Lines Matching +full:suspend +full:- +full:to +full:- +full:idle
5 (C) 2009-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
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,
34 device drivers are encouraged to use these functions.
53 The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks
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.
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.
78 enabled. However, the pm_runtime_irq_safe() helper function can be used to tell
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_
87 for handling the suspend of the device as appropriate, which may, but need not
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
91 knows what to do to handle the device).
93 * Once the subsystem-level suspend callback (or the driver suspend callback,
96 put into a low power state. It is supposed to mean, however, that the
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
113 mechanism allowing the device to request a change of its power state, such as
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
126 what to do to handle the device).
128 * Once the subsystem-level resume callback (or the driver resume callback, if
130 as fully operational, which means that the device _must_ be able to complete
135 fatal error and will refuse to run the helper functions described in Section
136 4 for the device, until its status is directly set to either 'active', or
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
148 idle callback with the device as its argument.
150 The action performed by the idle callback is totally dependent on the subsystem
151 (or driver) in question, but the expected and recommended action is to check
153 suspending the device are satisfied) and to queue up a suspend request for the
154 device in that case. If there is no idle callback, or if the callback returns
155 0, then the PM core will attempt to carry out a runtime suspend of the device,
157 call to pm_runtime_autosuspend(). To prevent this (for example, if the callback
158 routine has started a delayed suspend), the routine must return a non-zero
162 that the following constraints are met with respect to runtime PM callbacks for
165 (1) The callbacks are mutually exclusive (e.g. it is forbidden to execute
166 ->runtime_suspend() in parallel with ->runtime_resume() or with another
167 instance of ->runtime_suspend() for the same device) with the exception that
168 ->runtime_suspend() or ->runtime_resume() can be executed in parallel with
169 ->runtime_idle() (although ->runtime_idle() will not be started while any
172 (2) ->runtime_idle() and ->runtime_suspend() can only be executed for 'active'
173 devices (i.e. the PM core will only execute ->runtime_idle() or
174 ->runtime_suspend() for the devices the runtime PM status of which is
177 (3) ->runtime_idle() and ->runtime_suspend() can only be executed for a device
178 the usage counter of which is equal to zero _and_ either the counter of
179 'active' children of which is equal to zero, or the 'power.ignore_children'
182 (4) ->runtime_resume() can only be executed for 'suspended' devices (i.e. the
183 PM core will only execute ->runtime_resume() for the devices the runtime
189 * If ->runtime_suspend() is about to be executed or there's a pending request
190 to execute it, ->runtime_idle() will not be executed for the same device.
192 * A request to execute or to schedule the execution of ->runtime_suspend()
193 will cancel any pending requests to execute ->runtime_idle() for the same
196 * If ->runtime_resume() is about to be executed or there's a pending request
197 to execute it, the other callbacks will not be executed for the same device.
199 * A request to execute ->runtime_resume() will cancel any pending or
200 scheduled requests to execute the other callbacks for the same device,
210 - timer used for scheduling (delayed) suspend and autosuspend requests
213 - timer expiration time, in jiffies (if this is different from zero, the
218 - work structure used for queuing up requests (i.e. work items in pm_wq)
221 - wait queue used if any of the helper functions needs to wait for another
222 one to complete
225 - lock used for synchronization
228 - the usage counter of the device
231 - the count of 'active' children of the device
234 - if set, the value of child_count is ignored (but still updated)
237 - used for disabling the helper functions (they work normally if this is
238 equal to zero); the initial value of it is 1 (i.e. runtime PM is
242 - if set, there was a fatal error (one of the callbacks returned error code
248 - if set, ->runtime_idle() is being executed
251 - if set, there's a pending request (i.e. a work item queued up into pm_wq)
254 - type of request that's pending (valid if request_pending is set)
257 - set if ->runtime_resume() is about to be run while ->runtime_suspend() is
258 being executed for that device and it is not practical to wait for the
259 suspend to complete; means "start a resume as soon as you've suspended"
262 - the runtime PM status of the device; this field's initial value is
267 - the last runtime PM status of the device captured before disabling runtime
271 - if set, indicates that the user space has allowed the device driver to
277 - indicates that the device does not use the runtime PM callbacks (see
282 - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
286 - indicates that the device's driver supports delayed autosuspend (see
291 - indicates that the PM core should attempt to carry out an autosuspend
292 when the timer expires rather than a normal suspend
295 - the delay time (in milliseconds) to be used for autosuspend
298 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
311 - initialize the device runtime PM fields in 'struct dev_pm_info'
