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_can_wakeup() returns 'false' for the
109 device, then ->runtime_suspend() should return -EBUSY. On the other hand, if
110 device_can_wakeup() 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 - the runtime PM status of the device; this field's initial value is
258 RPM_SUSPENDED, which means that each device is initially regarded by the
262 - if set, indicates that the user space has allowed the device driver to
263 power manage the device at run time via the /sys/devices/.../power/control
264 interface; it may only be modified with the help of the pm_runtime_allow()
268 - indicates that the device does not use the runtime PM callbacks (see
269 Section 8); it may be modified only by the pm_runtime_no_callbacks()
273 - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
274 will be invoked with the spinlock held and interrupts disabled
277 - indicates that the device's driver supports delayed autosuspend (see
278 Section 9); it may be modified only by the
282 - indicates that the PM core should attempt to carry out an autosuspend
283 when the timer expires rather than a normal suspend
286 - the delay time (in milliseconds) to be used for autosuspend
289 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
293 All of the above fields are members of the 'power' member of 'struct device'.
301 - initialize the device runtime PM fields in 'struct dev_pm_info'
304 - make sure that the runtime PM of the device will be disabled after
305 removing the device from device hierarchy
308 - execute the subsystem-level idle callback for the device; returns an
310 already being executed; if there is no callback or the callback returns 0
314 - execute the subsystem-level suspend callback for the device; returns 0 on
315 success, 1 if the device's runtime PM status was already 'suspended', or
317 to suspend the device again in future and -EACCES means that
321 - same as pm_runtime_suspend() except that the autosuspend delay is taken
322 into account; if pm_runtime_autosuspend_expiration() says the delay has
323 not yet expired then an autosuspend is scheduled for the appropriate time
327 - execute the subsystem-level resume callback for the device; returns 0 on
328 success, 1 if the device's runtime PM status was already 'active' or
330 resume the device again in future, but 'power.runtime_error' should be
335 - submit a request to execute the subsystem-level idle callback for the
336 device (the request is represented by a work item in pm_wq); returns 0 on
337 success or error code if the request has not been queued up
340 - schedule the execution of the subsystem-level suspend callback for the
341 device when the autosuspend delay has expired; if the delay has already
342 expired then the work item is queued up immediately
345 - schedule the execution of the subsystem-level suspend callback for the
346 device in future, where 'delay' is the time to wait before queuing up a
347 suspend work item in pm_wq, in milliseconds (if 'delay' is zero, the work
348 item is queued up immediately); returns 0 on success, 1 if the device's PM
349 runtime status was already 'suspended', or error code if the request
350 hasn't been scheduled (or queued up if 'delay' is 0); if the execution of
351 ->runtime_suspend() is already scheduled and not yet expired, the new
352 value of 'delay' will be used as the time to wait
355 - submit a request to execute the subsystem-level resume callback for the
356 device (the request is represented by a work item in pm_wq); returns 0 on
357 success, 1 if the device's runtime PM status was already 'active', or
358 error code if the request hasn't been queued up
361 - increment the device's usage counter
364 - increment the device's usage counter, run pm_request_resume(dev) and
368 - increment the device's usage counter, run pm_runtime_resume(dev) and
372 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
373 runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
374 nonzero, increment the counter and return 1; otherwise return 0 without
375 changing the counter
378 - decrement the device's usage counter
381 - decrement the device's usage counter; if the result is 0 then run
385 - decrement the device's usage counter; if the result is 0 then run
389 - decrement the device's usage counter; if the result is 0 then run
393 - decrement the device's usage counter; if the result is 0 then run
397 - decrement the device's usage counter; if the result is 0 then run
401 - decrement the device's 'power.disable_depth' field; if that field is equal
402 to zero, the runtime PM helper functions can execute subsystem-level
403 callbacks described in Section 2 for the device
406 - increment the device's 'power.disable_depth' field (if the value of that
408 callbacks from being run for the device), make sure that all of the
409 pending runtime PM operations on the device are either completed or
411 necessary to execute the subsystem-level resume callback for the device
415 - check if there's a resume request pending for the device and resume it
419 necessary to execute the subsystem-level resume callback for the device to
423 - set/unset the power.ignore_children flag of the device
426 - clear the device's 'power.runtime_error' flag, set the device's runtime
430 zero); it will fail and return error code if the device has a parent
431 which is not active and the 'power.ignore_children' flag of which is unset
434 - clear the device's 'power.runtime_error' flag, set the device's runtime
441 - return true if the device's runtime PM status is 'active' or its
445 - return true if the device's runtime PM status is 'suspended' and its
449 - return true if the device's runtime PM status is 'suspended'
452 - set the power.runtime_auto flag for the device and decrease its usage
453 counter (used by the /sys/devices/.../power/control interface to
454 effectively allow the device to be power managed at run time)
457 - unset the power.runtime_auto flag for the device and increase its usage
458 counter (used by the /sys/devices/.../power/control interface to
459 effectively prevent the device from being power managed at run time)
462 - set the power.no_callbacks flag for the device and remove the runtime
464 added when the device is registered)
467 - set the power.irq_safe flag for the device, causing the runtime-PM
471 - return true if power.irq_safe flag was set for the device, causing
472 the runtime-PM callbacks to be invoked with interrupts off
475 - set the power.last_busy field to the current time
478 - set the power.use_autosuspend flag, enabling autosuspend delays; call
479 pm_runtime_get_sync if the flag was previously cleared and
483 - clear the power.use_autosuspend flag, disabling autosuspend delays;
484 decrement the device's usage counter if the flag was previously set and
488 - set the power.autosuspend_delay value to 'delay' (expressed in
491 called or the device's usage counter may be decremented and
497 - calculate the time when the current autosuspend delay period will expire,
498 based on power.last_busy and power.autosuspend_delay; if the delay time
499 is 1000 ms or larger then the expiration time is rounded up to the
500 nearest second; returns 0 if the delay period has already expired or
501 power.use_autosuspend isn't set, otherwise returns the expiration time
504 It is safe to execute the following helper functions from interrupt context:
523 If pm_runtime_irq_safe() has been called for a device then the following helper
537 Initially, the runtime PM is disabled for all devices, which means that the
538 majority of the runtime PM helper functions described in Section 4 will return
539 -EAGAIN until pm_runtime_enable() is called for the device.
