Move almost all the ntp related stuff from kern_clock.c to

kern_ntptime.c.  The only bit left over is that which is executed
in all calls to hardclock().  Various cleanups and staticizing
along the road.

1 files changed, 47 insertions, 660 deletions

diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index bd54b41..4d482e8 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -36,26 +36,9 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_clock.c	8.5 (Berkeley) 1/21/94
- * $Id: kern_clock.c,v 1.51 1998/01/11 00:44:27 phk Exp $
+ * $Id: kern_clock.c,v 1.52 1998/01/11 19:07:58 phk Exp $
  */
 
-/* Portions of this software are covered by the following: */
-/******************************************************************************
- *                                                                            *
- * Copyright (c) David L. Mills 1993, 1994                                    *
- *                                                                            *
- * Permission to use, copy, modify, and distribute this software and its      *
- * documentation for any purpose and without fee is hereby granted, provided  *
- * that the above copyright notice appears in all copies and that both the    *
- * copyright notice and this permission notice appear in supporting           *
- * documentation, and that the name University of Delaware not be used in     *
- * advertising or publicity pertaining to distribution of the software        *
- * without specific, written prior permission.  The University of Delaware    *
- * makes no representations about the suitability this software for any       *
- * purpose.  It is provided "as is" without express or implied warranty.      *
- *                                                                            *
- *****************************************************************************/
-
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/dkstat.h>
@@ -162,236 +145,6 @@ volatile struct	timeval time;
 volatile struct	timeval mono_time;
 
 /*
- * Phase/frequency-lock loop (PLL/FLL) definitions
- *
- * The following variables are read and set by the ntp_adjtime() system
- * call.
- *
- * time_state shows the state of the system clock, with values defined
- * in the timex.h header file.
- *
- * time_status shows the status of the system clock, with bits defined
- * in the timex.h header file.
- *
- * time_offset is used by the PLL/FLL to adjust the system time in small
- * increments.
- *
- * time_constant determines the bandwidth or "stiffness" of the PLL.
- *
- * time_tolerance determines maximum frequency error or tolerance of the
- * CPU clock oscillator and is a property of the architecture; however,
- * in principle it could change as result of the presence of external
- * discipline signals, for instance.
- *
- * time_precision is usually equal to the kernel tick variable; however,
- * in cases where a precision clock counter or external clock is
- * available, the resolution can be much less than this and depend on
- * whether the external clock is working or not.
- *
- * time_maxerror is initialized by a ntp_adjtime() call and increased by
- * the kernel once each second to reflect the maximum error
- * bound growth.
- *
- * time_esterror is set and read by the ntp_adjtime() call, but
- * otherwise not used by the kernel.
- */
-int time_status = STA_UNSYNC;	/* clock status bits */
-int time_state = TIME_OK;	/* clock state */
-long time_offset = 0;		/* time offset (us) */
-long time_constant = 0;		/* pll time constant */
-long time_tolerance = MAXFREQ;	/* frequency tolerance (scaled ppm) */
-long time_precision = 1;	/* clock precision (us) */
-long time_maxerror = MAXPHASE;	/* maximum error (us) */
-long time_esterror = MAXPHASE;	/* estimated error (us) */
-
-/*
- * The following variables establish the state of the PLL/FLL and the
- * residual time and frequency offset of the local clock. The scale
- * factors are defined in the timex.h header file.
- *
- * time_phase and time_freq are the phase increment and the frequency
- * increment, respectively, of the kernel time variable at each tick of
- * the clock.
- *
- * time_freq is set via ntp_adjtime() from a value stored in a file when
- * the synchronization daemon is first started. Its value is retrieved
- * via ntp_adjtime() and written to the file about once per hour by the
- * daemon.
- *
- * time_adj is the adjustment added to the value of tick at each timer
- * interrupt and is recomputed from time_phase and time_freq at each
- * seconds rollover.
- *
- * time_reftime is the second's portion of the system time on the last
- * call to ntp_adjtime(). It is used to adjust the time_freq variable
- * and to increase the time_maxerror as the time since last update
- * increases.
