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rtc.c

/*
 * linux/arch/sh/kernel/rtc-mpc1211.c -- MPC-1211 on-chip RTC support
 *
 *  Copyright (C) 2002  Saito.K & Jeanne
 *
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/bcd.h>
#include <linux/mc146818rtc.h>

unsigned long get_cmos_time(void)
{
      unsigned int year, mon, day, hour, min, sec;

      spin_lock(&rtc_lock);

      do {
            sec = CMOS_READ(RTC_SECONDS);
            min = CMOS_READ(RTC_MINUTES);
            hour = CMOS_READ(RTC_HOURS);
            day = CMOS_READ(RTC_DAY_OF_MONTH);
            mon = CMOS_READ(RTC_MONTH);
            year = CMOS_READ(RTC_YEAR);
      } while (sec != CMOS_READ(RTC_SECONDS));

      if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
            BCD_TO_BIN(sec);
            BCD_TO_BIN(min);
            BCD_TO_BIN(hour);
            BCD_TO_BIN(day);
            BCD_TO_BIN(mon);
            BCD_TO_BIN(year);
      }

      spin_unlock(&rtc_lock);

      year += 1900;
      if (year < 1970)
            year += 100;

      return mktime(year, mon, day, hour, min, sec);
}

void mpc1211_rtc_gettimeofday(struct timeval *tv)
{

      tv->tv_sec = get_cmos_time();
      tv->tv_usec = 0;
}

/* arc/i386/kernel/time.c */
/*
 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
 * called 500 ms after the second nowtime has started, because when
 * nowtime is written into the registers of the CMOS clock, it will
 * jump to the next second precisely 500 ms later. Check the Motorola
 * MC146818A or Dallas DS12887 data sheet for details.
 *
 * BUG: This routine does not handle hour overflow properly; it just
 *      sets the minutes. Usually you'll only notice that after reboot!
 */
static int set_rtc_mmss(unsigned long nowtime)
{
      int retval = 0;
      int real_seconds, real_minutes, cmos_minutes;
      unsigned char save_control, save_freq_select;

      /* gets recalled with irq locally disabled */
      spin_lock(&rtc_lock);
      save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
      CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);

      save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
      CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);

      cmos_minutes = CMOS_READ(RTC_MINUTES);
      if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
            BCD_TO_BIN(cmos_minutes);

      /*
       * since we're only adjusting minutes and seconds,
       * don't interfere with hour overflow. This avoids
       * messing with unknown time zones but requires your
       * RTC not to be off by more than 15 minutes
       */
      real_seconds = nowtime % 60;
      real_minutes = nowtime / 60;
      if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
            real_minutes += 30;           /* correct for half hour time zone */
      real_minutes %= 60;

      if (abs(real_minutes - cmos_minutes) < 30) {
            if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                  BIN_TO_BCD(real_seconds);
                  BIN_TO_BCD(real_minutes);
            }
            CMOS_WRITE(real_seconds,RTC_SECONDS);
            CMOS_WRITE(real_minutes,RTC_MINUTES);
      } else {
            printk(KERN_WARNING
                   "set_rtc_mmss: can't update from %d to %d\n",
                   cmos_minutes, real_minutes);
            retval = -1;
      }

      /* The following flags have to be released exactly in this order,
       * otherwise the DS12887 (popular MC146818A clone with integrated
       * battery and quartz) will not reset the oscillator and will not
       * update precisely 500 ms later. You won't find this mentioned in
       * the Dallas Semiconductor data sheets, but who believes data
       * sheets anyway ...                           -- Markus Kuhn
       */
      CMOS_WRITE(save_control, RTC_CONTROL);
      CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
      spin_unlock(&rtc_lock);

      return retval;
}

int mpc1211_rtc_settimeofday(const struct timeval *tv)
{
      unsigned long nowtime = tv->tv_sec;

      return set_rtc_mmss(nowtime);
}

void mpc1211_time_init(void)
{
      rtc_sh_get_time = mpc1211_rtc_gettimeofday;
      rtc_sh_set_time = mpc1211_rtc_settimeofday;
}


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