/*
 * 86Box    A hypervisor and IBM PC system emulator that specializes in
 *          running old operating systems and software designed for IBM
 *          PC systems and compatibles from 1981 through fairly recent
 *          system designs based on the PCI bus.
 *
 *          This file is part of the 86Box distribution.
 *
 *          Implementation of the Intel 8253/8254 Programmable Interval
 *          Timer.
 *
 * Authors: Miran Grca, <mgrca8@gmail.com>
 *
 *          Copyright 2019 Miran Grca.
 */
#include <inttypes.h>
#include <math.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#define HAVE_STDARG_H
#include <86box/86box.h>
#include "cpu.h"
#include <86box/device.h>
#include <86box/timer.h>
#include <86box/cassette.h>
#include <86box/dma.h>
#include <86box/io.h>
#include <86box/nmi.h>
#include <86box/pic.h>
#include <86box/timer.h>
#include <86box/pit.h>
#include <86box/pit_fast.h>
#include <86box/ppi.h>
#include <86box/machine.h>
#include <86box/sound.h>
#include <86box/snd_speaker.h>
#include <86box/video.h>
#include <86box/plat_unused.h>

pit_intf_t pit_devs[2];

double cpuclock;
double PITCONSTD;
double PAS16CONSTD;
double PAS16CONST2D;
double PASSCSICONSTD;
double SYSCLK;
double isa_timing;
double bus_timing;
double pci_timing;
double agp_timing;
double PCICLK;
double AGPCLK;

uint64_t PITCONST;
uint64_t PAS16CONST;
uint64_t PAS16CONST2;
uint64_t PASSCSICONST;
uint64_t ISACONST;
uint64_t CGACONST;
uint64_t MDACONST;
uint64_t HERCCONST;
uint64_t VGACONST1;
uint64_t VGACONST2;
uint64_t RTCCONST;
uint64_t ACPICONST;

int refresh_at_enable = 1;
int io_delay          = 5;

int64_t firsttime = 1;

#define PIT_PS2          16  /* The PIT is the PS/2's second PIT. */
#define PIT_EXT_IO       32  /* The PIT has externally specified port I/O. */
#define PIT_CUSTOM_CLOCK 64  /* The PIT uses custom clock inputs provided by another provider. */
#define PIT_SECONDARY    128 /* The PIT is secondary (ports 0048-004B). */

#ifdef ENABLE_PIT_LOG
int pit_do_log = ENABLE_PIT_LOG;

static void
pit_log(const char *fmt, ...)
{
    va_list ap;

    if (pit_do_log) {
        va_start(ap, fmt);
        pclog_ex(fmt, ap);
        va_end(ap);
    }
}
#else
#    define pit_log(fmt, ...)
#endif

static void
ctr_set_out(ctr_t *ctr, int out, void *priv)
{
    pit_t *pit = (pit_t *)priv;

    if (ctr == NULL)
        return;

    if (ctr->out_func != NULL)
        ctr->out_func(out, ctr->out, pit);

    ctr->out = out;
}

static void
ctr_decrease_count(ctr_t *ctr)
{
    if (ctr->bcd) {
        ctr->units--;
        if (ctr->units == -1) {
            ctr->units = -7;
            ctr->tens--;
            if (ctr->tens == -1) {
                ctr->tens = -7;
                ctr->hundreds--;
                if (ctr->hundreds == -1) {
                    ctr->hundreds = -7;
                    ctr->thousands--;
                    if (ctr->thousands == -1) {
                        ctr->thousands = -7;
                        ctr->myriads--;
                        if (ctr->myriads == -1)
                            ctr->myriads = -7; /* 0 - 1 should wrap around to 9999. */
                    }
                }
            }
        }
    } else
        ctr->count = (ctr->count - 1) & 0xffff;
}

static void
ctr_load_count(ctr_t *ctr)
{
    int l = ctr->l ? ctr->l : 0x10000;

    ctr->count = l;
    pit_log("ctr->count = %i\n", l);
    ctr->null_count = 0;
    ctr->newcount   = !!(l & 1);

