39c39
< * $Id: kern_clock.c,v 1.4 1994/08/18 22:34:58 wollman Exp $
---
> * $Id: kern_clock.c,v 1.5 1994/08/27 16:14:26 davidg Exp $
41a42,58
> /* 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. *
> * *
> *****************************************************************************/
>
48a66
> #include <sys/timex.h>
51a70
> #include <machine/clock.h>
130a150,381
> * Phase-lock loop (PLL) 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 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 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 at each timer interrupt.
> *
> * 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.
> */
> long time_phase = 0; /* phase offset (scaled us) */
> long time_freq = 0; /* frequency offset (scaled ppm) */
> long time_adj = 0; /* tick adjust (scaled 1 / hz) */
> long time_reftime = 0; /* time at last adjustment (s) */
>
> #ifdef PPS_SYNC
> /*
> * The following variables are used only if the 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_offset is the time offset produced by the time median filter
> * pps_tf[], while pps_jitter is the dispersion measured by this
> * filter.
> *
> * pps_freq is the frequency offset produced by the frequency median
> * filter pps_ff[], while pps_stabil is the dispersion 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_count counts the seconds of the calibration interval, the
> * duration of which is pps_shift in powers of two.
> *
> * 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 */
> #ifdef EXT_CLOCK
> /*
> * External clock definitions
> *
> * The following definitions and declarations are used only if an
> * external clock (HIGHBALL or TPRO) is configured on the system.
> */
> #define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */
>
> /*
> * The clock_count variable is set to CLOCK_INTERVAL at each PPS
> * interrupt and decremented once each second.
> */
> int clock_count = 0; /* CPU clock counter */
>
> #ifdef HIGHBALL
> /*
> * The clock_offset and clock_cpu variables are used by the HIGHBALL
> * interface. The clock_offset variable defines the offset between
> * system time and the HIGBALL counters. The clock_cpu variable contains
> * the offset between the system clock and the HIGHBALL clock for use in
> * disciplining the kernel time variable.
> */
> extern struct timeval clock_offset; /* Highball clock offset */
> long clock_cpu = 0; /* CPU clock adjust */
> #endif /* HIGHBALL */
> #endif /* EXT_CLOCK */
>
> /*
> * hardupdate() - local clock update
> *
> * This routine is called by ntp_adjtime() to update the local clock
> * phase and frequency. This is used to implement an adaptive-parameter,
> * first-order, type-II phase-lock loop. The code computes new time and
> * frequency offsets each time it is called. The hardclock() routine
> * amortizes these offsets at each tick interrupt. 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 default SHIFT_UPDATE = 12, the offset is limited to +-512 ms, the
> * maximum interval between updates is 4096 s and the maximum frequency
> * offset is +-31.25 ms/s.
> *
> * 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 */
> if (ltemp > MAXPHASE)
> time_offset = MAXPHASE << SHIFT_UPDATE;
> else if (ltemp < -MAXPHASE)
> time_offset = -(MAXPHASE << SHIFT_UPDATE);
> else
> time_offset = ltemp << SHIFT_UPDATE;
> mtemp = time.tv_sec - time_reftime;
> time_reftime = time.tv_sec;
> if (mtemp > MAXSEC)
> mtemp = 0;
>
> /* ugly multiply should be replaced */
> if (ltemp < 0)
> time_freq -= (-ltemp * mtemp) >> (time_constant +
> time_constant + SHIFT_KF - SHIFT_USEC);
> else
> time_freq += (ltemp * mtemp) >> (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;
> }
>
>
>
> /*
210,211c461
< * Increment the time-of-day. The increment is just ``tick'' unless
< * we are still adjusting the clock; see adjtime().
---
> * Increment the time-of-day.
214,218c464,617
< if (timedelta == 0)
< delta = tick;
< else {
< delta = tick + tickdelta;
< timedelta -= tickdelta;
---
> {
> int time_update;
> struct timeval newtime = time;
> long ltemp;
>
> if (timedelta == 0) {
> time_update = tick;
> } else {
> if (timedelta < 0) {
> time_update = tick - tickdelta;
> timedelta += tickdelta;
> } else {
> time_update = 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.
