Lines Matching refs:the
10 at the power management core (PM core) level by means of:
19 * A number of runtime PM fields in the 'power' member of 'struct device' (which
20 is of the type 'struct dev_pm_info', defined in include/linux/pm.h) that can
27 used for carrying out runtime PM operations in such a way that the
28 synchronization between them is taken care of by the PM core. Bus types and
31 The runtime PM callbacks present in 'struct dev_pm_ops', the device runtime PM
32 fields of 'struct dev_pm_info' and the core helper functions provided for
48 are executed by the PM core for the device's subsystem that may be either of
49 the following:
51 1. PM domain of the device, if the device's PM domain object, dev->pm_domain,
54 2. Device type of the device, if both dev->type and dev->type->pm are present.
56 3. Device class of the device, if both dev->class and dev->class->pm are
59 4. Bus type of the device, if both dev->bus and dev->bus->pm are present.
61 If the subsystem chosen by applying the above rules doesn't provide the relevant
62 callback, the PM core will invoke the corresponding driver callback stored in
65 The PM core always checks which callback to use in the order given above, so the
67 and bus type. Moreover, the high-priority one will always take precedence over
71 By default, the callbacks are always invoked in process context with interrupts
72 enabled. However, the pm_runtime_irq_safe() helper function can be used to tell
73 the PM core that it is safe to run the ->runtime_suspend(), ->runtime_resume()
74 and ->runtime_idle() callbacks for the given device in atomic context with
75 interrupts disabled. This implies that the callback routines in question must
76 not block or sleep, but it also means that the synchronous helper functions
77 listed at the end of Section 4 may be used for that device within an interrupt
81 for handling the suspend of the device as appropriate, which may, but need not
82 include executing the device driver's own ->runtime_suspend() callback (from the
84 callback in a device driver as long as the subsystem-level suspend callback
85 knows what to do to handle the device).
87 * Once the subsystem-level suspend callback (or the driver suspend callback,
88 if invoked directly) has completed successfully for the given device, the PM
89 core regards the device as suspended, which need not mean that it has been
90 put into a low power state. It is supposed to mean, however, that the
91 device will not process data and will not communicate with the CPU(s) and
92 RAM until the appropriate resume callback is executed for it. The runtime
93 PM status of a device after successful execution of the suspend callback is
96 * If the suspend callback returns -EBUSY or -EAGAIN, the device's runtime PM
97 status remains 'active', which means that the device _must_ be fully
100 * If the suspend callback returns an error code different from -EBUSY and
101 -EAGAIN, the PM core regards this as a fatal error and will refuse to run
102 the helper functions described in Section 4 for the device until its status
103 is directly set to either'active', or 'suspended' (the PM core provides
106 In particular, if the driver requires remote wakeup capability (i.e. hardware
107 mechanism allowing the device to request a change of its power state, such as
108 PCI PME) for proper functioning and device_run_wake() returns 'false' for the
109 device, then ->runtime_suspend() should return -EBUSY. On the other hand, if
110 device_run_wake() returns 'true' for the device and the device is put into a
111 low-power state during the execution of the suspend callback, it is expected
112 that remote wakeup will be enabled for the device. Generally, remote wakeup
116 handling the resume of the device as appropriate, which may, but need not
117 include executing the device driver's own ->runtime_resume() callback (from the
119 callback in a device driver as long as the subsystem-level resume callback knows
120 what to do to handle the device).
122 * Once the subsystem-level resume callback (or the driver resume callback, if
123 invoked directly) has completed successfully, the PM core regards the device
124 as fully operational, which means that the device _must_ be able to complete
125 I/O operations as needed. The runtime PM status of the device is then
128 * If the resume callback returns an error code, the PM core regards this as a
129 fatal error and will refuse to run the helper functions described in Section
130 4 for the device, until its status is directly set to either 'active', or
131 'suspended' (by means of special helper functions provided by the PM core
134 The idle callback (a subsystem-level one, if present, or the driver one) is
135 executed by the PM core whenever the device appears to be idle, which is
136 indicated to the PM core by two counters, the device's usage counter and the
137 counter of 'active' children of the device.
140 the PM core and it turns out to be equal to zero, the other counter is
141 checked. If that counter also is equal to zero, the PM core executes the
142 idle callback with the device as its argument.
