kern/kclock.c

   1 /* See COPYRIGHT for copyright information. */
   2
   3 /* Support for two time-related hardware gadgets: 1) the run time
   4  * clock with its NVRAM access functions; 2) the 8253 timer, which
   5  * generates interrupts on IRQ 0.
   6  */
   7
   8 #include <inc/x86.h>
   9 #include <inc/stdio.h>
  10 #include <inc/isareg.h>
  11 #include <inc/timerreg.h>
  12
  13 #include <kern/kclock.h>
  14 #include <kern/picirq.h>
  15
  16 unsigned
  17 mc146818_read(unsigned reg)
  18 {
  19         outb(IO_RTC, reg);
  20         return inb(IO_RTC+1);
  21 }
  22
  23 void
  24 mc146818_write(unsigned reg, unsigned datum)
  25 {
  26         outb(IO_RTC, reg);
  27         outb(IO_RTC+1, datum);
  28 }
  29
  30 void
  31 kclock_init(void)
  32 {
  33         /* initialize 8253 clock to interrupt 100 times/sec */
  34         outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
  35         outb(IO_TIMER1, TIMER_DIV(100) % 256);
  36         outb(IO_TIMER1, TIMER_DIV(100) / 256);
  37         cprintf("       Setup timer interrupts via 8259A\n");
  38         irq_setmask_8259A(irq_mask_8259A & ~(1<<0));
  39         cprintf("       unmasked timer interrupt\n");
  40 }
  41