    /* Undocumented feature - writing MSB after reload after writing LSB causes an instant reload. */
    ctr->incomplete = !!(ctr->wm & 0x80);
}

static void
ctr_tick(ctr_t *ctr, void *priv)
{
    pit_t *pit = (pit_t *)priv;
    uint8_t state = ctr->state;

    if ((state & 0x03) == 0x01) {
        /* This is true for all modes */
        ctr_load_count(ctr);
        ctr->state++;
        if (((ctr->m & 0x07) == 0x01) && (ctr->state == 2))
            ctr_set_out(ctr, 0, pit);
    } else  switch (ctr->m & 0x07) {
        case 0:
            /* Interrupt on terminal count */
            switch (state) {
                case 2:
                    if (ctr->gate && (ctr->count >= 1)) {
                        ctr_decrease_count(ctr);
                        if (ctr->count < 1) {
                            ctr->state = 3;
                            ctr_set_out(ctr, 1, pit);
                        }
                    }
                    break;
                case 3:
                    ctr_decrease_count(ctr);
                    break;

                default:
                    break;
            }
            break;
        case 1:
            /* Hardware retriggerable one-shot */
            switch (state) {
                case 2:
                    if (ctr->count >= 1) {
                        ctr_decrease_count(ctr);
                        if (ctr->count < 1) {
                            ctr->state = 3;
                            ctr_set_out(ctr, 1, pit);
                        }
                    }
                    break;
                case 3:
                case 6:
                    ctr_decrease_count(ctr);
                    break;

                default:
                    break;
            }
            break;
        case 2:
        case 6:
            /* Rate generator */
            switch (state) {
                case 3:
                    ctr_load_count(ctr);
                    ctr->state = 2;
                    ctr_set_out(ctr, 1, pit);
                    break;
                case 2:
                    if (ctr->gate == 0)
                        break;
                    else if (ctr->count >= 2) {
                        ctr_decrease_count(ctr);
                        if (ctr->count < 2) {
                            ctr->state = 3;
                            ctr_set_out(ctr, 0, pit);
                        }
                    }
                    break;

                default:
                    break;
            }
            break;
        case 3:
        case 7:
            /* Square wave mode */
            switch (state) {
                case 2:
                    if (ctr->gate == 0)
                        break;
                    else if (ctr->count >= 0) {
                        if (ctr->bcd) {
                            ctr_decrease_count(ctr);
                            if (!ctr->newcount)
                                ctr_decrease_count(ctr);
                        } else
                            ctr->count -= (ctr->newcount ? 1 : 2);
                        if (ctr->count == 0) {
                            ctr_set_out(ctr, 0, pit);
                            ctr_load_count(ctr);
                            ctr->state = 3;
                        } else if (ctr->newcount)
                            ctr->newcount = 0;
                    }
                    break;
                case 3:
                    if (ctr->gate == 0)
                        break;
                    else if (ctr->count >= 0) {
                        if (ctr->bcd) {
                            ctr_decrease_count(ctr);
                            ctr_decrease_count(ctr);
                            if (ctr->newcount)
                                ctr_decrease_count(ctr);
                        } else
                            ctr->count -= (ctr->newcount ? 3 : 2);
                        if (ctr->count == 0) {
                            ctr_set_out(ctr, 1, pit);
                            ctr_load_count(ctr);
                            ctr->state = 2;
                        } else if (ctr->newcount)
                            ctr->newcount = 0;
                    }
                    break;

                default:
                    break;
            }
            break;
        case 4:
        case 5:
            /* Software triggered strobe */
            /* Hardware triggered strobe */
            if ((ctr->gate != 0) || (ctr->m != 4)) {
                switch (state) {
                    case 0:
                    case 6:
                        ctr_decrease_count(ctr);
                        break;
                    case 2:
                        if (ctr->count >= 1) {
                            ctr_decrease_count(ctr);
                            if (ctr->count < 1) {
                                ctr->state = 3;
                                ctr_set_out(ctr, 0, pit);
                            }
                        }
                        break;
                    case 3:
                        ctr->state = 0;
                        ctr_set_out(ctr, 1, pit);
                        break;

                    default:
                        break;
                }
            }
            break;
        default:
            break;
    }
}

void
ctr_clock(void *data, int counter_id)
{
    pit_t *pit = (pit_t *) data;
    ctr_t *ctr = &pit->counters[counter_id];

    /* FIXME: Is this even needed? */
    if ((ctr->state == 3) && (ctr->m != 2) && (ctr->m != 3))
        return;

    if (ctr->using_timer)
        return;

    ctr_tick(ctr, pit);
}

static void
ctr_set_state_1(ctr_t *ctr)
{
    uint8_t mode = (ctr->m & 0x03);
    int do_reload = !!ctr->incomplete || (mode == 0) || (ctr->state == 0);
 
    ctr->incomplete = 0;

    if (do_reload)
        ctr->state = 1 + ((mode == 1) << 2);
}

static void
ctr_load(ctr_t *ctr)
{
    if (ctr->l == 1) {
        /* Count of 1 is illegal in modes 2 and 3. What happens here was
           determined experimentally. */
        if (ctr->m == 2)
            ctr->l = 2;
        else if (ctr->m == 3)
            ctr->l = 0;
    }

    if (ctr->using_timer)
        ctr->latch = 1;
    else
        ctr_set_state_1(ctr);

