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 * Single-precision macros for 64-bit machines
58 #define L_ADD(v, u) ((v) += (u))
59 #define L_SUB(v, u) ((v) -= (u))
60 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
61 #define L_NEG(v) ((v) = -(v))
62 #define L_RSHIFT(v, n) \
65 (v) = -(-(v) >> (n)); \
69 #define L_MPY(v, a) ((v) *= (a))
70 #define L_CLR(v) ((v) = 0)
71 #define L_ISNEG(v) ((v) < 0)
72 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32)
73 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
76 * Generic NTP kernel interface
78 * These routines constitute the Network Time Protocol (NTP) interfaces
79 * for user and daemon application programs. The ntp_gettime() routine
80 * provides the time, maximum error (synch distance) and estimated error
81 * (dispersion) to client user application programs. The ntp_adjtime()
82 * routine is used by the NTP daemon to adjust the system clock to an
83 * externally derived time. The time offset and related variables set by
84 * this routine are used by other routines in this module to adjust the
85 * phase and frequency of the clock discipline loop which controls the
88 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
89 * defined), the time at each tick interrupt is derived directly from
90 * the kernel time variable. When the kernel time is reckoned in
91 * microseconds, (NTP_NANO undefined), the time is derived from the
92 * kernel time variable together with a variable representing the
93 * leftover nanoseconds at the last tick interrupt. In either case, the
94 * current nanosecond time is reckoned from these values plus an
95 * interpolated value derived by the clock routines in another
96 * architecture-specific module. The interpolation can use either a
97 * dedicated counter or a processor cycle counter (PCC) implemented in
100 * Note that all routines must run at priority splclock or higher.
103 * Phase/frequency-lock loop (PLL/FLL) definitions
105 * The nanosecond clock discipline uses two variable types, time
106 * variables and frequency variables. Both types are represented as 64-
107 * bit fixed-point quantities with the decimal point between two 32-bit
108 * halves. On a 32-bit machine, each half is represented as a single
109 * word and mathematical operations are done using multiple-precision
110 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
113 * A time variable is a signed 64-bit fixed-point number in ns and
114 * fraction. It represents the remaining time offset to be amortized
115 * over succeeding tick interrupts. The maximum time offset is about
116 * 0.5 s and the resolution is about 2.3e-10 ns.
118 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
119 * 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
120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
122 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
124 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
126 * A frequency variable is a signed 64-bit fixed-point number in ns/s
127 * and fraction. It represents the ns and fraction to be added to the
128 * kernel time variable at each second. The maximum frequency offset is
129 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
131 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
132 * 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
133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
134 * |s s s s s s s s s s s s s| ns/s |
135 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
137 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
140 * The following variables establish the state of the PLL/FLL and the
141 * residual time and frequency offset of the local clock.
143 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
144 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
146 static int time_state = TIME_OK; /* clock state */
147 static int time_status = STA_UNSYNC; /* clock status bits */
148 static long time_tai; /* TAI offset (s) */
149 static long time_monitor; /* last time offset scaled (ns) */
150 static long time_constant; /* poll interval (shift) (s) */
151 static long time_precision = 1; /* clock precision (ns) */
152 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
153 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
154 static long time_reftime; /* time at last adjustment (s) */
155 static l_fp time_offset; /* time offset (ns) */
156 static l_fp time_freq; /* frequency offset (ns/s) */
157 static l_fp time_adj; /* tick adjust (ns/s) */
159 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
163 * The following variables are used when a pulse-per-second (PPS) signal
164 * is available and connected via a modem control lead. They establish
165 * the engineering parameters of the clock discipline loop when
166 * controlled by the PPS signal.
168 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
169 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
170 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
171 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
172 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
173 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
174 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
176 static struct timespec pps_tf[3]; /* phase median filter */
177 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
178 static long pps_fcount; /* frequency accumulator */
179 static long pps_jitter; /* nominal jitter (ns) */
180 static long pps_stabil; /* nominal stability (scaled ns/s) */
181 static long pps_lastsec; /* time at last calibration (s) */
182 static int pps_valid; /* signal watchdog counter */
183 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
184 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
185 static int pps_intcnt; /* wander counter */
188 * PPS signal quality monitors
190 static long pps_calcnt; /* calibration intervals */
191 static long pps_jitcnt; /* jitter limit exceeded */
192 static long pps_stbcnt; /* stability limit exceeded */
193 static long pps_errcnt; /* calibration errors */
194 #endif /* PPS_SYNC */
196 * End of phase/frequency-lock loop (PLL/FLL) definitions
199 static void ntp_init(void);
200 static void hardupdate(long offset);
201 static void ntp_gettime1(struct ntptimeval *ntvp);
202 static int ntp_is_time_error(void);
205 ntp_is_time_error(void)
208 * Status word error decode. If any of these conditions occur,
209 * an error is returned, instead of the status word. Most
210 * applications will care only about the fact the system clock
211 * may not be trusted, not about the details.
