i386/ucla/src/lab4/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
  17 unsigned
  18 mc146818_read(unsigned reg)
  19 {
  20         outb(IO_RTC, reg);
  21         return inb(IO_RTC+1);
  22 }
  23
  24 void
  25 mc146818_write(unsigned reg, unsigned datum)
  26 {
  27         outb(IO_RTC, reg);
  28         outb(IO_RTC+1, datum);
  29 }
  30
  31
  32 void
  33 kclock_init(void)
  34 {
  35         /* initialize 8253 clock to interrupt 100 times/sec */
  36         outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
  37         outb(IO_TIMER1, TIMER_DIV(100) % 256);
  38         outb(IO_TIMER1, TIMER_DIV(100) / 256);
  39         cprintf("       Setup timer interrupts via 8259A\n");
  40         irq_setmask_8259A(irq_mask_8259A & ~(1<<0));
  41         cprintf("       unmasked timer interrupt\n");
  42 }
  43