85 lines
3.3 KiB
Text
85 lines
3.3 KiB
Text
How to get s2ram working
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
2006 Linus Torvalds
|
|
2006 Pavel Machek
|
|
|
|
1) Check suspend.sf.net, program s2ram there has long whitelist of
|
|
"known ok" machines, along with tricks to use on each one.
|
|
|
|
2) If that does not help, try reading tricks.txt and
|
|
video.txt. Perhaps problem is as simple as broken module, and
|
|
simple module unload can fix it.
|
|
|
|
3) You can use Linus' TRACE_RESUME infrastructure, described below.
|
|
|
|
Using TRACE_RESUME
|
|
~~~~~~~~~~~~~~~~~~
|
|
|
|
I've been working at making the machines I have able to STR, and almost
|
|
always it's a driver that is buggy. Thank God for the suspend/resume
|
|
debugging - the thing that Chuck tried to disable. That's often the _only_
|
|
way to debug these things, and it's actually pretty powerful (but
|
|
time-consuming - having to insert TRACE_RESUME() markers into the device
|
|
driver that doesn't resume and recompile and reboot).
|
|
|
|
Anyway, the way to debug this for people who are interested (have a
|
|
machine that doesn't boot) is:
|
|
|
|
- enable PM_DEBUG, and PM_TRACE
|
|
|
|
- use a script like this:
|
|
|
|
#!/bin/sh
|
|
sync
|
|
echo 1 > /sys/power/pm_trace
|
|
echo mem > /sys/power/state
|
|
|
|
to suspend
|
|
|
|
- if it doesn't come back up (which is usually the problem), reboot by
|
|
holding the power button down, and look at the dmesg output for things
|
|
like
|
|
|
|
Magic number: 4:156:725
|
|
hash matches drivers/base/power/resume.c:28
|
|
hash matches device 0000:01:00.0
|
|
|
|
which means that the last trace event was just before trying to resume
|
|
device 0000:01:00.0. Then figure out what driver is controlling that
|
|
device (lspci and /sys/devices/pci* is your friend), and see if you can
|
|
fix it, disable it, or trace into its resume function.
|
|
|
|
If no device matches the hash (or any matches appear to be false positives),
|
|
the culprit may be a device from a loadable kernel module that is not loaded
|
|
until after the hash is checked. You can check the hash against the current
|
|
devices again after more modules are loaded using sysfs:
|
|
|
|
cat /sys/power/pm_trace_dev_match
|
|
|
|
For example, the above happens to be the VGA device on my EVO, which I
|
|
used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
|
|
that "radeonfb" simply cannot resume that device - it tries to set the
|
|
PLL's, and it just _hangs_. Using the regular VGA console and letting X
|
|
resume it instead works fine.
|
|
|
|
NOTE
|
|
====
|
|
pm_trace uses the system's Real Time Clock (RTC) to save the magic number.
|
|
Reason for this is that the RTC is the only reliably available piece of
|
|
hardware during resume operations where a value can be set that will
|
|
survive a reboot.
|
|
|
|
pm_trace is not compatible with asynchronous suspend, so it turns
|
|
asynchronous suspend off (which may work around timing or
|
|
ordering-sensitive bugs).
|
|
|
|
Consequence is that after a resume (even if it is successful) your system
|
|
clock will have a value corresponding to the magic number instead of the
|
|
correct date/time! It is therefore advisable to use a program like ntp-date
|
|
or rdate to reset the correct date/time from an external time source when
|
|
using this trace option.
|
|
|
|
As the clock keeps ticking it is also essential that the reboot is done
|
|
quickly after the resume failure. The trace option does not use the seconds
|
|
or the low order bits of the minutes of the RTC, but a too long delay will
|
|
corrupt the magic value.
|