2 ***********************************************************************
4 * Copyright (c) David L. Mills 1993-2001 *
6 * Permission to use, copy, modify, and distribute this software and *
7 * its documentation for any purpose and without fee is hereby *
8 * granted, provided that the above copyright notice appears in all *
9 * copies and that both the copyright notice and this permission *
10 * notice appear in supporting documentation, and that the name *
11 * University of Delaware not be used in advertising or publicity *
12 * pertaining to distribution of the software without specific, *
13 * written prior permission. The University of Delaware makes no *
14 * representations about the suitability this software for any *
15 * purpose. It is provided "as is" without express or implied *
18 **********************************************************************/
21 * Adapted from the original sources for FreeBSD and timecounters by:
22 * Poul-Henning Kamp <phk@FreeBSD.org>.
24 * The 32bit version of the "LP" macros seems a bit past its "sell by"
25 * date so I have retained only the 64bit version and included it directly
28 * Only minor changes done to interface with the timecounters over in
29 * sys/kern/kern_clock.c. Some of the comments below may be (even more)
30 * confusing and/or plain wrong in that context.
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/sysproto.h>
41 #include <sys/eventhandler.h>
42 #include <sys/kernel.h>
46 #include <sys/mutex.h>
48 #include <sys/timex.h>
49 #include <sys/timetc.h>
50 #include <sys/timepps.h>
51 #include <sys/syscallsubr.h>
52 #include <sys/sysctl.h>
55 FEATURE(pps_sync, "Support usage of external PPS signal by kernel PLL");
59 * Single-precision macros for 64-bit machines
62 #define L_ADD(v, u) ((v) += (u))
63 #define L_SUB(v, u) ((v) -= (u))
64 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
65 #define L_NEG(v) ((v) = -(v))
66 #define L_RSHIFT(v, n) \
69 (v) = -(-(v) >> (n)); \
73 #define L_MPY(v, a) ((v) *= (a))
74 #define L_CLR(v) ((v) = 0)
75 #define L_ISNEG(v) ((v) < 0)
76 #define L_LINT(v, a) \
79 ((v) = -((int64_t)(-(a)) << 32)); \
81 ((v) = (int64_t)(a) << 32); \
83 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
86 * Generic NTP kernel interface
88 * These routines constitute the Network Time Protocol (NTP) interfaces
89 * for user and daemon application programs. The ntp_gettime() routine
90 * provides the time, maximum error (synch distance) and estimated error
91 * (dispersion) to client user application programs. The ntp_adjtime()
92 * routine is used by the NTP daemon to adjust the system clock to an
93 * externally derived time. The time offset and related variables set by
94 * this routine are used by other routines in this module to adjust the
95 * phase and frequency of the clock discipline loop which controls the
98 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
99 * defined), the time at each tick interrupt is derived directly from
100 * the kernel time variable. When the kernel time is reckoned in
101 * microseconds, (NTP_NANO undefined), the time is derived from the
102 * kernel time variable together with a variable representing the
103 * leftover nanoseconds at the last tick interrupt. In either case, the
104 * current nanosecond time is reckoned from these values plus an
105 * interpolated value derived by the clock routines in another
106 * architecture-specific module. The interpolation can use either a
107 * dedicated counter or a processor cycle counter (PCC) implemented in
108 * some architectures.
110 * Note that all routines must run at priority splclock or higher.
113 * Phase/frequency-lock loop (PLL/FLL) definitions
115 * The nanosecond clock discipline uses two variable types, time
116 * variables and frequency variables. Both types are represented as 64-
117 * bit fixed-point quantities with the decimal point between two 32-bit
118 * halves. On a 32-bit machine, each half is represented as a single
119 * word and mathematical operations are done using multiple-precision
120 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
123 * A time variable is a signed 64-bit fixed-point number in ns and
124 * fraction. It represents the remaining time offset to be amortized
125 * over succeeding tick interrupts. The maximum time offset is about
126 * 0.5 s and the resolution is about 2.3e-10 ns.
