Espresso/drivers/pit.c

#include <types.h>
#include <port_io.h>
#include <stdio.h>

#include <drivers/pit.h>


#define PIT_CHANNEL0       0x40
#define PIT_COMMAND        0x43
#define PIT_IRQ_LINE       0
#define PIT_FREQUENCY_BASE 1193182

volatile uint64_t pit_ticks = 0;
bool pit_initialized = false;

void pit_init(void)
{
  uint16_t divisor = (uint16_t)1193;

  /* Send command byte */
  outb(PIT_COMMAND, 0x36);  /* Channel 0, low/high byte, mode 3 (square wave), binary */

  /* Send divisor low and high byte */
  outb(PIT_CHANNEL0, (uint8_t)(divisor & 0xFF));        /* Low byte */
  outb(PIT_CHANNEL0, (uint8_t)((divisor >> 8) & 0xFF)); /* High byte */
  
  pit_initialized = true;
}

void pit_handler(void)
{
  pit_ticks++;
}

void pit_sleep(uint64_t ms)
{
  uint64_t target = pit_ticks + ms;
  while (pit_ticks < target)
  {
    asm volatile ("hlt");
  }
}