Lines Matching +full:power +full:- +full:active +full:- +full:low
2 Runtime Power Management Framework for I/O Devices
5 (C) 2009-2011 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
14 Support for runtime power management (runtime PM) of I/O devices is provided
15 at the power management core (PM core) level by means of:
17 * The power management workqueue pm_wq in which bus types and device drivers can
18 put their PM-related work items. It is strongly recommended that pm_wq be
20 them to be synchronized with system-wide power transitions (suspend to RAM,
22 include/linux/pm_runtime.h and defined in kernel/power/main.c.
24 * A number of runtime PM fields in the 'power' member of 'struct device' (which
31 * A set of helper functions defined in drivers/base/power/runtime.c that can be
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).
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,
96 put into a low power state. It is supposed to mean, however, that the
102 * If the suspend callback returns -EBUSY or -EAGAIN, the device's runtime PM
103 status remains 'active', which means that the device _must_ be fully
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
128 * Once the subsystem-level resume callback (or the driver resume callback, if
132 'active'.
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
143 counter of 'active' children of the device.
160 started a delayed suspend), the routine must return a non-zero value. Negative
168 ->runtime_suspend() in parallel with ->runtime_resume() or with another
169 instance of ->runtime_suspend() for the same device) with the exception that
170 ->runtime_suspend() or ->runtime_resume() can be executed in parallel with
171 ->runtime_idle() (although ->runtime_idle() will not be started while any
174 (2) ->runtime_idle() and ->runtime_suspend() can only be executed for 'active'
175 devices (i.e. the PM core will only execute ->runtime_idle() or
176 ->runtime_suspend() for the devices the runtime PM status of which is
177 'active').
179 (3) ->runtime_idle() and ->runtime_suspend() can only be executed for a device
181 'active' children of which is equal to zero, or the 'power.ignore_children'
184 (4) ->runtime_resume() can only be executed for 'suspended' devices (i.e. the
185 PM core will only execute ->runtime_resume() for the devices the runtime
191 * If ->runtime_suspend() is about to be executed or there's a pending request
192 to execute it, ->runtime_idle() will not be executed for the same device.
194 * A request to execute or to schedule the execution of ->runtime_suspend()
195 will cancel any pending requests to execute ->runtime_idle() for the same
198 * If ->runtime_resume() is about to be executed or there's a pending request
201 * A request to execute ->runtime_resume() will cancel any pending or
212 - timer used for scheduling (delayed) suspend and autosuspend requests
215 - timer expiration time, in jiffies (if this is different from zero, the
220 - work structure used for queuing up requests (i.e. work items in pm_wq)
223 - wait queue used if any of the helper functions needs to wait for another
227 - lock used for synchronization
230 - the usage counter of the device
233 - the count of 'active' children of the device
236 - if set, the value of child_count is ignored (but still updated)
239 - used for disabling the helper functions (they work normally if this is
244 - if set, there was a fatal error (one of the callbacks returned error code
250 - if set, ->runtime_idle() is being executed
253 - if set, there's a pending request (i.e. a work item queued up into pm_wq)
256 - type of request that's pending (valid if request_pending is set)
