Merge git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6

[pandora-kernel.git] / Documentation / power / interface.txt

diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index 4117802..a66bec2 100644 (file)
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -52,3 +52,18 @@ suspend image will be as small as possible.
 
 Reading from this file will display the current image size limit, which
 is set to 500 MB by default.
 
 Reading from this file will display the current image size limit, which
 is set to 500 MB by default.

+
+/sys/power/pm_trace controls the code which saves the last PM event point in
+the RTC across reboots, so that you can debug a machine that just hangs
+during suspend (or more commonly, during resume).  Namely, the RTC is only
+used to save the last PM event point if this file contains '1'.  Initially it
+contains '0' which may be changed to '1' by writing a string representing a
+nonzero integer into it.
+
+To use this debugging feature you should attempt to suspend the machine, then
+reboot it and run
+
+       dmesg -s 1000000 | grep 'hash matches'
+
+CAUTION: Using it will cause your machine's real-time (CMOS) clock to be
+set to a random invalid time after a resume.