X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdevices%2Ftimer.c;h=ecf6c5aacdfee97c6577c8b60912475ef99e4e77;hb=64f0952217e8b1a53461f5a98a070cb2da266171;hp=4adca8989cf1192612a0c009d187f999c2d5e25a;hpb=f8cae751ac2163f5fe73d5b1372c93ada35dc9e3;p=pintos-anon

diff --git a/src/devices/timer.c b/src/devices/timer.c
index 4adca89..ecf6c5a 100644
--- a/src/devices/timer.c
+++ b/src/devices/timer.c
@@ -1,18 +1,31 @@
-#include "timer.h"
-#include "debug.h"
-#include "interrupt.h"
-#include "io.h"
+#include "devices/timer.h"
+#include <debug.h>
+#include <inttypes.h>
+#include <round.h>
+#include <stdio.h>
+#include "threads/interrupt.h"
+#include "threads/io.h"
+#include "threads/thread.h"
   
-static volatile uint64_t ticks;
+/* See [8254] for hardware details of the 8254 timer chip. */
 
-static void
-irq20_timer (struct intr_frame *args UNUSED)
-{
-  ticks++;
-  intr_yield_on_return ();
-}
+#if TIMER_FREQ < 19
+#error 8254 timer requires TIMER_FREQ >= 19
+#endif
+#if TIMER_FREQ > 1000
+#error TIMER_FREQ <= 1000 recommended
+#endif
+
+/* Number of timer ticks that a process gets before being
+   preempted. */
+#define TIME_SLICE 1
+
+/* Number of timer ticks since OS booted. */
+static volatile int64_t ticks;
+
+static intr_handler_func timer_interrupt;
 
-/* Sets up the 8254 Programmable Interrupt Timer (PIT) to
+/* Sets up the 8254 Programmable Interval Timer (PIT) to
    interrupt PIT_FREQ times per second, and registers the
    corresponding interrupt. */
 void
@@ -26,28 +39,76 @@ timer_init (void)
   outb (0x40, count & 0xff);
   outb (0x40, count >> 8);
 
-  intr_register (0x20, 0, IF_OFF, irq20_timer);
+  intr_register (0x20, 0, INTR_OFF, timer_interrupt, "8254 Timer");
 }
 
-uint64_t
+/* Returns the number of timer ticks since the OS booted. */
+int64_t
 timer_ticks (void) 
 {
-  enum if_level old_level = intr_disable ();
-  uint64_t t = ticks;
+  enum intr_level old_level = intr_disable ();
+  int64_t t = ticks;
   intr_set_level (old_level);
   return t;
 }
 
-uint64_t
-timer_elapsed (uint64_t then) 
+/* Returns the number of timer ticks elapsed since THEN, which
+   should be a value once returned by timer_ticks(). */
+int64_t
+timer_elapsed (int64_t then) 
 {
-  uint64_t now = timer_ticks ();
-  return now > then ? now - then : ((uint64_t) -1 - then) + now + 1;
+  return timer_ticks () - then;
 }
 
-/* Suspends execution for at least DURATION ticks. */
+/* Suspends execution for approximately TICKS timer ticks. */
 void
-timer_wait_until (uint64_t duration) 
+timer_sleep (int64_t ticks) 
 {
-  /* FIXME */
+  int64_t start = timer_ticks ();
+
+  ASSERT (intr_get_level () == INTR_ON);
+  while (timer_elapsed (start) < ticks) 
+    thread_yield ();
+}
+
+/* Returns MS milliseconds in timer ticks, rounding up. */
+int64_t
+timer_ms2ticks (int64_t ms) 
+{
+  /*       MS / 1000 s          
+     ------------------------ = MS * TIMER_FREQ / 1000 ticks. 
+     (1 / TIMER_FREQ) ticks/s
+  */
+  return DIV_ROUND_UP (ms * TIMER_FREQ, 1000);
+}
+
+/* Returns US microseconds in timer ticks, rounding up. */
+int64_t
+timer_us2ticks (int64_t us) 
+{
+  return DIV_ROUND_UP (us * TIMER_FREQ, 1000000);
+}
+
+/* Returns NS nanoseconds in timer ticks, rounding up. */
+int64_t
+timer_ns2ticks (int64_t ns) 
+{
+  return DIV_ROUND_UP (ns * TIMER_FREQ, 1000000000);
+}
+
+/* Prints timer statistics. */
+void
+timer_print_stats (void) 
+{
+  printf ("Timer: %"PRId64" ticks\n", ticks);
+}
+
+/* Timer interrupt handler. */
+static void
+timer_interrupt (struct intr_frame *args UNUSED)
+{
+  ticks++;
+  thread_tick ();
+  if (ticks % TIME_SLICE == 0)
+    intr_yield_on_return ();
 }