kc/core/pit8253.c


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#include "pit8253.h"
#include "pic8259.h"
#include "port.h"
#include "kprint.h"

#define PIT8253_DATA0 0x40
#define PIT8253_CMD 0x43

#define SEL_CHANNEL0 0x0
#define ACC_LOHI 0x30
#define MODE_RATE 0x04
#define BIN_COUNT 0x0

#define CONFIG_CHANNEL_0 (SEL_CHANNEL0|ACC_LOHI|MODE_RATE|BIN_COUNT)

#define PIT_HZ 1193182U

static uint64_t count = 0;

int pit8253_callback(uint8_t irq)
{
    (void)irq;
    count++;

    if (!(count % (185)))
    {
        kprintf("it's been about %lu seconds since starting\n", count / 18);
    }

    return 0;
}

void pit8253_init(void)
{
    kprintf(
            "initializing timer to an approximate frequency of %uHz\n",
            PIT_HZ / 0xffff);
    outb(PIT8253_CMD, CONFIG_CHANNEL_0);
    outb(PIT8253_DATA0, 0xff);
    outb(PIT8253_DATA0, 0xff);

    pic8259_irq_install(0, pit8253_callback);
    pic8259_irq_unmask(0);
}

void pit8253_start(void)
{
}

void pit8253_stop(void)
{
}

uint64_t pit8253_count(void)
{
    return count;
}

void pit8253_set_hz(uint16_t hz)
{
    (void)hz;
}