> *
> * With SHIFT_SCALE = 23, the maximum frequency adjustment is
> * +-256 us per tick, or 25.6 ms/s at a clock frequency of 100
> * Hz. The time contribution is shifted right a minimum of two
> * bits, while the frequency contribution is a right shift.
> * Thus, overflow is prevented if the frequency contribution is
> * limited to half the maximum or 15.625 ms/s.
> */
> if (newtime.tv_usec >= 1000000) {
> newtime.tv_usec -= 1000000;
> newtime.tv_sec++;
> time_maxerror += time_tolerance >> SHIFT_USEC;
> if (time_offset < 0) {
> ltemp = -time_offset >>
> (SHIFT_KG + time_constant);
> time_offset += ltemp;
> time_adj = -ltemp <<
> (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
> } else {
> ltemp = time_offset >>
> (SHIFT_KG + time_constant);
> time_offset -= ltemp;
> time_adj = ltemp <<
> (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
> }
> #ifdef PPS_SYNC
> /*
> * Gnaw on the watchdog counter and update the frequency
> * computed by the pll and the PPS signal.
> */
> 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);
>
> /*
> * 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;
> }
>
> /* 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;
>
> case TIME_OOP:
> time_state = TIME_WAIT;
> break;
>
> case TIME_WAIT:
> if (!(time_status & (STA_INS | STA_DEL)))
> time_state = TIME_OK;
> }
> }
> CPU_CLOCKUPDATE(&time, &newtime);
220,221d618
< BUMPTIME(&time, delta);
< BUMPTIME(&mono_time, delta);
565a963,1130
>
> /*#ifdef PPS_SYNC*/
> #if 0
> /* This code is completely bogus; if anybody ever wants to use it, get
> * the current version from Dave Mills. */
>
> /*
> * 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 integrates successive
> * phase differences between the two oscillators 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 designated PPS signal transition.
> */
> void
> hardpps(tvp, usec)
> struct timeval *tvp; /* time at PPS */
> long usec; /* hardware counter at PPS */
> {
> long u_usec, v_usec, bigtick;
> long cal_sec, cal_usec;
>
> /*
> * 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 -= ntp_pll.ybar;
> 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;
> ntp_pll.calcnt++;
> u_usec = 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 >> ntp_pll.shift);
> else
> v_usec = v_usec >> ntp_pll.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 > ntp_pll.tolerance || v_usec < -ntp_pll.tolerance) {
> ntp_pll.jitcnt++;
> ntp_pll.shift = NTP_PLL.SHIFT;
> pps_dispinc = PPS_DISPINC;
> ntp_pll.intcnt = 0;
> return;
> }
>
> /*
> * A three-stage median filter is used to help deglitch the pps
> * signal. The median sample becomes the offset estimate; the
> * difference between the other two samples becomes the
> * dispersion estimate.
> */
> pps_mf[2] = pps_mf[1];
> pps_mf[1] = pps_mf[0];
> pps_mf[0] = v_usec;
> if (pps_mf[0] > pps_mf[1]) {
> if (pps_mf[1] > pps_mf[2]) {
> u_usec = pps_mf[1]; /* 0 1 2 */
> v_usec = pps_mf[0] - pps_mf[2];
> } else if (pps_mf[2] > pps_mf[0]) {
> u_usec = pps_mf[0]; /* 2 0 1 */
> v_usec = pps_mf[2] - pps_mf[1];
> } else {
> u_usec = pps_mf[2]; /* 0 2 1 */
> v_usec = pps_mf[0] - pps_mf[1];
> }
> } else {
> if (pps_mf[1] < pps_mf[2]) {
> u_usec = pps_mf[1]; /* 2 1 0 */
> v_usec = pps_mf[2] - pps_mf[0];
> } else if (pps_mf[2] < pps_mf[0]) {
> u_usec = pps_mf[0]; /* 1 0 2 */
> v_usec = pps_mf[1] - pps_mf[2];
> } else {
> u_usec = pps_mf[2]; /* 1 2 0 */
> v_usec = pps_mf[1] - pps_mf[0];
> }
> }
>
> /*
> * Here the dispersion average is updated. If it is less than
> * the threshold pps_dispmax, the frequency average is updated
> * as well, but clamped to the tolerance.
