1. 實驗平台

cpu: omap4460 blaze tablet

memory: 1-GB DRAM

OS: android 4.0.3, kernel 3.0.31

2.流程分析

1). echo "mem" > /sys/power/state
2). state_store() kernel/power/main.c 3). request_suspend_states(PM_SUSPEND_MEM) kernel/power/earlysuspend.c
4). queue_work(suspend_work_queue, &early_suspend_work) kernel/power/earlysuspend.c early_suspend() // call device driver's early-suspend function to turn off multi-touch, LCM, frame buffer,sensors,release "main" wakelock
5). wake_unlock(&main_wake_lock) kernel/power/wakelock.c
// if system has no activate wakelock,call kernel/power/wakelock.c suspend() start suspend progress. 6). queue_work(suspend_work_queue, &suspend_work); 7). suspend() sys_sync() pm_suspend() // here enter suspend // return from this function means exit suspend(resume)
8). pm_suspend(PM_SUSPEND_MEM) enter_state() sys_sync() suspend_prepare() pm_notifier_call_chain(PM_SUSPEND_PREPARE) suspend_freeze_processes() freeze_processes() kernel/power/process.c // the same as hibernation process to freeze user space process and task in kernel pm_restrict_gfp_mask() // avoid i/o and fs to allocate memory during suspend progress // clear bit GFP_IOFS of gfp_allowed_mask suspend_devices_and_enter() omap4_pm_begin() arch/arm/mach-omap2/pm44xx.c suspend_prepare() drivers/regulator/core.c // regulator linked with regulator_list suspend_console() dpm_suspend_start(PMSG_SUSPEND) dpm_prepare(PMSG_SUSPEND) drivers/base/power/main.c // execute ->prepare() callback for all non-sysdev devices, device list movement dpm_list-->dpm_prepared_list dpm_suspend(PMSG_SUSPEND) // execute ->suspend() callback for all non-sysdev devices, device list movement dpm_prepared_list-->dpm_suspended_list suspend_enter() dpm_suspend_noirq(PMSG_SUSPEND) // execute "late suspend" suspend_device_irqs() kernel/irq/pm.c // disable all currently enabled interrupt lines // after this function, device will can't receive interrupt device_suspend_noirq() // execute -->suspend_noirq callback for all non-sysdev devices, device list movement dpm_suspended_list-->dpm_noirq_list disable_nonboot_cpus() arch_suspend_disable_irqs() kernel/power/suspend.c local_irq_disable() // disable local cpu interrupt,so there will no interrtup from now on syscore_suspend() driver/base/syscore.c // Execute all the registered system core suspend callbacks check_wakeup_irqs() kernel/irq/pm.c // check if any wakeup interrupts are pending, if ture, exit suspend // then to execute sysdev's suspend callback, all sysdev are linked with syscore_ops_list omap4_pm_enter() arch/arm/mach-omap2/pm4xx.c omap2_pm_wakeup_on_timer() arch/arm/mach-omap2/pm-debug.c // setup a hareware timer if debug enabled omap4_configure_pwrst(off_mode_enabled) // Program all powerdomain(except cpu0_pwrdm and cpu1_pwrdm) to required power domain state // powerdomain linked with pwrst_list // off_mode_enabled = 1 omap4_device_set_state_off(1) // setup device off state omap4_enter_sleep() pwrdm_clear_all_prev_pwrst() //Clear the powerdomain's previous power state omap4_device_clear_prev_off_state() pwrdm_read_next_pwrst() //get next powerdomain power state omap2_gpio_prepare_for_idle() omap2_gpio_set_wakeupenables() // enable wakeup gpio in the list omap_gpio_list omap4_print_wakeirq() // resuming. // Print wakeup interrupt for debug xxxxxxx