
194 * A request to execute or to schedule the execution of ->runtime_suspend()
195 will cancel any pending requests to execute ->runtime_idle() for the same
198 * If ->runtime_resume() is about to be executed or there's a pending request
201 * A request to execute ->runtime_resume() will cancel any pending or
205 3. Runtime PM Device Fields
208 The following device runtime PM fields are present in 'struct dev_pm_info', as
209 defined in include/linux/pm.h:
212 - timer used for scheduling (delayed) suspend and autosuspend requests
215 - timer expiration time, in jiffies (if this is different from zero, the
220 - work structure used for queuing up requests (i.e. work items in pm_wq)
223 - wait queue used if any of the helper functions needs to wait for another
227 - lock used for synchronization
230 - the usage counter of the device
233 - the count of 'active' children of the device
236 - if set, the value of child_count is ignored (but still updated)
239 - used for disabling the helper functions (they work normally if this is
240 equal to zero); the initial value of it is 1 (i.e. runtime PM is
244 - if set, there was a fatal error (one of the callbacks returned error code
250 - if set, ->runtime_idle() is being executed
253 - if set, there's a pending request (i.e. a work item queued up into pm_wq)
256 - type of request that's pending (valid if request_pending is set)
259 - set if ->runtime_resume() is about to be run while ->runtime_suspend() is
264 - the runtime PM status of the device; this field's initial value is
266 PM core as 'suspended', regardless of its real hardware status
269 - the last runtime PM status of the device captured before disabling runtime
270 PM for it (invalid initially and when disable_depth is 0)
273 - if set, indicates that the user space has allowed the device driver to
279 - indicates that the device does not use the runtime PM callbacks (see
284 - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
288 - indicates that the device's driver supports delayed autosuspend (see
293 - indicates that the PM core should attempt to carry out an autosuspend
297 - the delay time (in milliseconds) to be used for autosuspend
300 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
306 4. Runtime PM Device Helper Functions
309 The following runtime PM helper functions are defined in
313 - initialize the device runtime PM fields in 'struct dev_pm_info'
316 - make sure that the runtime PM of the device will be disabled after
320 - execute the subsystem-level idle callback for the device; returns an
321 error code on failure, where -EINPROGRESS means that ->runtime_idle() is
326 - execute the subsystem-level suspend callback for the device; returns 0 on
327 success, 1 if the device's runtime PM status was already 'suspended', or
328 error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
329 to suspend the device again in future and -EACCES means that
333 - same as pm_runtime_suspend() except that the autosuspend delay is taken
339 - execute the subsystem-level resume callback for the device; returns 0 on
340 success, 1 if the device's runtime PM status is already 'active' (also if
342 changing from 0 to 1) or error code on failure, where -EAGAIN means it may
344 'power.runtime_error' should be checked additionally, and -EACCES means
349 - run pm_runtime_resume(dev) and if successful, increment the device's
353 - submit a request to execute the subsystem-level idle callback for the
358 - schedule the execution of the subsystem-level suspend callback for the
363 - schedule the execution of the subsystem-level suspend callback for the
366 item is queued up immediately); returns 0 on success, 1 if the device's PM
369 ->runtime_suspend() is already scheduled and not yet expired, the new
373 - submit a request to execute the subsystem-level resume callback for the
375 success, 1 if the device's runtime PM status was already 'active', or
379 - increment the device's usage counter
382 - increment the device's usage counter, run pm_request_resume(dev) and
386 - increment the device's usage counter, run pm_runtime_resume(dev) and
394 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
395 runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
400 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
401 runtime PM status is RPM_ACTIVE, increment the counter and
405 - decrement the device's usage counter
408 - decrement the device's usage counter; if the result is 0 then run
412 - does the same as __pm_runtime_put_autosuspend() for now, but in the
416 - decrement the device's usage counter; if the result is 0 then run
420 - decrement the device's usage counter; if the result is 0 then run
424 - decrement the device's usage counter; if the result is 0 then run
428 - decrement the device's usage counter; if the result is 0 then run
432 - decrement the device's 'power.disable_depth' field; if that field is equal
433 to zero, the runtime PM helper functions can execute subsystem-level
437 - increment the device's 'power.disable_depth' field (if the value of that
438 field was previously zero, this prevents subsystem-level runtime PM
440 pending runtime PM operations on the device are either completed or
442 necessary to execute the subsystem-level resume callback for the device
446 - check if there's a resume request pending for the device and resume it
447 (synchronously) in that case, cancel any other pending runtime PM requests
