Android Suspend/resume 过程分析.

Android Suspend/resume 过程分析.
2011年08月16日
　　http://hi.baidu.com/linuxembedded/blog/item/4eeb14 3837879bd2d46225ca.html 当系统未处于 Suspend 状态下用户按下Power键时会在 /dev/input/event0 节点中产生一个信号, 上层的 WindowManager 会收到这个上节点的变化而得知当前应该进入休眠状态, 通知PowerManagerService, 它会做如下调用, private int setScreenStateLocked(boolean on) {
　　int err = Power.setScreenState(on);
　　setScreenState 最终会调用到. int
　　set_screen_state(int on)
　　{
　　enum {
　　ACQUIRE_PARTIAL_WAKE_LOCK = 0,
　　RELEASE_WAKE_LOCK,
　　REQUEST_STATE,
　　OUR_FD_COUNT
　　};
　　const char * const OLD_PATHS[] = {
　　"/sys/android_power/acquire_partial_wake_lock",
　　"/sys/android_power/release_wake_lock",
　　"/sys/android_power/request_state"
　　};
　　const char * const NEW_PATHS[] = {
　　"/sys/power/wake_lock",
　　"/sys/power/wake_unlock",
　　"/sys/power/state"
　　};
　　QEMU_FALLBACK(set_screen_state(on));
　　LOGI("*** set_screen_state %d", on);
　　initialize_fds();
　　//LOGI("go_to_sleep eventTime=%lld now=%lld g_error=%s\n", eventTime,
　　// systemTime(), strerror(g_error));
　　if (g_error) return g_error;
　　char buf[32];
　　int len;
　　if(on)
　　len = sprintf(buf, on_state);
　　else
　　len = sprintf(buf, off_state);
　　len = write(g_fds[REQUEST_STATE], buf, len);
　　if(len  /sys/power/state 时. 内核调用 state_store 函数在(具体过程未查) ./kernel/power/main.c 文件中. 在其中有如下代码 #ifdef CONFIG_EARLYSUSPEND
　　if (state == PM_SUSPEND_ON || valid_state(state)) {
　　error = 0;
　　request_suspend_state(state);
　　}
　　#else
　　error = enter_state(state);
　　#endif
　　可以看出.如果定义了 CONFIG_EARLYSUSPEND 的话. 会调用 request_suspend_state 函数在 ./kernel/power/earlysuspend.c 文件中. 其中有关键代码如下 void request_suspend_state(suspend_state_t new_state)
　　{
　　unsigned long irqflags;
　　int old_sleep;
　　spin_lock_irqsave(&state_lock, irqflags);
　　old_sleep = state & SUSPEND_REQUESTED;
　　... ...
　　if (!old_sleep && new_state != PM_SUSPEND_ON) {
　　state |= SUSPEND_REQUESTED;
　　queue_work(suspend_work_queue, &early_suspend_work);
　　} else if (old_sleep && new_state == PM_SUSPEND_ON) {
　　state &= ~SUSPEND_REQUESTED;
　　wake_lock(&main_wake_lock);
　　queue_work(suspend_work_queue, &late_resume_work);
　　}
　　requested_suspend_state = new_state;
　　spin_unlock_irqrestore(&state_lock, irqflags);
　　}
　　这里根据不同的 new_state 的不同而将不同的任务添加到工作队列中. 现在分析 suspend 的情况 early_suspend 主要工作如下 suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
　　static void early_suspend(struct work_struct *work)
　　{
　　struct early_suspend *pos;
　　unsigned long irqflags;
　　int abort = 0;
　　mutex_lock(&early_suspend_lock);
　　spin_lock_irqsave(&state_lock, irqflags);
　　if (state == SUSPEND_REQUESTED)
　　state |= SUSPENDED;
　　else
　　abort = 1;
　　spin_unlock_irqrestore(&state_lock, irqflags);
　　if (abort) {
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("early_suspend: abort, state %d\n", state);
　　mutex_unlock(&early_suspend_lock);
　　goto abort;
　　}
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("early_suspend: call handlers\n");
　　list_for_each_entry(pos, &early_suspend_handlers, link) {
　　if (pos->suspend != NULL)
　　pos->suspend(pos);
　　}
　　mutex_unlock(&early_suspend_lock);
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("early_suspend: sync\n");
　　sys_sync();
　　abort:
　　spin_lock_irqsave(&state_lock, irqflags);
　　if (state == SUSPEND_REQUESTED_AND_SUSPENDED)
　　wake_unlock(&main_wake_lock);
　　spin_unlock_irqrestore(&state_lock, irqflags);
　　}
　　在这里调用了事先注册的 early_syspend , 同步, 释放 main_wake_lock, 在释放 main_wake_lock 时.如下操作. static void suspend(struct work_struct *work)
　　{
　　int ret;
　　int entry_event_num;
