early_suspend【转】

匿名 (未验证) 提交于 2019-12-03 00:40:02

android 休眠唤醒机制分析(二) ― early_suspend

early_suspend是Android休眠流程的第一阶段即浅度休眠,不会受到wake_lock的阻止,一般用于关闭lcd、tp等设备为运行的应用节约电能。Android的PowerManagerService会根据用户的操作情况调整电源状态,如果需要休眠则会调用到HAL层的set_screen_state()接口,在set_screen_state()中会向/sys/power/state节点写入"mem"值让驱动层开始进入休眠流程。

Linux系统支持如下休眠唤醒等级

const char *const pm_states[PM_SUSPEND_MAX] = { #ifdef CONFIG_EARLYSUSPEND     [PM_SUSPEND_ON]     = "on", #endif     [PM_SUSPEND_STANDBY]    = "standby",     [PM_SUSPEND_MEM]    = "mem", };

但在Android中一般只支持"on"和"mem",其中"on"为唤醒设备,"mem"为休眠设备。/sys/power/state节点的读写操作如下:

static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,               char *buf) {     char *s = buf; #ifdef CONFIG_SUSPEND     int i;       for (i = 0; i < PM_SUSPEND_MAX; i++) {         if (pm_states[i] && valid_state(i))             s += sprintf(s,"%s ", pm_states[i]);  // 打印系统支持的休眠等级     } #endif #ifdef CONFIG_HIBERNATION     s += sprintf(s, "%s\n", "disk"); #else     if (s != buf)         /* convert the last space to a newline */         *(s-1) = '\n'; #endif     return (s - buf); }   static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,                const char *buf, size_t n) { #ifdef CONFIG_SUSPEND #ifdef CONFIG_EARLYSUSPEND     suspend_state_t state = PM_SUSPEND_ON; #else     suspend_state_t state = PM_SUSPEND_STANDBY; #endif     const char * const *s; #endif     char *p;     int len;     int error = -EINVAL;       p = memchr(buf, '\n', n);     len = p ? p - buf : n;       /* First, check if we are requested to hibernate */     if (len == 4 && !strncmp(buf, "disk", len)) {         error = hibernate();   goto Exit;     }   #ifdef CONFIG_SUSPEND     for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {         if (*s && len == strlen(*s) && !strncmp(buf, *s, len))             break;     }     if (state < PM_SUSPEND_MAX && *s) #ifdef CONFIG_EARLYSUSPEND         if (state == PM_SUSPEND_ON || valid_state(state)) {             error = 0;             request_suspend_state(state);  // 请求进入android的休眠流程         } #else         error = enter_state(state);  // linux的标准休眠流程 #endif #endif    Exit:     return error ? error : n; }   power_attr(state);

其中state_show()为节点的读函数,主要打印出系统支持的休眠等级;state_store()为节点的写函数,根据参数请求休眠或者唤醒流程。节点的创建代码如下:

static struct attribute * g[] = {     &state_attr.attr,        // state节点 #ifdef CONFIG_PM_TRACE     &pm_trace_attr.attr, #endif #if defined(CONFIG_PM_SLEEP) && defined(CONFIG_PM_DEBUG)     &pm_test_attr.attr,      // pm_test节点 #endif #ifdef CONFIG_USER_WAKELOCK     &wake_lock_attr.attr,    // wake_lock节点     &wake_unlock_attr.attr,  // wake_unlock节点 #endif     NULL, };   static struct attribute_group attr_group = {     .attrs = g, };   static int __init pm_init(void) {     int error = pm_start_workqueue();     if (error)         return error;     power_kobj = kobject_create_and_add("power", NULL);  // 创建power节点     if (!power_kobj)         return -ENOMEM;     return sysfs_create_group(power_kobj, &attr_group);  // 创建一组属性节点 }   core_initcall(pm_init); 
enum {     EARLY_SUSPEND_LEVEL_BLANK_SCREEN = 50,     EARLY_SUSPEND_LEVEL_STOP_DRAWING = 100,     EARLY_SUSPEND_LEVEL_DISABLE_FB = 150, }; struct early_suspend { #ifdef CONFIG_HAS_EARLYSUSPEND     struct list_head link;  // 链表节点     int level;              // 优先等级     void (*suspend)(struct early_suspend *h);     void (*resume)(struct early_suspend *h); #endif };

