PM / Runtime: fix autosuspend documentation
PATCH 1/2 PM / Runtime: fix autosuspend documentation
Update the autosuspend documentation which claimed that the autosuspend delay is not taken into account when using the non-autosuspend helper functions, something which is no longer true since commit d66e6db28df3 ("PM / Runtime: Respect autosuspend when idle triggers suspend").
This specifically means that drivers must now disable autosuspend before disabling runtime pm in probe error paths and remove callbacks if pm_runtime_put_sync was being used to suspend the device before returning. (If an idle callback can prevent suspend, pm_runtime_put_sync_suspend must be used instead of pm_runtime_put_sync as before.)
Also remove the claim that the autosuspend helpers behave "just like the non-autosuspend counterparts", something which have never really been true as some of the latter use idle notifications.
--- Documentation/power/runtime_pm.txt | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
Documentation/power/runtime_pm.txt +2 -3
@@ -836,9 +836,8 @@ of the non-autosuspend counterparts: Instead of: pm_runtime_put_sync use: pm_runtime_put_sync_autosuspend. Drivers may also continue to use the non-autosuspend helper functions; they -will behave normally, not taking the autosuspend delay into account. -Similarly, if the power.use_autosuspend field isn't set then the autosuspend -helper functions will behave just like the non-autosuspend counterparts. +will behave normally, which means sometimes taking the autosuspend delay into +account (see pm_runtime_idle). Under some circumstances a driver or subsystem may want to prevent a device from autosuspending immediately, even though the usage counter is zero and the
Signature · 1 line
2.12.2
PATCH 2/2 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).
--- Documentation/power/runtime_pm.txt | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
Documentation/power/runtime_pm.txt +11 -3
@@ -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,
Signature · 1 line
2.12.2
Re: [PATCH 2/2] PM / Runtime: document autosuspend-helper side effects
Quoted 10 lines · Johan Hovold
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 <[email protected]>
Quoted 12 lines · Johan Hovold
Update the autosuspend documentation which claimed that the autosuspend delay is not taken into account when using the non-autosuspend helper functions, something which is no longer true since commit
d66e6db28df3("PM / Runtime: Respect autosuspend when idle triggers suspend").This specifically means that drivers must now disable autosuspend before disabling runtime pm in probe error paths and remove callbacks if
pm_runtime_put_syncwas being used to suspend the device before returning. (If an idle callback can prevent suspend,pm_runtime_put_sync_suspendmust be used instead ofpm_runtime_put_syncas before.)
Quoted 5 lines
Also remove the claim that the autosuspend helpers behave "just like the non-autosuspend counterparts", something which have never really been true as some of the latter use idle notifications.
Signed-off-by Johan Hovold <[email protected]>