Suspend debugging
Usefull links
[PATCH v3 13/28] ARM: tegra: Add suspend and hotplug support
Linux Kernel and Android Suspend/Resume
suspend/resume debugging: device filter
Debugging hibernation and suspend
Linux Kernel and Android Suspend/Resume -blog archive
Doesn't want to wake up?
OK. With that understood.... In order to simulate your suspend/resume process, enter the following commands:
sudo sh -c "sync; echo 1 > /sys/power/pm_trace; pm-suspend"
At this point your computer should enter the suspend state within a few seconds. Usually the power LED will slowly flash when in the suspended state. When that has happened, initiate the resume process by pressing the power button. Observe closely if the disk light comes on briefly. This indicates that resume has begun. If resume fails to complete, then press the power button until the computer turns off. Power on your computer making sure that it loads the same kernel that exhibited the resume problem. You have about 3 minutes to start this boot process before the information saved in the RTC gets corrupted.
Start a console and enter:
dmesg > dmesg.txt
You can edit this file and find lines similar to these:
[ 11.323206] Magic number: 0:798:264 [ 11.323257] hash matches drivers/base/power/resume.c:46
There may well be another 'hash matches' line beyond that. If so, then you are in luck because the last one is the likely culprit. For example:
hash matches device i2c-9191
The only way to prove this is to remove the module prior to initiating suspend. Repeat as needed...
If you get a device number rather than name, lspci and /sys/devices/pci* are your friends.
Logs
suspend cm10 beta3 wifi on, no ac
Patches
https://gitorious.org/ac100/kernel/commit/b3380bae699f1cf315836f77b2abf05e3549e0fa
https://gitorious.org/ac100/kernel/commit/1d0d7ff80526d0f6451d230a81349dac01b466c1
Code analysis
Call stack (based on sources):
pm_suspend (kernel/power/main.c)
{
enter_state (kernel/power/suspend.c)
{
suspend_prepare (kernel/power/suspend.c)
suspend_test(TEST_FREEZER) (kernel/power/suspend.c)
suspend_devices_and_enter (kernel/power/suspend.c)
{
platform_suspend_begin (kernel/power/suspend.c)
suspend_console (kernel/printk/printk.c)
suspend_test_start (kernel/power/suspend_test.c)
dpm_suspend_start (drivers/base/power/main.c)
{
dpm_prepare
dpm_suspend
cpufreq_suspend
for_all( device_suspend )
}
suspend_test_finish (kernel/power/suspend_test.c)
suspend_test(TEST_DEVICES) (kernel/power/suspend.c)
suspend_enter (kernel/power/suspend.c)
{
platform_suspend_prepare
dpm_suspend_late
platform_suspend_prepare_late
dpm_suspend_noirq
platform_suspend_prepare_noirq
suspend_test(TEST_PLATFORM)
disable_nonboot_cpus
suspend_test(TEST_CPUS)
arch_suspend_disable_irqs
syscore_suspend
suspend_test(TEST_CORE)
suspend_ops->enter
syscore_resume
}
}
}
}
Important: function suspend_test(level) (kernel/power/suspend.c) - compares level and pm_test_level. If they match function do mdelay(5000) and abort suspend process. We can abort suspend/freeze process in specified states:
suspend_test(TEST_FREEZER) suspend_test(TEST_DEVICES) suspend_test(TEST_PLATFORM) suspend_test(TEST_CPUS) suspend_test(TEST_CORE)
This logic works only if CONFIG_PM_DEBUG is enabled.
Magic
There is PM_TRACE support for x86 architecture. The main idea is to keep some values between reboots. For x86 the data is saved in RTC. PM_TRACE is not implemented for ARM.
Tests
- don't disable serial console during suspend - no_console_suspend=1 (in cmdline)
- PM_DEBUG and PM_TRACE must be enabled
Looks like AC100 failes to resume from devices state.
cat /sys/power/pm_test # here will be available values echo freezer > /sys/power/pm_test echo mem > /sys/power/state # OK echo devices > /sys/power/pm_test echo mem > /sys/power/state # Fail (usually, wake up 1 time of 7)