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/*
 *  include/asm-i386/mach-default/mach_time.h
 *
 *  Machine specific set RTC function for generic.
 *  Split out from time.c by Osamu Tomita <tomita@cinet.co.jp>
 */
#ifndef _MACH_TIME_H
#define _MACH_TIME_H

#include <linux/mc146818rtc.h>

/* for check timing call set_rtc_mmss() 500ms     */
/* used in arch/i386/time.c::do_timer_interrupt() */
#define USEC_AFTER      500000
#define USEC_BEFORE     500000

/*
 * 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 inline int mach_set_rtc_mmss(unsigned long nowtime)
{
        int retval = 0;
        int real_seconds, real_minutes, cmos_minutes;
        unsigned char save_control, save_freq_select;

        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);

        return retval;
}

static inline unsigned long mach_get_cmos_time(void)
{
        unsigned int year, mon, day, hour, min, sec;
        int i;

        /* The Linux interpretation of the CMOS clock register contents:
         * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
         * RTC registers show the second which has precisely just started.
         * Let's hope other operating systems interpret the RTC the same way.
         */
        /* read RTC exactly on falling edge of update flag */
        for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
                if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
                        break;
        for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
                if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
                        break;
        do { /* Isn't this overkill ? UIP above should guarantee consistency */
                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);
          }
        if ((year += 1900) < 1970)
                year += 100;

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

#endif /* !_MACH_TIME_H */