timer: Fix timer calibration logic.

[pintos-anon] / src / devices / timer.c

diff --git a/src/devices/timer.c b/src/devices/timer.c
index 70234a808844e425d8309f6cd04c09ce11ad230e..8b923414e65248414512a63f5d27088ee3c3eb44 100644 (file)
--- a/src/devices/timer.c
+++ b/src/devices/timer.c
@@ -3,8 +3,8 @@
 #include <inttypes.h>
 #include <round.h>
 #include <stdio.h>
+#include "devices/pit.h"
 #include "threads/interrupt.h"
-#include "threads/io.h"
 #include "threads/synch.h"
 #include "threads/thread.h"
   
@@ -30,20 +30,12 @@ static void busy_wait (int64_t loops);
 static void real_time_sleep (int64_t num, int32_t denom);
 static void real_time_delay (int64_t num, int32_t denom);
 
-/* Sets up the 8254 Programmable Interval Timer (PIT) to
-   interrupt PIT_FREQ times per second, and registers the
-   corresponding interrupt. */
+/* Sets up the timer to interrupt TIMER_FREQ times per second,
+   and registers the corresponding interrupt. */
 void
 timer_init (void) 
 {
-  /* 8254 input frequency divided by TIMER_FREQ, rounded to
-     nearest. */
-  uint16_t count = (1193180 + TIMER_FREQ / 2) / TIMER_FREQ;
-
-  outb (0x43, 0x34);    /* CW: counter 0, LSB then MSB, mode 2, binary. */
-  outb (0x40, count & 0xff);
-  outb (0x40, count >> 8);
-
+  pit_configure_channel (0, 2, TIMER_FREQ);
   intr_register_ext (0x20, timer_interrupt, "8254 Timer");
 }
 
@@ -68,7 +60,7 @@ timer_calibrate (void)
   /* Refine the next 8 bits of loops_per_tick. */
   high_bit = loops_per_tick;
   for (test_bit = high_bit >> 1; test_bit != high_bit >> 10; test_bit >>= 1)
-    if (!too_many_loops (high_bit | test_bit))
+    if (!too_many_loops (loops_per_tick | test_bit))
       loops_per_tick |= test_bit;
 
   printf ("%'"PRIu64" loops/s.\n", (uint64_t) loops_per_tick * TIMER_FREQ);
@@ -81,7 +73,6 @@ timer_ticks (void)
   enum intr_level old_level = intr_disable ();
   int64_t t = ticks;
   intr_set_level (old_level);
-  barrier ();
   return t;
 }