/*
   * RTC subsystem, initialize system time on startup
   *
   * Copyright (C) 2005 Tower Technologies
   * Author: Alessandro Zummo <a.zummo@towertech.it>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
  */
  
  #include <linux/rtc.h>
  
  /* IMPORTANT: the RTC only stores whole seconds. It is arbitrary
   * whether it stores the most close value or the value with partial
   * seconds truncated. However, it is important that we use it to store
   * the truncated value. This is because otherwise it is necessary,
   * in an rtc sync function, to read both xtime.tv_sec and
   * xtime.tv_nsec. On some processors (i.e. ARM), an atomic read
   * of >32bits is not possible. So storing the most close value would
   * slow down the sync API. So here we have the truncated value and
   * the best guess is to add 0.5s.
   */

  int rtc_hctosys_ret = -ENODEV;

  static int __init rtc_hctosys(void)
  {

  	int err = -ENODEV;

  	struct rtc_time tm;

  	struct timespec tv = {
  		.tv_nsec = NSEC_PER_SEC >> 1,
  	};

  	struct rtc_device *rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);

  	if (rtc == NULL) {

  		pr_err("%s: unable to open rtc device (%s)
  ",

  			__FILE__, CONFIG_RTC_HCTOSYS_DEVICE);

  		goto err_open;

  	}

  	err = rtc_read_time(rtc, &tm);

  	if (err) {
  		dev_err(rtc->dev.parent,
  			"hctosys: unable to read the hardware clock
  ");
  		goto err_read;

  	}

  	err = rtc_valid_tm(&tm);
  	if (err) {
  		dev_err(rtc->dev.parent,
  			"hctosys: invalid date/time
  ");
  		goto err_invalid;
  	}

  	rtc_tm_to_time(&tm, &tv.tv_sec);

  	do_settimeofday(&tv);

  	dev_info(rtc->dev.parent,
  		"setting system clock to "
  		"%d-%02d-%02d %02d:%02d:%02d UTC (%u)
  ",
  		tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
  		tm.tm_hour, tm.tm_min, tm.tm_sec,
  		(unsigned int) tv.tv_sec);
  
  err_invalid:
  err_read:

  	rtc_class_close(rtc);

  err_open:
  	rtc_hctosys_ret = err;
  
  	return err;

  }
  
  late_initcall(rtc_hctosys);