448 regarding it and wait for all runtime PM operations on it in progress to
450 necessary to execute the subsystem-level resume callback for the device to
454 - set/unset the power.ignore_children flag of the device
457 - clear the device's 'power.runtime_error' flag, set the device's runtime
458 PM status to 'active' and update its parent's counter of 'active'
465 - clear the device's 'power.runtime_error' flag, set the device's runtime
466 PM status to 'suspended' and update its parent's counter of 'active'
472 - return true if the device's runtime PM status is 'active' or its
476 - return true if the device's runtime PM status is 'suspended' and its
480 - return true if the device's runtime PM status is 'suspended'
483 - set the power.runtime_auto flag for the device and decrease its usage
488 - unset the power.runtime_auto flag for the device and increase its usage
493 - set the power.no_callbacks flag for the device and remove the runtime
494 PM attributes from /sys/devices/.../power (or prevent them from being
498 - set the power.irq_safe flag for the device, causing the runtime-PM
502 - return true if power.irq_safe flag was set for the device, causing
503 the runtime-PM callbacks to be invoked with interrupts off
506 - set the power.last_busy field to the current time
509 - set the power.use_autosuspend flag, enabling autosuspend delays; call
514 - clear the power.use_autosuspend flag, disabling autosuspend delays;
519 - set the power.autosuspend_delay value to 'delay' (expressed in
528 - calculate the time when the current autosuspend delay period will expire,
537 - pm_request_idle()
538 - pm_request_autosuspend()
539 - pm_schedule_suspend()
540 - pm_request_resume()
541 - pm_runtime_get_noresume()
542 - pm_runtime_get()
543 - pm_runtime_put_noidle()
544 - pm_runtime_put()
545 - pm_runtime_put_autosuspend()
546 - __pm_runtime_put_autosuspend()
547 - pm_runtime_enable()
548 - pm_suspend_ignore_children()
549 - pm_runtime_set_active()
550 - pm_runtime_set_suspended()
551 - pm_runtime_suspended()
552 - pm_runtime_mark_last_busy()
553 - pm_runtime_autosuspend_expiration()
558 - pm_runtime_idle()
559 - pm_runtime_suspend()
560 - pm_runtime_autosuspend()
561 - pm_runtime_resume()
562 - pm_runtime_get_sync()
563 - pm_runtime_put_sync()
564 - pm_runtime_put_sync_suspend()
565 - pm_runtime_put_sync_autosuspend()
567 5. Runtime PM Initialization, Device Probing and Removal
570 Initially, the runtime PM is disabled for all devices, which means that the
571 majority of the runtime PM helper functions described in Section 4 will return
572 -EAGAIN until pm_runtime_enable() is called for the device.
574 In addition to that, the initial runtime PM status of all devices is
577 runtime PM status must be changed to 'active', with the help of
580 However, if the device has a parent and the parent's runtime PM is enabled,
583 parent won't be able to suspend at run time, using the PM core's helper
585 runtime PM is still disabled (i.e. pm_runtime_enable() hasn't been called for
588 should be called for it too as soon as reasonably possible or its runtime PM
592 If the default initial runtime PM status of the device (i.e. 'suspended')
593 reflects the actual state of the device, its bus type's or its driver's
594 ->probe() callback will likely need to wake it up using one of the PM core's
596 should be used. Of course, for this purpose the device's runtime PM has to be
605 It may be desirable to suspend the device once ->probe() has finished.
607 request to execute the subsystem-level idle callback for the device at that
609 update the last busy mark before returning from ->probe().
611 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
614 runtime PM functionality. It does so by calling pm_runtime_get_sync() before
619 To allow bus types and drivers to put devices into the suspended state by
620 calling pm_runtime_suspend() from their ->remove() routines, the driver core
622 notifications in __device_release_driver(). This requires bus types and
623 drivers to make their ->remove() callbacks avoid races with runtime PM directly,
627 Drivers in ->remove() callback should undo the runtime PM changes done
628 in ->probe(). Usually this means calling pm_runtime_disable(),
636 Namely, during the initialization the driver can make sure that the runtime PM
643 6. Runtime PM and System Sleep
646 Runtime PM and system sleep (i.e., system suspend and hibernation, also known
647 as suspend-to-RAM and suspend-to-disk) interact with each other in a couple of
651 The device may have different wake-up settings for runtime PM and system sleep.
652 For example, remote wake-up may be enabled for runtime suspend but disallowed
654 the subsystem-level system suspend callback is responsible for changing the
655 device's wake-up setting (it may leave that to the device driver's system
664 * The device might need to switch power levels, wake-up settings, etc.
666 * Remote wake-up events might have been lost by the firmware.
680 brought back to full power during resume, then its runtime PM status will have
681 to be updated to reflect the actual post-system sleep status. The way to do
684 - pm_runtime_disable(dev);
685 - pm_runtime_set_active(dev);
686 - pm_runtime_enable(dev);
688 The PM core always increments the runtime usage counter before calling the
689 ->suspend() callback and decrements it after calling the ->resume() callback.