    if (ctr->load_func != NULL) {
        uint32_t count = ctr->l ? ctr->l : 0x10000;
        if (ctr->bcd) {
            uint32_t bcd_count = (((count >> 16) & 0xf) * 10000) |
                                 (((count >> 12) & 0xf) * 1000 ) |
                                 (((count >> 8 ) & 0xf) * 100  ) |
                                 (((count >> 4 ) & 0xf) * 10   ) |
                                 (count & 0xf);
            ctr->load_func(ctr->m, bcd_count);
        } else
            ctr->load_func(ctr->m, ctr->l ? ctr->l : 0x10000);
    }

    pit_log("Counter loaded, state = %i, gate = %i, latch = %i\n", ctr->state, ctr->gate, ctr->latch);
}

static __inline void
ctr_latch_status(ctr_t *ctr)
{
    ctr->read_status    = (ctr->ctrl & 0x3f) | (ctr->out ? 0x80 : 0) | (ctr->null_count ? 0x40 : 0);
    ctr->do_read_status = 1;
}

static __inline void
ctr_latch_count(ctr_t *ctr)
{
    int count = (ctr->latch || (ctr->state == 1)) ? ctr->l : ctr->count;

    switch (ctr->rm & 0x03) {
        case 0x00:
            /* This should never happen. */
            break;
        case 0x01:
            /* Latch bits 0-7 only. */
            ctr->rl      = ((count << 8) & 0xff00) | (count & 0xff);
            ctr->latched = 1;
            break;
        case 0x02:
            /* Latch bit 8-15 only. */
            ctr->rl      = (count & 0xff00) | ((count >> 8) & 0xff);
            ctr->latched = 1;
            break;
        case 0x03:
            /* Latch all 16 bits. */
            ctr->rl      = count;
            ctr->latched = 2;
            break;

        default:
            break;
    }

    pit_log("rm = %x, latched counter = %04X\n", ctr->rm & 0x03, ctr->rl & 0xffff);
}

uint16_t
pit_ctr_get_count(void *data, int counter_id)
{
    const pit_t *pit = (pit_t *) data;
    const ctr_t *ctr = &pit->counters[counter_id];

    return (uint16_t) ctr->l;
}

void
pit_ctr_set_load_func(void *data, int counter_id, void (*func)(uint8_t new_m, int new_count))
{
    if (data == NULL)
        return;

    pit_t *pit = (pit_t *) data;
    ctr_t *ctr = &pit->counters[counter_id];

    ctr->load_func = func;
}

void
pit_ctr_set_out_func(void *data, int counter_id, void (*func)(int new_out, int old_out, void *priv))
{
    if (data == NULL)
        return;

    pit_t *pit = (pit_t *) data;
    ctr_t *ctr = &pit->counters[counter_id];

    ctr->out_func = func;
}

void
pit_ctr_set_gate(void *data, int counter_id, int gate)
{
    pit_t *pit = (pit_t *) data;
    ctr_t *ctr = &pit->counters[counter_id];

    int     old  = ctr->gate;
    uint8_t mode = ctr->m & 3;

    switch (mode) {
        case 1:
        case 2:
        case 3:
        case 5:
        case 6:
        case 7:
            if (!old && gate) {
                /* Here we handle the rising edges. */
                if (mode & 1) {
                    if (mode != 1)
                        ctr_set_out(ctr, 1, pit);
                    ctr->state = 1;
                } else if (mode == 2)
                    ctr->state = 3;
            } else if (old && !gate) {
                /* Here we handle the lowering edges. */
                if (mode & 2)
                    ctr_set_out(ctr, 1, pit);
            }
            break;

        default:
            break;
    }

    ctr->gate = gate;
}

static __inline void
pit_ctr_set_clock_common(ctr_t *ctr, int clock, void *priv)
{
    pit_t *pit = (pit_t *)priv;
    int old = ctr->clock;

    ctr->clock = clock;

    if (ctr->using_timer && ctr->latch) {
        if (old && !ctr->clock) {
            ctr_set_state_1(ctr);
            ctr->latch = 0;
        }
    } else if (ctr->using_timer && !ctr->latch) {
        if (ctr->state == 1) {
            if (!old && ctr->clock)
                ctr->s1_det = 1; /* Rising edge. */
            else if (old && !ctr->clock) {
                ctr->s1_det++; /* Falling edge. */
                if (ctr->s1_det >= 2) {
                    ctr->s1_det = 0;
                    ctr_tick(ctr, pit);
                }
            }
        } else if (old && !ctr->clock)
            ctr_tick(ctr, pit);
    }
}

void
pit_ctr_set_clock(ctr_t *ctr, int clock, void *priv)
{
    pit_ctr_set_clock_common(ctr, clock, priv);
}