> */
> v_usec = (v_usec >> 1) - ntp_pll.disp;
> if (v_usec < 0)
> ntp_pll.disp -= -v_usec >> PPS_AVG;
> else
> ntp_pll.disp += v_usec >> PPS_AVG;
> if (ntp_pll.disp > pps_dispmax) {
> ntp_pll.discnt++;
> return;
> }
> if (u_usec < 0) {
> ntp_pll.ybar -= -u_usec >> PPS_AVG;
> if (ntp_pll.ybar < -ntp_pll.tolerance)
> ntp_pll.ybar = -ntp_pll.tolerance;
> u_usec = -u_usec;
> } else {
> ntp_pll.ybar += u_usec >> PPS_AVG;
> if (ntp_pll.ybar > ntp_pll.tolerance)
> ntp_pll.ybar = ntp_pll.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 << ntp_pll.shift > bigtick >> 2) {
> ntp_pll.intcnt = 0;
> if (ntp_pll.shift > NTP_PLL.SHIFT) {
> ntp_pll.shift--;
> pps_dispinc <<= 1;
> }
> } else if (ntp_pll.intcnt >= 4) {
> ntp_pll.intcnt = 0;
> if (ntp_pll.shift < NTP_PLL.SHIFTMAX) {
> ntp_pll.shift++;
> pps_dispinc >>= 1;
> }
> } else
> ntp_pll.intcnt++;
> }
> #endif /* PPS_SYNC */
< * $Id: kern_clock.c,v 1.4 1994/08/18 22:34:58 wollman Exp $
---
> * $Id: kern_clock.c,v 1.5 1994/08/27 16:14:26 davidg Exp $
41a42,58
> /* 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. *
> * *
> *****************************************************************************/
>
48a66
> #include <sys/timex.h>
51a70
> #include <machine/clock.h>
130a150,381
> * Phase-lock loop (PLL) 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 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 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 at each timer interrupt.
> *
> * 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.
> */
> long time_phase = 0; /* phase offset (scaled us) */
> long time_freq = 0; /* frequency offset (scaled ppm) */
> long time_adj = 0; /* tick adjust (scaled 1 / hz) */
> long time_reftime = 0; /* time at last adjustment (s) */
>
> #ifdef PPS_SYNC
> /*
> * The following variables are used only if the 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_offset is the time offset produced by the time median filter
> * pps_tf[], while pps_jitter is the dispersion measured by this
> * filter.
> *
> * pps_freq is the frequency offset produced by the frequency median
> * filter pps_ff[], while pps_stabil is the dispersion 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_count counts the seconds of the calibration interval, the
> * duration of which is pps_shift in powers of two.
> *
> * 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 */
> #ifdef EXT_CLOCK
> /*
> * External clock definitions
> *
> * The following definitions and declarations are used only if an
> * external clock (HIGHBALL or TPRO) is configured on the system.
> */
> #define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */
>
> /*
> * The clock_count variable is set to CLOCK_INTERVAL at each PPS
> * interrupt and decremented once each second.
> */
> int clock_count = 0; /* CPU clock counter */
>
> #ifdef HIGHBALL
> /*
> * The clock_offset and clock_cpu variables are used by the HIGHBALL
> * interface. The clock_offset variable defines the offset between
> * system time and the HIGBALL counters. The clock_cpu variable contains
> * the offset between the system clock and the HIGHBALL clock for use in
> * disciplining the kernel time variable.