- */
-static long time_phase = 0;		/* phase offset (scaled us) */
-long time_freq = 0;			/* frequency offset (scaled ppm) */
-static long time_adj = 0;		/* tick adjust (scaled 1 / hz) */
-static long time_reftime = 0;		/* time at last adjustment (s) */
-
-#ifdef PPS_SYNC
-/*
- * The following variables are used only if the kernel PPS discipline
- * code is configured (PPS_SYNC). The scale factors are defined in the
- * timex.h header file.
- *
- * pps_time contains the time at each calibration interval, as read by
- * microtime(). pps_count counts the seconds of the calibration
- * interval, the duration of which is nominally pps_shift in powers of
- * two.
- *
- * pps_offset is the time offset produced by the time median filter
- * pps_tf[], while pps_jitter is the dispersion (jitter) measured by
- * this filter.
- *
- * pps_freq is the frequency offset produced by the frequency median
- * filter pps_ff[], while pps_stabil is the dispersion (wander) measured
- * by this filter.
- *
- * pps_usec is latched from a high resolution counter or external clock
- * at pps_time. Here we want the hardware counter contents only, not the
- * contents plus the time_tv.usec as usual.
- *
- * pps_valid counts the number of seconds since the last PPS update. It
- * is used as a watchdog timer to disable the PPS discipline should the
- * PPS signal be lost.
- *
- * pps_glitch counts the number of seconds since the beginning of an
- * offset burst more than tick/2 from current nominal offset. It is used
- * mainly to suppress error bursts due to priority conflicts between the
- * PPS interrupt and timer interrupt.
- *
- * pps_intcnt counts the calibration intervals for use in the interval-
- * adaptation algorithm. It's just too complicated for words.
- */
-struct timeval pps_time;	/* kernel time at last interval */
-long pps_offset = 0;		/* pps time offset (us) */
-long pps_jitter = MAXTIME;	/* pps time dispersion (jitter) (us) */
-long pps_tf[] = {0, 0, 0};	/* pps time offset median filter (us) */
-long pps_freq = 0;		/* frequency offset (scaled ppm) */
-long pps_stabil = MAXFREQ;	/* frequency dispersion (scaled ppm) */
-long pps_ff[] = {0, 0, 0};	/* frequency offset median filter */
-long pps_usec = 0;		/* microsec counter at last interval */
-long pps_valid = PPS_VALID;	/* pps signal watchdog counter */
-int pps_glitch = 0;		/* pps signal glitch counter */
-int pps_count = 0;		/* calibration interval counter (s) */
-int pps_shift = PPS_SHIFT;	/* interval duration (s) (shift) */
-int pps_intcnt = 0;		/* intervals at current duration */
-
-/*
- * PPS signal quality monitors
- *
- * pps_jitcnt counts the seconds that have been discarded because the
- * jitter measured by the time median filter exceeds the limit MAXTIME
- * (100 us).
- *
- * pps_calcnt counts the frequency calibration intervals, which are
- * variable from 4 s to 256 s.
- *
- * pps_errcnt counts the calibration intervals which have been discarded
- * because the wander exceeds the limit MAXFREQ (100 ppm) or where the
- * calibration interval jitter exceeds two ticks.
- *
- * pps_stbcnt counts the calibration intervals that have been discarded
- * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us).
- */
-long pps_jitcnt = 0;		/* jitter limit exceeded */
-long pps_calcnt = 0;		/* calibration intervals */
-long pps_errcnt = 0;		/* calibration errors */
-long pps_stbcnt = 0;		/* stability limit exceeded */
-#endif /* PPS_SYNC */
-
-/* XXX none of this stuff works under FreeBSD */
-
-/*
- * hardupdate() - local clock update
- *
- * This routine is called by ntp_adjtime() to update the local clock
- * phase and frequency. The implementation is of an adaptive-parameter,
- * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
- * time and frequency offset estimates for each call. If the kernel PPS
- * discipline code is configured (PPS_SYNC), the PPS signal itself
- * determines the new time offset, instead of the calling argument.
- * Presumably, calls to ntp_adjtime() occur only when the caller
- * believes the local clock is valid within some bound (+-128 ms with
- * NTP). If the caller's time is far different than the PPS time, an
- * argument will ensue, and it's not clear who will lose.