314 - make sure that the runtime PM of the device will be disabled after
318 - execute the subsystem-level idle callback for the device; returns an
319 error code on failure, where -EINPROGRESS means that ->runtime_idle() is
324 - execute the subsystem-level suspend callback for the device; returns 0 on
326 error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
327 to suspend the device again in future and -EACCES means that
331 - same as pm_runtime_suspend() except that a call to
336 - execute the subsystem-level resume callback for the device; returns 0 on
339 changing from 0 to 1) or error code on failure, where -EAGAIN means it may
340 be safe to attempt to resume the device again in future, but
341 'power.runtime_error' should be checked additionally, and -EACCES means
346 - run pm_runtime_resume(dev) and if successful, increment the device's
352 - submit a request to execute the subsystem-level idle callback for the
357 - Call pm_runtime_mark_last_busy() and schedule the execution of the
358 subsystem-level suspend callback for the device when the autosuspend delay
362 - schedule the execution of the subsystem-level suspend callback for the
363 device in future, where 'delay' is the time to wait before queuing up a
364 suspend work item in pm_wq, in milliseconds (if 'delay' is zero, the work
368 ->runtime_suspend() is already scheduled and not yet expired, the new
369 value of 'delay' will be used as the time to wait
372 - submit a request to execute the subsystem-level resume callback for the
378 - increment the device's usage counter
381 - increment the device's usage counter, run pm_request_resume(dev) and
385 - increment the device's usage counter, run pm_runtime_resume(dev) and
389 if its return value is checked by the caller, as this is likely to
393 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
399 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
404 - decrement the device's usage counter
407 - decrement the device's usage counter; if the result is 0 then run
411 - set the power.last_busy field to the current time and decrement 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 - set the power.last_busy field to the current time and decrement the
433 - decrement the device's 'power.disable_depth' field; if that field is equal
434 to zero, the runtime PM helper functions can execute subsystem-level
438 - increment the device's 'power.disable_depth' field (if the value of that
439 field was previously zero, this prevents subsystem-level runtime PM
443 necessary to execute the subsystem-level resume callback for the device
444 to satisfy that request, otherwise 0 is returned
447 - check if there's a resume request pending for the device and resume it
449 regarding it and wait for all runtime PM operations on it in progress to
451 necessary to execute the subsystem-level resume callback for the device to
455 - set/unset the power.ignore_children flag of the device
458 - clear the device's 'power.runtime_error' flag, set the device's runtime
459 PM status to 'active' and update its parent's counter of 'active'
460 children as appropriate (it is only valid to use this function if
466 - clear the device's 'power.runtime_error' flag, set the device's runtime
467 PM status to 'suspended' and update its parent's counter of 'active'
468 children as appropriate (it is only valid to use this function if
473 - return true if the device's runtime PM status is 'active' or its
474 'power.disable_depth' field is not equal to zero, or false otherwise
477 - return true if the device's runtime PM status is 'suspended' and its
478 'power.disable_depth' field is equal to zero, or false otherwise
481 - return true if the device's runtime PM status is 'suspended'
484 - set the power.runtime_auto flag for the device and decrease its usage
485 counter (used by the /sys/devices/.../power/control interface to
486 effectively allow the device to be power managed at run time)
489 - unset the power.runtime_auto flag for the device and increase its usage
490 counter (used by the /sys/devices/.../power/control interface to
494 - set the power.no_callbacks flag for the device and remove the runtime
499 - set the power.irq_safe flag for the device, causing the runtime-PM
500 callbacks to be invoked with interrupts off
503 - return true if power.irq_safe flag was set for the device, causing
504 the runtime-PM callbacks to be invoked with interrupts off
507 - set the power.last_busy field to the current time
510 - set the power.use_autosuspend flag, enabling autosuspend delays; call
515 - clear the power.use_autosuspend flag, disabling autosuspend delays;
520 - set the power.autosuspend_delay value to 'delay' (expressed in
525 changed to or from a negative value; if power.use_autosuspend is clear,
529 - calculate the time when the current autosuspend delay period will expire,
531 is 1000 ms or larger then the expiration time is rounded up to the
536 It is safe to execute the following helper functions from interrupt context:
538 - pm_request_idle()
539 - pm_request_autosuspend()
540 - pm_schedule_suspend()
541 - pm_request_resume()
542 - pm_runtime_get_noresume()
543 - pm_runtime_get()
544 - pm_runtime_put_noidle()
545 - pm_runtime_put()
546 - pm_runtime_put_autosuspend()
547 - __pm_runtime_put_autosuspend()
548 - pm_runtime_enable()
549 - pm_suspend_ignore_children()
550 - pm_runtime_set_active()
551 - pm_runtime_set_suspended()
552 - pm_runtime_suspended()
553 - pm_runtime_mark_last_busy()
554 - pm_runtime_autosuspend_expiration()
559 - pm_runtime_idle()
560 - pm_runtime_suspend()
561 - pm_runtime_autosuspend()
562 - pm_runtime_resume()
563 - pm_runtime_get_sync()
564 - pm_runtime_put_sync()
565 - pm_runtime_put_sync_suspend()
566 - pm_runtime_put_sync_autosuspend()
573 -EAGAIN until pm_runtime_enable() is called for the device.