　　if (has_wake_lock(WAKE_LOCK_SUSPEND)) {
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("suspend: abort suspend\n");
　　return;
　　}
　　entry_event_num = current_event_num;
　　sys_sync();
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("suspend: enter suspend\n");
　　ret = pm_suspend(requested_suspend_state);
　　if (debug_mask & DEBUG_EXIT_SUSPEND) {
　　struct timespec ts;
　　struct rtc_time tm;
　　getnstimeofday(&ts);
　　rtc_time_to_tm(ts.tv_sec, &tm);
　　pr_info("suspend: exit suspend, ret = %d "
　　"(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\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) {
　　if (debug_mask & DEBUG_SUSPEND)
　　pr_info("suspend: pm_suspend returned with no event\n");
　　wake_lock_timeout(&unknown_wakeup, HZ / 2);
　　}
　　}
　　static DECLARE_WORK(suspend_work, suspend);
　　void wake_unlock(struct wake_lock *lock)
　　{
　　int type;
　　unsigned long irqflags;
　　spin_lock_irqsave(&list_lock, irqflags);
　　type = lock->flags & WAKE_LOCK_TYPE_MASK;
　　#ifdef CONFIG_WAKELOCK_STAT
　　wake_unlock_stat_locked(lock, 0);
　　#endif
　　if (debug_mask & DEBUG_WAKE_LOCK)
　　pr_info("wake_unlock: %s\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) {
　　long has_lock = has_wake_lock_locked(type);
　　if (has_lock > 0) {
　　if (debug_mask & DEBUG_EXPIRE)
　　pr_info("wake_unlock: %s, start expire timer, "
　　"%ld\n", lock->name, has_lock);
　　mod_timer(&expire_timer, jiffies + has_lock);
　　} else {
　　if (del_timer(&expire_timer))
　　if (debug_mask & DEBUG_EXPIRE)
　　pr_info("wake_unlock: %s, stop expire "
　　"timer\n", lock->name);
　　if (has_lock == 0){
　　queue_work(suspend_work_queue, &suspend_work);
　　}
　　}
　　if (lock == &main_wake_lock) {
　　if (debug_mask & DEBUG_SUSPEND)
　　print_active_locks(WAKE_LOCK_SUSPEND);
　　#ifdef CONFIG_WAKELOCK_STAT
　　update_sleep_wait_stats_locked(0);
　　#endif
　　}
　　}
　　spin_unlock_irqrestore(&list_lock, irqflags);
　　}
　　在释放 main_wake_lock 时, 要判断 当没有 这个类型 锁的时候 要将 suspend_work 放到工作队列中.在 supsend 函数中 调用 了正常 suspend 的入口函数.ret = pm_suspend(requested_suspend_state);
　　在 pm_suspend 函数中 /**
　　* suspend_enter - enter the desired system sleep state.
　　* @state: state to enter
　　*
　　* This function should be called after devices have been suspended.
　　*/
　　static int suspend_enter(suspend_state_t state)
　　{
　　int error;
　　if (suspend_ops->prepare) {
　　error = suspend_ops->prepare();
　　if (error)
　　return error;
　　}
　　error = dpm_suspend_noirq(PMSG_SUSPEND);
　　if (error) {
　　printk(KERN_ERR "PM: Some devices failed to power down\n");
　　goto Platfrom_finish;
　　}
　　if (suspend_ops->prepare_late) {
　　error = suspend_ops->prepare_late();
　　if (error)
　　goto Power_up_devices;
　　}
　　if (suspend_test(TEST_PLATFORM))
　　goto Platform_wake;
　　error = disable_nonboot_cpus();
　　if (error || suspend_test(TEST_CPUS))
　　goto Enable_cpus;
　　arch_suspend_disable_irqs();
　　BUG_ON(!irqs_disabled());
　　error = sysdev_suspend(PMSG_SUSPEND);
　　if (!error) {
　　if (!suspend_test(TEST_CORE))
　　error = suspend_ops->enter(state);
　　sysdev_resume();
　　}
　　arch_suspend_enable_irqs();
　　BUG_ON(irqs_disabled());
　　Enable_cpus:
　　enable_nonboot_cpus();
　　Platform_wake:
　　if (suspend_ops->wake)
　　suspend_ops->wake();
　　Power_up_devices:
　　dpm_resume_noirq(PMSG_RESUME);
　　Platfrom_finish:
　　if (suspend_ops->finish)
　　suspend_ops->finish();
　　return error;
　　}
　　/**
　　* suspend_prepare - Do prep work before entering low-power state.
　　*
　　* This is common code that is called for each state that we're entering.
　　* Run suspend notifiers, allocate a console and stop all processes.
