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PM / runtime: Document autosuspend-helper side effects

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Document the fact that the autosuspend delay and enable helpers may
change the power.usage_count and resume or suspend a device depending on
the values of power.autosuspend_delay and power.use_autosuspend.

Note that this means that a driver must disable autosuspend before
disabling runtime pm on probe errors and on driver unbind if the device
is to be suspended upon return (as a negative delay may otherwise keep
the device resumed).

Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Johan Hovold 2017-04-10 13:38:25 +02:00 committed by Rafael J. Wysocki
parent 72ec2e17f9
commit bafdcde73b
1 changed files with 11 additions and 3 deletions
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14
Documentation/power/runtime_pm.txt
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@ -478,15 +478,23 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
- set the power.last_busy field to the current time
void pm_runtime_use_autosuspend(struct device *dev);
- set the power.use_autosuspend flag, enabling autosuspend delays
- set the power.use_autosuspend flag, enabling autosuspend delays; call
pm_runtime_get_sync if the flag was previously cleared and
power.autosuspend_delay is negative
void pm_runtime_dont_use_autosuspend(struct device *dev);
- clear the power.use_autosuspend flag, disabling autosuspend delays
- clear the power.use_autosuspend flag, disabling autosuspend delays;
decrement the device's usage counter if the flag was previously set and
power.autosuspend_delay is negative; call pm_runtime_idle
void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
- set the power.autosuspend_delay value to 'delay' (expressed in
milliseconds); if 'delay' is negative then runtime suspends are
prevented
prevented; if power.use_autosuspend is set, pm_runtime_get_sync may be
called or the device's usage counter may be decremented and
pm_runtime_idle called depending on if power.autosuspend_delay is
changed to or from a negative value; if power.use_autosuspend is clear,
pm_runtime_idle is called
unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
- calculate the time when the current autosuspend delay period will expire,