7 #error 8254 timer requires TIMER_FREQ >= 19
10 static volatile int64_t ticks;
13 irq20_timer (struct intr_frame *args UNUSED)
16 intr_yield_on_return ();
19 /* Sets up the 8254 Programmable Interrupt Timer (PIT) to
20 interrupt PIT_FREQ times per second, and registers the
21 corresponding interrupt. */
25 /* 8254 input frequency divided by TIMER_FREQ, rounded to
27 uint16_t count = (1193180 + TIMER_FREQ / 2) / TIMER_FREQ;
29 outb (0x43, 0x34); /* CW: counter 0, LSB then MSB, mode 2, binary. */
30 outb (0x40, count & 0xff);
31 outb (0x40, count >> 8);
33 intr_register (0x20, 0, IF_OFF, irq20_timer, "8254 Timer");
39 enum if_level old_level = intr_disable ();
41 intr_set_level (old_level);
46 timer_elapsed (int64_t then)
48 return timer_ticks () - then;
51 /* Suspends execution for approximately DURATION milliseconds. */
53 timer_msleep (int64_t ms)
55 int64_t ticks = (int64_t) ms * TIMER_FREQ / 1000;
56 int64_t start = timer_ticks ();
58 while (timer_elapsed (start) < ticks)
63 timer_usleep (int64_t us)
65 timer_msleep (us / 1000 + 1);
69 timer_nsleep (int64_t ns)
71 timer_msleep (ns / 1000000 + 1);