android休眠與喚醒驅(qū)動流程分析

1、android休眠與喚醒驅(qū)動流程分析標準linux休眠過程：powermanagementnotifiersareexecutedwithPM_SUSPEND_PREPAREtasksarefrozentargetsystemsleepstateisannouncedtotheplatform-handlingcodedevicesaresuspendedplatform-specificglobalsuspendpreparationmethodsareexecutednon-bootCPUsaretakenoff-lineinterruptsaredisabledontheremainin

2、g(main)CPUlatesuspendofdevicesiscarriedout(一般有一些BUSdriver的動作進行)?platform-specificglobalmethodsareinvokedtoputthesystemtosleep標準linux喚醒過程：themainCPUisswitchedtotheappropriatemode,ifnecessaryearlyresumeofdevicesiscarriedout(一般有一些BUSdriver的動作進行)?interruptsareenabledonthemainCPUnon-bootCPUsareenabledpla

3、tform-specificglobalresumepreparationmethodsareinvokeddevicesarewokenuptasksarethawedpowermanagementnotifiersareexecutedwithPM_POST_SUSPEND用戶可以通過sys文件系統(tǒng)控制系統(tǒng)進入休眠：查看系統(tǒng)支持的休眠方式：#cat/sys/power/state常見有standby(suspendtoRAM)、mem(suspendtoRAM)和disk(suspendtodisk)，只是standby耗電更多，返回到正常工作狀態(tài)的時間更短。通過#echomem>/

4、sys/power/state讓系統(tǒng)進入休眠。Android休眠與喚醒android是在傳統(tǒng)的linux內(nèi)核電源管理設(shè)計的基礎(chǔ)上，結(jié)合手機設(shè)計的實際需求而進化出的一套電源管理系統(tǒng)，其核心內(nèi)容有：wakelock、early_suspend與late_resume。wakelock在Android的電源管理系統(tǒng)中扮演一個核心的角色。wakelock是一種鎖的機制，只要有人拿著這個鎖，系統(tǒng)就無法進入休眠，可以被用戶態(tài)程序和內(nèi)核獲得。這個鎖可以是有超時的或者是沒有超時的，超時的鎖會在時間過去以后自動解鎖。如果沒有鎖了或者超時了，內(nèi)核就會啟動休眠的那套機制來進入休眠。當系統(tǒng)在啟動完畢后，會自己去加一把

5、名為“main'的鎖，而當系統(tǒng)有意愿去睡眠時則會先去釋放這把"main”鎖，在android中，在early_suspend的最后一步會去釋放“main”鎖(wake_unlock:main)。釋放完后則會去檢查是否還有其他存在的鎖，如果沒有則直接進入睡眠過程。它的缺點是，如果有某一應(yīng)用獲鎖而不釋放或者因一直在執(zhí)行某種操作而沒時間來釋放的話，則會導致系統(tǒng)一直進入不了睡眠狀態(tài)，功耗過大。early_suspend:先與linux內(nèi)核的睡眠過程被調(diào)用。一般在手機系統(tǒng)的設(shè)計中對背光的操作等采用此類方法，因為背光需要的能耗過大。當然此操作與late_resume是配套使用的。一些在內(nèi)

6、核中要預先進行處理的事件可以先注冊上會首先調(diào)用這些注冊的函數(shù)。early_suspend函數(shù)，當系統(tǒng)要進入睡眠之前本文中，linuxkernel版本為linux-2.6.29，android版本為android2.1與android休眠喚醒主要相關(guān)的文件主要有：linux_source/kernel/power/main.clinux_source/kernel/power/earlysuspend.clinux_source/kernel/power/wakelock.clinux_source/kernel/power/process.clinux_source/driver/base/p

7、ower/main.clinux_source/arch/xxx/mach-xxx/pm.c或linux_source/arch/xxx/plat-xxx/pm.cAndroid休眠過程如下：當用戶讀寫/sys/power/state時，linux_source/kernel/power/main.c中的state_store()函數(shù)會被調(diào)用。其中，android的early_suspend會執(zhí)行request_suspend_state(state);而標準的linux休眠貝U執(zhí)行error=enter_state(state);staticssize_tstate_store(struct

