Suspend debugging

Usefull links

[PATCH v3 13/28] ARM: tegra: Add suspend and hotplug support

Linux Kernel and Android Suspend/Resume

How to get s2ram working

suspend/resume debugging: device filter

Debugging hibernation and suspend

DebuggingKernelSuspend

Linux Kernel and Android Suspend/Resume -blog archive

Android Power Management

EC overview

Logs

lp1 early suspend crach 2

rel-15r7 suspend->wakeup

suspend cm10 beta3 wifi on, no ac

u-boot lp1 no nvec

Patches

https://gitorious.org/~marvin24/ac100/marvin24s-kernel/commit/312cef53a6ebfbe1f09b8a053fdc726515861d22

https://gitorious.org/ac100/kernel/commit/b3380bae699f1cf315836f77b2abf05e3549e0fa

https://gitorious.org/ac100/kernel/commit/1d0d7ff80526d0f6451d230a81349dac01b466c1

Suspend 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.

Tracing

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. NOTE: looks like pm_trace is x68/64 only.

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)

Plan

• set up tftpboot (for easier boot process between dev kernels)
• check devices suspend/resume on latest NVEC patches for mainline
• check suspend/resume with disabled PM for nvec
• check suspend/resume with disabled PM for i2c-2 (where nvec is placed)
• try to implement trace logic for suspend