- *
- * For uncompensated quartz crystal oscillatores and nominal update
- * intervals less than 1024 s, operation should be in phase-lock mode
- * (STA_FLL = 0), where the loop is disciplined to phase. For update
- * intervals greater than thiss, operation should be in frequency-lock
- * mode (STA_FLL = 1), where the loop is disciplined to frequency.
- *
- * Note: splclock() is in effect.
- */
-void
-hardupdate(offset)
-	long offset;
-{
-	long ltemp, mtemp;
-
-	if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME))
-		return;
-	ltemp = offset;
-#ifdef PPS_SYNC
-	if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
-		ltemp = pps_offset;
-#endif /* PPS_SYNC */
-
-	/*
-	 * Scale the phase adjustment and clamp to the operating range.
-	 */
-	if (ltemp > MAXPHASE)
-		time_offset = MAXPHASE << SHIFT_UPDATE;
-	else if (ltemp < -MAXPHASE)
-		time_offset = -(MAXPHASE << SHIFT_UPDATE);
-	else
-		time_offset = ltemp << SHIFT_UPDATE;
-
-	/*
-	 * Select whether the frequency is to be controlled and in which
-	 * mode (PLL or FLL). Clamp to the operating range. Ugly
-	 * multiply/divide should be replaced someday.
-	 */
-	if (time_status & STA_FREQHOLD || time_reftime == 0)
-		time_reftime = time.tv_sec;
-	mtemp = time.tv_sec - time_reftime;
-	time_reftime = time.tv_sec;
-	if (time_status & STA_FLL) {
-		if (mtemp >= MINSEC) {
-			ltemp = ((time_offset / mtemp) << (SHIFT_USEC -
-			    SHIFT_UPDATE));
-			if (ltemp < 0)
-				time_freq -= -ltemp >> SHIFT_KH;
-			else
-				time_freq += ltemp >> SHIFT_KH;
-		}
-	} else {
-		if (mtemp < MAXSEC) {
-			ltemp *= mtemp;
-			if (ltemp < 0)
-				time_freq -= -ltemp >> (time_constant +
-				    time_constant + SHIFT_KF -
-				    SHIFT_USEC);
-			else
-				time_freq += ltemp >> (time_constant +
-				    time_constant + SHIFT_KF -
-				    SHIFT_USEC);
-		}
-	}
-	if (time_freq > time_tolerance)
-		time_freq = time_tolerance;
-	else if (time_freq < -time_tolerance)
-		time_freq = -time_tolerance;
-}
-
-
-
-/*
  * Initialize clock frequencies and start both clocks running.
  */
 /* ARGSUSED*/
@@ -425,6 +178,9 @@ hardclock(frame)
 	register struct clockframe *frame;
 {
 	register struct proc *p;
+	int time_update;
+	struct timeval newtime = time;
+	long ltemp;
 
 	p = curproc;
 	if (p) {
@@ -456,182 +212,54 @@ hardclock(frame)
 	 * Increment the time-of-day.
 	 */
 	ticks++;
-	{
-		int time_update;
-		struct timeval newtime = time;
-		long ltemp;
-
-		if (timedelta == 0) {
-			time_update = CPU_THISTICKLEN(tick);
-		} else {
-			time_update = CPU_THISTICKLEN(tick) + tickdelta;
-			timedelta -= tickdelta;
-		}
-		BUMPTIME(&mono_time, time_update);
-
-		/*
-		 * Compute the phase adjustment. If the low-order bits
-		 * (time_phase) of the update overflow, bump the high-order bits
-		 * (time_update).
-		 */
-		time_phase += time_adj;
-		if (time_phase <= -FINEUSEC) {
-		  ltemp = -time_phase >> SHIFT_SCALE;
-		  time_phase += ltemp << SHIFT_SCALE;
-		  time_update -= ltemp;
-		}
-		else if (time_phase >= FINEUSEC) {
-		  ltemp = time_phase >> SHIFT_SCALE;
-		  time_phase -= ltemp << SHIFT_SCALE;
-		  time_update += ltemp;
-		}
-
-		newtime.tv_usec += time_update;
-		/*
-		 * On rollover of the second the phase adjustment to be used for
-		 * the next second is calculated. Also, the maximum error is
-		 * increased by the tolerance. If the PPS frequency discipline
-		 * code is present, the phase is increased to compensate for the
-		 * CPU clock oscillator frequency error.