8、kobject*kobj,structkobj_attribute*attr,constchar*buf,size_tn)-#ifdefCONFIG_SUSPEND#ifdefCONFIG_EARLYSUSPENDsuspend_state_tstate=PM_SUSPEND_ON;#elsesuspend_state_tstate=PM_SUSPEND_STANDBY;#endifconstchar*const*s;#endifchar*p;intlen;interror=-EINVAL;p=memchr(buf,'n',n);len=p?p-buf:n;/*First,ch

9、eckifwearerequestedtohibernate*/if(len=4&&!strncmp(buf,"disk",len)error=hibernate();gotoExit;#ifdefCONFIG_SUSPENDfor(s=&pm_statesstate;state<PM_SUSPEND_MAX;s+,state+)if(*s&&len=strlen(*s)&&!strncmp(buf,*s,len)break;if(state<PM_SUSPEND_MAX&&*s)#ifde

10、fCONFIG_EARLYSUSPENDif(state=PM_SUSPEND_ON|valid_state(state)error=0;request_suspend_state(state);-#elseerror=enter_state(state);#endif在request_suspend_state(state函數(shù)中，會調(diào)用early_suspend_work的工作隊列，從而進入early_suspend()函數(shù)中。staticDECLARE_WORK(early_suspend_work,early_suspend);voidrequest_suspend_state(susp

11、end_state_tnew_state)-unsignedlongirqflags;intold_sleep;spin_lock_irqsave(&state_lock,irqflags);old_sleep"=state&SUSPEND_REQUESTED;if(debug_mask&DEBUG_USER_STATE)structtimespects;structrtc_timetm;getnstimeofday(&ts);rtc_time_to_tm(ts.tv_sec,&tm);pr_info("request_suspend

12、_state:%s(%d->%d)at%lld"-"(%d-%02=%02d%02d:%O2d:%O2d.%O9luUTC)n",new_state!=PM_SUSPEND_ON?"sleep":"wakeup",requested_suspend_state,new_state,ktime_to_ns(ktime_get(),tm.tm_year+1900,tm.tm_mon+1,tm.tm_mday,tm.tm_hour,tm.tm_min,tm.tm_sec,ts.tv_nsec);-if(!old_sleep&

13、amp;&new_state!=PM_SUSPEND_ON)state|=SUSPEND_REQUESTED;queue_work(suspend_work_queue,&early_suspend_work);elseif(old_sleep&&new_state=PM_SUSPEND_ON)state&=SUSPEND_REQUESTED;wakeock(&main_wakeock);queue_work(suspend_work_queue,&late_resume_work);-requested_suspend_state=ne

14、w_state;spin_unlock_irqrestore(&state_lock,irqflags);-在early_suspend()函數(shù)中，首先要判斷當前請求的狀態(tài)是否還是suspend,若不是，則直接退出了；若是，函數(shù)會調(diào)用已經(jīng)注冊的early_suspend的函數(shù)。然后同步文件系統(tǒng)，最后釋放main_wake_lock。staticvoidearly_suspend(structwork_struct*work)-structearly_suspend*pos;unsignedlongirqflags;intabort=0;mutex_lock(&early_sus

15、pend_lock);spin_lock_irqsave(&state_lock,irqflags);if(state=SUSPEND_REQUESTED)state|=SUSPENDED;elseabort=1;spin_unlock_irqrestore(&state_lock,irqflags);if(abort)if(debug_mask&DEBUG_SUSPEND)pr_info("early_suspend:abort,state%dn",state);mutex_uniock(&early_suspend_lock);gotoa

16、bort;if(debug_mask&DEBUG_SUSPEND)pr_info("early_suspend:callhandlersn");list_for_each_entry(pos,&early_suspend_handlers,link)if(pos->suspend!=NULL)pos->suspend(pos);mutex_uniock(&early_suspend_lock);if(debug_mask&DEBUG_SUSPEND)pr_info("early_suspend:syncn”)；sys_s

