Archipelago » qemu

/*

 * QEMU MC146818 RTC emulation

 *

 * Copyright (c) 2003-2004 Fabrice Bellard

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "hw.h"

#include "qemu-timer.h"

#include "sysemu.h"

#include "pc.h"

#include "isa.h"

#include "hpet_emul.h"

//#define DEBUG_CMOS

#define RTC_SECONDS             0

#define RTC_SECONDS_ALARM       1

#define RTC_MINUTES             2

#define RTC_MINUTES_ALARM       3

#define RTC_HOURS               4

#define RTC_HOURS_ALARM         5

#define RTC_ALARM_DONT_CARE    0xC0

#define RTC_DAY_OF_WEEK         6

#define RTC_DAY_OF_MONTH        7

#define RTC_MONTH               8

#define RTC_YEAR                9

#define RTC_REG_A               10

#define RTC_REG_B               11

#define RTC_REG_C               12

#define RTC_REG_D               13

#define REG_A_UIP 0x80

#define REG_B_SET  0x80

#define REG_B_PIE  0x40

#define REG_B_AIE  0x20

#define REG_B_UIE  0x10

#define REG_B_SQWE 0x08

#define REG_B_DM   0x04

struct RTCState {

    uint8_t cmos_data[128];

    uint8_t cmos_index;

    struct tm current_tm;

    int base_year;

    qemu_irq irq;

    qemu_irq sqw_irq;

    int it_shift;

    /* periodic timer */

    QEMUTimer *periodic_timer;

    int64_t next_periodic_time;

    /* second update */

    int64_t next_second_time;

#ifdef TARGET_I386

    uint32_t irq_coalesced;

    uint32_t period;

    QEMUTimer *coalesced_timer;

#endif

    QEMUTimer *second_timer;

    QEMUTimer *second_timer2;

};

static void rtc_irq_raise(qemu_irq irq) {

    /* When HPET is operating in legacy mode, RTC interrupts are disabled

     * We block qemu_irq_raise, but not qemu_irq_lower, in case legacy

     * mode is established while interrupt is raised. We want it to

     * be lowered in any case

     */

#if defined TARGET_I386 || defined TARGET_X86_64

    if (!hpet_in_legacy_mode())

#endif

        qemu_irq_raise(irq);

}

static void rtc_set_time(RTCState *s);

static void rtc_copy_date(RTCState *s);

#ifdef TARGET_I386

static void rtc_coalesced_timer_update(RTCState *s)

{

    if (s->irq_coalesced == 0) {

        qemu_del_timer(s->coalesced_timer);

    } else {

        /* divide each RTC interval to 2 - 8 smaller intervals */

        int c = MIN(s->irq_coalesced, 7) + 1; 

        int64_t next_clock = qemu_get_clock(vm_clock) +

                muldiv64(s->period / c, ticks_per_sec, 32768);

        qemu_mod_timer(s->coalesced_timer, next_clock);

    }

}

static void rtc_coalesced_timer(void *opaque)

{

    RTCState *s = opaque;

    if (s->irq_coalesced != 0) {

        apic_reset_irq_delivered();

        s->cmos_data[RTC_REG_C] |= 0xc0;

        rtc_irq_raise(s->irq);

        if (apic_get_irq_delivered()) {

            s->irq_coalesced--;

        }

    }

    rtc_coalesced_timer_update(s);

}

#endif

static void rtc_timer_update(RTCState *s, int64_t current_time)

{

    int period_code, period;

    int64_t cur_clock, next_irq_clock;

    int enable_pie;

    period_code = s->cmos_data[RTC_REG_A] & 0x0f;

#if defined TARGET_I386 || defined TARGET_X86_64

    /* disable periodic timer if hpet is in legacy mode, since interrupts are

     * disabled anyway.

