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/*

 *  linux/arch/alpha/kernel/time.c

 *

 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds

 *

 * This file contains the PC-specific time handling details:

 * reading the RTC at bootup, etc..

 * 1994-07-02    Alan Modra

 *      fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime

 * 1995-03-26    Markus Kuhn

 *      fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887

 *      precision CMOS clock update

 */

#include <linux/errno.h>

#include <linux/sched.h>

#include <linux/kernel.h>

#include <linux/param.h>

#include <linux/string.h>

#include <linux/mm.h>

#include <asm/segment.h>

#include <asm/io.h>

#include <asm/hwrpb.h>

#include <linux/mc146818rtc.h>

#include <linux/timex.h>

#define TIMER_IRQ 0

extern struct hwrpb_struct *hwrpb;

static int set_rtc_mmss(unsigned long);

/*

 * Shift amount by which scaled_ticks_per_cycle is scaled.  Shifting

 * by 48 gives us 16 bits for HZ while keeping the accuracy good even

 * for large CPU clock rates.

 */

#define FIX_SHIFT       48

/* lump static variables together for more efficient access: */

static struct {

        __u32           last_time;              /* cycle counter last time it got invoked */

        __u32           max_cycles_per_tick;    /* more makes us think we lost an interrupt */

        unsigned long   scaled_ticks_per_cycle; /* ticks/cycle * 2^48 */

        long            last_rtc_update;        /* last time the cmos clock got updated */

} state;

static inline __u32 rpcc(void)

{

    __u32 result;

    asm volatile ("rpcc %0" : "r="(result));

    return result;

}

/*

 * timer_interrupt() needs to keep up the real-time clock,

 * as well as call the "do_timer()" routine every clocktick

 */

void timer_interrupt(struct pt_regs * regs)

{

        __u32 delta, now;

        now = rpcc();

        delta = now - state.last_time;

        state.last_time = now;

        if (delta > state.max_cycles_per_tick) {

                int i, missed_ticks;

                missed_ticks = ((delta * state.scaled_ticks_per_cycle) >> FIX_SHIFT) - 1;

                for (i = 0; i < missed_ticks; ++i) {

                        do_timer(regs);

                }

        }

        do_timer(regs);

        /*

         * If we have an externally synchronized Linux clock, then update

         * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be

         * called as close as possible to 500 ms before the new second starts.

         */

        if (time_state != TIME_BAD && xtime.tv_sec > state.last_rtc_update + 660 &&

            xtime.tv_usec > 500000 - (tick >> 1) &&

            xtime.tv_usec < 500000 + (tick >> 1))

          if (set_rtc_mmss(xtime.tv_sec) == 0)

            state.last_rtc_update = xtime.tv_sec;

          else

            state.last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */

}

/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.

 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59

 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.

 *

 * [For the Julian calendar (which was used in Russia before 1917,

 * Britain & colonies before 1752, anywhere else before 1582,

 * and is still in use by some communities) leave out the

 * -year/100+year/400 terms, and add 10.]

 *

 * This algorithm was first published by Gauss (I think).

 *

 * WARNING: this function will overflow on 2106-02-07 06:28:16 on

 * machines were long is 32-bit! (However, as time_t is signed, we

 * will already get problems at other places on 2038-01-19 03:14:08)

 */

static inline unsigned long mktime(unsigned int year, unsigned int mon,

        unsigned int day, unsigned int hour,

        unsigned int min, unsigned int sec)

{

        if (0 >= (int) (mon -= 2)) {     /* 1..12 -> 11,12,1..10 */

                mon += 12;      /* Puts Feb last since it has leap day */

                year -= 1;

        }

        return (((

            (unsigned long)(year/4 - year/100 + year/400 + 367*mon/12 + day) +

              year*365 - 719499

            )*24 + hour /* now have hours */

           )*60 + min /* now have minutes */

          )*60 + sec; /* finally seconds */

}

void time_init(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);

          }

#ifdef ALPHA_PRE_V1_2_SRM_CONSOLE

        /*

         * The meaning of life, the universe, and everything. Plus

         * this makes the year come out right on SRM consoles earlier

         * than v1.2.

         */

        year -= 42;

#endif

        if ((year += 1900) < 1970)

                year += 100;

        xtime.tv_sec = mktime(year, mon, day, hour, min, sec);

        xtime.tv_usec = 0;

        if (HZ > (1<<16)) {

                extern void __you_loose (void);

                __you_loose();

        }

        state.last_time = rpcc();

        state.scaled_ticks_per_cycle = ((unsigned long) HZ << FIX_SHIFT) / hwrpb->cycle_freq;

        state.max_cycles_per_tick = (2 * hwrpb->cycle_freq) / HZ;

        state.last_rtc_update = 0;

}

/*

 * We could get better timer accuracy by using the alpha

 * time counters or something.  Now this is limited to

 * the HZ clock frequency.

 */

void do_gettimeofday(struct timeval *tv)

{

        unsigned long flags;

        save_flags(flags);

        cli();

        *tv = xtime;

        restore_flags(flags);

}

void do_settimeofday(struct timeval *tv)

{

        cli();

        xtime = *tv;

        time_state = TIME_BAD;

        time_maxerror = 0x70000000;

        time_esterror = 0x70000000;

        sti();

}

/*

 * 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.

 */

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;

        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

                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;

}