diff options
| author | Rafael J. Wysocki | 2011-07-02 14:27:11 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki | 2011-07-02 14:27:11 +0200 |
| commit | f5da24dbed213d103f00aa9ef26e010b50d2db24 (patch) | |
| tree | e98c31872c95a0223b4436fa909c48749c1346c2 /Documentation/power | |
| parent | 5efb54cc3fc104585cda81c44676f05115bd9ddd (diff) | |
PM / Runtime: Update documentation regarding driver removal
Commit e1866b33b1e89f077b7132daae3dfd9a594e9a1a (PM / Runtime: Rework
runtime PM handling during driver removal) forgot to update the
documentation in Documentation/power/runtime_pm.txt to match the new
code in drivers/base/dd.c. Update that documentation to match the
code it describes.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 26 |
1 files changed, 21 insertions, 5 deletions
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 518d9be4c731..b24875b1ced5 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -501,13 +501,29 @@ helper functions described in Section 4. In that case, pm_runtime_resume() should be used. Of course, for this purpose the device's run-time PM has to be enabled earlier by calling pm_runtime_enable(). -If the device bus type's or driver's ->probe() or ->remove() callback runs +If the device bus type's or driver's ->probe() callback runs pm_runtime_suspend() or pm_runtime_idle() or their asynchronous counterparts, they will fail returning -EAGAIN, because the device's usage counter is -incremented by the core before executing ->probe() and ->remove(). Still, it -may be desirable to suspend the device as soon as ->probe() or ->remove() has -finished, so the PM core uses pm_runtime_put_sync() to invoke the -subsystem-level idle callback for the device at that time. +incremented by the driver core before executing ->probe(). Still, it may be +desirable to suspend the device as soon as ->probe() has finished, so the driver +core uses pm_runtime_put_sync() to invoke the subsystem-level idle callback for +the device at that time. + +Moreover, the driver core prevents runtime PM callbacks from racing with the bus +notifier callback in __device_release_driver(), which is necessary, because the +notifier is used by some subsystems to carry out operations affecting the +runtime PM functionality. It does so by calling pm_runtime_get_sync() before +driver_sysfs_remove() and the BUS_NOTIFY_UNBIND_DRIVER notifications. This +resumes the device if it's in the suspended state and prevents it from +being suspended again while those routines are being executed. + +To allow bus types and drivers to put devices into the suspended state by +calling pm_runtime_suspend() from their ->remove() routines, the driver core +executes pm_runtime_put_sync() after running the BUS_NOTIFY_UNBIND_DRIVER +notifications in __device_release_driver(). This requires bus types and +drivers to make their ->remove() callbacks avoid races with runtime PM directly, +but also it allows of more flexibility in the handling of devices during the +removal of their drivers. The user space can effectively disallow the driver of the device to power manage it at run time by changing the value of its /sys/devices/.../power/control |