     */

    enable_pie = !hpet_in_legacy_mode();

#else

    enable_pie = 1;

#endif

    if (period_code != 0

        && (((s->cmos_data[RTC_REG_B] & REG_B_PIE) && enable_pie)

            || ((s->cmos_data[RTC_REG_B] & REG_B_SQWE) && s->sqw_irq))) {

        if (period_code <= 2)

            period_code += 7;

        /* period in 32 Khz cycles */

        period = 1 << (period_code - 1);

#ifdef TARGET_I386

        if(period != s->period)

            s->irq_coalesced = (s->irq_coalesced * s->period) / period;

        s->period = period;

#endif

        /* compute 32 khz clock */

        cur_clock = muldiv64(current_time, 32768, ticks_per_sec);

        next_irq_clock = (cur_clock & ~(period - 1)) + period;

        s->next_periodic_time = muldiv64(next_irq_clock, ticks_per_sec, 32768) + 1;

        qemu_mod_timer(s->periodic_timer, s->next_periodic_time);

    } else {

#ifdef TARGET_I386

        s->irq_coalesced = 0;

#endif

        qemu_del_timer(s->periodic_timer);

    }

}

static void rtc_periodic_timer(void *opaque)

{

    RTCState *s = opaque;

    rtc_timer_update(s, s->next_periodic_time);

    if (s->cmos_data[RTC_REG_B] & REG_B_PIE) {

        s->cmos_data[RTC_REG_C] |= 0xc0;

#ifdef TARGET_I386

        if(rtc_td_hack) {

            apic_reset_irq_delivered();

            rtc_irq_raise(s->irq);

            if (!apic_get_irq_delivered()) {

                s->irq_coalesced++;

                rtc_coalesced_timer_update(s);

            }

        } else

#endif

        rtc_irq_raise(s->irq);

    }

    if (s->cmos_data[RTC_REG_B] & REG_B_SQWE) {

        /* Not square wave at all but we don't want 2048Hz interrupts!

           Must be seen as a pulse.  */

        qemu_irq_raise(s->sqw_irq);

    }

}

static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)

{

    RTCState *s = opaque;

    if ((addr & 1) == 0) {

        s->cmos_index = data & 0x7f;

    } else {

#ifdef DEBUG_CMOS

        printf("cmos: write index=0x%02x val=0x%02x\n",

               s->cmos_index, data);

#endif

        switch(s->cmos_index) {

        case RTC_SECONDS_ALARM:

        case RTC_MINUTES_ALARM:

        case RTC_HOURS_ALARM:

            /* XXX: not supported */

            s->cmos_data[s->cmos_index] = data;

            break;

        case RTC_SECONDS:

        case RTC_MINUTES:

        case RTC_HOURS:

        case RTC_DAY_OF_WEEK:

        case RTC_DAY_OF_MONTH:

        case RTC_MONTH:

        case RTC_YEAR:

            s->cmos_data[s->cmos_index] = data;

            /* if in set mode, do not update the time */

            if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {

                rtc_set_time(s);

            }

            break;

        case RTC_REG_A:

            /* UIP bit is read only */

            s->cmos_data[RTC_REG_A] = (data & ~REG_A_UIP) |

                (s->cmos_data[RTC_REG_A] & REG_A_UIP);

            rtc_timer_update(s, qemu_get_clock(vm_clock));

            break;

        case RTC_REG_B:

            if (data & REG_B_SET) {

                /* set mode: reset UIP mode */

                s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;

                data &= ~REG_B_UIE;

            } else {

                /* if disabling set mode, update the time */

                if (s->cmos_data[RTC_REG_B] & REG_B_SET) {

                    rtc_set_time(s);

                }

            }

            s->cmos_data[RTC_REG_B] = data;

            rtc_timer_update(s, qemu_get_clock(vm_clock));

            break;

        case RTC_REG_C:

        case RTC_REG_D:

            /* cannot write to them */

            break;

        default:

            s->cmos_data[s->cmos_index] = data;

            break;

        }

    }

}

static inline int to_bcd(RTCState *s, int a)

{

    if (s->cmos_data[RTC_REG_B] & REG_B_DM) {

        return a;

    } else {

        return ((a / 10) << 4) | (a % 10);

    }

}

static inline int from_bcd(RTCState *s, int a)

{

    if (s->cmos_data[RTC_REG_B] & REG_B_DM) {

        return a;