　　*/
　　static int suspend_prepare(void)
　　{
　　... ....
　　if (!suspend_ops || !suspend_ops->enter)
　　return -EPERM;
　　... ....
　　error = pm_notifier_call_chain(PM_SUSPEND_PREPARE);
　　if (error)
　　goto Finish;
　　error = usermodehelper_disable();
　　if (error)
　　goto Finish;
　　error = suspend_freeze_processes();
　　if (!error)
　　return 0;
　　suspend_thaw_processes();
　　usermodehelper_enable();
　　Finish:
　　pm_notifier_call_chain(PM_POST_SUSPEND);
　　pm_restore_console();
　　return error;
　　}
　　/**
　　* suspend_devices_and_enter - suspend devices and enter the desired system
　　* sleep state.
　　* @state: state to enter
　　*/
　　int suspend_devices_and_enter(suspend_state_t state)
　　{
　　int error;
　　if (!suspend_ops)
　　return -ENOSYS;
　　if (suspend_ops->begin) {
　　error = suspend_ops->begin(state);
　　if (error)
　　goto Close;
　　}
　　//suspend_console();
　　suspend_test_start();
　　error = dpm_suspend_start(PMSG_SUSPEND);
　　if (error) {
　　printk(KERN_ERR "PM: Some devices failed to suspend\n");
　　goto Recover_platform;
　　}
　　suspend_test_finish("suspend devices");
　　if (suspend_test(TEST_DEVICES)){
　　goto Recover_platform;
　　}
　　suspend_enter(state);
　　Resume_devices:
　　suspend_test_start();
　　dpm_resume_end(PMSG_RESUME);
　　suspend_test_finish("resume devices");
　　resume_console();
　　Close:
　　if (suspend_ops->end){
　　suspend_ops->end();
　　}
　　return error;
　　Recover_platform:
　　if (suspend_ops->recover){
　　suspend_ops->recover();
　　}
　　goto Resume_devices;
　　}
　　/**
　　* suspend_finish - Do final work before exiting suspend sequence.
　　*
　　* Call platform code to clean up, restart processes, and free the
　　* console that we've allocated. This is not called for suspend-to-disk.
　　*/
　　static void suspend_finish(void)
　　{
　　suspend_thaw_processes();
　　usermodehelper_enable();
　　pm_notifier_call_chain(PM_POST_SUSPEND);
　　pm_restore_console();
　　}
　　/**
　　* enter_state - Do common work of entering low-power state.
　　* @state: pm_state structure for state we're entering.
　　*
　　* Make sure we're the only ones trying to enter a sleep state. Fail
　　* if someone has beat us to it, since we don't want anything weird to
　　* happen when we wake up.
　　* Then, do the setup for suspend, enter the state, and cleaup (after
　　* we've woken up).
　　*/
　　int enter_state(suspend_state_t state)
　　{
　　int error;
　　if (!valid_state(state))
　　return -ENODEV;
　　if (!mutex_trylock(&pm_mutex))
　　return -EBUSY;
　　printk(KERN_INFO "PM: Syncing filesystems ... 1");
　　sys_sync();
　　printk("done.\n");
　　pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
　　error = suspend_prepare();
　　if (error)
　　goto Unlock;
　　if (suspend_test(TEST_FREEZER))
　　goto Finish;
　　pr_debug("PM: Entering %s sleep\n", pm_states[state]);
　　error = suspend_devices_and_enter(state);
　　Finish:
　　pr_debug("PM: Finishing wakeup.\n");
　　suspend_finish();
　　Unlock:
　　mutex_unlock(&pm_mutex);
　　return error;
　　}
　　/**
　　* pm_suspend - Externally visible function for suspending system.
　　* @state: Enumerated value of state to enter.
　　*
　　* Determine whether or not value is within range, get state
　　* structure, and enter (above).
　　*/
　　int pm_suspend(suspend_state_t state)
　　{
　　if (state > PM_SUSPEND_ON && state  enter_state(之后和标准 Linux 过程一致) -> suspend_prepare/suspend_devices_and_enter/suspend_ finish
　　在 suspend_prepare 函数中 分别通知上层已经进入 "PM_SUSPEND_PREPARE" 过程让上层做一些处理. 之后冻结用户层所有应用程序及服务进程.
　　suspend_devices_and_enter 函数中 进程休眠, 设备(驱动)休眠. cpu进入休眠. 应该是停止在 arch_suspend_disable_irqs 里.
　　来电 cpu上电后, 使能中断.使能非活动的Cpu. 复位驱动, 激活进程. 
　　suspend_finish 函数中 同样通知上层 PM_POST_SUSPEND 这个消息. 上层收到这个消息后.会调用 NvddkAudioFxSuspend(NV_FALSE); 然后再干什么就没跟住了...
　　这里同进入suspend 一致, 会把一个按键事件写入到 /dev/input/event0 中, 上层应用程序被激活后会检测这个事件源, 发现有按下, 会使能屏幕, 这时同 suspend 过程一样, 在用户层的最下端写一个 "on" 到 /sys/power/state 中, 内核层中调用 state_store -> request_suspend_state 这里会把一个 resume 的工作加入到 工作队列中. 调用了 已经注册的 late_resume 函数. 这里 eraly_suspend 及 late_resume 都是 android 加的补丁!