17、ync();abort:spin_lock_irqsave(&state_lock,irqflags);if(state=SUSPEND_rEqUESTED_AND_SUSPENDED)wake_unlock(&main_wake_lock);spin_unlock_irqrestore(&state_lock,irqflags);-在wake_unlock()中，刪除鏈表中wake_lock節(jié)點，判斷當前是否存在wake_lock，若wake_lock的數(shù)目為0,則調(diào)用工作隊列suspend_work，進入suspend狀態(tài)。staticDECLARE_WORK(su

18、spend_work,suspend);voidwake_unlock(structwake_lock*lock)-inttype;unsignedlongirqflags;spin_lock_irqsave(&list_lock,irqflags);type：lock->flags&wAkE_LOCK_TYPE_MASK;#ifdefCONFIG_WAKELOCK_STATwake_uniock_stat_locked(lock,0);#endifif(debug_mask&DEBUG_WAKE_LOCK)pr_info("wake_uniock:%s

19、n",lock->name);lock->flags&=(WAKE_LOCK_ACTIVE|WAKE_LOCK_AUTO_EXPIRE);list_del(&lock->link);list_add(&lock->link,&inactive_locks);if(type=WAKE_LOCK_SUSPEND)longhas_lock=has_wake_lock_locked(type);if(has_lock>0)if(debug_mask&DEBUG_EXPIRE)pr_info("wake_unioc

20、k:%s,startexpiretimer,""%ldn",lock->name,has_lock);mod_timer(&expire_timer,jiffies+has_lock);elseif(del_timer(&expire_timer)if(debug_mask&DEBUG_EXPIRE)pr_info("wake_uniock:%s,stopexpire""timern",lock->name);if(has_iock=0)queue_work(suspend_work_qu

21、eue,&suspend_work);-if(lock=&main_wakeock)if(debug_mask&DEBUG_SUSPEND)print_active_locks(WAKE_LOCK_SUSPEND);#ifdefCONFIG_WAKELOCK_STATupdate_sleep_wait_stats_locked(0);#endifspin_unlock_irqrestore(&list_lock,irqflags);-在suspend()函數(shù)中，先判斷當前是否有wake_lock，若有，則退出；然后同步文件系統(tǒng),最后調(diào)用pm_suspend()函

22、數(shù)。staticvoidsuspend(structwork_struct*work)-intret;intentry_event_num;if(has_wake_lock(WAKE_LOCK_SUSPEND)if(debug_mask&DEBUG_SUSPEND)pr_info("suspend:abortsuspendn”)；return;entry_event_num=current_event_num;sys_sync();if(dbug_mask&DEBUG_SUSPEND)pr_info("suspend:entersuspendn”)；ret=

23、pm_suspend(requested_suspend_state);if(debug_mask&DEBUG_EXIT_SUSPEND)structtimespects;structrtc_timetm;getnstimeofday(&ts);rtc_time_to_tm(ts.tv_sec,&tm);pr_info("suspend:exitsuspend,ret=%d"-"(%d-%02d-%02d%02d:%02d:%02d.%09luUTC)n",ret,tm.tm_year+1900,tm.tm_mon+1,tm.tm

24、_mday,tm.tm_hour,tm.tm_min,tm.tm_sec,ts.tv_nsec);-if(current_event_num=entry_event_num)if(debug_mask&DEBuG_SUSPEND)pr_info("suspend:pm_suspendreturnedwithnoevent'n”)；wakeock_timeout(&unknown_wakeup,HZ/2);-在pm_suspend()函數(shù)中，enter_state()函數(shù)被調(diào)用，從而進入標準linux休眠過程。intpm_suspend(suspend_stat