void
pit_ctr_set_using_timer(void *data, int counter_id, int using_timer)
{
    if (tsc > 0)
        timer_process();
    pit_t *pit       = (pit_t *) data;
    ctr_t *ctr       = &pit->counters[counter_id];
    ctr->using_timer = using_timer;
}

static void
pit_timer_over(void *priv)
{
    pit_t *dev = (pit_t *) priv;

    dev->clock ^= 1;

    for (uint8_t i = 0; i < NUM_COUNTERS; i++)
        pit_ctr_set_clock_common(&dev->counters[i], dev->clock, dev);

    timer_advance_u64(&dev->callback_timer, dev->pit_const >> 1ULL);
}

static void
pit_write(uint16_t addr, uint8_t val, void *priv)
{
    pit_t *dev = (pit_t *) priv;
    int    t   = (addr & 3);
    ctr_t *ctr;

    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
        pit_log("[%04X:%08X] pit_write(%04X, %02X, %016" PRIX64 ")\n",
                CS, cpu_state.pc, addr, val, (uint64_t) (uintptr_t) priv);
    }

    switch (addr & 3) {
        case 3: /* control */
            t = val >> 6;

            if (t == 3) {
                if (dev->flags & PIT_8254) {
                    /* This is 8254-only. */
                    if (!(val & 0x20)) {
                        if (val & 2)
                            ctr_latch_count(&dev->counters[0]);
                        if (val & 4)
                            ctr_latch_count(&dev->counters[1]);
                        if (val & 8)
                            ctr_latch_count(&dev->counters[2]);
                        if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                            pit_log("PIT %i: Initiated readback command\n", t);
                        }
                    }
                    if (!(val & 0x10)) {
                        if (val & 2)
                            ctr_latch_status(&dev->counters[0]);
                        if (val & 4)
                            ctr_latch_status(&dev->counters[1]);
                        if (val & 8)
                            ctr_latch_status(&dev->counters[2]);
                    }
                }
            } else {
                dev->ctrl = val;
                ctr       = &dev->counters[t];

                if (!(dev->ctrl & 0x30)) {
                    ctr_latch_count(ctr);
                    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                        pit_log("PIT %i: Initiated latched read, %i bytes latched\n",
                            t, ctr->latched);
                    }
                } else {
                    ctr->ctrl = val;
                    ctr->rm = ctr->wm = (ctr->ctrl >> 4) & 3;
                    ctr->m            = (val >> 1) & 7;
                    if (ctr->m > 5)
                        ctr->m &= 3;
                    ctr->null_count = 1;
                    ctr->bcd        = (ctr->ctrl & 0x01);
                    ctr_set_out(ctr, !!ctr->m, dev);
                    ctr->state = 0;
                    if (ctr->latched) {
                        if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                            pit_log("PIT %i: Reload while counter is latched\n", t);
                        }
                        ctr->rl--;
                    }

                    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                        pit_log("PIT %i: M = %i, RM/WM = %i, State = %i, Out = %i\n", t, ctr->m, ctr->rm, ctr->state, ctr->out);
                    }
                }
            }
            break;

        case 0:
        case 1:
        case 2: /* the actual timers */
            ctr = &dev->counters[t];

            switch (ctr->wm) {
                case 0:
                    /* This should never happen. */
                    break;
                case 1:
                    ctr->l = val;
                    ctr->lback = ctr->l;
                    ctr->lback2 = ctr->l;
                    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                        pit_log("PIT %i (1): Written byte %02X, latch now %04X\n", t, val, ctr->l);
                    }
                    if (ctr->m == 0)
                        ctr_set_out(ctr, 0, dev);
                    ctr_load(ctr);
                    break;
                case 2:
                    ctr->l = (val << 8);
                    ctr->lback = ctr->l;
                    ctr->lback2 = ctr->l;
                    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                        pit_log("PIT %i (2): Written byte %02X, latch now %04X\n", t, val, ctr->l);
                    }
                    if (ctr->m == 0)
                        ctr_set_out(ctr, 0, dev);
                    ctr_load(ctr);
                    break;
                case 3:
                case 0x83:
                    if (ctr->wm & 0x80) {
                        ctr->l = (ctr->l & 0x00ff) | (val << 8);
                        ctr->lback = ctr->l;
                        ctr->lback2 = ctr->l;
                        if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                            pit_log("PIT %i (0x83): Written high byte %02X, latch now %04X\n", t, val, ctr->l);
                        }
                        ctr_load(ctr);
                    } else {
                        ctr->l = (ctr->l & 0xff00) | val;
                        ctr->lback = ctr->l;
                        ctr->lback2 = ctr->l;
                        if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
                            pit_log("PIT %i (3): Written low byte %02X, latch now %04X\n", t, val, ctr->l);
                        }
                        if (ctr->m == 0) {
                            ctr->state = 0;
                            ctr_set_out(ctr, 0, dev);
                        }
                    }
                    if (ctr->wm & 0x80)
                        ctr->wm &= ~0x80;
                    else
                        ctr->wm |= 0x80;
                    break;

