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-d-d d:d:d. lu 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!
