text: /*
   * arch/sh/boards/dreamcast/rtc.c
   *
   * Dreamcast AICA RTC routines.
   *
   * Copyright (c) 2001, 2002 M. R. Brown <mrbrown@0xd6.org>
   * Copyright (c) 2002 Paul Mundt <lethal@chaoticdreams.org>
   *
   * Released under the terms of the GNU GPL v2.0.
   *
   */
  
  #include <linux/time.h>
  #include <asm/rtc.h>
  #include <asm/io.h>
  
  /* The AICA RTC has an Epoch of 1/1/1950, so we must subtract 20 years (in
     seconds) to get the standard Unix Epoch when getting the time, and add
     20 years when setting the time. */
  #define TWENTY_YEARS ((20 * 365LU + 5) * 86400)
  
  /* The AICA RTC is represented by a 32-bit seconds counter stored in 2 16-bit
     registers.*/
  #define AICA_RTC_SECS_H		0xa0710000
  #define AICA_RTC_SECS_L		0xa0710004
  
  /**
   * aica_rtc_gettimeofday - Get the time from the AICA RTC
   * @ts: pointer to resulting timespec
   *
   * Grabs the current RTC seconds counter and adjusts it to the Unix Epoch.
   */
  static void aica_rtc_gettimeofday(struct timespec *ts)
  {
  	unsigned long val1, val2;
  
  	do {
  		val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  
  		val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  	} while (val1 != val2);
  
  	ts->tv_sec = val1 - TWENTY_YEARS;
  
  	/* Can't get nanoseconds with just a seconds counter. */
  	ts->tv_nsec = 0;
  }
  
  /**
   * aica_rtc_settimeofday - Set the AICA RTC to the current time
   * @secs: contains the time_t to set
   *
   * Adjusts the given @tv to the AICA Epoch and sets the RTC seconds counter.
   */
  static int aica_rtc_settimeofday(const time_t secs)
  {
  	unsigned long val1, val2;
  	unsigned long adj = secs + TWENTY_YEARS;
  
  	do {
  		__raw_writel((adj & 0xffff0000) >> 16, AICA_RTC_SECS_H);
  		__raw_writel((adj & 0xffff), AICA_RTC_SECS_L);
  
  		val1 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  
  		val2 = ((__raw_readl(AICA_RTC_SECS_H) & 0xffff) << 16) |
  			(__raw_readl(AICA_RTC_SECS_L) & 0xffff);
  	} while (val1 != val2);
  
  	return 0;
  }
  
  void aica_time_init(void)
  {
  	rtc_sh_get_time = aica_rtc_gettimeofday;
  	rtc_sh_set_time = aica_rtc_settimeofday;
  }
  
  