144 The action performed by the idle callback is totally dependent on the subsystem
145 (or driver) in question, but the expected and recommended action is to check
146 if the device can be suspended (i.e. if all of the conditions necessary for
147 suspending the device are satisfied) and to queue up a suspend request for the
148 device in that case. If there is no idle callback, or if the callback returns
149 0, then the PM core will attempt to carry out a runtime suspend of the device,
151 call to pm_runtime_autosuspend() (do note that drivers needs to update the
152 device last busy mark, pm_runtime_mark_last_busy(), to control the delay under
153 this circumstance). To prevent this (for example, if the callback routine has
154 started a delayed suspend), the routine must return a non-zero value. Negative
155 error return codes are ignored by the PM core.
157 The helper functions provided by the PM core, described in Section 4, guarantee
158 that the following constraints are met with respect to runtime PM callbacks for
163 instance of ->runtime_suspend() for the same device) with the exception that
166 of the other callbacks is being executed for the same device).
169 devices (i.e. the PM core will only execute ->runtime_idle() or
170 ->runtime_suspend() for the devices the runtime PM status of which is
174 the usage counter of which is equal to zero _and_ either the counter of
175 'active' children of which is equal to zero, or the 'power.ignore_children'
178 (4) ->runtime_resume() can only be executed for 'suspended' devices (i.e. the
179 PM core will only execute ->runtime_resume() for the devices the runtime
182 Additionally, the helper functions provided by the PM core obey the following
186 to execute it, ->runtime_idle() will not be executed for the same device.
188 * A request to execute or to schedule the execution of ->runtime_suspend()
189 will cancel any pending requests to execute ->runtime_idle() for the same
193 to execute it, the other callbacks will not be executed for the same device.
196 scheduled requests to execute the other callbacks for the same device,
208 - timer expiration time, in jiffies (if this is different from zero, the
209 timer is running and will expire at that time, otherwise the timer is not
216 - wait queue used if any of the helper functions needs to wait for another
223 - the usage counter of the device
226 - the count of 'active' children of the device
229 - if set, the value of child_count is ignored (but still updated)
232 - used for disabling the helper functions (they work normally if this is
233 equal to zero); the initial value of it is 1 (i.e. runtime PM is
237 - if set, there was a fatal error (one of the callbacks returned error code
238 as described in Section 2), so the helper functions will not work until
239 this flag is cleared; this is the error code returned by the failing
253 being executed for that device and it is not practical to wait for the
257 - set if the device is capable of generating runtime wake-up events
260 - the runtime PM status of the device; this field's initial value is
261 RPM_SUSPENDED, which means that each device is initially regarded by the
265 - if set, indicates that the user space has allowed the device driver to
266 power manage the device at run time via the /sys/devices/.../power/control
267 interface; it may only be modified with the help of the pm_runtime_allow()