    } else {

        return ((a >> 4) * 10) + (a & 0x0f);

    }

}

static void rtc_set_time(RTCState *s)

{

    struct tm *tm = &s->current_tm;

    tm->tm_sec = from_bcd(s, s->cmos_data[RTC_SECONDS]);

    tm->tm_min = from_bcd(s, s->cmos_data[RTC_MINUTES]);

    tm->tm_hour = from_bcd(s, s->cmos_data[RTC_HOURS] & 0x7f);

    if (!(s->cmos_data[RTC_REG_B] & 0x02) &&

        (s->cmos_data[RTC_HOURS] & 0x80)) {

        tm->tm_hour += 12;

    }

    tm->tm_wday = from_bcd(s, s->cmos_data[RTC_DAY_OF_WEEK]) - 1;

    tm->tm_mday = from_bcd(s, s->cmos_data[RTC_DAY_OF_MONTH]);

    tm->tm_mon = from_bcd(s, s->cmos_data[RTC_MONTH]) - 1;

    tm->tm_year = from_bcd(s, s->cmos_data[RTC_YEAR]) + s->base_year - 1900;

}

static void rtc_copy_date(RTCState *s)

{

    const struct tm *tm = &s->current_tm;

    int year;

    s->cmos_data[RTC_SECONDS] = to_bcd(s, tm->tm_sec);

    s->cmos_data[RTC_MINUTES] = to_bcd(s, tm->tm_min);

    if (s->cmos_data[RTC_REG_B] & 0x02) {

        /* 24 hour format */

        s->cmos_data[RTC_HOURS] = to_bcd(s, tm->tm_hour);

    } else {

        /* 12 hour format */

        s->cmos_data[RTC_HOURS] = to_bcd(s, tm->tm_hour % 12);

        if (tm->tm_hour >= 12)

            s->cmos_data[RTC_HOURS] |= 0x80;

    }

    s->cmos_data[RTC_DAY_OF_WEEK] = to_bcd(s, tm->tm_wday + 1);

    s->cmos_data[RTC_DAY_OF_MONTH] = to_bcd(s, tm->tm_mday);

    s->cmos_data[RTC_MONTH] = to_bcd(s, tm->tm_mon + 1);

    year = (tm->tm_year - s->base_year) % 100;

    if (year < 0)

        year += 100;

    s->cmos_data[RTC_YEAR] = to_bcd(s, year);

}

/* month is between 0 and 11. */

static int get_days_in_month(int month, int year)

{

    static const int days_tab[12] = {

        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31

    };

    int d;

    if ((unsigned )month >= 12)

        return 31;

    d = days_tab[month];

    if (month == 1) {

        if ((year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0))

            d++;

    }

    return d;

}

/* update 'tm' to the next second */

static void rtc_next_second(struct tm *tm)

{

    int days_in_month;

    tm->tm_sec++;

    if ((unsigned)tm->tm_sec >= 60) {

        tm->tm_sec = 0;

        tm->tm_min++;

        if ((unsigned)tm->tm_min >= 60) {

            tm->tm_min = 0;

            tm->tm_hour++;

            if ((unsigned)tm->tm_hour >= 24) {

                tm->tm_hour = 0;

                /* next day */

                tm->tm_wday++;

                if ((unsigned)tm->tm_wday >= 7)

                    tm->tm_wday = 0;

                days_in_month = get_days_in_month(tm->tm_mon,

                                                  tm->tm_year + 1900);

                tm->tm_mday++;

                if (tm->tm_mday < 1) {

                    tm->tm_mday = 1;

                } else if (tm->tm_mday > days_in_month) {

                    tm->tm_mday = 1;

                    tm->tm_mon++;

                    if (tm->tm_mon >= 12) {

                        tm->tm_mon = 0;

                        tm->tm_year++;

                    }

                }

            }

        }

    }

}

static void rtc_update_second(void *opaque)

{

    RTCState *s = opaque;

    int64_t delay;

