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/*

 * QEMU 8253/8254 interval timer 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 "vl.h"

//#define DEBUG_PIT

#define RW_STATE_LSB 1

#define RW_STATE_MSB 2

#define RW_STATE_WORD0 3

#define RW_STATE_WORD1 4

typedef struct PITChannelState {

    int count; /* can be 65536 */

    uint16_t latched_count;

    uint8_t count_latched;

    uint8_t status_latched;

    uint8_t status;

    uint8_t read_state;

    uint8_t write_state;

    uint8_t write_latch;

    uint8_t rw_mode;

    uint8_t mode;

    uint8_t bcd; /* not supported */

    uint8_t gate; /* timer start */

    int64_t count_load_time;

    /* irq handling */

    int64_t next_transition_time;

    QEMUTimer *irq_timer;

    int irq;

} PITChannelState;

struct PITState {

    PITChannelState channels[3];

};

static PITState pit_state;

static void pit_irq_timer_update(PITChannelState *s, int64_t current_time);

static int pit_get_count(PITChannelState *s)

{

    uint64_t d;

    int counter;

    d = muldiv64(qemu_get_clock(vm_clock) - s->count_load_time, PIT_FREQ, ticks_per_sec);

    switch(s->mode) {

    case 0:

    case 1:

    case 4:

    case 5:

        counter = (s->count - d) & 0xffff;

        break;

    case 3:

        /* XXX: may be incorrect for odd counts */

        counter = s->count - ((2 * d) % s->count);

        break;

    default:

        counter = s->count - (d % s->count);

        break;

    }

    return counter;

}

/* get pit output bit */

static int pit_get_out1(PITChannelState *s, int64_t current_time)

{

    uint64_t d;

    int out;

    d = muldiv64(current_time - s->count_load_time, PIT_FREQ, ticks_per_sec);

    switch(s->mode) {

    default:

    case 0:

        out = (d >= s->count);

        break;

    case 1:

        out = (d < s->count);

        break;

    case 2:

        if ((d % s->count) == 0 && d != 0)

            out = 1;

        else

            out = 0;

        break;

    case 3:

        out = (d % s->count) < ((s->count + 1) >> 1);

        break;

    case 4:

    case 5:

        out = (d == s->count);

        break;

    }

    return out;

}

int pit_get_out(PITState *pit, int channel, int64_t current_time)

{

    PITChannelState *s = &pit->channels[channel];

    return pit_get_out1(s, current_time);

}

/* return -1 if no transition will occur.  */

static int64_t pit_get_next_transition_time(PITChannelState *s, 

                                            int64_t current_time)

{

    uint64_t d, next_time, base;

    int period2;

    d = muldiv64(current_time - s->count_load_time, PIT_FREQ, ticks_per_sec);

    switch(s->mode) {

    default:

    case 0:

    case 1:

        if (d < s->count)

            next_time = s->count;

        else

            return -1;

        break;

    case 2:

        base = (d / s->count) * s->count;

        if ((d - base) == 0 && d != 0)

            next_time = base + s->count;

        else

            next_time = base + s->count + 1;

        break;

    case 3:

        base = (d / s->count) * s->count;

        period2 = ((s->count + 1) >> 1);

        if ((d - base) < period2) 

            next_time = base + period2;

        else

            next_time = base + s->count;

        break;

    case 4:

    case 5:

        if (d < s->count)

            next_time = s->count;

        else if (d == s->count)

            next_time = s->count + 1;

        else

            return -1;

        break;

    }

    /* convert to timer units */

    next_time = s->count_load_time + muldiv64(next_time, ticks_per_sec, PIT_FREQ);

    /* fix potential rounding problems */

    /* XXX: better solution: use a clock at PIT_FREQ Hz */

    if (next_time <= current_time)

        next_time = current_time + 1;

    return next_time;

}

/* val must be 0 or 1 */

void pit_set_gate(PITState *pit, int channel, int val)

{

    PITChannelState *s = &pit->channels[channel];

    switch(s->mode) {

    default:

    case 0:

    case 4:

