-#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_args *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
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 ();
+
+ while (timer_elapsed (start) < ticks)
+ if (intr_get_level () == INTR_ON)
+ 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);
+}
+\f
+/* Timer interrupt handler. */
+static void
+timer_interrupt (struct intr_frame *args UNUSED)
+{
+ ticks++;
+ thread_tick ();
+ if (ticks % TIME_SLICE == 0)
+ intr_yield_on_return ();
}