> */
> extern struct timeval clock_offset; /* Highball clock offset */
> long clock_cpu = 0; /* CPU clock adjust */
> #endif /* HIGHBALL */
> #endif /* EXT_CLOCK */
>
> /*
> * hardupdate() - local clock update
> *
> * This routine is called by ntp_adjtime() to update the local clock
> * phase and frequency. This is used to implement an adaptive-parameter,
> * first-order, type-II phase-lock loop. The code computes new time and
> * frequency offsets each time it is called. The hardclock() routine
> * amortizes these offsets at each tick interrupt. 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 default SHIFT_UPDATE = 12, the offset is limited to +-512 ms, the
> * maximum interval between updates is 4096 s and the maximum frequency
> * offset is +-31.25 ms/s.
> *
> * 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 */
> if (ltemp > MAXPHASE)
> time_offset = MAXPHASE << SHIFT_UPDATE;
> else if (ltemp < -MAXPHASE)
> time_offset = -(MAXPHASE << SHIFT_UPDATE);
> else
> time_offset = ltemp << SHIFT_UPDATE;
> mtemp = time.tv_sec - time_reftime;
> time_reftime = time.tv_sec;
> if (mtemp > MAXSEC)
> mtemp = 0;
>
> /* ugly multiply should be replaced */
> if (ltemp < 0)
> time_freq -= (-ltemp * mtemp) >> (time_constant +
> time_constant + SHIFT_KF - SHIFT_USEC);
> else
> time_freq += (ltemp * mtemp) >> (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;
> }
>
>
>
> /*
210,211c461
< * Increment the time-of-day. The increment is just ``tick'' unless
< * we are still adjusting the clock; see adjtime().
---
> * Increment the time-of-day.
214,218c464,617
< if (timedelta == 0)
< delta = tick;
< else {
< delta = tick + tickdelta;
< timedelta -= tickdelta;
---
> {
> int time_update;
> struct timeval newtime = time;
> long ltemp;
>
> if (timedelta == 0) {
> time_update = tick;
> } else {
> if (timedelta < 0) {
> time_update = tick - tickdelta;
> timedelta += tickdelta;
> } else {
> time_update = 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.
> *
> * With SHIFT_SCALE = 23, the maximum frequency adjustment is
> * +-256 us per tick, or 25.6 ms/s at a clock frequency of 100
> * Hz. The time contribution is shifted right a minimum of two
> * bits, while the frequency contribution is a right shift.
> * Thus, overflow is prevented if the frequency contribution is
> * limited to half the maximum or 15.625 ms/s.
> */
> if (newtime.tv_usec >= 1000000) {
> newtime.tv_usec -= 1000000;
> newtime.tv_sec++;
> time_maxerror += time_tolerance >> SHIFT_USEC;
> if (time_offset < 0) {
> ltemp = -time_offset >>
> (SHIFT_KG + time_constant);
> time_offset += ltemp;
> time_adj = -ltemp <<
> (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
> } else {
> ltemp = time_offset >>
> (SHIFT_KG + time_constant);
> time_offset -= ltemp;
> time_adj = ltemp <<
> (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
> }
> #ifdef PPS_SYNC
> /*
> * Gnaw on the watchdog counter and update the frequency
> * computed by the pll and the PPS signal.
> */
> 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);
>
> /*
> * 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;
> }
>
> /* 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;
>
> case TIME_OOP:
> time_state = TIME_WAIT;
> break;
>
> case TIME_WAIT:
> if (!(time_status & (STA_INS | STA_DEL)))
> time_state = TIME_OK;
> }
> }
> CPU_CLOCKUPDATE(&time, &newtime);
220,221d618
< BUMPTIME(&time, delta);
< BUMPTIME(&mono_time, delta);
565a963,1130
>
> /*#ifdef PPS_SYNC*/
> #if 0
> /* This code is completely bogus; if anybody ever wants to use it, get
> * the current version from Dave Mills. */
>
> /*
> * 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 integrates successive
> * phase differences between the two oscillators 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 designated PPS signal transition.
