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authorRafael J. Wysocki <rjw@sisk.pl>2006-09-26 02:32:58 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-26 11:49:04 -0400
commitc5c6ba4e08ab9c9e390a0f3a7d9a5c332f5cc6ef (patch)
tree4e13a9eebd8f3901dcc187c585369ef843d1e1a7 /Documentation
parent7d145aa3abf4d96c91f37c012facd5cfbb9010d1 (diff)
[PATCH] PM: Add pm_trace switch
Add the pm_trace attribute in /sys/power which has to be explicitly set to one to really enable the "PM tracing" code compiled in when CONFIG_PM_TRACE is set (which modifies the machine's CMOS clock in unpredictable ways). Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/power/interface.txt15
1 files changed, 15 insertions, 0 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index 4117802af0f8..a66bec222b16 100644
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -52,3 +52,18 @@ suspend image will be as small as possible.
52 52
53Reading from this file will display the current image size limit, which 53Reading from this file will display the current image size limit, which
54is set to 500 MB by default. 54is set to 500 MB by default.
55
56/sys/power/pm_trace controls the code which saves the last PM event point in
57the RTC across reboots, so that you can debug a machine that just hangs
58during suspend (or more commonly, during resume). Namely, the RTC is only
59used to save the last PM event point if this file contains '1'. Initially it
60contains '0' which may be changed to '1' by writing a string representing a
61nonzero integer into it.
62
63To use this debugging feature you should attempt to suspend the machine, then
64reboot it and run
65
66 dmesg -s 1000000 | grep 'hash matches'
67
68CAUTION: Using it will cause your machine's real-time (CMOS) clock to be
69set to a random invalid time after a resume.