Lines Matching refs:PM
9 Support for runtime power management (runtime PM) of I/O devices is provided
10 at the power management core (PM core) level by means of:
13 put their PM-related work items. It is strongly recommended that pm_wq be
14 used for queuing all work items related to runtime PM, because this allows
19 * A number of runtime PM fields in the 'power' member of 'struct device' (which
21 be used for synchronizing runtime PM operations with one another.
23 * Three device runtime PM callbacks in 'struct dev_pm_ops' (defined in
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
33 runtime PM are described below.
35 2. Device Runtime PM Callbacks
37 There are three device runtime PM callbacks defined in 'struct dev_pm_ops':
48 are executed by the PM core for the device's subsystem that may be either of
51 1. PM domain of the device, if the device's PM domain object, dev->pm_domain,
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
66 priority order of callbacks from high to low is: PM domain, device type, class
68 a low-priority one. The PM domain, bus type, device type and class callbacks
73 the PM core that it is safe to run the ->runtime_suspend(), ->runtime_resume()
83 PM core's point of view it is not necessary to implement a ->runtime_suspend()
88 if invoked directly) has completed successfully for the given device, the PM
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
101 -EAGAIN, the PM core regards this as a fatal error and will refuse to run
103 is directly set to either'active', or 'suspended' (the PM core provides
118 PM core's point of view it is not necessary to implement a ->runtime_resume()
123 invoked directly) has completed successfully, the PM core regards the device
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
131 'suspended' (by means of special helper functions provided by the PM core
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
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
149 0, then the PM core will attempt to carry out a runtime suspend of the device,
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
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
179 PM core will only execute ->runtime_resume() for the devices the runtime
180 PM status of which is 'suspended').
182 Additionally, the helper functions provided by the PM core obey the following
199 3. Runtime PM Device Fields
201 The following device runtime PM fields are present in 'struct dev_pm_info', as
233 equal to zero); the initial value of it is 1 (i.e. runtime PM is
260 - the runtime PM status of the device; this field's initial value is
262 PM core as 'suspended', regardless of its real hardware status
271 - indicates that the device does not use the runtime PM callbacks (see
285 - indicates that the PM core should attempt to carry out an autosuspend
298 4. Runtime PM Device Helper Functions
300 The following runtime PM helper functions are defined in
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
318 success, 1 if the device's runtime PM status was already 'suspended', or
331 success, 1 if the device's runtime PM status was already 'active' or
351 item is queued up immediately); returns 0 on success, 1 if the device's PM
360 success, 1 if the device's runtime PM status was already 'active', or
399 to zero, the runtime PM helper functions can execute subsystem-level
404 field was previously zero, this prevents subsystem-level runtime PM
406 pending runtime PM operations on the device are either completed or
413 (synchronously) in that case, cancel any other pending runtime PM requests
414 regarding it and wait for all runtime PM operations on it in progress to
424 PM status to 'active' and update its parent's counter of 'active'
432 PM status to 'suspended' and update its parent's counter of 'active'
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
464 PM attributes from /sys/devices/.../power (or prevent them from being
468 - set the power.irq_safe flag for the device, causing the runtime-PM
473 the runtime-PM callbacks to be invoked with interrupts off
528 5. Runtime PM Initialization, Device Probing and Removal
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
534 In addition to that, the initial runtime PM status of all devices is
537 runtime PM status must be changed to 'active', with the help of
540 However, if the device has a parent and the parent's runtime PM is enabled,
543 parent won't be able to suspend at run time, using the PM core's helper
545 runtime PM is still disabled (i.e. pm_runtime_enable() hasn't been called for
548 should be called for it too as soon as reasonably possible or its runtime PM
552 If the default initial runtime PM status of the device (i.e. 'suspended')
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
565 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
568 runtime PM functionality. It does so by calling pm_runtime_get_sync() before
577 drivers to make their ->remove() callbacks avoid races with runtime PM directly,
586 Namely, during the initialization the driver can make sure that the runtime PM
593 6. Runtime PM and System Sleep
595 Runtime PM and system sleep (i.e., system suspend and hibernation, also known
600 The device may have different wake-up settings for runtime PM and system sleep.
629 brought back to full power during resume, then its runtime PM status will have
637 The PM core always increments the runtime usage counter before calling the
639 Hence disabling runtime PM temporarily like this will not cause any runtime
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
661 left in runtime suspend. If that happens, the PM core will not execute any
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
675 subsystem-level .suspend() callback for it. In addition to that the PM core
688 management callbacks provided by the PM core, defined in
711 if successful, change the device's runtime PM status to 'active'
748 if successful, change the device's runtime PM status to 'active'
753 These functions are the defaults used by the PM core, if a subsystem doesn't
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
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
805 the appropriate PM routines); rather it means that runtime suspends will
836 pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
842 However such use inevitably involves races, because the PM core can't