> */
> void
> hardpps(tvp, usec)
> struct timeval *tvp; /* time at PPS */
> long usec; /* hardware counter at PPS */
> {
> long u_usec, v_usec, bigtick;
> long cal_sec, cal_usec;
>
> /*
> * 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 -= ntp_pll.ybar;
> 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;
> ntp_pll.calcnt++;
> u_usec = 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 >> ntp_pll.shift);
> else
> v_usec = v_usec >> ntp_pll.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 > ntp_pll.tolerance || v_usec < -ntp_pll.tolerance) {
> ntp_pll.jitcnt++;
> ntp_pll.shift = NTP_PLL.SHIFT;
> pps_dispinc = PPS_DISPINC;
> ntp_pll.intcnt = 0;
> return;
> }
>
> /*
> * A three-stage median filter is used to help deglitch the pps
> * signal. The median sample becomes the offset estimate; the
> * difference between the other two samples becomes the
> * dispersion estimate.
> */
> pps_mf[2] = pps_mf[1];
> pps_mf[1] = pps_mf[0];
> pps_mf[0] = v_usec;
> if (pps_mf[0] > pps_mf[1]) {
> if (pps_mf[1] > pps_mf[2]) {
> u_usec = pps_mf[1]; /* 0 1 2 */
> v_usec = pps_mf[0] - pps_mf[2];
> } else if (pps_mf[2] > pps_mf[0]) {
> u_usec = pps_mf[0]; /* 2 0 1 */
> v_usec = pps_mf[2] - pps_mf[1];
> } else {
> u_usec = pps_mf[2]; /* 0 2 1 */
> v_usec = pps_mf[0] - pps_mf[1];
> }
> } else {
> if (pps_mf[1] < pps_mf[2]) {
> u_usec = pps_mf[1]; /* 2 1 0 */
> v_usec = pps_mf[2] - pps_mf[0];
> } else if (pps_mf[2] < pps_mf[0]) {
> u_usec = pps_mf[0]; /* 1 0 2 */
> v_usec = pps_mf[1] - pps_mf[2];
> } else {
> u_usec = pps_mf[2]; /* 1 2 0 */
> v_usec = pps_mf[1] - pps_mf[0];
> }
> }
>
> /*
> * Here the dispersion average is updated. If it is less than
> * the threshold pps_dispmax, the frequency average is updated
> * as well, but clamped to the tolerance.
> */
> v_usec = (v_usec >> 1) - ntp_pll.disp;
> if (v_usec < 0)
> ntp_pll.disp -= -v_usec >> PPS_AVG;
> else
> ntp_pll.disp += v_usec >> PPS_AVG;
> if (ntp_pll.disp > pps_dispmax) {
> ntp_pll.discnt++;
> return;
> }
> if (u_usec < 0) {
> ntp_pll.ybar -= -u_usec >> PPS_AVG;
> if (ntp_pll.ybar < -ntp_pll.tolerance)
> ntp_pll.ybar = -ntp_pll.tolerance;
> u_usec = -u_usec;
> } else {
> ntp_pll.ybar += u_usec >> PPS_AVG;
> if (ntp_pll.ybar > ntp_pll.tolerance)
> ntp_pll.ybar = ntp_pll.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 << ntp_pll.shift > bigtick >> 2) {
> ntp_pll.intcnt = 0;
> if (ntp_pll.shift > NTP_PLL.SHIFT) {
> ntp_pll.shift--;
> pps_dispinc <<= 1;
> }
> } else if (ntp_pll.intcnt >= 4) {
> ntp_pll.intcnt = 0;
> if (ntp_pll.shift < NTP_PLL.SHIFTMAX) {
> ntp_pll.shift++;
> pps_dispinc >>= 1;
> }
> } else
> ntp_pll.intcnt++;
> }
> #endif /* PPS_SYNC */