PM / Sleep: Implement opportunistic sleep, v2

Introduce a mechanism by which the kernel can trigger global
transitions to a sleep state chosen by user space if there are no
active wakeup sources.

It consists of a new sysfs attribute, /sys/power/autosleep, that
can be written one of the strings returned by reads from
/sys/power/state, an ordered workqueue and a work item carrying out
the "suspend" operations.  If a string representing the system's
sleep state is written to /sys/power/autosleep, the work item
triggering transitions to that state is queued up and it requeues
itself after every execution until user space writes "off" to
/sys/power/autosleep.

That work item enables the detection of wakeup events using the
functions already defined in drivers/base/power/wakeup.c (with one
small modification) and calls either pm_suspend(), or hibernate() to
put the system into a sleep state.  If a wakeup event is reported
while the transition is in progress, it will abort the transition and
the "system suspend" work item will be queued up again.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NeilBrown <neilb@suse.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index deb5461e3216..67947083f842 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -103,6 +103,14 @@ config PM_SLEEP_SMP
         select HOTPLUG
         select HOTPLUG_CPU
 
+config PM_AUTOSLEEP
+        bool "Opportunistic sleep"
+        depends on PM_SLEEP
+        default n
+        ---help---
+        Allow the kernel to trigger a system transition into a global sleep
+        state automatically whenever there are no active wakeup sources.
+
 config PM_RUNTIME
         bool "Run-time PM core functionality"
         depends on !IA64_HP_SIM