-		 *
-		 * On a 32-bit machine and given parameters in the timex.h
-		 * header file, the maximum phase adjustment is +-512 ms and
-		 * maximum frequency offset is a tad less than) +-512 ppm. On a
-		 * 64-bit machine, you shouldn't need to ask.
-		 */
-		if (newtime.tv_usec >= 1000000) {
-		  newtime.tv_usec -= 1000000;
-		  newtime.tv_sec++;
-		  time_maxerror += time_tolerance >> SHIFT_USEC;
-
-		  /*
-		   * Compute the phase adjustment for the next second. In
-		   * PLL mode, the offset is reduced by a fixed factor
-		   * times the time constant. In FLL mode the offset is
-		   * used directly. In either mode, the maximum phase
-		   * adjustment for each second is clamped so as to spread
-		   * the adjustment over not more than the number of
-		   * seconds between updates.
-		   */
-		  if (time_offset < 0) {
-		    ltemp = -time_offset;
-		    if (!(time_status & STA_FLL))
-			ltemp >>= SHIFT_KG + time_constant;
-		    if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
-			ltemp = (MAXPHASE / MINSEC) <<
-			    SHIFT_UPDATE;
-		    time_offset += ltemp;
-		    time_adj = -ltemp << (SHIFT_SCALE - SHIFT_HZ -
-			SHIFT_UPDATE);
-		    } else {
-		        ltemp = time_offset;
-			if (!(time_status & STA_FLL))
-				ltemp >>= SHIFT_KG + time_constant;
-			if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
-				ltemp = (MAXPHASE / MINSEC) <<
-				    SHIFT_UPDATE;
-			time_offset -= ltemp;
-			time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ -
-			    SHIFT_UPDATE);
-		    }
-
-		  /*
-		   * Compute the frequency estimate and additional phase
-		   * adjustment due to frequency error for the next
-		   * second. When the PPS signal is engaged, gnaw on the
-		   * watchdog counter and update the frequency computed by
-		   * the pll and the PPS signal.
-		   */
-#ifdef PPS_SYNC
-		  pps_valid++;
-		  if (pps_valid == PPS_VALID) {
-		    pps_jitter = MAXTIME;
-		    pps_stabil = MAXFREQ;
-		    time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
-				     STA_PPSWANDER | STA_PPSERROR);
-		  }
-		  ltemp = time_freq + pps_freq;
-#else
-		  ltemp = time_freq;
-#endif /* PPS_SYNC */
-		  if (ltemp < 0)
-		    time_adj -= -ltemp >>
-		      (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
-		  else
-		    time_adj += ltemp >>
-		      (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
-
-#if SHIFT_HZ == 7
-		  /*
-		   * When the CPU clock oscillator frequency is not a
-		   * power of two in Hz, the SHIFT_HZ is only an
-		   * approximate scale factor. In the SunOS kernel, this
-		   * results in a PLL gain factor of 1/1.28 = 0.78 what it
-		   * should be. In the following code the overall gain is
-		   * increased by a factor of 1.25, which results in a
-		   * residual error less than 3 percent.
-		   */
-		  /* Same thing applies for FreeBSD --GAW */
-		  if (hz == 100) {
-		    if (time_adj < 0)
-		      time_adj -= -time_adj >> 2;
-		    else
-		      time_adj += time_adj >> 2;
-		  }
-#endif /* SHIFT_HZ */
-
-		  /* XXX - this is really bogus, but can't be fixed until
-		     xntpd's idea of the system clock is fixed to know how
-		     the user wants leap seconds handled; in the mean time,
-		     we assume that users of NTP are running without proper
-		     leap second support (this is now the default anyway) */
-		  /*
-		   * Leap second processing. If in leap-insert state at
-		   * the end of the day, the system clock is set back one
-		   * second; if in leap-delete state, the system clock is
-		   * set ahead one second. The microtime() routine or
-		   * external clock driver will insure that reported time
-		   * is always monotonic. The ugly divides should be
-		   * replaced.