128 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
129 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
136 * A frequency variable is a signed 64-bit fixed-point number in ns/s
137 * and fraction. It represents the ns and fraction to be added to the
138 * kernel time variable at each second. The maximum frequency offset is
139 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
141 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
142 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
143 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
144 * |s s s s s s s s s s s s s| ns/s |
145 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
147 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
150 * The following variables establish the state of the PLL/FLL and the
151 * residual time and frequency offset of the local clock.
153 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
154 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
156 static int time_state = TIME_OK; /* clock state */
157 int time_status = STA_UNSYNC; /* clock status bits */
158 static long time_tai; /* TAI offset (s) */
159 static long time_monitor; /* last time offset scaled (ns) */
160 static long time_constant; /* poll interval (shift) (s) */
161 static long time_precision = 1; /* clock precision (ns) */
162 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
163 long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
164 static long time_reftime; /* uptime at last adjustment (s) */
165 static l_fp time_offset; /* time offset (ns) */
166 static l_fp time_freq; /* frequency offset (ns/s) */
167 static l_fp time_adj; /* tick adjust (ns/s) */
169 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
171 static struct mtx ntp_lock;
172 MTX_SYSINIT(ntp, &ntp_lock, "ntp", MTX_SPIN);
174 #define NTP_LOCK() mtx_lock_spin(&ntp_lock)
175 #define NTP_UNLOCK() mtx_unlock_spin(&ntp_lock)
176 #define NTP_ASSERT_LOCKED() mtx_assert(&ntp_lock, MA_OWNED)
180 * The following variables are used when a pulse-per-second (PPS) signal
181 * is available and connected via a modem control lead. They establish
182 * the engineering parameters of the clock discipline loop when
183 * controlled by the PPS signal.
185 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
186 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
187 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
188 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
189 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
190 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
191 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
193 static struct timespec pps_tf[3]; /* phase median filter */
194 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
195 static long pps_fcount; /* frequency accumulator */
196 static long pps_jitter; /* nominal jitter (ns) */
197 static long pps_stabil; /* nominal stability (scaled ns/s) */
198 static long pps_lastsec; /* time at last calibration (s) */
199 static int pps_valid; /* signal watchdog counter */
200 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
201 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
202 static int pps_intcnt; /* wander counter */
205 * PPS signal quality monitors
207 static long pps_calcnt; /* calibration intervals */
208 static long pps_jitcnt; /* jitter limit exceeded */
209 static long pps_stbcnt; /* stability limit exceeded */
210 static long pps_errcnt; /* calibration errors */
211 #endif /* PPS_SYNC */
213 * End of phase/frequency-lock loop (PLL/FLL) definitions
216 static void hardupdate(long offset);
217 static void ntp_gettime1(struct ntptimeval *ntvp);
218 static bool ntp_is_time_error(int tsl);
221 ntp_is_time_error(int tsl)
225 * Status word error decode. If any of these conditions occur,
226 * an error is returned, instead of the status word. Most
227 * applications will care only about the fact the system clock
228 * may not be trusted, not about the details.
230 * Hardware or software error
232 if ((tsl & (STA_UNSYNC | STA_CLOCKERR)) ||
235 * PPS signal lost when either time or frequency synchronization
238 (tsl & (STA_PPSFREQ | STA_PPSTIME) &&
239 !(tsl & STA_PPSSIGNAL)) ||
242 * PPS jitter exceeded when time synchronization requested
244 (tsl & STA_PPSTIME && tsl & STA_PPSJITTER) ||
247 * PPS wander exceeded or calibration error when frequency
248 * synchronization requested
250 (tsl & STA_PPSFREQ &&
251 tsl & (STA_PPSWANDER | STA_PPSERROR)))
258 ntp_gettime1(struct ntptimeval *ntvp)
260 struct timespec atv; /* nanosecond time */
265 ntvp->time.tv_sec = atv.tv_sec;
266 ntvp->time.tv_nsec = atv.tv_nsec;
267 ntvp->maxerror = time_maxerror;
268 ntvp->esterror = time_esterror;
269 ntvp->tai = time_tai;
270 ntvp->time_state = time_state;
272 if (ntp_is_time_error(time_status))
273 ntvp->time_state = TIME_ERROR;
277 * ntp_gettime() - NTP user application interface
279 * See the timex.h header file for synopsis and API description. Note that
280 * the TAI offset is returned in the ntvtimeval.tai structure member.