575 In addition to that, the initial runtime PM status of all devices is
577 Thus, if the device is initially active (i.e. it is able to process I/O), its
578 runtime PM status must be changed to 'active', with the help of
584 parent won't be able to suspend at run time, using the PM core's helper
590 status should be changed back to 'suspended' with the help of
595 ->probe() callback will likely need to wake it up using one of the PM core's
597 should be used. Of course, for this purpose the device's runtime PM has to be
603 appropriate to ensure that the device is not put back to sleep during the
606 It may be desirable to suspend the device once ->probe() has finished.
607 Therefore the driver core uses the asynchronous pm_request_idle() to submit a
608 request to execute the subsystem-level idle callback for the device at that
609 time. A driver that makes use of the runtime autosuspend feature may want to
610 update the last busy mark before returning from ->probe().
614 notifier is used by some subsystems to carry out operations affecting the
620 To allow bus types and drivers to put devices into the suspended state by
621 calling pm_runtime_suspend() from their ->remove() routines, the driver core
624 drivers to make their ->remove() callbacks avoid races with runtime PM directly,
628 Drivers in ->remove() callback should undo the runtime PM changes done
629 in ->probe(). Usually this means calling pm_runtime_disable(),
632 The user space can effectively disallow the driver of the device to power manage
634 attribute to "on", which causes pm_runtime_forbid() to be called. In principle,
635 this mechanism may also be used by the driver to effectively turn off the
640 value of /sys/devices/.../power/control to "auto" to allow the driver to power
647 Runtime PM and system sleep (i.e., system suspend and hibernation, also known
648 as suspend-to-RAM and suspend-to-disk) interact with each other in a couple of
652 The device may have different wake-up settings for runtime PM and system sleep.
653 For example, remote wake-up may be enabled for runtime suspend but disallowed
655 the subsystem-level system suspend callback is responsible for changing the
656 device's wake-up setting (it may leave that to the device driver's system
657 suspend routine). It may be necessary to resume the device and suspend it again
658 in order to do so. The same is true if the driver uses different power levels
659 or other settings for runtime suspend and system sleep.
661 During system resume, the simplest approach is to bring all devices back to full
662 power, even if they had been suspended before the system suspend began. There
665 * The device might need to switch power levels, wake-up settings, etc.
667 * Remote wake-up events might have been lost by the firmware.
669 * The device's children may need the device to be at full power in order
670 to resume themselves.
675 * The device might need to be reset.
680 If the device had been suspended before the system suspend began and it's
681 brought back to full power during resume, then its runtime PM status will have
682 to be updated to reflect the actual post-system sleep status. The way to do
685 - pm_runtime_disable(dev);
686 - pm_runtime_set_active(dev);
687 - pm_runtime_enable(dev);
690 ->suspend() callback and decrements it after calling the ->resume() callback.
692 suspend attempts to be permanently lost. If the usage count goes to zero
693 following the return of the ->resume() callback, the ->runtime_idle() callback
697 or hardware operation. Instead, all hardware components are put into low-power
703 known to it. If that is the case and none of the situations listed above takes
705 be more efficient to leave the devices that had been suspended before the system
706 suspend began in the suspended state.
