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Merge back PM core material for v4.16.

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Rafael J. Wysocki
2017-12-16 02:05:48 +01:00
parent 3487972d7f 34fb8f0ba9
commit c51a024e39
7 changed files with 253 additions and 133 deletions
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27
Documentation/driver-api/pm/devices.rst
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@ -788,6 +788,29 @@ must reflect the "active" status for runtime PM in that case.
During system-wide resume from a sleep state it's easiest to put devices into
the full-power state, as explained in :file:`Documentation/power/runtime_pm.txt`.
Refer to that document for more information regarding this particular issue as
[Refer to that document for more information regarding this particular issue as
well as for information on the device runtime power management framework in
general.
general.]
However, it often is desirable to leave devices in suspend after system
transitions to the working state, especially if those devices had been in
runtime suspend before the preceding system-wide suspend (or analogous)
transition. Device drivers can use the ``DPM_FLAG_LEAVE_SUSPENDED`` flag to
indicate to the PM core (and middle-layer code) that they prefer the specific
devices handled by them to be left suspended and they have no problems with
skipping their system-wide resume callbacks for this reason. Whether or not the
devices will actually be left in suspend may depend on their state before the
given system suspend-resume cycle and on the type of the system transition under
way. In particular, devices are not left suspended if that transition is a
restore from hibernation, as device states are not guaranteed to be reflected
by the information stored in the hibernation image in that case.
The middle-layer code involved in the handling of the device is expected to
indicate to the PM core if the device may be left in suspend by setting its
:c:member:`power.may_skip_resume` status bit which is checked by the PM core
during the "noirq" phase of the preceding system-wide suspend (or analogous)
transition. The middle layer is then responsible for handling the device as
appropriate in its "noirq" resume callback, which is executed regardless of
whether or not the device is left suspended, but the other resume callbacks
(except for ``->complete``) will be skipped automatically by the PM core if the
device really can be left in suspend.