Lines Matching +full:pm +full:- +full:related
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:
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,
158 routine has started a delayed suspend), the routine must return a non-zero
159 value. Negative error return codes are ignored by the PM core.
161 The helper functions provided by the PM core, described in Section 4, guarantee
162 that the following constraints are met with respect to runtime PM callbacks for
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
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
184 PM status of which is 'suspended').
186 Additionally, the helper functions provided by the PM core obey the following
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
199 * A request to execute ->runtime_resume() will cancel any pending or
203 3. Runtime PM Device Fields
206 The following device runtime PM fields are present in 'struct dev_pm_info', as
207 defined in include/linux/pm.h:
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
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
262 - the runtime PM status of the device; this field's initial value is
264 PM core as 'suspended', regardless of its real hardware status
267 - the last runtime PM status of the device captured before disabling runtime
268 PM for it (invalid initially and when disable_depth is 0)
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
295 - the delay time (in milliseconds) to be used for autosuspend
298 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
304 4. Runtime PM Device Helper Functions
307 The following runtime PM helper functions are defined in
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
325 success, 1 if the device's runtime PM status was already 'suspended', or
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
337 success, 1 if the device's runtime PM status is already 'active' (also if
339 changing from 0 to 1) or error code on failure, where -EAGAIN means it may
341 'power.runtime_error' should be checked additionally, and -EACCES means
346 - run pm_runtime_resume(dev) and if successful, increment the device's
348 runtime PM status was already 'active') or the error code from
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
365 item is queued up immediately); returns 0 on success, 1 if the device's PM
368 ->runtime_suspend() is already scheduled and not yet expired, the new
372 - submit a request to execute the subsystem-level resume callback for the
374 success, 1 if the device's runtime PM status was already 'active', or
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
393 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
394 runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
399 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
400 runtime PM status is RPM_ACTIVE, increment the counter and
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
441 pending runtime PM operations on the device are either completed or
443 necessary to execute the subsystem-level resume callback for the device
447 - check if there's a resume request pending for the device and resume it
448 (synchronously) in that case, cancel any other pending runtime PM requests
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'
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'
473 - return true if the device's runtime PM status is 'active' or its
477 - return true if the device's runtime PM status is 'suspended' and its
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
489 - unset the power.runtime_auto flag for the device and increase its usage
494 - set the power.no_callbacks flag for the device and remove the runtime
495 PM attributes from /sys/devices/.../power (or prevent them from being
499 - set the power.irq_safe flag for the device, causing the runtime-PM
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
529 - calculate the time when the current autosuspend delay period will expire,
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()
568 5. Runtime PM Initialization, Device Probing and Removal
571 Initially, the runtime PM is disabled for all devices, which means that the
572 majority of the runtime PM helper functions described in Section 4 will return
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
578 runtime PM status must be changed to 'active', with the help of
581 However, if the device has a parent and the parent's runtime PM is enabled,
584 parent won't be able to suspend at run time, using the PM core's helper
586 runtime PM is still disabled (i.e. pm_runtime_enable() hasn't been called for
589 should be called for it too as soon as reasonably possible or its runtime PM
593 If the default initial runtime PM status of the device (i.e. 'suspended')
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
606 It may be desirable to suspend the device once ->probe() has finished.
608 request to execute the subsystem-level idle callback for the device at that
610 update the last busy mark before returning from ->probe().
612 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
615 runtime PM functionality. It does so by calling pm_runtime_get_sync() before
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(),
637 Namely, during the initialization the driver can make sure that the runtime PM
644 6. Runtime PM and System Sleep
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
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.
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);
689 The PM core always increments the runtime usage counter before calling the
690 ->suspend() callback and decrements it after calling the ->resume() callback.
691 Hence disabling runtime PM temporarily like this will not cause any runtime
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
708 To this end, the PM core provides a mechanism allowing some coordination between
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
713 left in runtime suspend. If that happens, the PM core will not execute any
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
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
741 management callbacks provided by the PM core, defined in
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
806 These functions are the defaults used by the PM core if a subsystem doesn't
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.
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().
830 Subsystems can tell the PM core about these devices by calling
834 prevent the non-debugging runtime PM sysfs attributes from being created.
836 When power.no_callbacks is set, the PM core will not invoke the
837 ->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks.
841 As a consequence, the PM core will never directly inform the device's subsystem
848 the runtime PM callbacks needs to be implemented, a platform dependent PM
851 in subsystems/drivers, the PM core allows runtime PM callbacks to be
852 unassigned. More precisely, if a callback pointer is NULL, the PM core will act
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
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.
869 the appropriate PM routines); rather it means that runtime suspends will
881 instead of the non-autosuspend counterparts::
888 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_put_autosuspend(&foo->dev);
927 unlock(&foo->private_lock);
936 lock(&foo->private_lock);
937 if (foo->num_pending_requests > 0) {
938 ret = -EBUSY;
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);
969 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
972 -EAGAIN.