time.c

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/*
 *  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>

void read_persistent_clock(struct timespec *ts)
{
    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;

    ts->tv_sec = mktime(year, mon, day, hour, min, sec);
    ts->tv_nsec = 0;
}

/*
 * 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_once(KERN_NOTICE
               "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]);
}