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 bd4ffb5..a66bec2 100644 (file)
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -44,7 +44,7 @@ it.
 /sys/power/image_size controls the size of the image created by
 the suspend-to-disk mechanism.  It can be written a string
 representing a non-negative integer that will be used as an upper
-limit of the image size, in megabytes.  The suspend-to-disk mechanism will
+limit of the image size, in bytes.  The suspend-to-disk mechanism will
 do its best to ensure the image size will not exceed that number.  However,
 if this turns out to be impossible, it will try to suspend anyway using the
 smallest image possible.  In particular, if "0" is written to this file, the
@@ -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.
+
+/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.