690 Hence disabling runtime PM temporarily like this will not cause any runtime
692 following the return of the ->resume() callback, the ->runtime_idle() callback
696 or hardware operation. Instead, all hardware components are put into low-power
707 To this end, the PM core provides a mechanism allowing some coordination between
709 callback returns a positive number for a device, that indicates to the PM core
710 that the device appears to be runtime-suspended and its state is fine, so it
712 left in runtime suspend. If that happens, the PM core will not execute any
716 related to hibernation (see Documentation/driver-api/pm/devices.rst for more
719 The PM core does its best to reduce the probability of race conditions between
720 the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
724 right before executing the subsystem-level .prepare() callback for it and
726 subsystem-level .suspend() callback for it. In addition to that the PM core
728 device right before executing the subsystem-level .suspend_late() callback
732 every device right after executing the subsystem-level .resume_early()
733 callback and right after executing the subsystem-level .complete() callback
740 management callbacks provided by the PM core, defined in
744 - invoke the ->runtime_suspend() callback provided by the driver of this
748 - invoke the ->runtime_resume() callback provided by the driver of this
752 - if the device has not been suspended at run time, invoke the ->suspend()
757 - if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
762 - invoke the ->resume() callback provided by the driver of this device and,
763 if successful, change the device's runtime PM status to 'active'
766 - invoke the ->resume_noirq() callback provided by the driver of this device
769 - if the device has not been suspended at run time, invoke the ->freeze()
774 - if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
779 - if the device has not been suspended at run time, invoke the ->thaw()
784 - if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
789 - if the device has not been suspended at run time, invoke the ->poweroff()
794 - if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
799 - invoke the ->restore() callback provided by the driver of this device and,
800 if successful, change the device's runtime PM status to 'active'
803 - invoke the ->restore_noirq() callback provided by the device's driver
805 These functions are the defaults used by the PM core if a subsystem doesn't
806 provide its own callbacks for ->runtime_idle(), ->runtime_suspend(),
807 ->runtime_resume(), ->suspend(), ->suspend_noirq(), ->resume(),
808 ->resume_noirq(), ->freeze(), ->freeze_noirq(), ->thaw(), ->thaw_noirq(),
809 ->poweroff(), ->poweroff_noirq(), ->restore(), ->restore_noirq() in the
810 subsystem-level dev_pm_ops structure.
818 8. "No-Callback" Devices
821 Some "devices" are only logical sub-devices of their parent and cannot be
822 power-managed on their own. (The prototype example is a USB interface. Entire
823 USB devices can go into low-power mode or send wake-up requests, but neither is
825 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
826 and ->runtime_resume() would always return 0 without doing anything else and
827 ->runtime_idle() would always call pm_runtime_suspend().
829 Subsystems can tell the PM core about these devices by calling
833 prevent the non-debugging runtime PM sysfs attributes from being created.
835 When power.no_callbacks is set, the PM core will not invoke the
836 ->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks.
840 As a consequence, the PM core will never directly inform the device's subsystem
847 the runtime PM callbacks needs to be implemented, a platform dependent PM
850 in subsystems/drivers, the PM core allows runtime PM callbacks to be
851 unassigned. More precisely, if a callback pointer is NULL, the PM core will act
854 9. Autosuspend, or automatically-delayed suspends
858 A device should be put in a low-power state only when there's some reason to
863 the heuristic ends up being non-optimal, it will still prevent devices from
864 "bouncing" too rapidly between low-power and full-power states.
868 the appropriate PM routines); rather it means that runtime suspends will
882 instead of the non-autosuspend counterparts::
889 Drivers may also continue to use the non-autosuspend helper functions; they
895 autosuspend delay time has expired. If the ->runtime_suspend() callback
896 returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
898 pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
899 autosuspend. The ->runtime_suspend() callback can't do this rescheduling
904 However such use inevitably involves races, because the PM core can't
905 synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
907 Here is a schematic pseudo-code example::
911 lock(&foo->private_lock);
913 if (foo->num_pending_requests++ == 0)
914 pm_runtime_get(&foo->dev);
915 if (!foo->is_suspended)
917 unlock(&foo->private_lock);
922 lock(&foo->private_lock);
923 if (--foo->num_pending_requests == 0) {
924 pm_runtime_mark_last_busy(&foo->dev);
925 __pm_runtime_put_autosuspend(&foo->dev);
929 unlock(&foo->private_lock);
938 lock(&foo->private_lock);
939 if (foo->num_pending_requests > 0) {
940 ret = -EBUSY;
943 foo->is_suspended = 1;
945 unlock(&foo->private_lock);
953 lock(&foo->private_lock);
955 foo->is_suspended = 0;
956 pm_runtime_mark_last_busy(&foo->dev);
957 if (foo->num_pending_requests > 0)
959 unlock(&foo->private_lock);
971 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
974 -EAGAIN.