    /* if the oscillator is not in normal operation, we do not update */

    if ((s->cmos_data[RTC_REG_A] & 0x70) != 0x20) {

        s->next_second_time += ticks_per_sec;

        qemu_mod_timer(s->second_timer, s->next_second_time);

    } else {

        rtc_next_second(&s->current_tm);

        if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {

            /* update in progress bit */

            s->cmos_data[RTC_REG_A] |= REG_A_UIP;

        }

        /* should be 244 us = 8 / 32768 seconds, but currently the

           timers do not have the necessary resolution. */

        delay = (ticks_per_sec * 1) / 100;

        if (delay < 1)

            delay = 1;

        qemu_mod_timer(s->second_timer2,

                       s->next_second_time + delay);

    }

}

static void rtc_update_second2(void *opaque)

{

    RTCState *s = opaque;

    if (!(s->cmos_data[RTC_REG_B] & REG_B_SET)) {

        rtc_copy_date(s);

    }

    /* check alarm */

    if (s->cmos_data[RTC_REG_B] & REG_B_AIE) {

        if (((s->cmos_data[RTC_SECONDS_ALARM] & 0xc0) == 0xc0 ||

             s->cmos_data[RTC_SECONDS_ALARM] == s->current_tm.tm_sec) &&

            ((s->cmos_data[RTC_MINUTES_ALARM] & 0xc0) == 0xc0 ||

             s->cmos_data[RTC_MINUTES_ALARM] == s->current_tm.tm_mon) &&

            ((s->cmos_data[RTC_HOURS_ALARM] & 0xc0) == 0xc0 ||

             s->cmos_data[RTC_HOURS_ALARM] == s->current_tm.tm_hour)) {

            s->cmos_data[RTC_REG_C] |= 0xa0;

            rtc_irq_raise(s->irq);

        }

    }

    /* update ended interrupt */

    if (s->cmos_data[RTC_REG_B] & REG_B_UIE) {

        s->cmos_data[RTC_REG_C] |= 0x90;

        rtc_irq_raise(s->irq);

    }

    /* clear update in progress bit */

    s->cmos_data[RTC_REG_A] &= ~REG_A_UIP;

    s->next_second_time += ticks_per_sec;

    qemu_mod_timer(s->second_timer, s->next_second_time);

}

static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)

{

    RTCState *s = opaque;

    int ret;

    if ((addr & 1) == 0) {

        return 0xff;

    } else {

        switch(s->cmos_index) {

        case RTC_SECONDS:

        case RTC_MINUTES:

        case RTC_HOURS:

        case RTC_DAY_OF_WEEK:

        case RTC_DAY_OF_MONTH:

        case RTC_MONTH:

        case RTC_YEAR:

            ret = s->cmos_data[s->cmos_index];

            break;

        case RTC_REG_A:

            ret = s->cmos_data[s->cmos_index];

            break;

        case RTC_REG_C:

            ret = s->cmos_data[s->cmos_index];

            qemu_irq_lower(s->irq);

            s->cmos_data[RTC_REG_C] = 0x00;

            break;

        default:

            ret = s->cmos_data[s->cmos_index];

            break;

        }

#ifdef DEBUG_CMOS

        printf("cmos: read index=0x%02x val=0x%02x\n",

               s->cmos_index, ret);

#endif

        return ret;

    }

}

void rtc_set_memory(RTCState *s, int addr, int val)

{

    if (addr >= 0 && addr <= 127)

        s->cmos_data[addr] = val;

}

void rtc_set_date(RTCState *s, const struct tm *tm)

{

    s->current_tm = *tm;

    rtc_copy_date(s);

}

/* PC cmos mappings */

#define REG_IBM_CENTURY_BYTE        0x32

#define REG_IBM_PS2_CENTURY_BYTE    0x37

static void rtc_set_date_from_host(RTCState *s)

{

    struct tm tm;

    int val;

    /* set the CMOS date */

    qemu_get_timedate(&tm, 0);

    rtc_set_date(s, &tm);

    val = to_bcd(s, (tm.tm_year / 100) + 19);

    rtc_set_memory(s, REG_IBM_CENTURY_BYTE, val);

    rtc_set_memory(s, REG_IBM_PS2_CENTURY_BYTE, val);