708 To this end, the PM core provides a mechanism allowing some coordination between
709 different levels of device hierarchy. Namely, if a system suspend .prepare()
710 callback returns a positive number for a device, that indicates to the PM core
711 that the device appears to be runtime-suspended and its state is fine, so it
712 may be left in runtime suspend provided that all of its descendants are also
713 left in runtime suspend. If that happens, the PM core will not execute any
714 system suspend and resume callbacks for all of those devices, except for the
716 as appropriate. This only applies to system suspend transitions that are not
717 related to hibernation (see Documentation/driver-api/pm/devices.rst for more
720 The PM core does its best to reduce the probability of race conditions between
721 the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
724 * During system suspend pm_runtime_get_noresume() is called for every device
725 right before executing the subsystem-level .prepare() callback for it and
727 subsystem-level .suspend() callback for it. In addition to that the PM core
729 device right before executing the subsystem-level .suspend_late() callback
733 every device right after executing the subsystem-level .resume_early()
734 callback and right after executing the subsystem-level .complete() callback
740 Subsystems may wish to conserve code space by using the set of generic power
745 - invoke the ->runtime_suspend() callback provided by the driver of this
749 - invoke the ->runtime_resume() callback provided by the driver of this
753 - if the device has not been suspended at run time, invoke the ->suspend()
758 - if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
763 - invoke the ->resume() callback provided by the driver of this device and,
764 if successful, change the device's runtime PM status to 'active'
767 - invoke the ->resume_noirq() callback provided by the driver of this device
770 - if the device has not been suspended at run time, invoke the ->freeze()
775 - if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
780 - if the device has not been suspended at run time, invoke the ->thaw()
785 - if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
790 - if the device has not been suspended at run time, invoke the ->poweroff()
795 - if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
800 - invoke the ->restore() callback provided by the driver of this device and,
801 if successful, change the device's runtime PM status to 'active'
804 - invoke the ->restore_noirq() callback provided by the device's driver
807 provide its own callbacks for ->runtime_idle(), ->runtime_suspend(),
808 ->runtime_resume(), ->suspend(), ->suspend_noirq(), ->resume(),
809 ->resume_noirq(), ->freeze(), ->freeze_noirq(), ->thaw(), ->thaw_noirq(),
810 ->poweroff(), ->poweroff_noirq(), ->restore(), ->restore_noirq() in the
811 subsystem-level dev_pm_ops structure.
813 Device drivers that wish to use the same function as a system suspend, freeze,
814 poweroff and runtime suspend callback, and similarly for system resume, thaw,
817 last argument to NULL).
819 8. "No-Callback" Devices
822 Some "devices" are only logical sub-devices of their parent and cannot be
823 power-managed on their own. (The prototype example is a USB interface. Entire
824 USB devices can go into low-power mode or send wake-up requests, but neither is
826 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
827 and ->runtime_resume() would always return 0 without doing anything else and
828 ->runtime_idle() would always call pm_runtime_suspend().
834 prevent the non-debugging runtime PM sysfs attributes from being created.
837 ->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks.
838 Instead it will assume that suspends and resumes always succeed and that idle
846 Note that, in some cases it may not be desirable for subsystems/drivers to call
848 the runtime PM callbacks needs to be implemented, a platform dependent PM
849 domain could get attached to the device or that the device is power managed
850 through a supplier device link. For these reasons and to avoid boilerplate code
851 in subsystems/drivers, the PM core allows runtime PM callbacks to be
855 9. Autosuspend, or automatically-delayed suspends
859 A device should be put in a low-power state only when there's some reason to
861 says that a device which hasn't been used for a while is liable to remain
862 unused; following this advice, drivers should not allow devices to be suspended
864 the heuristic ends up being non-optimal, it will still prevent devices from
865 "bouncing" too rapidly between low-power and full-power states.
868 device is automatically suspended (the subsystem or driver still has to call
878 In order to use autosuspend, subsystems or drivers must call
881 instead of the non-autosuspend counterparts::
888 Drivers may also continue to use the non-autosuspend helper functions; they
893 Under some circumstances a driver or subsystem may want to prevent a device
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
899 autosuspend. The ->runtime_suspend() callback can't do this rescheduling
900 itself because no suspend requests of any kind are accepted while the device is
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_put_autosuspend(&foo->dev);
927 unlock(&foo->private_lock);
928 /* Send req result back to the user ... */
936 lock(&foo->private_lock);
937 if (foo->num_pending_requests > 0) {
938 ret = -EBUSY;
940 /* ... suspend the device ... */
941 foo->is_suspended = 1;
943 unlock(&foo->private_lock);
951 lock(&foo->private_lock);
953 foo->is_suspended = 0;
954 pm_runtime_mark_last_busy(&foo->dev);
955 if (foo->num_pending_requests > 0)
957 unlock(&foo->private_lock);
963 Therefore foo_runtime_suspend() has to check whether there are any pending I/O
964 requests (while holding the private lock) before allowing the suspend to
969 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
972 -EAGAIN.