path: root/hw/i8254.c

/*
 * 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 <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <getopt.h>
#include <inttypes.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include <malloc.h>
#include <termios.h>
#include <sys/poll.h>
#include <errno.h>
#include <sys/wait.h>
#include <netinet/in.h>

#include "cpu.h"
#include "vl.h"

#define RW_STATE_LSB 0
#define RW_STATE_MSB 1
#define RW_STATE_WORD0 2
#define RW_STATE_WORD1 3
#define RW_STATE_LATCHED_WORD0 4
#define RW_STATE_LATCHED_WORD1 5

PITChannelState pit_channels[3];

static int pit_get_count(PITChannelState *s)
{
    uint64_t d;
    int counter;

    d = muldiv64(cpu_get_ticks() - 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 */
int pit_get_out(PITChannelState *s)
{
    uint64_t d;
    int out;

    d = muldiv64(cpu_get_ticks() - 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;
}

/* get the number of 0 to 1 transitions we had since we call this
   function */
/* XXX: maybe better to use ticks precision to avoid getting edges
   twice if checks are done at very small intervals */
int pit_get_out_edges(PITChannelState *s)
{
    uint64_t d1, d2;
    int64_t ticks;
    int ret, v;

    ticks = cpu_get_ticks();
    d1 = muldiv64(s->count_last_edge_check_time - s->count_load_time, 
                 PIT_FREQ, ticks_per_sec);
    d2 = muldiv64(ticks - s->count_load_time, 
                  PIT_FREQ, ticks_per_sec);
    s->count_last_edge_check_time = ticks;
    switch(s->mode) {
    default:
    case 0:
        if (d1 < s->count && d2 >= s->count)
            ret = 1;
        else
            ret = 0;
        break;
    case 1:
        ret = 0;
        break;
    case 2:
        d1 /= s->count;
        d2 /= s->count;
        ret = d2 - d1;
        break;
    case 3:
        v = s->count - ((s->count + 1) >> 1);
        d1 = (d1 + v) / s->count;
        d2 = (d2 + v) / s->count;
        ret = d2 - d1;
        break;
    case 4:
    case 5:
        if (d1 < s->count && d2 >= s->count)
            ret = 1;
        else
            ret = 0;
        break;
    }
    return ret;
}

/* val must be 0 or 1 */
void pit_set_gate(PITChannelState *s, int val)
{
    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 = cpu_get_ticks();
            s->count_last_edge_check_time = s->count_load_time;
        }
        break;
    case 2:
    case 3:
        if (s->gate < val) {
            /* restart counting on rising edge */
            s->count_load_time = cpu_get_ticks();
            s->count_last_edge_check_time = s->count_load_time;
        }
        /* XXX: disable/enable counting */
        break;
    }
    s->gate = val;
}

static inline void pit_load_count(PITChannelState *s, int val)
{
    if (val == 0)
        val = 0x10000;
    s->count_load_time = cpu_get_ticks();
    s->count_last_edge_check_time = s->count_load_time;
    s->count = val;
    if (s == &pit_channels[0] && val <= pit_min_timer_count) {
        fprintf(stderr, 
                "\nWARNING: qemu: on your system, accurate timer emulation is impossible if its frequency is more than %d Hz. If using a 2.6 guest Linux kernel, you must patch asm/param.h to change HZ from 1000 to 100.\n\n", 
                PIT_FREQ / pit_min_timer_count);
    }
}

static void pit_ioport_write(void *opaque, uint32_t addr, uint32_t val)
{
    int channel, access;
    PITChannelState *s;

    addr &= 3;
    if (addr == 3) {
        channel = val >> 6;
        if (channel == 3)
            return;
        s = &pit_channels[channel];
        access = (val >> 4) & 3;
        switch(access) {
        case 0:
            s->latched_count = pit_get_count(s);
            s->rw_state = RW_STATE_LATCHED_WORD0;
            break;
        default:
            s->mode = (val >> 1) & 7;
            s->bcd = val & 1;
            s->rw_state = access - 1 +  RW_STATE_LSB;
            break;
        }
    } else {
        s = &pit_channels[addr];
        switch(s->rw_state) {
        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:
        case RW_STATE_WORD1:
            if (s->rw_state & 1) {
                pit_load_count(s, (s->latched_count & 0xff) | (val << 8));
            } else {
                s->latched_count = val;
            }
            s->rw_state ^= 1;
            break;
        }
    }
}

static uint32_t pit_ioport_read(void *opaque, uint32_t addr)
{
    int ret, count;
    PITChannelState *s;
    
    addr &= 3;
    s = &pit_channels[addr];
    switch(s->rw_state) {
    case RW_STATE_LSB:
    case RW_STATE_MSB:
    case RW_STATE_WORD0:
    case RW_STATE_WORD1:
        count = pit_get_count(s);
        if (s->rw_state & 1)
            ret = (count >> 8) & 0xff;
        else
            ret = count & 0xff;
        if (s->rw_state & 2)
            s->rw_state ^= 1;
        break;
    default:
    case RW_STATE_LATCHED_WORD0:
    case RW_STATE_LATCHED_WORD1:
        if (s->rw_state & 1)
            ret = s->latched_count >> 8;
        else
            ret = s->latched_count & 0xff;
        s->rw_state ^= 1;
        break;
    }
    return ret;
}

void pit_init(int base)
{
    PITChannelState *s;
    int i;

    for(i = 0;i < 3; i++) {
        s = &pit_channels[i];
        s->mode = 3;
        s->gate = (i != 2);
        pit_load_count(s, 0);
    }

    register_ioport_write(base, 4, 1, pit_ioport_write, NULL);
    register_ioport_read(base, 3, 1, pit_ioport_read, NULL);
}