                default:
                    break;
            }
            break;

        default:
            break;
    }
}

extern uint8_t *ram;

uint8_t
pit_read_reg(void *priv, uint8_t reg)
{
    pit_t  *dev = (pit_t *) priv;
    uint8_t ret = 0xff;

    switch (reg) {
        case 0x00:
        case 0x02:
        case 0x04:
            ret = dev->counters[reg >> 1].l & 0xff;
            break;
        case 0x01:
        case 0x03:
        case 0x05:
            ret = (dev->counters[reg >> 1].l >> 8) & 0xff;
            break;
        case 0x06:
            ret = dev->ctrl;
            break;
        case 0x07:
            /* The SiS 551x datasheet is unclear about how exactly
               this register is structured.
               Update: But the SiS 5571 datasheet is clear. */
            ret = (dev->counters[0].rm & 0x80) ? 0x01 : 0x00;
            ret |= (dev->counters[1].rm & 0x80) ? 0x02 : 0x00;
            ret |= (dev->counters[2].rm & 0x80) ? 0x04 : 0x00;
            ret |= (dev->counters[0].wm & 0x80) ? 0x08 : 0x00;
            ret |= (dev->counters[1].wm & 0x80) ? 0x10 : 0x00;
            ret |= (dev->counters[2].wm & 0x80) ? 0x20 : 0x00;
            break;
    }

    return ret;
}

static uint8_t
pit_read(uint16_t addr, void *priv)
{
    pit_t  *dev = (pit_t *) priv;
    uint8_t ret = 0xff;
    int     count;
    int     t = (addr & 3);
    ctr_t  *ctr;

    switch (addr & 3) {
        case 3: /* Control. */
            /* This is 8254-only, 8253 returns 0x00. */
            ret = (dev->flags & PIT_8254) ? dev->ctrl : 0x00;
            break;

        case 0:
        case 1:
        case 2: /* The actual timers. */
            ctr = &dev->counters[t];

            if (ctr->do_read_status) {
                ctr->do_read_status = 0;
                ret                 = ctr->read_status;
                break;
            }

            count = (ctr->state == 1) ? ctr->l : ctr->count;

            if (ctr->latched) {
                ret = (ctr->rl) >> ((ctr->rm & 0x80) ? 8 : 0);

                if (ctr->rm & 0x80)
                    ctr->rm &= ~0x80;
                else
                    ctr->rm |= 0x80;

                ctr->latched--;
            } else
                switch (ctr->rm) {
                    case 0:
                    case 0x80:
                        ret = 0x00;
                        break;

                    case 1:
                        ret = count & 0xff;
                        break;

                    case 2:
                        ret = count >> 8;
                        break;

                    case 3:
                    case 0x83:
                        /* Yes, wm is correct here - this is to ensure correct readout while the
                           count is being written. */
                        if (ctr->wm & 0x80)
                            ret = ~(ctr->l & 0xff);
                        else
                            ret = count >> ((ctr->rm & 0x80) ? 8 : 0);

                        if (ctr->rm & 0x80)
                            ctr->rm &= ~0x80;
                        else
                            ctr->rm |= 0x80;
                        break;

                    default:
                        break;
                }
            break;

        default:
            break;
    }

    if ((dev->flags & (PIT_8254 | PIT_EXT_IO))) {
        pit_log("[%04X:%08X] pit_read(%04X, %016" PRIX64 ") = %02X\n",
                CS, cpu_state.pc, addr, (uint64_t) (uintptr_t) priv, ret);
    }

    return ret;
}

void
pit_irq0_timer_ps2(int new_out, int old_out, UNUSED(void *priv))
{
    if (new_out && !old_out) {
        picint(1);
        pit_devs[1].set_gate(pit_devs[1].data, 0, 1);
    }

    if (!new_out)
        picintc(1);

    if (!new_out && old_out)
        pit_devs[1].ctr_clock(pit_devs[1].data, 0);
}

void
pit_refresh_timer_xt(int new_out, int old_out, UNUSED(void *priv))
{
    if (new_out && !old_out)
        dma_channel_read(0);
}

void
pit_refresh_timer_at(int new_out, int old_out, UNUSED(void *priv))
{
    if (refresh_at_enable && new_out && !old_out)
        ppi.pb ^= 0x10;
}

void
pit_speaker_timer(int new_out, UNUSED(int old_out), UNUSED(void *priv))
{
    int l;

