107 lines
5.1 KiB
Plaintext
107 lines
5.1 KiB
Plaintext
Debugging suspend and resume
|
|
(C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
|
|
|
|
1. Testing suspend to disk (STD)
|
|
|
|
To verify that the STD works, you can try to suspend in the "reboot" mode:
|
|
|
|
# echo reboot > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
and the system should suspend, reboot, resume and get back to the command prompt
|
|
where you have started the transition. If that happens, the STD is most likely
|
|
to work correctly, but you need to repeat the test at least a couple of times in
|
|
a row for confidence. This is necessary, because some problems only show up on
|
|
a second attempt at suspending and resuming the system. You should also test
|
|
the "platform" and "shutdown" modes of suspend:
|
|
|
|
# echo platform > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
or
|
|
|
|
# echo shutdown > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
in which cases you will have to press the power button to make the system
|
|
resume. If that does not work, you will need to identify what goes wrong.
|
|
|
|
a) Test mode of STD
|
|
|
|
To verify if there are any drivers that cause problems you can run the STD
|
|
in the test mode:
|
|
|
|
# echo test > /sys/power/disk
|
|
# echo disk > /sys/power/state
|
|
|
|
in which case the system should freeze tasks, suspend devices, disable nonboot
|
|
CPUs (if any), wait for 5 seconds, enable nonboot CPUs, resume devices, thaw
|
|
tasks and return to your command prompt. If that fails, most likely there is
|
|
a driver that fails to either suspend or resume (in the latter case the system
|
|
may hang or be unstable after the test, so please take that into consideration).
|
|
To find this driver, you can carry out a binary search according to the rules:
|
|
- if the test fails, unload a half of the drivers currently loaded and repeat
|
|
(that would probably involve rebooting the system, so always note what drivers
|
|
have been loaded before the test),
|
|
- if the test succeeds, load a half of the drivers you have unloaded most
|
|
recently and repeat.
|
|
|
|
Once you have found the failing driver (there can be more than just one of
|
|
them), you have to unload it every time before the STD transition. In that case
|
|
please make sure to report the problem with the driver.
|
|
|
|
It is also possible that a cycle can still fail after you have unloaded
|
|
all modules. In that case, you would want to look in your kernel configuration
|
|
for the drivers that can be compiled as modules (testing again with them as
|
|
modules), and possibly also try boot time options such as "noapic" or "noacpi".
|
|
|
|
b) Testing minimal configuration
|
|
|
|
If the test mode of STD works, you can boot the system with "init=/bin/bash"
|
|
and attempt to suspend in the "reboot", "shutdown" and "platform" modes. If
|
|
that does not work, there probably is a problem with a driver statically
|
|
compiled into the kernel and you can try to compile more drivers as modules,
|
|
so that they can be tested individually. Otherwise, there is a problem with a
|
|
modular driver and you can find it by loading a half of the modules you normally
|
|
use and binary searching in accordance with the algorithm:
|
|
- if there are n modules loaded and the attempt to suspend and resume fails,
|
|
unload n/2 of the modules and try again (that would probably involve rebooting
|
|
the system),
|
|
- if there are n modules loaded and the attempt to suspend and resume succeeds,
|
|
load n/2 modules more and try again.
|
|
|
|
Again, if you find the offending module(s), it(they) must be unloaded every time
|
|
before the STD transition, and please report the problem with it(them).
|
|
|
|
c) Advanced debugging
|
|
|
|
In case the STD does not work on your system even in the minimal configuration
|
|
and compiling more drivers as modules is not practical or some modules cannot
|
|
be unloaded, you can use one of the more advanced debugging techniques to find
|
|
the problem. First, if there is a serial port in your box, you can boot the
|
|
kernel with the 'no_console_suspend' parameter and try to log kernel
|
|
messages using the serial console. This may provide you with some information
|
|
about the reasons of the suspend (resume) failure. Alternatively, it may be
|
|
possible to use a FireWire port for debugging with firescope
|
|
(ftp://ftp.firstfloor.org/pub/ak/firescope/). On i386 it is also possible to
|
|
use the PM_TRACE mechanism documented in Documentation/s2ram.txt .
|
|
|
|
2. Testing suspend to RAM (STR)
|
|
|
|
To verify that the STR works, it is generally more convenient to use the s2ram
|
|
tool available from http://suspend.sf.net and documented at
|
|
http://en.opensuse.org/s2ram . However, before doing that it is recommended to
|
|
carry out the procedure described in section 1.
|
|
|
|
Assume you have resolved the problems with the STD and you have found some
|
|
failing drivers. These drivers are also likely to fail during the STR or
|
|
during the resume, so it is better to unload them every time before the STR
|
|
transition. Now, you can follow the instructions at
|
|
http://en.opensuse.org/s2ram to test the system, but if it does not work
|
|
"out of the box", you may need to boot it with "init=/bin/bash" and test
|
|
s2ram in the minimal configuration. In that case, you may be able to search
|
|
for failing drivers by following the procedure analogous to the one described in
|
|
1b). If you find some failing drivers, you will have to unload them every time
|
|
before the STR transition (ie. before you run s2ram), and please report the
|
|
problems with them.
|