Android suspend-to-mem 流程分析

1. 实验平台

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