282 #ifndef _SYS_SYSPROTO_H_
283 struct ntp_gettime_args {
284 struct ntptimeval *ntvp;
289 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
291 struct ntptimeval ntv;
293 memset(&ntv, 0, sizeof(ntv));
299 td->td_retval[0] = ntv.time_state;
300 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
304 ntp_sysctl(SYSCTL_HANDLER_ARGS)
306 struct ntptimeval ntv; /* temporary structure */
308 memset(&ntv, 0, sizeof(ntv));
314 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
317 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
319 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE | CTLFLAG_RD |
320 CTLFLAG_MPSAFE, 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval",
324 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW,
325 &pps_shiftmax, 0, "Max interval duration (sec) (shift)");
326 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW,
327 &pps_shift, 0, "Interval duration (sec) (shift)");
328 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD,
329 &time_monitor, 0, "Last time offset scaled (ns)");
331 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
333 "Scaled frequency offset (ns/sec)");
334 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
336 "Frequency offset (ns/sec)");
340 * ntp_adjtime() - NTP daemon application interface
342 * See the timex.h header file for synopsis and API description. Note that
343 * the timex.constant structure member has a dual purpose to set the time
344 * constant and to set the TAI offset.
347 kern_ntp_adjtime(struct thread *td, struct timex *ntv, int *retvalp)
349 long freq; /* frequency ns/s) */
350 int modes; /* mode bits from structure */
354 * Update selected clock variables - only the superuser can
355 * change anything. Note that there is no error checking here on
356 * the assumption the superuser should know what it is doing.
357 * Note that either the time constant or TAI offset are loaded
358 * from the ntv.constant member, depending on the mode bits. If
359 * the STA_PLL bit in the status word is cleared, the state and
360 * status words are reset to the initial values at boot.
365 error = priv_check(td, PRIV_NTP_ADJTIME);
369 if (modes & MOD_MAXERROR)
370 time_maxerror = ntv->maxerror;
371 if (modes & MOD_ESTERROR)
372 time_esterror = ntv->esterror;
373 if (modes & MOD_STATUS) {
374 if (time_status & STA_PLL && !(ntv->status & STA_PLL)) {
375 time_state = TIME_OK;
376 time_status = STA_UNSYNC;
378 pps_shift = PPS_FAVG;
379 #endif /* PPS_SYNC */
381 time_status &= STA_RONLY;
382 time_status |= ntv->status & ~STA_RONLY;
384 if (modes & MOD_TIMECONST) {
385 if (ntv->constant < 0)
387 else if (ntv->constant > MAXTC)
388 time_constant = MAXTC;
390 time_constant = ntv->constant;
392 if (modes & MOD_TAI) {
393 if (ntv->constant > 0) /* XXX zero & negative numbers ? */
394 time_tai = ntv->constant;
397 if (modes & MOD_PPSMAX) {
398 if (ntv->shift < PPS_FAVG)
399 pps_shiftmax = PPS_FAVG;
400 else if (ntv->shift > PPS_FAVGMAX)
401 pps_shiftmax = PPS_FAVGMAX;
403 pps_shiftmax = ntv->shift;
405 #endif /* PPS_SYNC */
406 if (modes & MOD_NANO)
407 time_status |= STA_NANO;
408 if (modes & MOD_MICRO)
409 time_status &= ~STA_NANO;
410 if (modes & MOD_CLKB)
411 time_status |= STA_CLK;
412 if (modes & MOD_CLKA)
413 time_status &= ~STA_CLK;
414 if (modes & MOD_FREQUENCY) {
415 freq = (ntv->freq * 1000LL) >> 16;
417 L_LINT(time_freq, MAXFREQ);
418 else if (freq < -MAXFREQ)
419 L_LINT(time_freq, -MAXFREQ);
422 * ntv->freq is [PPM * 2^16] = [us/s * 2^16]