25、e_tstate)-if(state>PM_SUSPEND_ON&&state<=PM_SUSPEND_MAX)returnenter_state(state);return-EINVAL;在enter_state()函數(shù)中，首先檢查一些狀態(tài)參數(shù)，再同步文件系統(tǒng)，然后調(diào)用suspend_prepare()來凍結(jié)進程，最后調(diào)用suspend_devices_and_enter()讓外設(shè)進入休眠。staticintenter_state(suspend_state_tstate)interror;if(!valid_state(state)return-ENODEV;i

26、f(!mutextrylock(&pmmutex)return-EBUSY;-printk(KERN_INFO"PM:Syncingfilesystems.");sys_sync();printk("done.n");pr_debug("PM:Preparingsystemfor%ssleepn",pm_statesstate);error=suspend_prepare();if(error)gotoUniock;if(suspend_test(TEST_FREEZER)gotoFinish;pr_debug("P

27、M:Entering%ssleepn",pm_statesstate);error=suspend_devices_and_enter(state);Finish:pr_debug("PM:Finishingwakeup.'n");suspend_finish();Unlock:mutex_uniock(&pm_mutex);returnerror;在suspend_prepare()函數(shù)中，先通過pm_prepare_console();給suspend分配一個虛擬終端來輸出信息，再廣播一個系統(tǒng)進入suspend的通報，關(guān)閉用戶態(tài)的helper進

28、程，然后調(diào)用suspend_freeze_processes(來凍結(jié)進程，最后會嘗試釋放一些內(nèi)存。staticintsuspend_prepare(void)-interror;unsignedintfree_pages;if(!suspend_ops|!suspend_ops->enter)return-EPERM;pm_prepare_console();error=pm_notifier_call_chain(PM_SUSPEND_PREPARE);if(error)gotoFinish;error=usermodehelper_disable();if(error)gotoFin

29、ish;if(suspend_freeze_processes()error=-EAGAIN;gotoThaw;free_pages=global_page_state(NR_FREE_PAGES);if(free_pages<FREE_PAGE_NUMBER)pr_debug("PM:freesomememory'n");shrink_all_memory(FREE_PAGE_NUMBER-free_pages);if(nr_free_pages()<FREE_PAGE_NUMBER)-error=-ENOMEM;printk(KERN_ERR&quo

30、t;PM:Noenoughmemory'n");-if(!error)return0;Thaw:suspend_thaw_processes();usermodehelper_enable();Finish:pm_notifier_call_chain(PM_POST_SUSPEND);pm_restore_console();returnerror;在suspend_freeze_processes(函數(shù)中調(diào)用了freeze_processes()函數(shù)，而freeze_processes()函數(shù)中又調(diào)用了try_to_freeze_tasks()來完成凍結(jié)任務(wù)。在凍結(jié)過程中

31、，會判斷當前進程是否有wake_lock，若有，則凍結(jié)失敗，函數(shù)會放棄凍結(jié)。staticinttry_to_freeze_tasks(boolsig_only)""-structtask_struct*g,*p;unsignedlongend_time;unsignedinttodo;structtimevalstart,end;u64elapsed_csecs64;unsignedintelapsed_csecs;unsignedintwakeup=0;do_gettimeofday(&start);end_time=jiffies+TIMEOUT;dotodo=

32、0;readock(&tasklist_lock);do_each_thread(g,p)if(frozen(p)|!freezeable(p)continue;if(!freeze_task(p,sig_only)continue;/* Nowthatwe'vedoneset_freeze_flag,don't* perturbataskinTASK_STOPPEDorTASK_TRACED.* Itis"frozenenough".Ifthetaskdoeswake* up,itwillimmediatelycalltry_to_freeze.*

33、/if(!task_is_stopped_or_traced(p)&&!freezer_should_skip(p)todo+;while_each_thread(g,p);read_unlock(&tasklist_lock);yield();/*Yieldisokayhere*/if(todo&&has_wake_lock(WAKE_LOCK_SUSPEND)wakeup=1;break;if(time_after(jiffies,end_time)break;while(todo);do_gettimeofday(&end);elapsed