        /* XXX: just disable/enable counting */

        break;

    case 1:

    case 5:

        if (s->gate < val) {

            /* restart counting on rising edge */

            s->count_load_time = qemu_get_clock(vm_clock);

            pit_irq_timer_update(s, s->count_load_time);

        }

        break;

    case 2:

    case 3:

        if (s->gate < val) {

            /* restart counting on rising edge */

            s->count_load_time = qemu_get_clock(vm_clock);

            pit_irq_timer_update(s, s->count_load_time);

        }

        /* XXX: disable/enable counting */

        break;

    }

    s->gate = val;

}

int pit_get_gate(PITState *pit, int channel)

{

    PITChannelState *s = &pit->channels[channel];

    return s->gate;

}

static inline void pit_load_count(PITChannelState *s, int val)

{

    if (val == 0)

        val = 0x10000;

    s->count_load_time = qemu_get_clock(vm_clock);

    s->count = val;

    pit_irq_timer_update(s, s->count_load_time);

}

/* if already latched, do not latch again */

static void pit_latch_count(PITChannelState *s)

{

    if (!s->count_latched) {

        s->latched_count = pit_get_count(s);

        s->count_latched = s->rw_mode;

    }

}

static void pit_ioport_write(void *opaque, uint32_t addr, uint32_t val)

{

    PITState *pit = opaque;

    int channel, access;

    PITChannelState *s;

    addr &= 3;

    if (addr == 3) {

        channel = val >> 6;

        if (channel == 3) {

            /* read back command */

            for(channel = 0; channel < 3; channel++) {

                s = &pit->channels[channel];

                if (val & (2 << channel)) {

                    if (!(val & 0x20)) {

                        pit_latch_count(s);

                    }

                    if (!(val & 0x10) && !s->status_latched) {

                        /* status latch */

                        /* XXX: add BCD and null count */

                        s->status =  (pit_get_out1(s, qemu_get_clock(vm_clock)) << 7) |

                            (s->rw_mode << 4) |

                            (s->mode << 1) |

                            s->bcd;

                        s->status_latched = 1;

                    }

                }

            }

        } else {

            s = &pit->channels[channel];

            access = (val >> 4) & 3;

            if (access == 0) {

                pit_latch_count(s);

            } else {

                s->rw_mode = access;

                s->read_state = access;

                s->write_state = access;

                s->mode = (val >> 1) & 7;

                s->bcd = val & 1;

                /* XXX: update irq timer ? */

            }

        }

    } else {

        s = &pit->channels[addr];

        switch(s->write_state) {

        default:

        case RW_STATE_LSB:

            pit_load_count(s, val);

            break;

        case RW_STATE_MSB:

            pit_load_count(s, val << 8);

            break;

        case RW_STATE_WORD0:

            s->write_latch = val;

            s->write_state = RW_STATE_WORD1;

            break;

        case RW_STATE_WORD1:

            pit_load_count(s, s->write_latch | (val << 8));

            s->write_state = RW_STATE_WORD0;

            break;

        }

    }

}

static uint32_t pit_ioport_read(void *opaque, uint32_t addr)

{

    PITState *pit = opaque;

    int ret, count;

    PITChannelState *s;

    addr &= 3;

    s = &pit->channels[addr];

    if (s->status_latched) {

        s->status_latched = 0;

        ret = s->status;

    } else if (s->count_latched) {

        switch(s->count_latched) {

        default:

        case RW_STATE_LSB:

            ret = s->latched_count & 0xff;

            s->count_latched = 0;

            break;

        case RW_STATE_MSB:

            ret = s->latched_count >> 8;

            s->count_latched = 0;

            break;

        case RW_STATE_WORD0:

            ret = s->latched_count & 0xff;

            s->count_latched = RW_STATE_MSB;

            break;