541 In addition to that, the initial runtime PM status of all devices is
542 'suspended', but it need not reflect the actual physical state of the device.
543 Thus, if the device is initially active (i.e. it is able to process I/O), its
544 runtime PM status must be changed to 'active', with the help of
545 pm_runtime_set_active(), before pm_runtime_enable() is called for the device.
547 However, if the device has a parent and the parent's runtime PM is enabled,
548 calling pm_runtime_set_active() for the device will affect the parent, unless
549 the parent's 'power.ignore_children' flag is set. Namely, in that case the
550 parent won't be able to suspend at run time, using the PM core's helper
551 functions, as long as the child's status is 'active', even if the child's
553 the child yet or pm_runtime_disable() has been called for it). For this reason,
554 once pm_runtime_set_active() has been called for the device, pm_runtime_enable()
556 status should be changed back to 'suspended' with the help of
559 If the default initial runtime PM status of the device (i.e. 'suspended')
560 reflects the actual state of the device, its bus type's or its driver's
561 ->probe() callback will likely need to wake it up using one of the PM core's
563 should be used. Of course, for this purpose the device's runtime PM has to be
566 Note, if the device may execute pm_runtime calls during the probe (such as
567 if it is registers with a subsystem that may call back in) then the
569 appropriate to ensure that the device is not put back to sleep during the
570 probe. This can happen with systems such as the network device layer.
572 It may be desirable to suspend the device once ->probe() has finished.
573 Therefore the driver core uses the asynchronous pm_request_idle() to submit a
574 request to execute the subsystem-level idle callback for the device at that
575 time. A driver that makes use of the runtime autosuspend feature, may want to
576 update the last busy mark before returning from ->probe().
578 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
579 notifier callback in __device_release_driver(), which is necessary, because the
580 notifier is used by some subsystems to carry out operations affecting the
582 driver_sysfs_remove() and the BUS_NOTIFY_UNBIND_DRIVER notifications. This
583 resumes the device if it's in the suspended state and prevents it from
586 To allow bus types and drivers to put devices into the suspended state by
587 calling pm_runtime_suspend() from their ->remove() routines, the driver core
588 executes pm_runtime_put_sync() after running the BUS_NOTIFY_UNBIND_DRIVER
591 but also it allows of more flexibility in the handling of devices during the
594 Drivers in ->remove() callback should undo the runtime PM changes done
598 The user space can effectively disallow the driver of the device to power manage
599 it at run time by changing the value of its /sys/devices/.../power/control
601 this mechanism may also be used by the driver to effectively turn off the
602 runtime power management of the device until the user space turns it on.
603 Namely, during the initialization the driver can make sure that the runtime PM
604 status of the device is 'active' and call pm_runtime_forbid(). It should be
605 noted, however, that if the user space has already intentionally changed the
606 value of /sys/devices/.../power/control to "auto" to allow the driver to power
607 manage the device at run time, the driver may confuse it by using
615 straightforward. But what should happen if the device is already suspended?
620 the subsystem-level system suspend callback is responsible for changing the
621 device's wake-up setting (it may leave that to the device driver's system
622 suspend routine). It may be necessary to resume the device and suspend it again
623 in order to do so. The same is true if the driver uses different power levels
626 During system resume, the simplest approach is to bring all devices back to full
627 power, even if they had been suspended before the system suspend began. There
632 * Remote wake-up events might have been lost by the firmware.
634 * The device's children may need the device to be at full power in order
637 * The driver's idea of the device state may not agree with the device's
642 * Even though the device was suspended, if its usage counter was > 0 then most
643 likely it would need a runtime resume in the near future anyway.
645 If the device had been suspended before the system suspend began and it's
647 to be updated to reflect the actual post-system sleep status. The way to do
654 The PM core always increments the runtime usage counter before calling the
655 ->suspend() callback and decrements it after calling the ->resume() callback.