可以看到early_suspend由两个函数指针、链表节点、优先等级组成;内核默认定义了3个优先等级,在suspend的时候先执行优先等级低的handler,在resume的时候则先执行等级高的handler,用户可以定义自己的优先等级;early_suspend向内核空间提供了2个接口用于注册和注销handler:

void register_early_suspend(struct early_suspend *handler); void unregister_early_suspend(struct early_suspend *handler);

其中register_early_suspend()用于注册,unregister_early_suspend用于注销;一般early_suspend的使用方式如下:

ts->earlysuspend.suspend = sitronix_i2c_suspend_early; ts->earlysuspend.resume = sitronix_i2c_resume_late; ts->earlysuspend.level = EARLY_SUSPEND_LEVEL_BLANK_SCREEN; register_early_suspend(&ts->earlysuspend);

设置好suspendresume接口,定义优先等级,然后注册结构即可。

我们看一下early_suspend需要用到的一些数据:

static DEFINE_MUTEX(early_suspend_lock); static LIST_HEAD(early_suspend_handlers);  // 初始化浅度休眠链表 // 声明3个工作队列用于同步、浅度休眠和唤醒 static void early_sys_sync(struct work_struct *work); static void early_suspend(struct work_struct *work); static void late_resume(struct work_struct *work); static DECLARE_WORK(early_sys_sync_work,early_sys_sync); static DECLARE_WORK(early_suspend_work, early_suspend); static DECLARE_WORK(late_resume_work, late_resume); static DEFINE_SPINLOCK(state_lock); enum {     SUSPEND_REQUESTED = 0x1,  // 当前正在请求浅度休眠     SUSPENDED = 0x2,          // 浅度休眠完成     SUSPEND_REQUESTED_AND_SUSPENDED = SUSPEND_REQUESTED | SUSPENDED, }; static int state; 

初始化了一个链表early_suspend_handlers用于管理early_suspend,还定义读写链表用到的互斥体;另外还声明了3个工作队列,分别用于缓存同步、浅度休眠和唤醒;还声明了early_suspend操作的3个状态。

void register_early_suspend(struct early_suspend *handler) {     struct list_head *pos;       mutex_lock(&early_suspend_lock);     // 遍历浅度休眠链表     list_for_each(pos, &early_suspend_handlers) {         struct early_suspend *e;         e = list_entry(pos, struct early_suspend, link);         // 判断当前节点的优先等级是否大于handler的优先等级         // 以此决定handler在链表中的顺序         if (e->level > handler->level)             break;     }     // 将handler加入当前节点之前,优先等级越低越靠前     list_add_tail(&handler->link, pos);     if ((state & SUSPENDED) && handler->suspend)         handler->suspend(handler);     mutex_unlock(&early_suspend_lock); } EXPORT_SYMBOL(register_early_suspend);

注册的流程比较简单,首先遍历链表,依次比较每个节点的优先等级,如果遇到优先等级比新节点优先等级高则跳出,然后将新节点加入优先等级较高的节点前面,这样就确保了链表是优先等级低在前高在后的顺序;在将节点加入链表后查看当前状态是否为浅度休眠完成状态,如果是则执行handler的suspend函数。

4、request_suspend_state

前面我们看到用户空间在写/sys/power/state节点的时候会执行request_suspend_state()函数,该函数代码如下:

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;     // 打印当前状态     if (debug_mask & DEBUG_USER_STATE) {         struct timespec ts;         struct rtc_time tm;         getnstimeofday(&ts);         rtc_time_to_tm(ts.tv_sec, &tm);         pr_info("request_suspend_state: %s (%d->%d) at %lld "             "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\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);     }     // 如果新状态是休眠状态     if (!old_sleep && new_state != PM_SUSPEND_ON) {         state |= SUSPEND_REQUESTED;         pr_info("sys_sync_work_queue early_sys_sync_work.\n");         // 执行缓存同步与浅度休眠的工作队列         queue_work(sys_sync_work_queue, &early_sys_sync_work);         queue_work(suspend_work_queue, &early_suspend_work);     } else if (old_sleep && new_state == PM_SUSPEND_ON) {     // 如果新状态是唤醒状态         state &= ~SUSPEND_REQUESTED;         // 激活内核锁         wake_lock(&main_wake_lock);         // 执行浅度唤醒的工作队列         queue_work(suspend_work_queue, &late_resume_work);     }     // 更新全局状态     requested_suspend_state = new_state;     spin_unlock_irqrestore(&state_lock, irqflags); } 

函数首先打印出当前状态变化的log,然后判断新状态,如果是休眠状态则置位SUSPEND_REQUESTED标志,然后将同步缓存、浅度休眠工作队列加入相应的内核线程执行;如果新状态是唤醒则首先将main_wake_lock激活,然后再将浅度唤醒工作队列加入内核线程执行;最后更新全局状态变量,因为提供了一个内核空间接口用于获取当前休眠唤醒状态:

// 返回系统状态值 suspend_state_t get_suspend_state(void) {     return requested_suspend_state; }
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)  // 判断当前状态是否在请求浅度休眠         state |= SUSPENDED;      // 如果是则置位SUSPENDED     else         abort = 1;     spin_unlock_irqrestore(&state_lock, irqflags);       if (abort) {  // 取消early_suspend         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");     // 遍历浅度休眠链表并执行其中所有suspend函数     // 执行顺序根据优先等级而定,等级越低越先执行     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");       /* Remove sys_sync from early_suspend, and use work queue to complete sys_sync */     //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suspend流程中首先判断当前状态是否为SUSPEND_REQUESTED,如果是则置位SUSPENDED标志,如果不是则取消suspend流程;然后遍历浅度休眠链表,从链表头部到尾部依次调用各节点的suspend()函数,执行完后判断当前状态是否为SUSPEND_REQUESTED_AND_SUSPENDED,如果是则释放main_wake_lock,当前系统中如果只存在main_wake_lock这个有效锁,则会在wake_unlock()里面启动深度休眠线程,如果还有其他其他wake_lock则保持当前状态。

static void late_resume(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 == SUSPENDED)  // 清除浅度休眠完成标志         state &= ~SUSPENDED;     else         abort = 1;     spin_unlock_irqrestore(&state_lock, irqflags);       if (abort) {         if (debug_mask & DEBUG_SUSPEND)             pr_info("late_resume: abort, state %d\n", state);         goto abort;     }     if (debug_mask & DEBUG_SUSPEND)         pr_info("late_resume: call handlers\n");     // 反向遍历浅度休眠链表并执行其中所有resume函数     // 执行顺序根据优先等级而定,等级越高越先执行     list_for_each_entry_reverse(pos, &early_suspend_handlers, link)         if (pos->resume != NULL)             pos->resume(pos);     if (debug_mask & DEBUG_SUSPEND)         pr_info("late_resume: done\n"); abort:     mutex_unlock(&early_suspend_lock); } 

在resume流程中同样首先判断当前状态是否为SUSPENDED,如果是则清除SUSPENDED标志,然后反向遍历浅度休眠链表,按照优先等级从高到低的顺序执行节点的resume()函数。

static void early_sys_sync(struct work_struct *work) {     wake_lock(&sys_sync_wake_lock);     sys_sync();     wake_unlock(&sys_sync_wake_lock); } 

内核专门为缓存同步建立了一个线程,同时还创建了sys_sync_wake_lock防止在同步缓存时系统进入深度休眠。

原文:https://www.cnblogs.com/linhaostudy/p/9279648.html

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