    if (cassette != NULL)
        pc_cas_set_out(cassette, new_out);

    speaker_update();

    uint16_t count = pit_devs[0].get_count(pit_devs[0].data, 2);
    l              = count ? count : 0x10000;
    if (l < 25)
        speakon = 0;
    else
        speakon = new_out;

    ppispeakon = new_out;
}

void
pit_nmi_timer_ps2(int new_out, UNUSED(int old_out), UNUSED(void *priv))
{
    nmi = new_out;

    if (nmi)
        nmi_auto_clear = 1;
}

static void
ctr_reset(ctr_t *ctr)
{
    ctr->ctrl        = 0;
    ctr->m           = 0;
    ctr->gate        = 0;
    ctr->l           = 0xffff;
    ctr->using_timer = 1;
    ctr->state       = 0;
    ctr->null_count  = 1;

    ctr->latch = 0;

    ctr->s1_det = 0;
    ctr->l_det  = 0;
}

void
pit_device_reset(pit_t *dev)
{
    dev->clock = 0;

    for (uint8_t i = 0; i < NUM_COUNTERS; i++)
        ctr_reset(&dev->counters[i]);
}

void
pit_reset(pit_t *dev)
{
    memset(dev, 0, sizeof(pit_t));

    dev->clock = 0;

    for (uint8_t i = 0; i < NUM_COUNTERS; i++)
        ctr_reset(&dev->counters[i]);

    /* Disable speaker gate. */
    dev->counters[2].gate = 0;
}

void
pit_handler(int set, uint16_t base, int size, void *priv)
{
    io_handler(set, base, size, pit_read, NULL, NULL, pit_write, NULL, NULL, priv);
}

void
pit_set_pit_const(void *data, uint64_t pit_const)
{
    pit_t *pit = (pit_t *) data;

    pit->pit_const = pit_const;
}

static void
pit_speed_changed(void *priv)
{
    pit_set_pit_const(priv, PITCONST);
}

static void
pit_close(void *priv)
{
    pit_t *dev = (pit_t *) priv;

    if (dev == pit_devs[0].data)
        pit_devs[0].data = NULL;

    if (dev == pit_devs[1].data)
        pit_devs[1].data = NULL;

    if (dev != NULL)
        free(dev);
}

static void *
pit_init(const device_t *info)
{
    pit_t *dev = (pit_t *) malloc(sizeof(pit_t));

    pit_reset(dev);

    pit_set_pit_const(dev, PITCONST);

    if (!(dev->flags & PIT_PS2) && !(dev->flags & PIT_CUSTOM_CLOCK)) {
        timer_add(&dev->callback_timer, pit_timer_over, (void *) dev, 0);
        timer_set_delay_u64(&dev->callback_timer, dev->pit_const >> 1ULL);
    }

    dev->flags = info->local;
    dev->dev_priv = NULL;

    if (!(dev->flags & PIT_EXT_IO)) {
        io_sethandler((dev->flags & PIT_SECONDARY) ? 0x0048 : 0x0040, 0x0004,
                      pit_read, NULL, NULL, pit_write, NULL, NULL, dev);
    }

    return dev;
}

const device_t i8253_device = {
    .name          = "Intel 8253/8253-5 Programmable Interval Timer",
    .internal_name = "i8253",
    .flags         = DEVICE_ISA | DEVICE_PIT,
    .local         = PIT_8253,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = pit_speed_changed,
    .force_redraw  = NULL,
    .config        = NULL
};

const device_t i8253_ext_io_device = {
    .name          = "Intel 8253 Programmable Interval Timer (External I/O)",
    .internal_name = "i8253_ext_io",
    .flags         = DEVICE_ISA,
    .local         = PIT_8253 | PIT_EXT_IO,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = NULL,
    .force_redraw  = NULL,
    .config        = NULL
};

const device_t i8254_device = {
    .name          = "Intel 8254 Programmable Interval Timer",
    .internal_name = "i8254",
    .flags         = DEVICE_ISA | DEVICE_PIT,
    .local         = PIT_8254,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = pit_speed_changed,
    .force_redraw  = NULL,
    .config        = NULL
};

const device_t i8254_sec_device = {
    .name          = "Intel 8254 Programmable Interval Timer (Secondary)",
    .internal_name = "i8254_sec",
    .flags         = DEVICE_ISA,
    .local         = PIT_8254 | PIT_SECONDARY,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = pit_speed_changed,
    .force_redraw  = NULL,
    .config        = NULL
};

const device_t i8254_ext_io_device = {
    .name          = "Intel 8254 Programmable Interval Timer (External I/O)",
    .internal_name = "i8254_ext_io",
    .flags         = DEVICE_ISA,
    .local         = PIT_8254 | PIT_EXT_IO,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = NULL,
    .force_redraw  = NULL,
    .config        = NULL
};