657 suspend attempts to be permanently lost. If the usage count goes to zero
658 following the return of the ->resume() callback, the ->runtime_idle() callback
663 states directly by the kernel in a coordinated way. Then, the system sleep
664 state effectively follows from the states the hardware components end up in
665 and the system is woken up from that state by a hardware interrupt or a similar
666 mechanism entirely under the kernel's control. As a result, the kernel never
667 gives control away and the states of all devices during resume are precisely
668 known to it. If that is the case and none of the situations listed above takes
669 place (in particular, if the system is not waking up from hibernation), it may
670 be more efficient to leave the devices that had been suspended before the system
671 suspend began in the suspended state.
673 To this end, the PM core provides a mechanism allowing some coordination between
675 callback returns a positive number for a device, that indicates to the PM core
676 that the device appears to be runtime-suspended and its state is fine, so it
678 left in runtime suspend. If that happens, the PM core will not execute any
679 system suspend and resume callbacks for all of those devices, except for the
680 complete callback, which is then entirely responsible for handling the device
685 The PM core does its best to reduce the probability of race conditions between
686 the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
687 out the following operations:
690 right before executing the subsystem-level .prepare() callback for it and
691 pm_runtime_barrier() is called for every device right before executing the
692 subsystem-level .suspend() callback for it. In addition to that the PM core
693 calls __pm_runtime_disable() with 'false' as the second argument for every
694 device right before executing the subsystem-level .suspend_late() callback
698 every device right after executing the subsystem-level .resume_early()
699 callback and right after executing the subsystem-level .complete() callback
704 Subsystems may wish to conserve code space by using the set of generic power
705 management callbacks provided by the PM core, defined in
709 - invoke the ->runtime_suspend() callback provided by the driver of this
713 - invoke the ->runtime_resume() callback provided by the driver of this
717 - if the device has not been suspended at run time, invoke the ->suspend()
722 - if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
723 callback provided by the device's driver and return its result, or return
727 - invoke the ->resume() callback provided by the driver of this device and,
728 if successful, change the device's runtime PM status to 'active'
731 - invoke the ->resume_noirq() callback provided by the driver of this device
734 - if the device has not been suspended at run time, invoke the ->freeze()
739 - if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
740 callback provided by the device's driver and return its result, or return
744 - if the device has not been suspended at run time, invoke the ->thaw()
749 - if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
750 callback provided by the device's driver and return its result, or return
754 - if the device has not been suspended at run time, invoke the ->poweroff()
759 - if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
760 callback provided by the device's driver and return its result, or return
764 - invoke the ->restore() callback provided by the driver of this device and,
765 if successful, change the device's runtime PM status to 'active'
768 - invoke the ->restore_noirq() callback provided by the device's driver
770 These functions are the defaults used by the PM core, if a subsystem doesn't
774 ->poweroff(), ->poweroff_noirq(), ->restore(), ->restore_noirq() in the
777 Device drivers that wish to use the same function as a system suspend, freeze,
779 restore, and runtime resume, can achieve this with the help of the
789 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
793 Subsystems can tell the PM core about these devices by calling
794 pm_runtime_no_callbacks(). This should be done after the device structure is
796 also okay). The routine will set the device's power.no_callbacks flag and
797 prevent the non-debugging runtime PM sysfs attributes from being created.
799 When power.no_callbacks is set, the PM core will not invoke the
804 As a consequence, the PM core will never directly inform the device's subsystem
805 or driver about runtime power changes. Instead, the driver for the device's
806 parent must take responsibility for telling the device's driver when the
817 the heuristic ends up being non-optimal, it will still prevent devices from
820 The term "autosuspend" is an historical remnant. It doesn't mean that the
821 device is automatically suspended (the subsystem or driver still has to call
822 the appropriate PM routines); rather it means that runtime suspends will
823 automatically be delayed until the desired period of inactivity has elapsed.
825 Inactivity is determined based on the power.last_busy field. Drivers should
828 of the inactivity period is a matter of policy. Subsystems can set this length
830 registration the length should be controlled by user space, using the
834 pm_runtime_use_autosuspend() (preferably before registering the device), and
835 thereafter they should use the various *_autosuspend() helper functions instead
836 of the non-autosuspend counterparts:
843 Drivers may also continue to use the non-autosuspend helper functions; they
844 will behave normally, which means sometimes taking the autosuspend delay into
848 from autosuspending immediately, even though the usage counter is zero and the
849 autosuspend delay time has expired. If the ->runtime_suspend() callback
850 returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
851 in the future (as it normally would be if the callback invoked
852 pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
854 itself because no suspend requests of any kind are accepted while the device is
855 suspending (i.e., while the callback is running).
858 However such use inevitably involves races, because the PM core can't
859 synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
860 This synchronization must be handled by the driver, using its private lock.
884 /* Send req result back to the user ... */
896 /* ... suspend the device ... */
908 /* ... resume the device ... */
918 the foo_runtime_suspend() callback may race with foo_read_or_write().
920 requests (while holding the private lock) before allowing the suspend to
923 In addition, the power.autosuspend_delay field can be changed by user space at
925 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
926 callback while holding its private lock. If the function returns a nonzero
927 value then the delay has not yet expired and the callback should return