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time.c

/*
 *  linux/arch/mips/dec/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *  Copyright (C) 2000, 2003  Maciej W. Rozycki
 *
 * This file contains the time handling details for PC-style clocks as
 * found in some MIPS systems.
 *
 */
#include <linux/bcd.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/param.h>

#include <asm/cpu-features.h>
#include <asm/ds1287.h>
#include <asm/time.h>
#include <asm/dec/interrupts.h>
#include <asm/dec/ioasic.h>
#include <asm/dec/machtype.h>

unsigned long read_persistent_clock(void)
{
      unsigned int year, mon, day, hour, min, sec, real_year;
      unsigned long flags;

      spin_lock_irqsave(&rtc_lock, flags);

      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);
            /*
             * The PROM will reset the year to either '72 or '73.
             * Therefore we store the real year separately, in one
             * of unused BBU RAM locations.
             */
            real_year = CMOS_READ(RTC_DEC_YEAR);
      } while (sec != CMOS_READ(RTC_SECONDS));

      spin_unlock_irqrestore(&rtc_lock, flags);

      if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
            sec = BCD2BIN(sec);
            min = BCD2BIN(min);
            hour = BCD2BIN(hour);
            day = BCD2BIN(day);
            mon = BCD2BIN(mon);
            year = BCD2BIN(year);
      }

      year += real_year - 72 + 2000;

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

/*
 * In order to set the CMOS clock precisely, rtc_mips_set_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 Dallas
 * DS1287 data sheet for details.
 */
int rtc_mips_set_mmss(unsigned long nowtime)
{
      int retval = 0;
      int real_seconds, real_minutes, cmos_minutes;
      unsigned char save_control, save_freq_select;

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

      /* stop and reset prescaler */
      save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
      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)
            cmos_minutes = BCD2BIN(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) {
                  real_seconds = BIN2BCD(real_seconds);
                  real_minutes = BIN2BCD(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 DS1287 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;
}

void __init plat_time_init(void)
{
      u32 start, end;
      int i = HZ / 10;

      /* Set up the rate of periodic DS1287 interrupts. */
      ds1287_set_base_clock(HZ);

      if (cpu_has_counter) {
            while (!ds1287_timer_state())
                  ;

            start = read_c0_count();

            while (i--)
                  while (!ds1287_timer_state())
                        ;

            end = read_c0_count();

            mips_hpt_frequency = (end - start) * 10;
            printk(KERN_INFO "MIPS counter frequency %dHz\n",
                  mips_hpt_frequency);
      } else if (IOASIC)
            /* For pre-R4k systems we use the I/O ASIC's counter.  */
            dec_ioasic_clocksource_init();

      ds1287_clockevent_init(dec_interrupt[DEC_IRQ_RTC]);
}

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