423 * time_freq is [ns/s * 2^32]
425 time_freq = ntv->freq * 1000LL * 65536LL;
428 pps_freq = time_freq;
429 #endif /* PPS_SYNC */
431 if (modes & MOD_OFFSET) {
432 if (time_status & STA_NANO)
433 hardupdate(ntv->offset);
435 hardupdate(ntv->offset * 1000);
439 * Retrieve all clock variables. Note that the TAI offset is
440 * returned only by ntp_gettime();
442 if (time_status & STA_NANO)
443 ntv->offset = L_GINT(time_offset);
445 ntv->offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
446 ntv->freq = L_GINT((time_freq / 1000LL) << 16);
447 ntv->maxerror = time_maxerror;
448 ntv->esterror = time_esterror;
449 ntv->status = time_status;
450 ntv->constant = time_constant;
451 if (time_status & STA_NANO)
452 ntv->precision = time_precision;
454 ntv->precision = time_precision / 1000;
455 ntv->tolerance = MAXFREQ * SCALE_PPM;
457 ntv->shift = pps_shift;
458 ntv->ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
459 if (time_status & STA_NANO)
460 ntv->jitter = pps_jitter;
462 ntv->jitter = pps_jitter / 1000;
463 ntv->stabil = pps_stabil;
464 ntv->calcnt = pps_calcnt;
465 ntv->errcnt = pps_errcnt;
466 ntv->jitcnt = pps_jitcnt;
467 ntv->stbcnt = pps_stbcnt;
468 #endif /* PPS_SYNC */
469 retval = ntp_is_time_error(time_status) ? TIME_ERROR : time_state;
476 #ifndef _SYS_SYSPROTO_H_
477 struct ntp_adjtime_args {
483 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
488 error = copyin(uap->tp, &ntv, sizeof(ntv));
490 error = kern_ntp_adjtime(td, &ntv, &retval);
492 error = copyout(&ntv, uap->tp, sizeof(ntv));
494 td->td_retval[0] = retval;
501 * second_overflow() - called after ntp_tick_adjust()
503 * This routine is ordinarily called immediately following the above
504 * routine ntp_tick_adjust(). While these two routines are normally
505 * combined, they are separated here only for the purposes of
509 ntp_update_second(int64_t *adjustment, time_t *newsec)
512 l_fp ftemp; /* 32/64-bit temporary */
517 * On rollover of the second both the nanosecond and microsecond
518 * clocks are updated and the state machine cranked as
519 * necessary. The phase adjustment to be used for the next
520 * second is calculated and the maximum error is increased by
523 time_maxerror += MAXFREQ / 1000;
526 * Leap second processing. If in leap-insert state at
527 * the end of the day, the system clock is set back one
528 * second; if in leap-delete state, the system clock is
529 * set ahead one second. The nano_time() routine or
530 * external clock driver will insure that reported time
531 * is always monotonic.
533 switch (time_state) {
538 if (time_status & STA_INS)
539 time_state = TIME_INS;
540 else if (time_status & STA_DEL)
541 time_state = TIME_DEL;
545 * Insert second 23:59:60 following second
549 if (!(time_status & STA_INS))
550 time_state = TIME_OK;
551 else if ((*newsec) % 86400 == 0) {
553 time_state = TIME_OOP;
559 * Delete second 23:59:59.
562 if (!(time_status & STA_DEL))
563 time_state = TIME_OK;
564 else if (((*newsec) + 1) % 86400 == 0) {
567 time_state = TIME_WAIT;
572 * Insert second in progress.
575 time_state = TIME_WAIT;
579 * Wait for status bits to clear.
582 if (!(time_status & (STA_INS | STA_DEL)))
583 time_state = TIME_OK;
587 * Compute the total time adjustment for the next second
588 * in ns. The offset is reduced by a factor depending on
589 * whether the PPS signal is operating. Note that the
590 * value is in effect scaled by the clock frequency,
591 * since the adjustment is added at each tick interrupt.
