timer.c

// Intel 8253/8254/82C54 Programmable Interval Timer (PIT).
// Only used on uniprocessors;
// SMP machines use the local APIC timer.

#include <sys/types.h>
#include "defs.h"
#include "traps.h"
#include "gaia.h"

#define IO_TIMER1       0x040           // 8253 Timer #1

// Frequency of all three count-down timers;
// (TIMER_FREQ/freq) is the appropriate count
// to generate a frequency of freq Hz.

#define TIMER_FREQ      1193182
#define TIMER_DIV(x)    ((TIMER_FREQ+(x)/2)/(x))

#define TIMER_MODE      (IO_TIMER1 + 3) // timer mode port
#define TIMER_SEL0      0x00    // select counter 0
#define TIMER_RATEGEN   0x04    // mode 2, rate generator
#define TIMER_16BIT     0x30    // r/w counter 16 bits, LSB first

void
timerinit(void)
{
  // The timer on our GAIA board always causes interrupts 100 times/sec,
  // and we have no method to configure it. So, do nothing here.
}