-		   */
-		  switch (time_state) {
 
-		  case TIME_OK:
-		    if (time_status & STA_INS)
-		      time_state = TIME_INS;
-		    else if (time_status & STA_DEL)
-		      time_state = TIME_DEL;
-		    break;
-
-		  case TIME_INS:
-		    if (newtime.tv_sec % 86400 == 0) {
-		      newtime.tv_sec--;
-		      time_state = TIME_OOP;
-		    }
-		    break;
-
-		  case TIME_DEL:
-		    if ((newtime.tv_sec + 1) % 86400 == 0) {
-		      newtime.tv_sec++;
-		      time_state = TIME_WAIT;
-		    }
-		    break;
+	if (timedelta == 0) {
+		time_update = CPU_THISTICKLEN(tick);
+	} else {
+		time_update = CPU_THISTICKLEN(tick) + tickdelta;
+		timedelta -= tickdelta;
+	}
+	BUMPTIME(&mono_time, time_update);
 
-		  case TIME_OOP:
-		    time_state = TIME_WAIT;
-		    break;
+	/*
+	 * Compute the phase adjustment. If the low-order bits
+	 * (time_phase) of the update overflow, bump the high-order bits
+	 * (time_update).
+	 */
+	time_phase += time_adj;
+	if (time_phase <= -FINEUSEC) {
+		ltemp = -time_phase >> SHIFT_SCALE;
+		time_phase += ltemp << SHIFT_SCALE;
+		time_update -= ltemp;
+	}
+	else if (time_phase >= FINEUSEC) {
+		ltemp = time_phase >> SHIFT_SCALE;
+		time_phase -= ltemp << SHIFT_SCALE;
+		time_update += ltemp;
+	}
 
-		  case TIME_WAIT:
-		    if (!(time_status & (STA_INS | STA_DEL)))
-		      time_state = TIME_OK;
-		  }
-		}
-		CPU_CLOCKUPDATE(&time, &newtime);
+	newtime.tv_usec += time_update;
+	/*
+	 * On rollover of the second the phase adjustment to be used for
+	 * the next second is calculated. Also, the maximum error is
+	 * increased by the tolerance. If the PPS frequency discipline
+	 * code is present, the phase is increased to compensate for the
+	 * CPU clock oscillator frequency error.
+	 *
+	 * On a 32-bit machine and given parameters in the timex.h
+	 * header file, the maximum phase adjustment is +-512 ms and
+	 * maximum frequency offset is a tad less than) +-512 ppm. On a
+	 * 64-bit machine, you shouldn't need to ask.
+	 */
+	if (newtime.tv_usec >= 1000000) {
+		newtime.tv_usec -= 1000000;
+		newtime.tv_sec++;
+		ntp_update_second(&newtime.tv_sec);
 	}
-	
-	if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
+	CPU_CLOCKUPDATE(&time, &newtime);
+
+	if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL)
 		setsoftclock();
-	}
 }
 
 void
@@ -900,244 +528,3 @@ sysctl_kern_clockrate SYSCTL_HANDLER_ARGS
 SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
 	0, 0, sysctl_kern_clockrate, "S,clockinfo","");
 
-#ifdef PPS_SYNC
-
-/* We need this ugly monster twice, so lets macroize it... */
-
-#define MEDIAN3(a, m, s)				\
-	do {						\
-		if (a[0] > a[1]) {			\
-			if (a[1] > a[2]) {		\
-				/* 0 1 2 */		\
-				m = a[1];		\
-				s = a[0] - a[2];	\
-			} else if (a[2] > a[0]) {	\
-				/* 2 0 1 */		\
-				m = a[0];		\
-				s = a[2] - a[1];	\
-			} else {			\
-				/* 0 2 1 */		\
-				m = a[2];		\
-				s = a[0] - a[1];	\
-			}				\
-		} else {				\
-			if (a[1] < a[2]) {		\
-				/* 2 1 0 */		\
-				m = a[1];		\
-				s = a[2] - a[0];	\
-			} else  if (a[2] < a[0]) {	\
-				/* 1 0 2 */		\
-				m = a[0];		\
-				s = a[1] - a[2];	\
-			} else {			\
-				/* 1 2 0 */		\
-				m = a[2];		\
-				s = a[1] - a[0];	\
-			}				\
-		}					\
-	} while (0)
-
-/*
- * hardpps() - discipline CPU clock oscillator to external PPS signal
- *
- * This routine is called at each PPS interrupt in order to discipline
- * the CPU clock oscillator to the PPS signal. It measures the PPS phase
- * and leaves it in a handy spot for the hardclock() routine. It
- * integrates successive PPS phase differences and calculates the
- * frequency offset. This is used in hardclock() to discipline the CPU
- * clock oscillator so that intrinsic frequency error is cancelled out.
