PM: Add a switch for disabling/enabling asynchronous suspend/resume

Add sysfs attribute /sys/power/pm_async allowing the user space to
disable/enable asynchronous suspend/resume of devices.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index dcff4d0623ad..d6a801f45b48 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -101,3 +101,16 @@ Description:
 
                 CAUTION: Using it will cause your machine's real-time (CMOS)
                 clock to be set to a random invalid time after a resume.
+
+What:           /sys/power/pm_async
+Date:           January 2009
+Contact:        Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+                The /sys/power/pm_async file controls the switch allowing the
+                user space to enable or disable asynchronous suspend and resume
+                of devices.  If enabled, this feature will cause some device
+                drivers' suspend and resume callbacks to be executed in parallel
+                with each other and with the main suspend thread.  It is enabled
+                if this file contains "1", which is the default.  It may be
+                disabled by writing "0" to this file, in which case all devices
+                will be suspended and resumed synchronously.