34、_csecs64=timeval_to_ns(&end)-timeval_to_ns(&start);do_div(elapsed_csecs64,NSEC_PER_SEC/100);elapsed_csecs=elapsed_csecs64;if(todo)/*Thisdoesnotunfreezeprocessesthatarealreadyfrozen* (wehaveslightlyuglycallingconventioninthatrespect,* andcallermustcallthaw_processes()ifsomethingfails),* butit

35、cleansupleftoverPF_FREEZErequests.*/-if(wakeup)printk("n");printk(KERN_ERR"Freezingof%sabortedn",sig_only?"userspace":"tasks");-elseprintk("n");printk(KERN_ERR"Freezingoftasksfailedafter%d.%02dseconds""(%dtasksrefusingtofreeze):n"

36、,elapsed_csecs/100,elapsed_csecs%100,todo);show_state();-readock(&tasklist_lock);do_each_thread(g,p)task_lock(p);if(freezing(p)&&!freezer_should_skip(p)printk(KERN_ERR"%sn",p->comm);cancel_freezing(p);task_uniock(p);while_each_thread(g,p);read_unlock(&tasklist_lock);else

37、printk("(elapsed%d.%02dseconds)",elapsed_csecs/100,elapsed_csecs%100);-returntodo?-EBUSY:0;到現(xiàn)在，所有的進程(也包括workqueue/kthread)都已經(jīng)停止了，內(nèi)核態(tài)進程有可能在停止的時候握有一些信號量，所以如果這時候在外設(shè)里面去解鎖這個信號量有可能會發(fā)生死鎖，所以在外設(shè)suspend()函數(shù)里面作lock/unlock鎖要非常小心，建議不要在外設(shè)的suspend()里面等待鎖。而且suspend的過程中，有一些log是無法輸出的，所以一旦出現(xiàn)問題，非常難調(diào)試。回到enter_

38、state()函數(shù)中，再凍結(jié)進程完成后，調(diào)用suspend_devices_and_enter()函數(shù)讓外設(shè)進入休眠。該函數(shù)中，首先休眠串口(之后不能再顯示log，解決方法為在kernel配置選項的cmdine中，添加”o_console_suspend"選項)，再通過device_suspend()函數(shù)調(diào)用各驅(qū)動的suspend函數(shù)。當外設(shè)進入休眠后，suspend_ops->prepare()被調(diào)用，suspend_ops是板級的PM操作(本文中粉紅色的函數(shù)，依賴于具體的平臺)，以S3C6410為例，其注冊在linux_source/arch/arm/plat-s3c64x

39、x/pm.c中，只定義了suspend_ops->enter()函數(shù)。staticstructplatform_suspend_opss3c6410_pm_ops=.enter=s3c6410_pm_enter,.valid=suspend_valid_only_mem,;-接下來，多CPU中的非啟動CPU被關(guān)閉。intsuspend_devices_and_enter(suspend_state_tstate)-interror;if(!suspend_ops)return-ENOSYS;if(suspend_ops->begin)error=suspend_ops->be

40、gin(state);if(error)gotoClose;suspend_console();suspend_test_start();error=device_suspend(PMSG_SUSPEND);if(error)printk(KERN_ERR"PM:Somedevicesfailedtosuspendn");gotoRecover_platform;-suspend_test_finish("suspenddevices");if(suspend_test(TEST_DEVICES)gotoRecover_platform;if(suspe

41、nd_ops->prepare)error=suspend_ops->prepare();if(error)gotoResume_devices;-if(suspend_test(TEST_PLATFORM)gotoFinish;error=disable_nonboot_cpus();if(!error&&!suspend_test(TEST_CPUS)suspend_enter(state);enable_nonboot_cpus();Finish:if(suspend_ops->finish)suspend_ops->finish();Resume

42、_devices:suspend_test_start();device_resume(PMSG_RESUME);suspend_test_finish("resumedevices");resume_console();Close:if(suspend_ops->end)suspend_ops->end();returnerror;Recover_platform:if(suspend_ops->recover)suspend_ops->recover();gotoResume_devices;-接下來suspend_enter()被調(diào)用，該函數(shù)首