259 - set if ->runtime_resume() is about to be run while ->runtime_suspend() is
264 - the runtime PM status of the device; this field's initial value is
269 - the last runtime PM status of the device captured before disabling runtime
273 - if set, indicates that the user space has allowed the device driver to
274 power manage the device at run time via the /sys/devices/.../power/control
279 - indicates that the device does not use the runtime PM callbacks (see
284 - indicates that the ->runtime_suspend() and ->runtime_resume() callbacks
288 - indicates that the device's driver supports delayed autosuspend (see
293 - indicates that the PM core should attempt to carry out an autosuspend
297 - the delay time (in milliseconds) to be used for autosuspend
300 - the time (in jiffies) when the pm_runtime_mark_last_busy() helper
304 All of the above fields are members of the 'power' member of 'struct device'.
310 drivers/base/power/runtime.c and include/linux/pm_runtime.h:
313 - initialize the device runtime PM fields in 'struct dev_pm_info'
316 - make sure that the runtime PM of the device will be disabled after
320 - execute the subsystem-level idle callback for the device; returns an
321 error code on failure, where -EINPROGRESS means that ->runtime_idle() is
326 - execute the subsystem-level suspend callback for the device; returns 0 on
328 error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt
329 to suspend the device again in future and -EACCES means that
330 'power.disable_depth' is different from 0
333 - same as pm_runtime_suspend() except that the autosuspend delay is taken
339 - execute the subsystem-level resume callback for the device; returns 0 on
340 success, 1 if the device's runtime PM status is already 'active' (also if
341 'power.disable_depth' is nonzero, but the status was 'active' when it was
342 changing from 0 to 1) or error code on failure, where -EAGAIN means it may
344 'power.runtime_error' should be checked additionally, and -EACCES means
345 that the callback could not be run, because 'power.disable_depth' was
349 - run pm_runtime_resume(dev) and if successful, increment the device's
351 runtime PM status was already 'active') or the error code from
355 - submit a request to execute the subsystem-level idle callback for the
360 - schedule the execution of the subsystem-level suspend callback for the
365 - schedule the execution of the subsystem-level suspend callback for the
371 ->runtime_suspend() is already scheduled and not yet expired, the new
375 - submit a request to execute the subsystem-level resume callback for the
377 success, 1 if the device's runtime PM status was already 'active', or
381 - increment the device's usage counter
384 - increment the device's usage counter, run pm_request_resume(dev) and
388 - increment the device's usage counter, run pm_runtime_resume(dev) and
396 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
402 - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the
407 - decrement the device's usage counter
410 - decrement the device's usage counter; if the result is 0 then run
414 - does the same as __pm_runtime_put_autosuspend() for now, but in the
418 - decrement the device's usage counter; if the result is 0 then run
422 - decrement the device's usage counter; if the result is 0 then run
426 - decrement the device's usage counter; if the result is 0 then run
430 - decrement the device's usage counter; if the result is 0 then run
434 - decrement the device's 'power.disable_depth' field; if that field is equal
435 to zero, the runtime PM helper functions can execute subsystem-level
439 - increment the device's 'power.disable_depth' field (if the value of that
440 field was previously zero, this prevents subsystem-level runtime PM
444 necessary to execute the subsystem-level resume callback for the device
448 - check if there's a resume request pending for the device and resume it
452 necessary to execute the subsystem-level resume callback for the device to
456 - set/unset the power.ignore_children flag of the device
459 - clear the device's 'power.runtime_error' flag, set the device's runtime
460 PM status to 'active' and update its parent's counter of 'active'
462 'power.runtime_error' is set or 'power.disable_depth' is greater than
464 which is not active and the 'power.ignore_children' flag of which is unset
467 - clear the device's 'power.runtime_error' flag, set the device's runtime
468 PM status to 'suspended' and update its parent's counter of 'active'
470 'power.runtime_error' is set or 'power.disable_depth' is greater than
474 - return true if the device's runtime PM status is 'active' or its
475 'power.disable_depth' field is not equal to zero, or false otherwise
478 - return true if the device's runtime PM status is 'suspended' and its
479 'power.disable_depth' field is equal to zero, or false otherwise
482 - return true if the device's runtime PM status is 'suspended'