271 - indicates that the device does not use the runtime PM callbacks (see
272 Section 8); it may be modified only by the pm_runtime_no_callbacks()
276 - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
277 will be invoked with the spinlock held and interrupts disabled
280 - indicates that the device's driver supports delayed autosuspend (see
281 Section 9); it may be modified only by the
285 - indicates that the PM core should attempt to carry out an autosuspend
286 when the timer expires rather than a normal suspend
289 - the delay time (in milliseconds) to be used for autosuspend
292 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
296 All of the above fields are members of the 'power' member of 'struct device'.
304 - initialize the device runtime PM fields in 'struct dev_pm_info'
307 - make sure that the runtime PM of the device will be disabled after
308 removing the device from device hierarchy
311 - execute the subsystem-level idle callback for the device; returns an
313 already being executed; if there is no callback or the callback returns 0
317 - execute the subsystem-level suspend callback for the device; returns 0 on
318 success, 1 if the device's runtime PM status was already 'suspended', or
320 to suspend the device again in future and -EACCES means that
324 - same as pm_runtime_suspend() except that the autosuspend delay is taken
325 into account; if pm_runtime_autosuspend_expiration() says the delay has
326 not yet expired then an autosuspend is scheduled for the appropriate time
330 - execute the subsystem-level resume callback for the device; returns 0 on
331 success, 1 if the device's runtime PM status was already 'active' or
333 resume the device again in future, but 'power.runtime_error' should be
338 - submit a request to execute the subsystem-level idle callback for the
339 device (the request is represented by a work item in pm_wq); returns 0 on
340 success or error code if the request has not been queued up
343 - schedule the execution of the subsystem-level suspend callback for the
344 device when the autosuspend delay has expired; if the delay has already
345 expired then the work item is queued up immediately
348 - schedule the execution of the subsystem-level suspend callback for the
349 device in future, where 'delay' is the time to wait before queuing up a
350 suspend work item in pm_wq, in milliseconds (if 'delay' is zero, the work
351 item is queued up immediately); returns 0 on success, 1 if the device's PM
352 runtime status was already 'suspended', or error code if the request
353 hasn't been scheduled (or queued up if 'delay' is 0); if the execution of
354 ->runtime_suspend() is already scheduled and not yet expired, the new
355 value of 'delay' will be used as the time to wait
358 - submit a request to execute the subsystem-level resume callback for the
359 device (the request is represented by a work item in pm_wq); returns 0 on
360 success, 1 if the device's runtime PM status was already 'active', or
361 error code if the request hasn't been queued up
364 - increment the device's usage counter
367 - increment the device's usage counter, run pm_request_resume(dev) and
371 - increment the device's usage counter, run pm_runtime_resume(dev) and
375 - decrement the device's usage counter
378 - decrement the device's usage counter; if the result is 0 then run
382 - decrement the device's usage counter; if the result is 0 then run
386 - decrement the device's usage counter; if the result is 0 then run
390 - decrement the device's usage counter; if the result is 0 then run
394 - decrement the device's usage counter; if the result is 0 then run
398 - decrement the device's 'power.disable_depth' field; if that field is equal
399 to zero, the runtime PM helper functions can execute subsystem-level
400 callbacks described in Section 2 for the device
403 - increment the device's 'power.disable_depth' field (if the value of that
405 callbacks from being run for the device), make sure that all of the
406 pending runtime PM operations on the device are either completed or
408 necessary to execute the subsystem-level resume callback for the device
412 - check if there's a resume request pending for the device and resume it
416 necessary to execute the subsystem-level resume callback for the device to
420 - set/unset the power.ignore_children flag of the device
423 - clear the device's 'power.runtime_error' flag, set the device's runtime
427 zero); it will fail and return error code if the device has a parent
428 which is not active and the 'power.ignore_children' flag of which is unset
431 - clear the device's 'power.runtime_error' flag, set the device's runtime
438 - return true if the device's runtime PM status is 'active' or its
442 - return true if the device's runtime PM status is 'suspended' and its
446 - return true if the device's runtime PM status is 'suspended'
449 - return true if the device's runtime PM status is 'suspended' and its
453 - set the power.runtime_auto flag for the device and decrease its usage
454 counter (used by the /sys/devices/.../power/control interface to
455 effectively allow the device to be power managed at run time)
458 - unset the power.runtime_auto flag for the device and increase its usage
459 counter (used by the /sys/devices/.../power/control interface to
460 effectively prevent the device from being power managed at run time)
463 - set the power.no_callbacks flag for the device and remove the runtime
465 added when the device is registered)
468 - set the power.irq_safe flag for the device, causing the runtime-PM
472 - return true if power.irq_safe flag was set for the device, causing
473 the runtime-PM callbacks to be invoked with interrupts off
476 - set the power.last_busy field to the current time
479 - set the power.use_autosuspend flag, enabling autosuspend delays
482 - clear the power.use_autosuspend flag, disabling autosuspend delays
485 - set the power.autosuspend_delay value to 'delay' (expressed in
490 - calculate the time when the current autosuspend delay period will expire,
491 based on power.last_busy and power.autosuspend_delay; if the delay time
492 is 1000 ms or larger then the expiration time is rounded up to the
493 nearest second; returns 0 if the delay period has already expired or
494 power.use_autosuspend isn't set, otherwise returns the expiration time
497 It is safe to execute the following helper functions from interrupt context:
516 If pm_runtime_irq_safe() has been called for a device then the following helper
530 Initially, the runtime PM is disabled for all devices, which means that the
531 majority of the runtime PM helper functions described in Section 4 will return
532 -EAGAIN until pm_runtime_enable() is called for the device.
534 In addition to that, the initial runtime PM status of all devices is
535 'suspended', but it need not reflect the actual physical state of the device.
536 Thus, if the device is initially active (i.e. it is able to process I/O), its
537 runtime PM status must be changed to 'active', with the help of
538 pm_runtime_set_active(), before pm_runtime_enable() is called for the device.