595 /* XXX even if PPS signal dies we should finish adjustment ? */
596 if (time_status & STA_PPSTIME && time_status &
598 L_RSHIFT(ftemp, pps_shift);
600 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
602 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
603 #endif /* PPS_SYNC */
605 L_SUB(time_offset, ftemp);
606 L_ADD(time_adj, time_freq);
609 * Apply any correction from adjtime(2). If more than one second
610 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500 PPM)
611 * until the last second is slewed the final < 500 usecs.
613 if (time_adjtime != 0) {
614 if (time_adjtime > 1000000)
616 else if (time_adjtime < -1000000)
618 else if (time_adjtime > 500)
620 else if (time_adjtime < -500)
623 tickrate = time_adjtime;
624 time_adjtime -= tickrate;
625 L_LINT(ftemp, tickrate * 1000);
626 L_ADD(time_adj, ftemp);
628 *adjustment = time_adj;
634 time_status &= ~STA_PPSSIGNAL;
635 #endif /* PPS_SYNC */
641 * hardupdate() - local clock update
643 * This routine is called by ntp_adjtime() to update the local clock
644 * phase and frequency. The implementation is of an adaptive-parameter,
645 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
646 * time and frequency offset estimates for each call. If the kernel PPS
647 * discipline code is configured (PPS_SYNC), the PPS signal itself
648 * determines the new time offset, instead of the calling argument.
649 * Presumably, calls to ntp_adjtime() occur only when the caller
650 * believes the local clock is valid within some bound (+-128 ms with
651 * NTP). If the caller's time is far different than the PPS time, an
652 * argument will ensue, and it's not clear who will lose.
654 * For uncompensated quartz crystal oscillators and nominal update
655 * intervals less than 256 s, operation should be in phase-lock mode,
656 * where the loop is disciplined to phase. For update intervals greater
657 * than 1024 s, operation should be in frequency-lock mode, where the
658 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
659 * is selected by the STA_MODE status bit.
662 hardupdate(long offset /* clock offset (ns) */)
670 * Select how the phase is to be controlled and from which
671 * source. If the PPS signal is present and enabled to
672 * discipline the time, the PPS offset is used; otherwise, the
673 * argument offset is used.
675 if (!(time_status & STA_PLL))
677 if (!(time_status & STA_PPSTIME && time_status &
679 if (offset > MAXPHASE)
680 time_monitor = MAXPHASE;
681 else if (offset < -MAXPHASE)
682 time_monitor = -MAXPHASE;
684 time_monitor = offset;
685 L_LINT(time_offset, time_monitor);
689 * Select how the frequency is to be controlled and in which
690 * mode (PLL or FLL). If the PPS signal is present and enabled
691 * to discipline the frequency, the PPS frequency is used;
692 * otherwise, the argument offset is used to compute it.
694 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
695 time_reftime = time_uptime;
698 if (time_status & STA_FREQHOLD || time_reftime == 0)
699 time_reftime = time_uptime;
700 mtemp = time_uptime - time_reftime;
701 L_LINT(ftemp, time_monitor);
702 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
704 L_ADD(time_freq, ftemp);
705 time_status &= ~STA_MODE;
706 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
708 L_LINT(ftemp, (time_monitor << 4) / mtemp);
709 L_RSHIFT(ftemp, SHIFT_FLL + 4);
710 L_ADD(time_freq, ftemp);
711 time_status |= STA_MODE;
713 time_reftime = time_uptime;
714 if (L_GINT(time_freq) > MAXFREQ)
715 L_LINT(time_freq, MAXFREQ);
716 else if (L_GINT(time_freq) < -MAXFREQ)
717 L_LINT(time_freq, -MAXFREQ);
722 * hardpps() - discipline CPU clock oscillator to external PPS signal
724 * This routine is called at each PPS interrupt in order to discipline
725 * the CPU clock oscillator to the PPS signal. There are two independent
726 * first-order feedback loops, one for the phase, the other for the
727 * frequency. The phase loop measures and grooms the PPS phase offset
728 * and leaves it in a handy spot for the seconds overflow routine. The
729 * frequency loop averages successive PPS phase differences and
730 * calculates the PPS frequency offset, which is also processed by the
731 * seconds overflow routine. The code requires the caller to capture the
732 * time and architecture-dependent hardware counter values in
733 * nanoseconds at the on-time PPS signal transition.