43、先關(guān)閉IRQ，然后調(diào)用device_power_down(),它會調(diào)用suspend_late()函數(shù)，這個函數(shù)是系統(tǒng)真正進入休眠最后調(diào)用的函數(shù)，通常會在這個函數(shù)中作最后的檢查，接下來休眠所有的系統(tǒng)設(shè)備和總線。最后調(diào)用suspend_pos->enter()來使CPU進入省電狀態(tài)。這時候，整個休眠過程完成，代碼的執(zhí)行也就停在這里了。staticintsuspend_enter(suspend_state_tstate)-interror=0;device_pm_lock();#ifdefcOnFG_CPU_FREQcpufreq_get_cpufreq_name(0);strcpy(go

44、vernor_name,cpufreq_governor_name);if(strnicmp(governor_name,userspace_governor,CPUFREQ_NAME_LEN)cpufreq_set_policy(0,"performanee");-#endif/*CONFIG_CPU_FREQ*/arch_suspend_disable_irqs();BUG_ON(!irqs_disabled();if(error=device_power_down(PMSG_SUSPEND)printk(KERN_ERR"PM:Somedevicesfail

45、edtopowerdownn");gotoDone;error=sysdev_suspend(PMSG_SUSPEND);if(!error)if(!suspend_test(TEST_CORE)error=suspend_ops->enter(state);sysdev_resume();-device_power_up(PMSG_RESUME);Done:arch_suspend_enable_irqs();#ifdefCONFIG_CPU_FREQif(strnicmp(governor_name,userspace_governor,CPUFREQ_NAME_LEN)c

46、pufreq_set_policy(0,governor_name);-#endif/*CONFIG_CPU_FREQ*/BUG_ON(irqs_disabled();device_pm_uniock();returnerror;在suspend_pos->enter()所對應(yīng)的函數(shù)中，代碼最終停止在pm_cpu_sleep();處。staticints3c6410_pm_enter(suspend_state_tstate)-s3c6410_pm_do_save(gpio_save,ARRAY_SIZE(gpio_save);s3c6410_pm_do_save(irq_save,AR

47、RAY_SIZE(irq_save);s3c6410_pm_do_save(core_save,ARRAY_SIZE(core_save);s3c6410_pm_do_save(sromc_save,ARRAY_SIZE(sromc_save);/*ClearWAKEUP_STATregisterfornextwakeup-jc.lee*/*Ifthisregisterdonotbecleared,Wakeupwillbefailed*/_raw_writel(_raw_readl(S3C_WAKEUP_STAT),S3C_WAKEUP_STAT);#ifdefCONFIG_MACH_SMDK

48、6410/*ALLsubblock"ON"beforeenterringsleepmode-EVT0bug*/_raw_writel(0xffffff00,S3C_NORMAL_CFG);/*Openallclockgatetoentersleepmode-EVT0bug*/_raw_writel(0xffffffff,S3C_HCLK_GATE);_raw_writel(0xffffffff,S3C_PCLK_GATE);_raw_writel(0xffffffff,S3C_SCLK_GATE);/*s3c6410_cpu_savewillalsoactasourretu

49、rnpointfromwhen* weresumeasitsavesitsownregisterstate,sousethereturn* codetodifferentiatereturnfromsaveandreturnfromsleep*/if(s3c6410_cpu_save(regs_save)=0)flush_cache_all();pm_cpu_sleep();-/*restorethecpustate*/cpu_init();_raw_writel(s3c_eint_mask_val,S3C_EINT_MASK);/*restorethesystemstate*/s3c6410_pm_do_restore_core(core_save,ARRAY_SIZE(core_save);s3c6410_pm_do_restore(sromc_save,ARRAY_SIZE(sromc_save);Android喚醒過程如下：如果在休眠中系統(tǒng)被中斷或者其他