}

static void rtc_save(QEMUFile *f, void *opaque)

{

    RTCState *s = opaque;

    qemu_put_buffer(f, s->cmos_data, 128);

    qemu_put_8s(f, &s->cmos_index);

    qemu_put_be32(f, s->current_tm.tm_sec);

    qemu_put_be32(f, s->current_tm.tm_min);

    qemu_put_be32(f, s->current_tm.tm_hour);

    qemu_put_be32(f, s->current_tm.tm_wday);

    qemu_put_be32(f, s->current_tm.tm_mday);

    qemu_put_be32(f, s->current_tm.tm_mon);

    qemu_put_be32(f, s->current_tm.tm_year);

    qemu_put_timer(f, s->periodic_timer);

    qemu_put_be64(f, s->next_periodic_time);

    qemu_put_be64(f, s->next_second_time);

    qemu_put_timer(f, s->second_timer);

    qemu_put_timer(f, s->second_timer2);

}

static int rtc_load(QEMUFile *f, void *opaque, int version_id)

{

    RTCState *s = opaque;

    if (version_id != 1)

        return -EINVAL;

    qemu_get_buffer(f, s->cmos_data, 128);

    qemu_get_8s(f, &s->cmos_index);

    s->current_tm.tm_sec=qemu_get_be32(f);

    s->current_tm.tm_min=qemu_get_be32(f);

    s->current_tm.tm_hour=qemu_get_be32(f);

    s->current_tm.tm_wday=qemu_get_be32(f);

    s->current_tm.tm_mday=qemu_get_be32(f);

    s->current_tm.tm_mon=qemu_get_be32(f);

    s->current_tm.tm_year=qemu_get_be32(f);

    qemu_get_timer(f, s->periodic_timer);

    s->next_periodic_time=qemu_get_be64(f);

    s->next_second_time=qemu_get_be64(f);

    qemu_get_timer(f, s->second_timer);

    qemu_get_timer(f, s->second_timer2);

    return 0;

}

#ifdef TARGET_I386

static void rtc_save_td(QEMUFile *f, void *opaque)

{

    RTCState *s = opaque;

    qemu_put_be32(f, s->irq_coalesced);

    qemu_put_be32(f, s->period);

}

static int rtc_load_td(QEMUFile *f, void *opaque, int version_id)

{

    RTCState *s = opaque;

    if (version_id != 1)

        return -EINVAL;

    s->irq_coalesced = qemu_get_be32(f);

    s->period = qemu_get_be32(f);

    rtc_coalesced_timer_update(s);

    return 0;

}

#endif

RTCState *rtc_init_sqw(int base, qemu_irq irq, qemu_irq sqw_irq, int base_year)

{

    RTCState *s;

    s = qemu_mallocz(sizeof(RTCState));

    s->irq = irq;

    s->sqw_irq = sqw_irq;

    s->cmos_data[RTC_REG_A] = 0x26;

    s->cmos_data[RTC_REG_B] = 0x02;

    s->cmos_data[RTC_REG_C] = 0x00;

    s->cmos_data[RTC_REG_D] = 0x80;

    s->base_year = base_year;

    rtc_set_date_from_host(s);

    s->periodic_timer = qemu_new_timer(vm_clock,

                                       rtc_periodic_timer, s);

#ifdef TARGET_I386

    if (rtc_td_hack)

        s->coalesced_timer = qemu_new_timer(vm_clock, rtc_coalesced_timer, s);

#endif

    s->second_timer = qemu_new_timer(vm_clock,

                                     rtc_update_second, s);

    s->second_timer2 = qemu_new_timer(vm_clock,

                                      rtc_update_second2, s);

    s->next_second_time = qemu_get_clock(vm_clock) + (ticks_per_sec * 99) / 100;

    qemu_mod_timer(s->second_timer2, s->next_second_time);

    register_ioport_write(base, 2, 1, cmos_ioport_write, s);

    register_ioport_read(base, 2, 1, cmos_ioport_read, s);

    register_savevm("mc146818rtc", base, 1, rtc_save, rtc_load, s);