735 * Note that, on some Unix systems this routine runs at an interrupt
736 * priority level higher than the timer interrupt routine hardclock().
737 * Therefore, the variables used are distinct from the hardclock()
738 * variables, except for the actual time and frequency variables, which
739 * are determined by this routine and updated atomically.
741 * tsp - time at current PPS event
742 * delta_nsec - time elapsed between the previous and current PPS event
745 hardpps(struct timespec *tsp, long delta_nsec)
747 long u_sec, u_nsec, v_nsec; /* temps */
753 * The signal is first processed by a range gate and frequency
754 * discriminator. The range gate rejects noise spikes outside
755 * the range +-500 us. The frequency discriminator rejects input
756 * signals with apparent frequency outside the range 1 +-500
757 * PPM. If two hits occur in the same second, we ignore the
758 * later hit; if not and a hit occurs outside the range gate,
759 * keep the later hit for later comparison, but do not process
762 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
763 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
764 pps_valid = PPS_VALID;
766 u_nsec = tsp->tv_nsec;
767 if (u_nsec >= (NANOSECOND >> 1)) {
768 u_nsec -= NANOSECOND;
771 v_nsec = u_nsec - pps_tf[0].tv_nsec;
772 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - MAXFREQ)
774 pps_tf[2] = pps_tf[1];
775 pps_tf[1] = pps_tf[0];
776 pps_tf[0].tv_sec = u_sec;
777 pps_tf[0].tv_nsec = u_nsec;
780 * Update the frequency accumulator using the difference between the
781 * current and previous PPS event measured directly by the timecounter.
783 pps_fcount += delta_nsec - NANOSECOND;
784 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
786 time_status &= ~STA_PPSJITTER;
789 * A three-stage median filter is used to help denoise the PPS
790 * time. The median sample becomes the time offset estimate; the
791 * difference between the other two samples becomes the time
792 * dispersion (jitter) estimate.
794 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
795 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
796 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
797 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
798 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
799 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
800 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
802 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
803 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
806 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
807 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
808 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
809 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
810 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
811 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
813 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
814 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
819 * Nominal jitter is due to PPS signal noise and interrupt
820 * latency. If it exceeds the popcorn threshold, the sample is
821 * discarded. otherwise, if so enabled, the time offset is
822 * updated. We can tolerate a modest loss of data here without
823 * much degrading time accuracy.
825 * The measurements being checked here were made with the system
826 * timecounter, so the popcorn threshold is not allowed to fall below
827 * the number of nanoseconds in two ticks of the timecounter. For a
828 * timecounter running faster than 1 GHz the lower bound is 2ns, just
829 * to avoid a nonsensical threshold of zero.
831 if (u_nsec > lmax(pps_jitter << PPS_POPCORN,
832 2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) {
833 time_status |= STA_PPSJITTER;
835 } else if (time_status & STA_PPSTIME) {
836 time_monitor = -v_nsec;
837 L_LINT(time_offset, time_monitor);
839 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
840 u_sec = pps_tf[0].tv_sec - pps_lastsec;
841 if (u_sec < (1 << pps_shift))
845 * At the end of the calibration interval the difference between
846 * the first and last counter values becomes the scaled
847 * frequency. It will later be divided by the length of the
848 * interval to determine the frequency update. If the frequency
849 * exceeds a sanity threshold, or if the actual calibration
850 * interval is not equal to the expected length, the data are
851 * discarded. We can tolerate a modest loss of data here without
852 * much degrading frequency accuracy.
