fedora core 6 1.2949 + vserver 2.2.0

[linux-2.6.git] / Documentation / power / interface.txt

diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index f5ebda5..74311d7 100644 (file)
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -30,6 +30,17 @@ testing). The system will support either 'firmware' or 'platform', and
 that is known a priori. But, the user may choose 'shutdown' or
 'reboot' as alternatives. 
 
 that is known a priori. But, the user may choose 'shutdown' or
 'reboot' as alternatives. 
 

+Additionally, /sys/power/disk can be used to turn on one of the two testing
+modes of the suspend-to-disk mechanism: 'testproc' or 'test'.  If the
+suspend-to-disk mechanism is in the 'testproc' mode, writing 'disk' to
+/sys/power/state will cause the kernel to disable nonboot CPUs and freeze
+tasks, wait for 5 seconds, unfreeze tasks and enable nonboot CPUs.  If it is
+in the 'test' mode, writing 'disk' to /sys/power/state will cause the kernel
+to disable nonboot CPUs and freeze tasks, shrink memory, suspend devices, wait
+for 5 seconds, resume devices, unfreeze tasks and enable nonboot CPUs.  Then,
+we are able to look in the log messages and work out, for example, which code
+is being slow and which device drivers are misbehaving.
+

 Reading from this file will display what the mode is currently set
 to. Writing to this file will accept one of
 
 Reading from this file will display what the mode is currently set
 to. Writing to this file will accept one of
 


@@ -37,7 +48,35 @@ to. Writing to this file will accept one of
        'platform'
        'shutdown'
        'reboot'
        'platform'
        'shutdown'
        'reboot'

+       'testproc'
+       'test'

 
 It will only change to 'firmware' or 'platform' if the system supports
 it. 
 
 
 It will only change to 'firmware' or 'platform' if the system supports
 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 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
+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.