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Linus posted quite nice TRACE_RESUME how-to, and I think it is too nice to be hidden in archives of mailing list, so I turned it into Documentation piece. Signed-off-by: Pavel Machek <pavel@suse.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
57 lines
2.0 KiB
Plaintext
57 lines
2.0 KiB
Plaintext
How to get s2ram working
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~~~~~~~~~~~~~~~~~~~~~~~~
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2006 Linus Torvalds
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2006 Pavel Machek
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1) Check suspend.sf.net, program s2ram there has long whitelist of
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"known ok" machines, along with tricks to use on each one.
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2) If that does not help, try reading tricks.txt and
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video.txt. Perhaps problem is as simple as broken module, and
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simple module unload can fix it.
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3) You can use Linus' TRACE_RESUME infrastructure, described below.
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Using TRACE_RESUME
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~~~~~~~~~~~~~~~~~~
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I've been working at making the machines I have able to STR, and almost
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always it's a driver that is buggy. Thank God for the suspend/resume
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debugging - the thing that Chuck tried to disable. That's often the _only_
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way to debug these things, and it's actually pretty powerful (but
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time-consuming - having to insert TRACE_RESUME() markers into the device
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driver that doesn't resume and recompile and reboot).
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Anyway, the way to debug this for people who are interested (have a
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machine that doesn't boot) is:
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- enable PM_DEBUG, and PM_TRACE
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- use a script like this:
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#!/bin/sh
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sync
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echo 1 > /sys/power/pm_trace
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echo mem > /sys/power/state
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to suspend
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- if it doesn't come back up (which is usually the problem), reboot by
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holding the power button down, and look at the dmesg output for things
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like
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Magic number: 4:156:725
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hash matches drivers/base/power/resume.c:28
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hash matches device 0000:01:00.0
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which means that the last trace event was just before trying to resume
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device 0000:01:00.0. Then figure out what driver is controlling that
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device (lspci and /sys/devices/pci* is your friend), and see if you can
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fix it, disable it, or trace into its resume function.
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For example, the above happens to be the VGA device on my EVO, which I
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used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
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that "radeonfb" simply cannot resume that device - it tries to set the
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PLL's, and it just _hangs_. Using the regular VGA console and letting X
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resume it instead works fine.
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