855 v_nsec = -pps_fcount;
856 pps_lastsec = pps_tf[0].tv_sec;
858 u_nsec = MAXFREQ << pps_shift;
859 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << pps_shift)) {
860 time_status |= STA_PPSERROR;
866 * Here the raw frequency offset and wander (stability) is
867 * calculated. If the wander is less than the wander threshold
868 * for four consecutive averaging intervals, the interval is
869 * doubled; if it is greater than the threshold for four
870 * consecutive intervals, the interval is halved. The scaled
871 * frequency offset is converted to frequency offset. The
872 * stability metric is calculated as the average of recent
873 * frequency changes, but is used only for performance
876 L_LINT(ftemp, v_nsec);
877 L_RSHIFT(ftemp, pps_shift);
878 L_SUB(ftemp, pps_freq);
879 u_nsec = L_GINT(ftemp);
880 if (u_nsec > PPS_MAXWANDER) {
881 L_LINT(ftemp, PPS_MAXWANDER);
883 time_status |= STA_PPSWANDER;
885 } else if (u_nsec < -PPS_MAXWANDER) {
886 L_LINT(ftemp, -PPS_MAXWANDER);
888 time_status |= STA_PPSWANDER;
893 if (pps_intcnt >= 4) {
895 if (pps_shift < pps_shiftmax) {
899 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
901 if (pps_shift > PPS_FAVG) {
908 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
911 * The PPS frequency is recalculated and clamped to the maximum
912 * MAXFREQ. If enabled, the system clock frequency is updated as
915 L_ADD(pps_freq, ftemp);
916 u_nsec = L_GINT(pps_freq);
917 if (u_nsec > MAXFREQ)
918 L_LINT(pps_freq, MAXFREQ);
919 else if (u_nsec < -MAXFREQ)
920 L_LINT(pps_freq, -MAXFREQ);
921 if (time_status & STA_PPSFREQ)
922 time_freq = pps_freq;
927 #endif /* PPS_SYNC */
929 #ifndef _SYS_SYSPROTO_H_
930 struct adjtime_args {
931 struct timeval *delta;
932 struct timeval *olddelta;
937 sys_adjtime(struct thread *td, struct adjtime_args *uap)
939 struct timeval delta, olddelta, *deltap;
943 error = copyin(uap->delta, &delta, sizeof(delta));
949 error = kern_adjtime(td, deltap, &olddelta);
950 if (uap->olddelta && error == 0)
951 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
956 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
963 error = priv_check(td, PRIV_ADJTIME);
966 ltw = (int64_t)delta->tv_sec * 1000000 + delta->tv_usec;
973 if (olddelta != NULL) {
974 atv.tv_sec = ltr / 1000000;
975 atv.tv_usec = ltr % 1000000;
976 if (atv.tv_usec < 0) {
977 atv.tv_usec += 1000000;
985 static struct callout resettodr_callout;
986 static int resettodr_period = 1800;
989 periodic_resettodr(void *arg __unused)
993 * Read of time_status is lock-less, which is fine since
994 * ntp_is_time_error() operates on the consistent read value.
996 if (!ntp_is_time_error(time_status))
998 if (resettodr_period > 0)
999 callout_schedule(&resettodr_callout, resettodr_period * hz);
1003 shutdown_resettodr(void *arg __unused, int howto __unused)
1006 callout_drain(&resettodr_callout);
1007 /* Another unlocked read of time_status */
1008 if (resettodr_period > 0 && !ntp_is_time_error(time_status))
1013 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
1017 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
1018 if (error || !req->newptr)
1022 if (resettodr_period == 0)
1023 callout_stop(&resettodr_callout);
1025 callout_reset(&resettodr_callout, resettodr_period * hz,
1026 periodic_resettodr, NULL);
1031 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT | CTLFLAG_RWTUN |
1032 CTLFLAG_MPSAFE, &resettodr_period, 1800, sysctl_resettodr_period, "I",
1033 "Save system time to RTC with this period (in seconds)");
1036 start_periodic_resettodr(void *arg __unused)
1039 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
1040 SHUTDOWN_PRI_FIRST);
1041 callout_init(&resettodr_callout, 1);
1042 if (resettodr_period == 0)
1044 callout_reset(&resettodr_callout, resettodr_period * hz,
1045 periodic_resettodr, NULL);
1048 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE,
1049 start_periodic_resettodr, NULL);