#ifdef TARGET_I386

    if (rtc_td_hack)

        register_savevm("mc146818rtc-td", base, 1, rtc_save_td, rtc_load_td, s);

#endif

    return s;

}

RTCState *rtc_init(int base, qemu_irq irq, int base_year)

{

    return rtc_init_sqw(base, irq, NULL, base_year);

}

/* Memory mapped interface */

static uint32_t cmos_mm_readb (void *opaque, target_phys_addr_t addr)

{

    RTCState *s = opaque;

    return cmos_ioport_read(s, addr >> s->it_shift) & 0xFF;

}

static void cmos_mm_writeb (void *opaque,

                            target_phys_addr_t addr, uint32_t value)

{

    RTCState *s = opaque;

    cmos_ioport_write(s, addr >> s->it_shift, value & 0xFF);

}

static uint32_t cmos_mm_readw (void *opaque, target_phys_addr_t addr)

{

    RTCState *s = opaque;

    uint32_t val;

    val = cmos_ioport_read(s, addr >> s->it_shift) & 0xFFFF;

#ifdef TARGET_WORDS_BIGENDIAN

    val = bswap16(val);

#endif

    return val;

}

static void cmos_mm_writew (void *opaque,

                            target_phys_addr_t addr, uint32_t value)

{

    RTCState *s = opaque;

#ifdef TARGET_WORDS_BIGENDIAN

    value = bswap16(value);

#endif

    cmos_ioport_write(s, addr >> s->it_shift, value & 0xFFFF);

}

static uint32_t cmos_mm_readl (void *opaque, target_phys_addr_t addr)

{

    RTCState *s = opaque;

    uint32_t val;

    val = cmos_ioport_read(s, addr >> s->it_shift);

#ifdef TARGET_WORDS_BIGENDIAN

    val = bswap32(val);

#endif

    return val;

}

static void cmos_mm_writel (void *opaque,

                            target_phys_addr_t addr, uint32_t value)

{

    RTCState *s = opaque;

#ifdef TARGET_WORDS_BIGENDIAN

    value = bswap32(value);

#endif

    cmos_ioport_write(s, addr >> s->it_shift, value);

}

static CPUReadMemoryFunc *rtc_mm_read[] = {

    &cmos_mm_readb,

    &cmos_mm_readw,

    &cmos_mm_readl,

};

static CPUWriteMemoryFunc *rtc_mm_write[] = {

    &cmos_mm_writeb,

    &cmos_mm_writew,

    &cmos_mm_writel,

};

RTCState *rtc_mm_init(target_phys_addr_t base, int it_shift, qemu_irq irq,

                      int base_year)

{

    RTCState *s;

    int io_memory;

    s = qemu_mallocz(sizeof(RTCState));

    s->irq = irq;

    s->cmos_data[RTC_REG_A] = 0x26;

    s->cmos_data[RTC_REG_B] = 0x02;

    s->cmos_data[RTC_REG_C] = 0x00;

    s->cmos_data[RTC_REG_D] = 0x80;

    s->base_year = base_year;

    rtc_set_date_from_host(s);

    s->periodic_timer = qemu_new_timer(vm_clock,

                                       rtc_periodic_timer, s);

    s->second_timer = qemu_new_timer(vm_clock,

                                     rtc_update_second, s);

    s->second_timer2 = qemu_new_timer(vm_clock,

                                      rtc_update_second2, s);

    s->next_second_time = qemu_get_clock(vm_clock) + (ticks_per_sec * 99) / 100;

    qemu_mod_timer(s->second_timer2, s->next_second_time);

    io_memory = cpu_register_io_memory(0, rtc_mm_read, rtc_mm_write, s);

    cpu_register_physical_memory(base, 2 << it_shift, io_memory);

    register_savevm("mc146818rtc", base, 1, rtc_save, rtc_load, s);

#ifdef TARGET_I386

    if (rtc_td_hack)

        register_savevm("mc146818rtc-td", base, 1, rtc_save_td, rtc_load_td, s);

#endif

    return s;

}