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authorJames Hogan <james@albanarts.com>2010-10-11 18:00:25 -0400
committerRafael J. Wysocki <rjw@sisk.pl>2010-10-16 19:57:50 -0400
commitd33ac60beaf2c7dee5cd90aba7c1eb385dd70937 (patch)
tree7393c5f323433f39d2c64e7d9990aa7565397214 /Documentation/ABI
parent2ac21c6bc4249ee6d922f18dbec7266377592c32 (diff)
PM: Add sysfs attr for rechecking dev hash from PM trace
If the device which fails to resume is part of a loadable kernel module it won't be checked at startup against the magic number stored in the RTC. Add a read-only sysfs attribute /sys/power/pm_trace_dev_match which contains a list of newline separated devices (usually just the one) which currently match the last magic number. This allows the device which is failing to resume to be found after the modules are loaded again. Signed-off-by: James Hogan <james@albanarts.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-power29
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index 2875f1f74a0..194ca446ac2 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -99,9 +99,38 @@ Description:
99 99
100 dmesg -s 1000000 | grep 'hash matches' 100 dmesg -s 1000000 | grep 'hash matches'
101 101
102 If you do not get any matches (or they appear to be false
103 positives), it is possible that the last PM event point
104 referred to a device created by a loadable kernel module. In
105 this case cat /sys/power/pm_trace_dev_match (see below) after
106 your system is started up and the kernel modules are loaded.
107
102 CAUTION: Using it will cause your machine's real-time (CMOS) 108 CAUTION: Using it will cause your machine's real-time (CMOS)
103 clock to be set to a random invalid time after a resume. 109 clock to be set to a random invalid time after a resume.
104 110
111What; /sys/power/pm_trace_dev_match
112Date: October 2010
113Contact: James Hogan <james@albanarts.com>
114Description:
115 The /sys/power/pm_trace_dev_match file contains the name of the
116 device associated with the last PM event point saved in the RTC
117 across reboots when pm_trace has been used. More precisely it
118 contains the list of current devices (including those
119 registered by loadable kernel modules since boot) which match
120 the device hash in the RTC at boot, with a newline after each
121 one.
122
123 The advantage of this file over the hash matches printed to the
124 kernel log (see /sys/power/pm_trace), is that it includes
125 devices created after boot by loadable kernel modules.
126
127 Due to the small hash size necessary to fit in the RTC, it is
128 possible that more than one device matches the hash, in which
129 case further investigation is required to determine which
130 device is causing the problem. Note that genuine RTC clock
131 values (such as when pm_trace has not been used), can still
132 match a device and output it's name here.
133
105What: /sys/power/pm_async 134What: /sys/power/pm_async
106Date: January 2009 135Date: January 2009
107Contact: Rafael J. Wysocki <rjw@sisk.pl> 136Contact: Rafael J. Wysocki <rjw@sisk.pl>