* kernel PLL updated to 1994-12-13 specs (rfc-1589)
* 1997-08-30 Ulrich Windl
* Added new constant NTP_PHASE_LIMIT
+ * 2004-08-12 Christoph Lameter
+ * Reworked time interpolation logic
*/
#ifndef _LINUX_TIMEX_H
#define _LINUX_TIMEX_H
#ifdef CONFIG_TIME_INTERPOLATION
-struct time_interpolator {
- /* cache-hot stuff first: */
- unsigned long (*get_offset) (void);
- void (*update) (long);
- void (*reset) (void);
+#define TIME_SOURCE_CPU 0
+#define TIME_SOURCE_MMIO64 1
+#define TIME_SOURCE_MMIO32 2
+#define TIME_SOURCE_FUNCTION 3
+
+/* For proper operations time_interpolator clocks must run slightly slower
+ * than the standard clock since the interpolator may only correct by having
+ * time jump forward during a tick. A slower clock is usually a side effect
+ * of the integer divide of the nanoseconds in a second by the frequency.
+ * The accuracy of the division can be increased by specifying a shift.
+ * However, this may cause the clock not to be slow enough.
+ * The interpolator will self-tune the clock by slowing down if no
+ * resets occur or speeding up if the time jumps per analysis cycle
+ * become too high.
+ *
+ * Setting jitter compensates for a fluctuating timesource by comparing
+ * to the last value read from the timesource to insure that an earlier value
+ * is not returned by a later call. The price to pay
+ * for the compensation is that the timer routines are not as scalable anymore.
+ */
- /* cache-cold stuff follows here: */
- struct time_interpolator *next;
+#define INTERPOLATOR_ADJUST 65536
+#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
+
+struct time_interpolator {
+ unsigned short source; /* time source flags */
+ unsigned char shift; /* increases accuracy of multiply by shifting. */
+ /* Note that bits may be lost if shift is set too high */
+ unsigned char jitter; /* if set compensate for fluctuations */
+ unsigned nsec_per_cyc; /* set by register_time_interpolator() */
+ void *addr; /* address of counter or function */
+ unsigned long offset; /* nsec offset at last update of interpolator */
+ unsigned long last_counter; /* counter value in units of the counter at last update */
+ unsigned long last_cycle; /* Last timer value if TIME_SOURCE_JITTER is set */
unsigned long frequency; /* frequency in counts/second */
long drift; /* drift in parts-per-million (or -1) */
+ unsigned long skips; /* skips forward */
+ unsigned long ns_skipped; /* nanoseconds skipped */
+ struct time_interpolator *next;
};
-extern volatile unsigned long last_nsec_offset;
-#ifndef __HAVE_ARCH_CMPXCHG
-extern spin_lock_t last_nsec_offset_lock;
-#endif
-extern struct time_interpolator *time_interpolator;
-
extern void register_time_interpolator(struct time_interpolator *);
extern void unregister_time_interpolator(struct time_interpolator *);
-
-/* Called with xtime WRITE-lock acquired. */
-static inline void
-time_interpolator_update(long delta_nsec)
-{
- struct time_interpolator *ti = time_interpolator;
-
- if (last_nsec_offset > 0) {
-#ifdef __HAVE_ARCH_CMPXCHG
- unsigned long new, old;
-
- do {
- old = last_nsec_offset;
- if (old > delta_nsec)
- new = old - delta_nsec;
- else
- new = 0;
- } while (cmpxchg(&last_nsec_offset, old, new) != old);
-#else
- /*
- * This really hurts, because it serializes gettimeofday(), but without an
- * atomic single-word compare-and-exchange, there isn't all that much else
- * we can do.
- */
- spin_lock(&last_nsec_offset_lock);
- {
- last_nsec_offset -= min(last_nsec_offset, delta_nsec);
- }
- spin_unlock(&last_nsec_offset_lock);
-#endif
- }
-
- if (ti)
- (*ti->update)(delta_nsec);
-}
-
-/* Called with xtime WRITE-lock acquired. */
-static inline void
-time_interpolator_reset(void)
-{
- struct time_interpolator *ti = time_interpolator;
-
- last_nsec_offset = 0;
- if (ti)
- (*ti->reset)();
-}
-
-/* Called with xtime READ-lock acquired. */
-static inline unsigned long
-time_interpolator_get_offset(void)
-{
- struct time_interpolator *ti = time_interpolator;
- if (ti)
- return (*ti->get_offset)();
- return last_nsec_offset;
-}
+extern void time_interpolator_reset(void);
+extern unsigned long time_interpolator_resolution(void);
+extern unsigned long time_interpolator_get_offset(void);
#else /* !CONFIG_TIME_INTERPOLATION */
-static inline void
-time_interpolator_update(long delta_nsec)
-{
-}
-
static inline void
time_interpolator_reset(void)
{
}
-static inline unsigned long
-time_interpolator_get_offset(void)
-{
- return 0;
-}
-
#endif /* !CONFIG_TIME_INTERPOLATION */
#endif /* KERNEL */
git://git.onelab.eu / linux-2.6.git / blobdiff