540 However, if the device has a parent and the parent's runtime PM is enabled,
541 calling pm_runtime_set_active() for the device will affect the parent, unless
542 the parent's 'power.ignore_children' flag is set. Namely, in that case the
543 parent won't be able to suspend at run time, using the PM core's helper
544 functions, as long as the child's status is 'active', even if the child's
546 the child yet or pm_runtime_disable() has been called for it). For this reason,
547 once pm_runtime_set_active() has been called for the device, pm_runtime_enable()
549 status should be changed back to 'suspended' with the help of
552 If the default initial runtime PM status of the device (i.e. 'suspended')
553 reflects the actual state of the device, its bus type's or its driver's
554 ->probe() callback will likely need to wake it up using one of the PM core's
556 should be used. Of course, for this purpose the device's runtime PM has to be
559 It may be desirable to suspend the device once ->probe() has finished.
560 Therefore the driver core uses the asyncronous pm_request_idle() to submit a
561 request to execute the subsystem-level idle callback for the device at that
562 time. A driver that makes use of the runtime autosuspend feature, may want to
563 update the last busy mark before returning from ->probe().
565 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
566 notifier callback in __device_release_driver(), which is necessary, because the
567 notifier is used by some subsystems to carry out operations affecting the
569 driver_sysfs_remove() and the BUS_NOTIFY_UNBIND_DRIVER notifications. This
570 resumes the device if it's in the suspended state and prevents it from
573 To allow bus types and drivers to put devices into the suspended state by
574 calling pm_runtime_suspend() from their ->remove() routines, the driver core
575 executes pm_runtime_put_sync() after running the BUS_NOTIFY_UNBIND_DRIVER
578 but also it allows of more flexibility in the handling of devices during the
581 The user space can effectively disallow the driver of the device to power manage
582 it at run time by changing the value of its /sys/devices/.../power/control
584 this mechanism may also be used by the driver to effectively turn off the
585 runtime power management of the device until the user space turns it on.
586 Namely, during the initialization the driver can make sure that the runtime PM
587 status of the device is 'active' and call pm_runtime_forbid(). It should be
588 noted, however, that if the user space has already intentionally changed the
589 value of /sys/devices/.../power/control to "auto" to allow the driver to power
590 manage the device at run time, the driver may confuse it by using
598 straightforward. But what should happen if the device is already suspended?
603 the subsystem-level system suspend callback is responsible for changing the
604 device's wake-up setting (it may leave that to the device driver's system
605 suspend routine). It may be necessary to resume the device and suspend it again
606 in order to do so. The same is true if the driver uses different power levels
609 During system resume, the simplest approach is to bring all devices back to full
610 power, even if they had been suspended before the system suspend began. There
615 * Remote wake-up events might have been lost by the firmware.
617 * The device's children may need the device to be at full power in order
620 * The driver's idea of the device state may not agree with the device's
625 * Even though the device was suspended, if its usage counter was > 0 then most
626 likely it would need a runtime resume in the near future anyway.
628 If the device had been suspended before the system suspend began and it's
630 to be updated to reflect the actual post-system sleep status. The way to do
637 The PM core always increments the runtime usage counter before calling the
638 ->suspend() callback and decrements it after calling the ->resume() callback.
640 suspend attempts to be permanently lost. If the usage count goes to zero
641 following the return of the ->resume() callback, the ->runtime_idle() callback
646 states directly by the kernel in a coordinated way. Then, the system sleep
647 state effectively follows from the states the hardware components end up in
648 and the system is woken up from that state by a hardware interrupt or a similar
649 mechanism entirely under the kernel's control. As a result, the kernel never
650 gives control away and the states of all devices during resume are precisely
651 known to it. If that is the case and none of the situations listed above takes
652 place (in particular, if the system is not waking up from hibernation), it may
653 be more efficient to leave the devices that had been suspended before the system
654 suspend began in the suspended state.