- * The code requires the caller to capture the time and hardware counter
- * value at the on-time PPS signal transition.
- *
- * Note that, on some Unix systems, this routine runs at an interrupt
- * priority level higher than the timer interrupt routine hardclock().
- * Therefore, the variables used are distinct from the hardclock()
- * variables, except for certain exceptions: The PPS frequency pps_freq
- * and phase pps_offset variables are determined by this routine and
- * updated atomically. The time_tolerance variable can be considered a
- * constant, since it is infrequently changed, and then only when the
- * PPS signal is disabled. The watchdog counter pps_valid is updated
- * once per second by hardclock() and is atomically cleared in this
- * routine.
- */
-void
-hardpps(tvp, p_usec)
-	struct timeval *tvp;		/* time at PPS */
-	long p_usec;			/* hardware counter at PPS */
-{
-	long u_usec, v_usec, bigtick;
-	long cal_sec, cal_usec;
-
-	/*
-	 * An occasional glitch can be produced when the PPS interrupt
-	 * occurs in the hardclock() routine before the time variable is
-	 * updated. Here the offset is discarded when the difference
-	 * between it and the last one is greater than tick/2, but not
-	 * if the interval since the first discard exceeds 30 s.
-	 */
-	time_status |= STA_PPSSIGNAL;
-	time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
-	pps_valid = 0;
-	u_usec = -tvp->tv_usec;
-	if (u_usec < -500000)
-		u_usec += 1000000;
-	v_usec = pps_offset - u_usec;
-	if (v_usec < 0)
-		v_usec = -v_usec;
-	if (v_usec > (tick >> 1)) {
-		if (pps_glitch > MAXGLITCH) {
-			pps_glitch = 0;
-			pps_tf[2] = u_usec;
-			pps_tf[1] = u_usec;
-		} else {
-			pps_glitch++;
-			u_usec = pps_offset;
-		}
-	} else
-		pps_glitch = 0;
-
-	/*
-	 * A three-stage median filter is used to help deglitch the pps
-	 * time. The median sample becomes the time offset estimate; the
-	 * difference between the other two samples becomes the time
-	 * dispersion (jitter) estimate.
-	 */
-	pps_tf[2] = pps_tf[1];
-	pps_tf[1] = pps_tf[0];
-	pps_tf[0] = u_usec;
-
-	MEDIAN3(pps_tf, pps_offset, v_usec);
-
-	if (v_usec > MAXTIME)
-		pps_jitcnt++;
-	v_usec = (v_usec << PPS_AVG) - pps_jitter;
-	if (v_usec < 0)
-		pps_jitter -= -v_usec >> PPS_AVG;
-	else
-		pps_jitter += v_usec >> PPS_AVG;
-	if (pps_jitter > (MAXTIME >> 1))
-		time_status |= STA_PPSJITTER;
-
-	/*
-	 * During the calibration interval adjust the starting time when
-	 * the tick overflows. At the end of the interval compute the
-	 * duration of the interval and the difference of the hardware
-	 * counters at the beginning and end of the interval. This code
-	 * is deliciously complicated by the fact valid differences may
-	 * exceed the value of tick when using long calibration
-	 * intervals and small ticks. Note that the counter can be
-	 * greater than tick if caught at just the wrong instant, but
-	 * the values returned and used here are correct.
