RTC 时间设置

最新推荐文章于 2025-06-28 11:24:35 发布

zhenwenxian

最新推荐文章于 2025-06-28 11:24:35 发布

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CC 4.0 BY-SA版权

文章标签： android struct file user cmd timer

本文链接：https://blog.youkuaiyun.com/zhenwenxian/article/details/6066852

本文介绍Android系统中如何通过ioctl命令设置RTC实时时钟。从MMI层调用至内核层，详细解析了时间参数从用户空间传递到硬件RTC芯片的过程，包括秒数到日期时间格式的转换、系统时钟同步及RTC驱动的具体调用。

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MMI

alarm.c----alarm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)--case ANDROID_ALARM_SET_RTC:

interface.c----rtc_set_time(alarm_rtc_dev, &rtc_new_rtc_time);

rtc-m41t94.c---- m41t94_set_time(struct device *dev, struct rtc_time *tm)

static long alarm_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

{

;

case ANDROID_ALARM_SET_RTC:
  if (copy_from_user(&new_rtc_time, (void __user *)arg,
      sizeof(new_rtc_time))) {
   rv = -EFAULT;
   goto err1;
  }
  rtc_time_to_tm(new_rtc_time.tv_sec, &rtc_new_rtc_time);

  ANDROID_ALARM_DPRINTF(ANDROID_ALARM_PRINT_IO,
   "set rtc %ld %ld - rtc %02d:%02d:%02d %02d/%02d/%04d/n",
   new_rtc_time.tv_sec, new_rtc_time.tv_nsec,
   rtc_new_rtc_time.tm_hour, rtc_new_rtc_time.tm_min,
   rtc_new_rtc_time.tm_sec, rtc_new_rtc_time.tm_mon + 1,
   rtc_new_rtc_time.tm_mday,
   rtc_new_rtc_time.tm_year + 1900);

  mutex_lock(&alarm_setrtc_mutex);
  spin_lock_irqsave(&alarm_slock, flags);
  for (i = 0; i < ANDROID_ALARM_SYSTEMTIME; i++)
   hrtimer_try_to_cancel(&alarm_timer[i]);
  getnstimeofday(&tmp_time);
  elapsed_rtc_delta = timespec_sub(elapsed_rtc_delta,
     timespec_sub(tmp_time, new_rtc_time));
  spin_unlock_irqrestore(&alarm_slock, flags);
  rv = do_settimeofday(&new_rtc_time);
  spin_lock_irqsave(&alarm_slock, flags);
  for (i = 0; i < ANDROID_ALARM_SYSTEMTIME; i++)
   alarm_start_hrtimer(i);
  spin_unlock_irqrestore(&alarm_slock, flags);
  if (rv < 0) {
   ANDROID_ALARM_DPRINTF(ANDROID_ALARM_PRINT_ERRORS,
           "Failed to set time/n");
   mutex_unlock(&alarm_setrtc_mutex);
   goto err1;
  }
  rv = rtc_set_time(alarm_rtc_dev, &rtc_new_rtc_time);
  spin_lock_irqsave(&alarm_slock, flags);
  alarm_pending |= ANDROID_ALARM_TIME_CHANGE_MASK;
  wake_up(&alarm_wait_queue);
  spin_unlock_irqrestore(&alarm_slock, flags);
  mutex_unlock(&alarm_setrtc_mutex);
  if (rv < 0) {
   ANDROID_ALARM_DPRINTF(ANDROID_ALARM_PRINT_ERRORS,
       "Failed to set RTC, time will be lost on reboot/n");
   goto err1;
  }
  break;

}

android RTC 时间设置,

1，用户设置时间，MMI通过ioctrl命令调用，

2，内核执行alarm_ioctl的

case ANDROID_ALARM_SET_RTC:

3，

将用户空间的时间参数通过copy_from_user取出。为绝对的秒保持在new_rtc_time.tv_sec

4，通过rtc_time_to_tm(new_rtc_time.tv_sec, &rtc_new_rtc_time);将绝对的秒转换为年月日时分秒格式放到rtc_new_rtc_time

struct rtc_time {
int tm_sec;
int tm_min;
int tm_hour;
int tm_mday;
int tm_mon;
int tm_year;
int tm_wday;
int tm_yday;
int tm_isdst;
};
5，因为要对RTC操作，要用mutex_lock(&alarm_setrtc_mutex);加锁

要清除alarm，要用 spin_lock_irqsave(&alarm_slock, flags);加锁

getnstimeofday(&tmp_time);获得ns级的时间

然后可调用do_settimeofday同步系统时钟：

通过函数

rv = rtc_set_time(alarm_rtc_dev, &rtc_new_rtc_time);

调用interface.c 的

err = mutex_lock_interruptible(&rtc->ops_lock);

err = rtc->ops->set_time(rtc->dev.parent, tm);
mutex_unlock(&rtc->ops_lock);

调用硬件RTC的驱动

static const struct rtc_class_ops m41t94_rtc_ops = {
.read_time = m41t94_read_time,
.set_time = m41t94_set_time,
};

的m41t94_set_time设置到硬件RTC芯片

spin_lock_irqsave(&alarm_slock, flags);
  alarm_pending |= ANDROID_ALARM_TIME_CHANGE_MASK;
  wake_up(&alarm_wait_queue);
  spin_unlock_irqrestore(&alarm_slock, flags); 释放原来申请的锁
  mutex_unlock(&alarm_setrtc_mutex);   释放原来申请的锁

因为时间改了。唤醒alarm队列，释放原来申请的锁alarm_slock和alarm_setrtc_mutex