#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"
/* See [8254] for hardware details of the 8254 timer chip. */
#endif
/* Number of timer ticks since OS booted. */
-static volatile int64_t ticks;
+static int64_t ticks;
/* Number of loops per timer tick.
Initialized by timer_calibrate(). */
static bool too_many_loops (unsigned loops);
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");
}
return timer_ticks () - then;
}
-/* Suspends execution for approximately TICKS timer ticks. */
+/* Sleeps for approximately TICKS timer ticks. Interrupts must
+ be turned on. */
void
timer_sleep (int64_t ticks)
{
thread_yield ();
}
-/* Suspends execution for approximately MS milliseconds. */
+/* Sleeps for approximately MS milliseconds. Interrupts must be
+ turned on. */
void
timer_msleep (int64_t ms)
{
real_time_sleep (ms, 1000);
}
-/* Suspends execution for approximately US microseconds. */
+/* Sleeps for approximately US microseconds. Interrupts must be
+ turned on. */
void
timer_usleep (int64_t us)
{
real_time_sleep (us, 1000 * 1000);
}
-/* Suspends execution for approximately NS nanoseconds. */
+/* Sleeps for approximately NS nanoseconds. Interrupts must be
+ turned on. */
void
timer_nsleep (int64_t ns)
{
real_time_sleep (ns, 1000 * 1000 * 1000);
}
+/* Busy-waits for approximately MS milliseconds. Interrupts need
+ not be turned on.
+
+ Busy waiting wastes CPU cycles, and busy waiting with
+ interrupts off for the interval between timer ticks or longer
+ will cause timer ticks to be lost. Thus, use timer_msleep()
+ instead if interrupts are enabled. */
+void
+timer_mdelay (int64_t ms)
+{
+ real_time_delay (ms, 1000);
+}
+
+/* Sleeps for approximately US microseconds. Interrupts need not
+ be turned on.
+
+ Busy waiting wastes CPU cycles, and busy waiting with
+ interrupts off for the interval between timer ticks or longer
+ will cause timer ticks to be lost. Thus, use timer_usleep()
+ instead if interrupts are enabled. */
+void
+timer_udelay (int64_t us)
+{
+ real_time_delay (us, 1000 * 1000);
+}
+
+/* Sleeps execution for approximately NS nanoseconds. Interrupts
+ need not be turned on.
+
+ Busy waiting wastes CPU cycles, and busy waiting with
+ interrupts off for the interval between timer ticks or longer
+ will cause timer ticks to be lost. Thus, use timer_nsleep()
+ instead if interrupts are enabled.*/
+void
+timer_ndelay (int64_t ns)
+{
+ real_time_delay (ns, 1000 * 1000 * 1000);
+}
+
/* Prints timer statistics. */
void
timer_print_stats (void)
static bool
too_many_loops (unsigned loops)
{
- int64_t start;
-
/* Wait for a timer tick. */
- start = ticks;
+ int64_t start = ticks;
while (ticks == start)
- continue;
+ barrier ();
/* Run LOOPS loops. */
start = ticks;
busy_wait (loops);
/* If the tick count changed, we iterated too long. */
+ barrier ();
return start != ticks;
}
differently in different places the results would be difficult
to predict. */
static void NO_INLINE
-busy_wait (volatile int64_t loops)
+busy_wait (int64_t loops)
{
while (loops-- > 0)
- continue;
+ barrier ();
}
/* Sleep for approximately NUM/DENOM seconds. */
else
{
/* Otherwise, use a busy-wait loop for more accurate
- sub-tick timing. We scale the numerator and denominator
- down by 1000 to avoid the possibility of overflow. */
- ASSERT (denom % 1000 == 0);
- busy_wait (loops_per_tick * num / 1000 * TIMER_FREQ / (denom / 1000));
+ sub-tick timing. */
+ real_time_delay (num, denom);
}
}
+/* Busy-wait for approximately NUM/DENOM seconds. */
+static void
+real_time_delay (int64_t num, int32_t denom)
+{
+ /* Scale the numerator and denominator down by 1000 to avoid
+ the possibility of overflow. */
+ ASSERT (denom % 1000 == 0);
+ busy_wait (loops_per_tick * num / 1000 * TIMER_FREQ / (denom / 1000));
+}