From 8dc9c7911421d8e45901ffaf483b5dca99cbb055 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Thu, 3 Nov 2011 23:39:18 +0100 Subject: PM / Runtime: Automatically retry failed autosuspends commit 886486b792e4f6f96d4fbe8ec5bf20811cab7d6a upstream. Originally, the runtime PM core would send an idle notification whenever a suspend attempt failed. The idle callback routine could then schedule a delayed suspend for some time later. However this behavior was changed by commit f71648d73c1650b8b4aceb3856bebbde6daa3b86 (PM / Runtime: Remove idle notification after failing suspend). No notifications were sent, and there was no clear mechanism to retry failed suspends. This caused problems for the usbhid driver, because it fails autosuspend attempts as long as a key is being held down. Therefore this patch (as1492) adds a mechanism for retrying failed autosuspends. If the callback routine updates the last_busy field so that the next autosuspend expiration time is in the future, the autosuspend will automatically be rescheduled. Signed-off-by: Alan Stern Tested-by: Henrik Rydberg Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- Documentation/power/runtime_pm.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation') diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index b24875b..6ade987 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -708,6 +708,16 @@ 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. +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 +autosuspend delay time has expired. If the ->runtime_suspend() callback +returns -EAGAIN or -EBUSY, and if the next autosuspend delay expiration time is +in the future (as it normally would be if the callback invoked +pm_runtime_mark_last_busy()), the PM core will automatically reschedule the +autosuspend. The ->runtime_suspend() callback can't do this rescheduling +itself because no suspend requests of any kind are accepted while the device is +suspending (i.e., while the callback is running). + The implementation is well suited for asynchronous use in interrupt contexts. However such use inevitably involves races, because the PM core can't synchronize ->runtime_suspend() callbacks with the arrival of I/O requests. -- cgit v1.1