const device_t i8254_ps2_device = {
    .name          = "Intel 8254 Programmable Interval Timer (PS/2)",
    .internal_name = "i8254_ps2",
    .flags         = DEVICE_ISA,
    .local         = PIT_8254 | PIT_PS2 | PIT_EXT_IO,
    .init          = pit_init,
    .close         = pit_close,
    .reset         = NULL,
    .available     = NULL,
    .speed_changed = pit_speed_changed,
    .force_redraw  = NULL,
    .config        = NULL
};

pit_t *
pit_common_init(int type, void (*out0)(int new_out, int old_out, void *priv), void (*out1)(int new_out, int old_out, void *priv))
{
    void *pit;

    pit_intf_t *pit_intf = &pit_devs[0];

    switch (type) {
        default:
        case PIT_8253:
            pit       = device_add(&i8253_device);
            *pit_intf = pit_classic_intf;
            break;
        case PIT_8254:
            pit       = device_add(&i8254_device);
            *pit_intf = pit_classic_intf;
            break;
        case PIT_8253_FAST:
            pit       = device_add(&i8253_fast_device);
            *pit_intf = pit_fast_intf;
            break;
        case PIT_8254_FAST:
            pit       = device_add(&i8254_fast_device);
            *pit_intf = pit_fast_intf;
            break;
    }

    pit_intf->data = pit;

    for (uint8_t i = 0; i < 3; i++) {
        pit_intf->set_gate(pit_intf->data, i, 1);
        pit_intf->set_using_timer(pit_intf->data, i, 1);
    }

    pit_intf->set_out_func(pit_intf->data, 0, out0);
    pit_intf->set_out_func(pit_intf->data, 1, out1);
    pit_intf->set_out_func(pit_intf->data, 2, pit_speaker_timer);
    pit_intf->set_load_func(pit_intf->data, 2, speaker_set_count);

    pit_intf->set_gate(pit_intf->data, 2, 0);

    return pit;
}

pit_t *
pit_ps2_init(int type)
{
    void *pit;

    pit_intf_t *ps2_pit = &pit_devs[1];

    switch (type) {
        default:
        case PIT_8254:
            pit      = device_add(&i8254_ps2_device);
            *ps2_pit = pit_classic_intf;
            break;

        case PIT_8254_FAST:
            pit      = device_add(&i8254_ps2_fast_device);
            *ps2_pit = pit_fast_intf;
            break;
    }

    ps2_pit->data = pit;

    ps2_pit->set_gate(ps2_pit->data, 0, 0);
    for (int i = 0; i < 3; i++) {
        ps2_pit->set_using_timer(ps2_pit->data, i, 0);
    }

    io_sethandler(0x0044, 0x0001, ps2_pit->read, NULL, NULL, ps2_pit->write, NULL, NULL, pit);
    io_sethandler(0x0047, 0x0001, ps2_pit->read, NULL, NULL, ps2_pit->write, NULL, NULL, pit);

    pit_devs[0].set_out_func(pit_devs[0].data, 0, pit_irq0_timer_ps2);
    ps2_pit->set_out_func(ps2_pit->data, 0, pit_nmi_timer_ps2);

    return pit;
}

void
pit_change_pas16_consts(double prescale)
{
    PAS16CONST  = (uint64_t) ((PAS16CONSTD / prescale) * (double) (1ULL << 32));
    PAS16CONST2 = (uint64_t) ((PAS16CONST2D / prescale) * (double) (1ULL << 32));
}

void
pit_set_clock(uint32_t clock)
{
    /* Set default CPU/crystal clock and xt_cpu_multi. */
    if (cpu_s->cpu_type >= CPU_286) {
        uint32_t remainder = (clock % 100000000);
        if (remainder == 66666666)
            cpuclock = (double) (clock - remainder) + (200000000.0 / 3.0);
        else if (remainder == 33333333)
            cpuclock = (double) (clock - remainder) + (100000000.0 / 3.0);
        else
            cpuclock = (double) clock;