656 To this end, the PM core provides a mechanism allowing some coordination between
658 callback returns a positive number for a device, that indicates to the PM core
659 that the device appears to be runtime-suspended and its state is fine, so it
661 left in runtime suspend. If that happens, the PM core will not execute any
662 system suspend and resume callbacks for all of those devices, except for the
663 complete callback, which is then entirely responsible for handling the device
668 The PM core does its best to reduce the probability of race conditions between
669 the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
670 out the following operations:
673 right before executing the subsystem-level .prepare() callback for it and
674 pm_runtime_barrier() is called for every device right before executing the
675 subsystem-level .suspend() callback for it. In addition to that the PM core
676 calls __pm_runtime_disable() with 'false' as the second argument for every
677 device right before executing the subsystem-level .suspend_late() callback
681 every device right after executing the subsystem-level .resume_early()
682 callback and right after executing the subsystem-level .complete() callback
687 Subsystems may wish to conserve code space by using the set of generic power
688 management callbacks provided by the PM core, defined in
692 - invoke the ->runtime_suspend() callback provided by the driver of this
696 - invoke the ->runtime_resume() callback provided by the driver of this
700 - if the device has not been suspended at run time, invoke the ->suspend()
705 - if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
706 callback provided by the device's driver and return its result, or return
710 - invoke the ->resume() callback provided by the driver of this device and,
711 if successful, change the device's runtime PM status to 'active'
714 - invoke the ->resume_noirq() callback provided by the driver of this device
717 - if the device has not been suspended at run time, invoke the ->freeze()
722 - if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
723 callback provided by the device's driver and return its result, or return
727 - if the device has not been suspended at run time, invoke the ->thaw()
732 - if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
733 callback provided by the device's driver and return its result, or return
737 - if the device has not been suspended at run time, invoke the ->poweroff()
742 - if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
743 callback provided by the device's driver and return its result, or return
747 - invoke the ->restore() callback provided by the driver of this device and,
748 if successful, change the device's runtime PM status to 'active'
751 - invoke the ->restore_noirq() callback provided by the device's driver
753 These functions are the defaults used by the PM core, if a subsystem doesn't
757 ->poweroff(), ->poweroff_noirq(), ->restore(), ->restore_noirq() in the
760 Device drivers that wish to use the same function as a system suspend, freeze,
762 restore, and runtime resume, can achieve this with the help of the
772 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
776 Subsystems can tell the PM core about these devices by calling
777 pm_runtime_no_callbacks(). This should be done after the device structure is
779 also okay). The routine will set the device's power.no_callbacks flag and
780 prevent the non-debugging runtime PM sysfs attributes from being created.
782 When power.no_callbacks is set, the PM core will not invoke the
787 As a consequence, the PM core will never directly inform the device's subsystem
788 or driver about runtime power changes. Instead, the driver for the device's
789 parent must take responsibility for telling the device's driver when the
800 the heuristic ends up being non-optimal, it will still prevent devices from
803 The term "autosuspend" is an historical remnant. It doesn't mean that the
804 device is automatically suspended (the subsystem or driver still has to call
805 the appropriate PM routines); rather it means that runtime suspends will
806 automatically be delayed until the desired period of inactivity has elapsed.
808 Inactivity is determined based on the power.last_busy field. Drivers should
811 of the inactivity period is a matter of policy. Subsystems can set this length
813 registration the length should be controlled by user space, using the
817 pm_runtime_use_autosuspend() (preferably before registering the device), and
818 thereafter they should use the various *_autosuspend() helper functions instead
819 of the non-autosuspend counterparts:
826 Drivers may also continue to use the non-autosuspend helper functions; they
827 will behave normally, not taking the autosuspend delay into account.
828 Similarly, if the power.use_autosuspend field isn't set then the autosuspend
829 helper functions will behave just like the non-autosuspend counterparts.
832 from autosuspending immediately, even though the usage counter is zero and the
833 autosuspend delay time has expired. If the ->runtime_suspend() callback
834 returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
835 in the future (as it normally would be if the callback invoked
836 pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
838 itself because no suspend requests of any kind are accepted while the device is
839 suspending (i.e., while the callback is running).
842 However such use inevitably involves races, because the PM core can't
843 synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
844 This synchronization must be handled by the driver, using its private lock.
868 /* Send req result back to the user ... */
880 /* ... suspend the device ... */
892 /* ... resume the device ... */
902 the foo_runtime_suspend() callback may race with foo_read_or_write().
904 requests (while holding the private lock) before allowing the suspend to
907 In addition, the power.autosuspend_delay field can be changed by user space at
909 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
910 callback while holding its private lock. If the function returns a nonzero
911 value then the delay has not yet expired and the callback should return