Commit bafdcde7 authored by Johan Hovold's avatar Johan Hovold Committed by Rafael J. Wysocki
Browse files

PM / runtime: Document autosuspend-helper side effects 



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: default avatarJohan Hovold <johan@kernel.org>
Acked-by: default avatarTony Lindgren <tony@atomide.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 72ec2e17

Documentation/power/runtime_pm.txt

+11 −3
Original line number Diff line number Diff line
@@ -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,

CRA Git | Maintained and supported by SUSTech CRA and CCSE