        PITCONSTD    = (cpuclock / 1193182.0);
        PITCONST     = (uint64_t) (PITCONSTD * (double) (1ULL << 32));
#ifdef IMPRECISE_CGACONST
        CGACONST     = (uint64_t) ((cpuclock / (19687503.0 / 11.0)) * (double) (1ULL << 32));
#else
        CGACONST     = (uint64_t) ((cpuclock / (157500000.0 / 88.0)) * (double) (1ULL << 32));
#endif
        ISACONST     = (uint64_t) ((cpuclock / (double) cpu_isa_speed) * (double) (1ULL << 32));
        xt_cpu_multi = 1ULL;
    } else {
        cpuclock     = (157500000.0 / 11.0);
        PITCONSTD    = 12.0;
        PITCONST     = (12ULL << 32ULL);
        CGACONST     = (8ULL << 32ULL);
        xt_cpu_multi = 3ULL;

        switch (cpu_s->rspeed) {
            case 7159092:
                if (cpu_s->cpu_flags & CPU_ALTERNATE_XTAL) {
                    cpuclock     = 28636368.0;
                    xt_cpu_multi = 4ULL;
                } else
                    xt_cpu_multi = 2ULL;
                break;

            case 8000000:
                cpuclock = 24000000.0;
                break;
            case 9545456:
                cpuclock = 28636368.0;
                break;
            case 10000000:
                cpuclock = 30000000.0;
                break;
            case 12000000:
                cpuclock = 36000000.0;
                break;
            case 16000000:
                cpuclock = 48000000.0;
                break;

            default:
                if (cpu_s->cpu_flags & CPU_ALTERNATE_XTAL) {
                    cpuclock     = 28636368.0;
                    xt_cpu_multi = 6ULL;
                }
                break;
        }

        if (cpuclock == 28636368.0) {
            PITCONSTD = 24.0;
            PITCONST  = (24ULL << 32LL);
            CGACONST  = (16ULL << 32LL);
        } else if (cpuclock != 14318184.0) {
            PITCONSTD = (cpuclock / 1193182.0);
            PITCONST  = (uint64_t) (PITCONSTD * (double) (1ULL << 32));
#ifdef IMPRECISE_CGACONST
            CGACONST  = (uint64_t) ((cpuclock / (19687503.0 / 11.0)) * (double) (1ULL << 32));
#else
            CGACONST  = (uint64_t) ((cpuclock / (157500000.0 / 88.0)) * (double) (1ULL << 32));
#endif
        }

        ISACONST = (1ULL << 32ULL);
    }
    xt_cpu_multi <<= 32ULL;

    /* Delay for empty I/O ports. */
    io_delay = (int) round(((double) cpu_s->rspeed) / 3000000.0);

#ifdef WRONG_MDACONST
    MDACONST  = (uint64_t) (cpuclock / 2032125.0 * (double) (1ULL << 32));
#else
    MDACONST  = (uint64_t) (cpuclock / (16257000.0 / 9.0) * (double) (1ULL << 32));
#endif
    HERCCONST = MDACONST;
    VGACONST1 = (uint64_t) (cpuclock / 25175000.0 * (double) (1ULL << 32));
    VGACONST2 = (uint64_t) (cpuclock / 28322000.0 * (double) (1ULL << 32));
    RTCCONST  = (uint64_t) (cpuclock / 32768.0 * (double) (1ULL << 32));

    TIMER_USEC = (uint64_t) ((cpuclock / 1000000.0) * (double) (1ULL << 32));

    PAS16CONSTD = (cpuclock / 441000.0);
    PAS16CONST  = (uint64_t) (PAS16CONSTD * (double) (1ULL << 32));

    PAS16CONST2D = (cpuclock / 1008000.0);
    PAS16CONST2  = (uint64_t) (PAS16CONST2D * (double) (1ULL << 32));

    PASSCSICONSTD = (cpuclock / (28224000.0 / 14.0));
    PASSCSICONST  = (uint64_t) (PASSCSICONSTD * (double) (1ULL << 32));

    isa_timing = (cpuclock / (double) cpu_isa_speed);
    if (cpu_64bitbus)
        bus_timing = (cpuclock / (cpu_busspeed / 2));
    else
        bus_timing = (cpuclock / cpu_busspeed);
    pci_timing = (cpuclock / (double) cpu_pci_speed);
    agp_timing = (cpuclock / (double) cpu_agp_speed);

    /* PCICLK in us for use with timer_on_auto(). */
    PCICLK = pci_timing / (cpuclock / 1000000.0);
    AGPCLK = agp_timing / (cpuclock / 1000000.0);

    if (cpu_busspeed >= 30000000)
        SYSCLK = bus_timing * 4.0;
    else
        SYSCLK = bus_timing * 3.0;

    video_update_timing();

    device_speed_changed();
}

const pit_intf_t pit_classic_intf = {
    .read            = &pit_read,
    .write           = &pit_write,
    .get_count       = &pit_ctr_get_count,
    .set_gate        = &pit_ctr_set_gate,
    .set_using_timer = &pit_ctr_set_using_timer,
    .set_out_func    = &pit_ctr_set_out_func,
    .set_load_func   = &pit_ctr_set_load_func,
    .ctr_clock       = &ctr_clock,
    .set_pit_const   = &pit_set_pit_const,
    .data            = NULL,
};