485 - set the power.runtime_auto flag for the device and decrease its usage
486 counter (used by the /sys/devices/.../power/control interface to
487 effectively allow the device to be power managed at run time)
490 - unset the power.runtime_auto flag for the device and increase its usage
491 counter (used by the /sys/devices/.../power/control interface to
492 effectively prevent the device from being power managed at run time)
495 - set the power.no_callbacks flag for the device and remove the runtime
496 PM attributes from /sys/devices/.../power (or prevent them from being
500 - set the power.irq_safe flag for the device, causing the runtime-PM
504 - return true if power.irq_safe flag was set for the device, causing
505 the runtime-PM callbacks to be invoked with interrupts off
508 - set the power.last_busy field to the current time
511 - set the power.use_autosuspend flag, enabling autosuspend delays; call
513 power.autosuspend_delay is negative
516 - clear the power.use_autosuspend flag, disabling autosuspend delays;
518 power.autosuspend_delay is negative; call pm_runtime_idle
521 - set the power.autosuspend_delay value to 'delay' (expressed in
523 prevented; if power.use_autosuspend is set, pm_runtime_get_sync may be
525 pm_runtime_idle called depending on if power.autosuspend_delay is
526 changed to or from a negative value; if power.use_autosuspend is clear,
530 - calculate the time when the current autosuspend delay period will expire,
531 based on power.last_busy and power.autosuspend_delay; if the delay time
534 power.use_autosuspend isn't set, otherwise returns the expiration time
539 - pm_request_idle()
540 - pm_request_autosuspend()
541 - pm_schedule_suspend()
542 - pm_request_resume()
543 - pm_runtime_get_noresume()
544 - pm_runtime_get()
545 - pm_runtime_put_noidle()
546 - pm_runtime_put()
547 - pm_runtime_put_autosuspend()
548 - __pm_runtime_put_autosuspend()
549 - pm_runtime_enable()
550 - pm_suspend_ignore_children()
551 - pm_runtime_set_active()
552 - pm_runtime_set_suspended()
553 - pm_runtime_suspended()
554 - pm_runtime_mark_last_busy()
555 - pm_runtime_autosuspend_expiration()
560 - pm_runtime_idle()
561 - pm_runtime_suspend()
562 - pm_runtime_autosuspend()
563 - pm_runtime_resume()
564 - pm_runtime_get_sync()
565 - pm_runtime_put_sync()
566 - pm_runtime_put_sync_suspend()
567 - pm_runtime_put_sync_autosuspend()
574 -EAGAIN until pm_runtime_enable() is called for the device.
578 Thus, if the device is initially active (i.e. it is able to process I/O), its
579 runtime PM status must be changed to 'active', with the help of
584 the parent's 'power.ignore_children' flag is set. Namely, in that case the
586 functions, as long as the child's status is 'active', even if the child's
596 ->probe() callback will likely need to wake it up using one of the PM core's
607 It may be desirable to suspend the device once ->probe() has finished.
609 request to execute the subsystem-level idle callback for the device at that
611 update the last busy mark before returning from ->probe().
622 calling pm_runtime_suspend() from their ->remove() routines, the driver core
625 drivers to make their ->remove() callbacks avoid races with runtime PM directly,
629 Drivers in ->remove() callback should undo the runtime PM changes done
630 in ->probe(). Usually this means calling pm_runtime_disable(),
633 The user space can effectively disallow the driver of the device to power manage
634 it at run time by changing the value of its /sys/devices/.../power/control
637 runtime power management of the device until the user space turns it on.
639 status of the device is 'active' and call pm_runtime_forbid(). It should be
641 value of /sys/devices/.../power/control to "auto" to allow the driver to power
649 as suspend-to-RAM and suspend-to-disk) interact with each other in a couple of
650 ways. If a device is active when a system sleep starts, everything is
653 The device may have different wake-up settings for runtime PM and system sleep.
654 For example, remote wake-up may be enabled for runtime suspend but disallowed
656 the subsystem-level system suspend callback is responsible for changing the
657 device's wake-up setting (it may leave that to the device driver's system
659 in order to do so. The same is true if the driver uses different power levels
663 power, even if they had been suspended before the system suspend began. There
666 * The device might need to switch power levels, wake-up settings, etc.
668 * Remote wake-up events might have been lost by the firmware.
670 * The device's children may need the device to be at full power in order
682 brought back to full power during resume, then its runtime PM status will have
683 to be updated to reflect the actual post-system sleep status. The way to do
686 - pm_runtime_disable(dev);
687 - pm_runtime_set_active(dev);
688 - pm_runtime_enable(dev);
691 ->suspend() callback and decrements it after calling the ->resume() callback.
