1			How to get s2ram working
2			~~~~~~~~~~~~~~~~~~~~~~~~
3			2006 Linus Torvalds
4			2006 Pavel Machek
5
61) Check suspend.sf.net, program s2ram there has long whitelist of
7   "known ok" machines, along with tricks to use on each one.
8
92) If that does not help, try reading tricks.txt and
10   video.txt. Perhaps problem is as simple as broken module, and
11   simple module unload can fix it.
12
133) You can use Linus' TRACE_RESUME infrastructure, described below.
14
15		      Using TRACE_RESUME
16		      ~~~~~~~~~~~~~~~~~~
17
18I've been working at making the machines I have able to STR, and almost
19always it's a driver that is buggy. Thank God for the suspend/resume
20debugging - the thing that Chuck tried to disable. That's often the _only_
21way to debug these things, and it's actually pretty powerful (but
22time-consuming - having to insert TRACE_RESUME() markers into the device
23driver that doesn't resume and recompile and reboot).
24
25Anyway, the way to debug this for people who are interested (have a
26machine that doesn't boot) is:
27
28 - enable PM_DEBUG, and PM_TRACE
29
30 - use a script like this:
31
32	#!/bin/sh
33	sync
34	echo 1 > /sys/power/pm_trace
35	echo mem > /sys/power/state
36
37   to suspend
38
39 - if it doesn't come back up (which is usually the problem), reboot by
40   holding the power button down, and look at the dmesg output for things
41   like
42
43	Magic number: 4:156:725
44	hash matches drivers/base/power/resume.c:28
45	hash matches device 0000:01:00.0
46
47   which means that the last trace event was just before trying to resume
48   device 0000:01:00.0. Then figure out what driver is controlling that
49   device (lspci and /sys/devices/pci* is your friend), and see if you can
50   fix it, disable it, or trace into its resume function.
51
52For example, the above happens to be the VGA device on my EVO, which I
53used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
54that "radeonfb" simply cannot resume that device - it tries to set the
55PLL's, and it just _hangs_. Using the regular VGA console and letting X
56resume it instead works fine.
57