-	 */
-	bigtick = (long)tick << SHIFT_USEC;
-	pps_usec -= pps_freq;
-	if (pps_usec >= bigtick)
-		pps_usec -= bigtick;
-	if (pps_usec < 0)
-		pps_usec += bigtick;
-	pps_time.tv_sec++;
-	pps_count++;
-	if (pps_count < (1 << pps_shift))
-		return;
-	pps_count = 0;
-	pps_calcnt++;
-	u_usec = p_usec << SHIFT_USEC;
-	v_usec = pps_usec - u_usec;
-	if (v_usec >= bigtick >> 1)
-		v_usec -= bigtick;
-	if (v_usec < -(bigtick >> 1))
-		v_usec += bigtick;
-	if (v_usec < 0)
-		v_usec = -(-v_usec >> pps_shift);
-	else
-		v_usec = v_usec >> pps_shift;
-	pps_usec = u_usec;
-	cal_sec = tvp->tv_sec;
-	cal_usec = tvp->tv_usec;
-	cal_sec -= pps_time.tv_sec;
-	cal_usec -= pps_time.tv_usec;
-	if (cal_usec < 0) {
-		cal_usec += 1000000;
-		cal_sec--;
-	}
-	pps_time = *tvp;
-
-	/*
-	 * Check for lost interrupts, noise, excessive jitter and
-	 * excessive frequency error. The number of timer ticks during
-	 * the interval may vary +-1 tick. Add to this a margin of one
-	 * tick for the PPS signal jitter and maximum frequency
-	 * deviation. If the limits are exceeded, the calibration
-	 * interval is reset to the minimum and we start over.
-	 */
-	u_usec = (long)tick << 1;
-	if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec))
-	    || (cal_sec == 0 && cal_usec < u_usec))
-	    || v_usec > time_tolerance || v_usec < -time_tolerance) {
-		pps_errcnt++;
-		pps_shift = PPS_SHIFT;
-		pps_intcnt = 0;
-		time_status |= STA_PPSERROR;
-		return;
-	}
-
-	/*
-	 * A three-stage median filter is used to help deglitch the pps
-	 * frequency. The median sample becomes the frequency offset
-	 * estimate; the difference between the other two samples
-	 * becomes the frequency dispersion (stability) estimate.
-	 */
-	pps_ff[2] = pps_ff[1];
-	pps_ff[1] = pps_ff[0];
-	pps_ff[0] = v_usec;
-
-	MEDIAN3(pps_ff, u_usec, v_usec);
-
-	/*
-	 * Here the frequency dispersion (stability) is updated. If it
-	 * is less than one-fourth the maximum (MAXFREQ), the frequency
-	 * offset is updated as well, but clamped to the tolerance. It
-	 * will be processed later by the hardclock() routine.
-	 */
-	v_usec = (v_usec >> 1) - pps_stabil;
-	if (v_usec < 0)
-		pps_stabil -= -v_usec >> PPS_AVG;
-	else
-		pps_stabil += v_usec >> PPS_AVG;
-	if (pps_stabil > MAXFREQ >> 2) {
-		pps_stbcnt++;
-		time_status |= STA_PPSWANDER;
-		return;
-	}
-	if (time_status & STA_PPSFREQ) {
-		if (u_usec < 0) {
-			pps_freq -= -u_usec >> PPS_AVG;
-			if (pps_freq < -time_tolerance)
-				pps_freq = -time_tolerance;
-			u_usec = -u_usec;
-		} else {
-			pps_freq += u_usec >> PPS_AVG;
-			if (pps_freq > time_tolerance)
-				pps_freq = time_tolerance;
-		}
-	}
-
-	/*
-	 * Here the calibration interval is adjusted. If the maximum
-	 * time difference is greater than tick / 4, reduce the interval
-	 * by half. If this is not the case for four consecutive
-	 * intervals, double the interval.
-	 */
-	if (u_usec << pps_shift > bigtick >> 2) {
-		pps_intcnt = 0;
-		if (pps_shift > PPS_SHIFT)
-			pps_shift--;
-	} else if (pps_intcnt >= 4) {
-		pps_intcnt = 0;
-		if (pps_shift < PPS_SHIFTMAX)
-			pps_shift++;
-	} else
-		pps_intcnt++;
-}
-#endif /* PPS_SYNC */
-