694 following the return of the ->resume() callback, the ->runtime_idle() callback
698 or hardware operation. Instead, all hardware components are put into low-power
712 that the device appears to be runtime-suspended and its state is fine, so it
718 related to hibernation (see Documentation/driver-api/pm/devices.rst for more
726 right before executing the subsystem-level .prepare() callback for it and
728 subsystem-level .suspend() callback for it. In addition to that the PM core
730 device right before executing the subsystem-level .suspend_late() callback
734 every device right after executing the subsystem-level .resume_early()
735 callback and right after executing the subsystem-level .complete() callback
741 Subsystems may wish to conserve code space by using the set of generic power
743 driver/base/power/generic_ops.c:
746 - invoke the ->runtime_suspend() callback provided by the driver of this
750 - invoke the ->runtime_resume() callback provided by the driver of this
754 - if the device has not been suspended at run time, invoke the ->suspend()
759 - if pm_runtime_suspended(dev) returns "false", invoke the ->suspend_noirq()
764 - invoke the ->resume() callback provided by the driver of this device and,
765 if successful, change the device's runtime PM status to 'active'
768 - invoke the ->resume_noirq() callback provided by the driver of this device
771 - if the device has not been suspended at run time, invoke the ->freeze()
776 - if pm_runtime_suspended(dev) returns "false", invoke the ->freeze_noirq()
781 - if the device has not been suspended at run time, invoke the ->thaw()
786 - if pm_runtime_suspended(dev) returns "false", invoke the ->thaw_noirq()
791 - if the device has not been suspended at run time, invoke the ->poweroff()
796 - if pm_runtime_suspended(dev) returns "false", run the ->poweroff_noirq()
801 - invoke the ->restore() callback provided by the driver of this device and,
802 if successful, change the device's runtime PM status to 'active'
805 - invoke the ->restore_noirq() callback provided by the device's driver
808 provide its own callbacks for ->runtime_idle(), ->runtime_suspend(),
809 ->runtime_resume(), ->suspend(), ->suspend_noirq(), ->resume(),
810 ->resume_noirq(), ->freeze(), ->freeze_noirq(), ->thaw(), ->thaw_noirq(),
811 ->poweroff(), ->poweroff_noirq(), ->restore(), ->restore_noirq() in the
812 subsystem-level dev_pm_ops structure.
820 8. "No-Callback" Devices
823 Some "devices" are only logical sub-devices of their parent and cannot be
824 power-managed on their own. (The prototype example is a USB interface. Entire
825 USB devices can go into low-power mode or send wake-up requests, but neither is
827 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
828 and ->runtime_resume() would always return 0 without doing anything else and
829 ->runtime_idle() would always call pm_runtime_suspend().
834 also okay). The routine will set the device's power.no_callbacks flag and
835 prevent the non-debugging runtime PM sysfs attributes from being created.
837 When power.no_callbacks is set, the PM core will not invoke the
838 ->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks.
843 or driver about runtime power changes. Instead, the driver for the device's
845 parent's power state changes.
850 domain could get attached to the device or that the device is power managed
856 9. Autosuspend, or automatically-delayed suspends
859 Changing a device's power state isn't free; it requires both time and energy.
860 A device should be put in a low-power state only when there's some reason to
865 the heuristic ends up being non-optimal, it will still prevent devices from
866 "bouncing" too rapidly between low-power and full-power states.
873 Inactivity is determined based on the power.last_busy field. Drivers should
879 /sys/devices/.../power/autosuspend_delay_ms attribute.
884 instead of the non-autosuspend counterparts::
891 Drivers may also continue to use the non-autosuspend helper functions; they
897 autosuspend delay time has expired. If the ->runtime_suspend() callback
898 returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is
901 autosuspend. The ->runtime_suspend() callback can't do this rescheduling
907 synchronize ->runtime_suspend() callbacks with the arrival of I/O requests.
909 Here is a schematic pseudo-code example::
913 lock(&foo->private_lock);
915 if (foo->num_pending_requests++ == 0)
916 pm_runtime_get(&foo->dev);
917 if (!foo->is_suspended)
919 unlock(&foo->private_lock);
924 lock(&foo->private_lock);
925 if (--foo->num_pending_requests == 0) {
926 pm_runtime_mark_last_busy(&foo->dev);
927 __pm_runtime_put_autosuspend(&foo->dev);
931 unlock(&foo->private_lock);
940 lock(&foo->private_lock);
941 if (foo->num_pending_requests > 0) {
942 ret = -EBUSY;
945 foo->is_suspended = 1;
947 unlock(&foo->private_lock);
955 lock(&foo->private_lock);
957 foo->is_suspended = 0;
958 pm_runtime_mark_last_busy(&foo->dev);
959 if (foo->num_pending_requests > 0)
961 unlock(&foo->private_lock);
971 In addition, the power.autosuspend_delay field can be changed by user space at
973 pm_runtime_autosuspend_expiration() from within the ->runtime_suspend()
976 -EAGAIN.