Lines Matching refs:PM
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
24 * A number of runtime PM fields in the 'power' member of 'struct device' (which
26 be used for synchronizing runtime PM operations with one another.
28 * Three device runtime PM callbacks in 'struct dev_pm_ops' (defined in
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'::
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,
68 callback, the PM core will invoke the corresponding driver callback stored in
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
74 a low-priority one. The PM domain, bus type, device type and class callbacks
79 the PM core that it is safe to run the ->runtime_suspend(), ->runtime_resume()
89 PM core's point of view it is not necessary to implement a ->runtime_suspend()
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
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
124 PM core's point of view it is not necessary to implement a ->runtime_resume()
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
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,
161 error return codes are ignored by the PM core.
163 The helper functions provided by the PM core, described in Section 4, guarantee
164 that the following constraints are met with respect to runtime PM callbacks for
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
185 PM core will only execute ->runtime_resume() for the devices the runtime
186 PM status of which is 'suspended').
188 Additionally, the helper functions provided by the PM core obey the following
205 3. Runtime PM Device Fields
208 The following device runtime PM fields are present in 'struct dev_pm_info', as
240 equal to zero); the initial value of it is 1 (i.e. runtime PM is
264 - the runtime PM status of the device; this field's initial value is
266 PM core as 'suspended', regardless of its real hardware status
275 - indicates that the device does not use the runtime PM callbacks (see
289 - indicates that the PM core should attempt to carry out an autosuspend
302 4. Runtime PM Device Helper Functions
305 The following runtime PM helper functions are defined in
309 - initialize the device runtime PM fields in 'struct dev_pm_info'
312 - make sure that the runtime PM of the device will be disabled after
323 success, 1 if the device's runtime PM status was already 'suspended', or
336 success, 1 if the device's runtime PM status was already 'active' or
356 item is queued up immediately); returns 0 on success, 1 if the device's PM
365 success, 1 if the device's runtime PM status was already 'active', or
381 runtime PM status is RPM_ACTIVE and the runtime PM usage counter is
387 runtime PM status is RPM_ACTIVE, and either ign_usage_count is true
416 to zero, the runtime PM helper functions can execute subsystem-level
421 field was previously zero, this prevents subsystem-level runtime PM
423 pending runtime PM operations on the device are either completed or
430 (synchronously) in that case, cancel any other pending runtime PM requests
431 regarding it and wait for all runtime PM operations on it in progress to
441 PM status to 'active' and update its parent's counter of 'active'
449 PM status to 'suspended' and update its parent's counter of 'active'
455 - return true if the device's runtime PM status is 'active' or its
459 - return true if the device's runtime PM status is 'suspended' and its
463 - return true if the device's runtime PM status is 'suspended'
477 PM attributes from /sys/devices/.../power (or prevent them from being
481 - set the power.irq_safe flag for the device, causing the runtime-PM
486 the runtime-PM callbacks to be invoked with interrupts off
549 5. Runtime PM Initialization, Device Probing and Removal
552 Initially, the runtime PM is disabled for all devices, which means that the
553 majority of the runtime PM helper functions described in Section 4 will return
556 In addition to that, the initial runtime PM status of all devices is
559 runtime PM status must be changed to 'active', with the help of
562 However, if the device has a parent and the parent's runtime PM is enabled,
565 parent won't be able to suspend at run time, using the PM core's helper
567 runtime PM is still disabled (i.e. pm_runtime_enable() hasn't been called for
570 should be called for it too as soon as reasonably possible or its runtime PM
574 If the default initial runtime PM status of the device (i.e. 'suspended')
576 ->probe() callback will likely need to wake it up using one of the PM core's
578 should be used. Of course, for this purpose the device's runtime PM has to be
593 Moreover, the driver core prevents runtime PM callbacks from racing with the bus
596 runtime PM functionality. It does so by calling pm_runtime_get_sync() before
605 drivers to make their ->remove() callbacks avoid races with runtime PM directly,
609 Drivers in ->remove() callback should undo the runtime PM changes done
618 Namely, during the initialization the driver can make sure that the runtime PM
625 6. Runtime PM and System Sleep
628 Runtime PM and system sleep (i.e., system suspend and hibernation, also known
633 The device may have different wake-up settings for runtime PM and system sleep.
662 brought back to full power during resume, then its runtime PM status will have
670 The PM core always increments the runtime usage counter before calling the
672 Hence disabling runtime PM temporarily like this will not cause any runtime
689 To this end, the PM core provides a mechanism allowing some coordination between
691 callback returns a positive number for a device, that indicates to the PM core
694 left in runtime suspend. If that happens, the PM core will not execute any
701 The PM core does its best to reduce the probability of race conditions between
702 the runtime PM and system suspend/resume (and hibernation) callbacks by carrying
708 subsystem-level .suspend() callback for it. In addition to that the PM core
721 management callbacks provided by the PM core, defined in
744 if successful, change the device's runtime PM status to 'active'
781 if successful, change the device's runtime PM status to 'active'
786 These functions are the defaults used by the PM core, if a subsystem doesn't
806 need of runtime PM callbacks; if the callbacks did exist, ->runtime_suspend()
810 Subsystems can tell the PM core about these devices by calling
814 prevent the non-debugging runtime PM sysfs attributes from being created.
816 When power.no_callbacks is set, the PM core will not invoke the
821 As a consequence, the PM core will never directly inform the device's subsystem
840 the appropriate PM routines); rather it means that runtime suspends will
870 pm_runtime_mark_last_busy()), the PM core will automatically reschedule the
876 However such use inevitably involves races, because the PM core can't