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time.c

/*
 *  arch/arm/mach-footbridge/include/mach/time.h
 *
 *  Copyright (C) 1998 Russell King.
 *  Copyright (C) 1998 Phil Blundell
 *
 * CATS has a real-time clock, though the evaluation board doesn't.
 *
 * Changelog:
 *  21-Mar-1998   RMK   Created
 *  27-Aug-1998   PJB   CATS support
 *  28-Dec-1998   APH   Made leds optional
 *  20-Jan-1999   RMK   Started merge of EBSA285, CATS and NetWinder
 *  16-Mar-1999   RMK   More support for EBSA285-like machines with RTCs in
 */

#define RTC_PORT(x)           (rtc_base+(x))
#define RTC_ALWAYS_BCD        0

#include <linux/timex.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mc146818rtc.h>
#include <linux/bcd.h>
#include <linux/io.h>

#include <mach/hardware.h>

#include <asm/mach/time.h>
#include "common.h"

static int rtc_base;

static unsigned long __init get_isa_cmos_time(void)
{
      unsigned int year, mon, day, hour, min, sec;

      // check to see if the RTC makes sense.....
      if ((CMOS_READ(RTC_VALID) & RTC_VRT) == 0)
            return mktime(1970, 1, 1, 0, 0, 0);

      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) {
            sec = bcd2bin(sec);
            min = bcd2bin(min);
            hour = bcd2bin(hour);
            day = bcd2bin(day);
            mon = bcd2bin(mon);
            year = bcd2bin(year);
      }
      if ((year += 1900) < 1970)
            year += 100;
      return mktime(year, mon, day, hour, min, sec);
}

static int set_isa_cmos_time(void)
{
      int retval = 0;
      int real_seconds, real_minutes, cmos_minutes;
      unsigned char save_control, save_freq_select;
      unsigned long nowtime = xtime.tv_sec;

      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)
            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
            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);

      return retval;
}

void __init isa_rtc_init(void)
{
      if (machine_is_personal_server())
            /*
             * Add-in 21285s shouldn't access the RTC
             */
            rtc_base = 0;
      else
            rtc_base = 0x70;

      if (rtc_base) {
            int reg_d, reg_b;

            /*
             * Probe for the RTC.
             */
            reg_d = CMOS_READ(RTC_REG_D);

            /*
             * make sure the divider is set
             */
            CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_REG_A);

            /*
             * Set control reg B
             *   (24 hour mode, update enabled)
             */
            reg_b = CMOS_READ(RTC_REG_B) & 0x7f;
            reg_b |= 2;
            CMOS_WRITE(reg_b, RTC_REG_B);

            if ((CMOS_READ(RTC_REG_A) & 0x7f) == RTC_REF_CLCK_32KHZ &&
                CMOS_READ(RTC_REG_B) == reg_b) {
                  struct timespec tv;

                  /*
                   * We have a RTC.  Check the battery
                   */
                  if ((reg_d & 0x80) == 0)
                        printk(KERN_WARNING "RTC: *** warning: CMOS battery bad\n");

                  tv.tv_nsec = 0;
                  tv.tv_sec = get_isa_cmos_time();
                  do_settimeofday(&tv);
                  set_rtc = set_isa_cmos_time;
            } else
                  rtc_base = 0;
      }
}

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