某500强android学习资料-第十三章-Android内核驱动-电源管理

ndroid13.1基本原理earlysuspend是一种低功耗的状态,某些设备可以选择进入某种功耗较低的状态,比如CDsuspend是指除电源管理以外的其他外围模块以及cpu均不工作,只有内存保持自刷新的hibernation是指所有内存镜像都被写入磁盘中,然后系统关机,恢复后系统将能恢复到“关机”之前的状态。13.2电源管理机制的实现statevoidrequestsuspendstatesuspend_state_tnew_state){unsignedlongirqflags;intold_sleep;spin_lock_irqsave(&state_lock,irqflags);dsleepstateSUSPENDREQUESTEDNDREQUESTED一个early_suspend_workqueueworksuspendworkqueueearlysuspendwork);}elseif(old_sleep&&new_state==PM_SUSPEND_ON){ENDREQUESTEDwake_lock(&main_wake_lock);eresumeworkqueue_work(suspend_work_queue,&late_resume_work);}requested_suspend_state=new_state;spin_unlock_irqrestore(&state_lock,irqflags);}staticDECLARE_WORK(early_suspend_work,early_suspend);staticDECLARE_WORK(late_resume_work,late_resume);register_early_suspend和unregister_early_suspend两个函数供驱动调用，分别完成设备early_suspend的那些设备。代码如下：oidearlysuspendstructworkstructwork{structearly_suspend*pos;unsignedlongirqflags;intabort=0;mutex_lock(&early_suspend_lock);spin_lock_irqsave(&state_lock,irqflags);SUSPENDREQUESTEDDEDabort=1;spin_unlock_irqrestore(&state_lock,irqflags);if(abort){ugmaskDEBUGSUSPENDmutex_unlock(&early_suspend_lock);gotoabort;}ugmaskDEBUGSUSPENDndlerlist_for_each_entry(pos,&early_suspend_handlers,link){uspendNULLpos->suspend(pos);}mutex_unlock(&early_suspend_lock);ugmaskDEBUGSUSPENDsys_sync();spin_lock_irqsave(&state_lock,irqflags);ateSUSPENDREQUESTEDANDSUSPENDEDwake_unlock(&main_wake_lock);spin_unlock_irqrestore(&state_lock,irqflags);}oidlateresumestructworkstructwork{structearly_suspend*pos;unsignedlongirqflags;intabort=0;mutex_lock(&early_suspend_lock);spin_lock_irqsave(&state_lock,irqflags);USPENDEDNDEDabort=1;spin_unlock_irqrestore(&state_lock,irqflags);if(abort){ugmaskDEBUGSUSPENDgotoabort;}ugmaskDEBUGSUSPENDresumehandlerstforeachentryreverseposearlysuspendhandlerslinkesumeNULLpos->resume(pos);ugmaskDEBUGSUSPENDnmutex_unlock(&early_suspend_lock);}register_early_suspend函数完成的功能就是把驱动提供的earlysuspendhandler挂到fbearlysuspendcconsoleearlysuspendclcdframebuffer的earlysuspend支持和console的earlysuspend支持。实际上这两个文件就是利用上面Hibernate.c文件实现hibernation低功耗状态，是最彻底的低功耗模式，它把所有内存镜像都写入磁盘中，然后系统关机。该文件还在sysfs文件系统中创建了多个entry，分别是swakelock可以阻止处于正常运行(active)或者空闲(idle)状态的系统进入睡眠等低功耗状会自动解除。KELOCKAUTOEXPIREtimeoutWAKE_LOCK_IDLE这种锁不会影响系统的suspend,用于阻止系统持有锁的过程中进入activeactivekwakelocksinit事情：初始化acitive_wake_locks链表wake_lock_init()函数初始化一个锁,就是初始化表示一个wakelock的数据结构structwakelocklockakelocktimeoutstructwakelocklocklongtimeout用wake_unlock否则永远inactivelocks到active_wake_locks链表上。如果是超期锁则设置ocked查所有处于活动状态的WAKE_LOCK_SUSPEND锁(即在active_wake_locks链表上的同时它还检查链表上有没有非超期锁,如果有则直接返回-1,否则它最终返回的是所有超期时间的最大值如果has_wake_lock_locked函数返回的是-1(表示当前活动锁有非超时锁)或者0(表ndghaswakelocklockedinttype{structwake_lock*lock,*n;longmax_timeout=0;BUG_ON(type>=WAKE_LOCK_TYPE_COUNT);list_for_each_entry_safe(lock,n,&active_wake_locks[type],link){if(lock->flags&WAKE_LOCK_AUTO_EXPIRE){longtimeout=lock->expires-jiffies;iftimeout0)expire_wake_lock(lock);lseiftimeoutmaxtimeoutmax_timeout=timeout;return-1;}returnmax_timeout;}staticDEFINE_TIMER(expire_timer,expire_wake_locks,0,0);edexpirewakelocksunsignedlongdata{unsignedlongirqflags;maskDEBUGEXPIREspin_lock_irqsave(&list_lock,irqflags);ugmaskDEBUGSUSPENDprint_active_locks(WAKE_LOCK_SUSPEND);has_lock=has_wake_lock_locked(WAKE_LOCK_SUSPEND);maskDEBUGEXPIREockqueue_work(suspend_work_queue,&suspend_work);spin_unlock_irqrestore(&list_lock,irqflags);}suspend函数完成suspend系统的任务，它是suspend_work这个工作的处理函数，rkpm_suspend(request_suspend_state)，接下来pm_suspend()就会调用enter_state()来进入idsuspendstructworkstructwork{intret;entnumif(has_wake_lock(WAKE_LOCK_SUSPEND)){ugmaskDEBUGSUSPENDreturn;}ntryeventnumcurrenteventnumsys_sync();ugmaskDEBUGSUSPENDret=pm_suspend(requested_suspend_state);if(debug_mask&DEBUG_EXIT_SUSPEND){structtimespects;etmgetnstimeofday(&ts);rtc_time_to_tm(ts.tv_sec,&tm);"(%d-%02d-%02d%02d：%02d：%02d.%09luUTC)\n",ret,tm.tm_year+1900,tm.tm_mon+1,tm.tm_mday,tm.tm_hour,tm.tm_min,tm.tm_sec,ts.tv_nsec);}if(current_event_num==entry_event_num){ugmaskDEBUGSUSPENDwake_lock_timeout(&unknown_wakeup,HZ/2);}}active锁)，遍历找到最晚过期时间，然后修因为wakelock在实现的过程中，默认初始化并添加一个suspendlock类型的非过期型锁13.3用户接口ockkmemsyspowerstates