        }

    } else {

        switch(s->read_state) {

        default:

        case RW_STATE_LSB:

            count = pit_get_count(s);

            ret = count & 0xff;

            break;

        case RW_STATE_MSB:

            count = pit_get_count(s);

            ret = (count >> 8) & 0xff;

            break;

        case RW_STATE_WORD0:

            count = pit_get_count(s);

            ret = count & 0xff;

            s->read_state = RW_STATE_WORD1;

            break;

        case RW_STATE_WORD1:

            count = pit_get_count(s);

            ret = (count >> 8) & 0xff;

            s->read_state = RW_STATE_WORD0;

            break;

        }

    }

    return ret;

}

static void pit_irq_timer_update(PITChannelState *s, int64_t current_time)

{

    int64_t expire_time;

    int irq_level;

    if (!s->irq_timer)

        return;

    expire_time = pit_get_next_transition_time(s, current_time);

    irq_level = pit_get_out1(s, current_time);

    pic_set_irq(s->irq, irq_level);

#ifdef DEBUG_PIT

    printf("irq_level=%d next_delay=%f\n",

           irq_level, 

           (double)(expire_time - current_time) / ticks_per_sec);

#endif

    s->next_transition_time = expire_time;

    if (expire_time != -1)

        qemu_mod_timer(s->irq_timer, expire_time);

    else

        qemu_del_timer(s->irq_timer);

}

static void pit_irq_timer(void *opaque)

{

    PITChannelState *s = opaque;

    pit_irq_timer_update(s, s->next_transition_time);

}

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

{

    PITState *pit = opaque;

    PITChannelState *s;

    int i;

    for(i = 0; i < 3; i++) {

        s = &pit->channels[i];

        qemu_put_be32s(f, &s->count);

        qemu_put_be16s(f, &s->latched_count);

        qemu_put_8s(f, &s->count_latched);

        qemu_put_8s(f, &s->status_latched);

        qemu_put_8s(f, &s->status);

        qemu_put_8s(f, &s->read_state);

        qemu_put_8s(f, &s->write_state);

        qemu_put_8s(f, &s->write_latch);

        qemu_put_8s(f, &s->rw_mode);

        qemu_put_8s(f, &s->mode);

        qemu_put_8s(f, &s->bcd);

        qemu_put_8s(f, &s->gate);

        qemu_put_be64s(f, &s->count_load_time);

        if (s->irq_timer) {

            qemu_put_be64s(f, &s->next_transition_time);

            qemu_put_timer(f, s->irq_timer);

        }

    }

}

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

{

    PITState *pit = opaque;

    PITChannelState *s;

    int i;

    if (version_id != 1)

        return -EINVAL;

    for(i = 0; i < 3; i++) {

        s = &pit->channels[i];

        qemu_get_be32s(f, &s->count);

        qemu_get_be16s(f, &s->latched_count);

        qemu_get_8s(f, &s->count_latched);

        qemu_get_8s(f, &s->status_latched);

        qemu_get_8s(f, &s->status);

        qemu_get_8s(f, &s->read_state);

        qemu_get_8s(f, &s->write_state);

        qemu_get_8s(f, &s->write_latch);

        qemu_get_8s(f, &s->rw_mode);

        qemu_get_8s(f, &s->mode);

        qemu_get_8s(f, &s->bcd);

        qemu_get_8s(f, &s->gate);

        qemu_get_be64s(f, &s->count_load_time);

        if (s->irq_timer) {

            qemu_get_be64s(f, &s->next_transition_time);

            qemu_get_timer(f, s->irq_timer);

        }

    }

    return 0;

}

PITState *pit_init(int base, int irq)

{

    PITState *pit = &pit_state;

    PITChannelState *s;

    int i;

    for(i = 0;i < 3; i++) {

        s = &pit->channels[i];

        if (i == 0) {

            /* the timer 0 is connected to an IRQ */

            s->irq_timer = qemu_new_timer(vm_clock, pit_irq_timer, s);

            s->irq = irq;

        }

        s->mode = 3;

        s->gate = (i != 2);

        pit_load_count(s, 0);

    }

    register_savevm("i8254", base, 1, pit_save, pit_load, pit);

    register_ioport_write(base, 4, 1, pit_ioport_write, pit);

    register_ioport_read(base, 3, 1, pit_ioport_read, pit);

    return pit;

}