213 * Hardware or software error
215 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
218 * PPS signal lost when either time or frequency synchronization
221 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
222 !(time_status & STA_PPSSIGNAL)) ||
225 * PPS jitter exceeded when time synchronization requested
227 (time_status & STA_PPSTIME &&
228 time_status & STA_PPSJITTER) ||
231 * PPS wander exceeded or calibration error when frequency
232 * synchronization requested
234 (time_status & STA_PPSFREQ &&
235 time_status & (STA_PPSWANDER | STA_PPSERROR)))
242 ntp_gettime1(struct ntptimeval *ntvp)
244 struct timespec atv; /* nanosecond time */
249 ntvp->time.tv_sec = atv.tv_sec;
250 ntvp->time.tv_nsec = atv.tv_nsec;
251 ntvp->maxerror = time_maxerror;
252 ntvp->esterror = time_esterror;
253 ntvp->tai = time_tai;
254 ntvp->time_state = time_state;
256 if (ntp_is_time_error())
257 ntvp->time_state = TIME_ERROR;
261 * ntp_gettime() - NTP user application interface
263 * See the timex.h header file for synopsis and API description. Note that
264 * the TAI offset is returned in the ntvtimeval.tai structure member.
266 #ifndef _SYS_SYSPROTO_H_
267 struct ntp_gettime_args {
268 struct ntptimeval *ntvp;
273 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
275 struct ntptimeval ntv;
281 td->td_retval[0] = ntv.time_state;
282 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
286 ntp_sysctl(SYSCTL_HANDLER_ARGS)
288 struct ntptimeval ntv; /* temporary structure */
292 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
295 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
296 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
297 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
300 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
301 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
302 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
304 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
305 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
309 * ntp_adjtime() - NTP daemon application interface
311 * See the timex.h header file for synopsis and API description. Note that
312 * the timex.constant structure member has a dual purpose to set the time
313 * constant and to set the TAI offset.
315 #ifndef _SYS_SYSPROTO_H_
316 struct ntp_adjtime_args {
322 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
324 struct timex ntv; /* temporary structure */
325 long freq; /* frequency ns/s) */
326 int modes; /* mode bits from structure */
327 int s; /* caller priority */
330 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
335 * Update selected clock variables - only the superuser can
336 * change anything. Note that there is no error checking here on
337 * the assumption the superuser should know what it is doing.
338 * Note that either the time constant or TAI offset are loaded
339 * from the ntv.constant member, depending on the mode bits. If
340 * the STA_PLL bit in the status word is cleared, the state and
341 * status words are reset to the initial values at boot.
346 error = priv_check(td, PRIV_NTP_ADJTIME);
350 if (modes & MOD_MAXERROR)
351 time_maxerror = ntv.maxerror;
352 if (modes & MOD_ESTERROR)
353 time_esterror = ntv.esterror;
354 if (modes & MOD_STATUS) {
355 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
356 time_state = TIME_OK;
357 time_status = STA_UNSYNC;
359 pps_shift = PPS_FAVG;
360 #endif /* PPS_SYNC */
362 time_status &= STA_RONLY;
363 time_status |= ntv.status & ~STA_RONLY;
365 if (modes & MOD_TIMECONST) {
366 if (ntv.constant < 0)
368 else if (ntv.constant > MAXTC)
369 time_constant = MAXTC;
371 time_constant = ntv.constant;
373 if (modes & MOD_TAI) {
374 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
375 time_tai = ntv.constant;
378 if (modes & MOD_PPSMAX) {
379 if (ntv.shift < PPS_FAVG)
380 pps_shiftmax = PPS_FAVG;
381 else if (ntv.shift > PPS_FAVGMAX)
382 pps_shiftmax = PPS_FAVGMAX;
384 pps_shiftmax = ntv.shift;
386 #endif /* PPS_SYNC */
387 if (modes & MOD_NANO)
388 time_status |= STA_NANO;
389 if (modes & MOD_MICRO)
390 time_status &= ~STA_NANO;
391 if (modes & MOD_CLKB)
392 time_status |= STA_CLK;
393 if (modes & MOD_CLKA)
394 time_status &= ~STA_CLK;
395 if (modes & MOD_FREQUENCY) {
396 freq = (ntv.freq * 1000LL) >> 16;
398 L_LINT(time_freq, MAXFREQ);
399 else if (freq < -MAXFREQ)
400 L_LINT(time_freq, -MAXFREQ);
403 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
404 * time_freq is [ns/s * 2^32]
406 time_freq = ntv.freq * 1000LL * 65536LL;
409 pps_freq = time_freq;
410 #endif /* PPS_SYNC */
412 if (modes & MOD_OFFSET) {
413 if (time_status & STA_NANO)
414 hardupdate(ntv.offset);
416 hardupdate(ntv.offset * 1000);
420 * Retrieve all clock variables. Note that the TAI offset is
421 * returned only by ntp_gettime();
423 if (time_status & STA_NANO)
424 ntv.offset = L_GINT(time_offset);
426 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
427 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
428 ntv.maxerror = time_maxerror;
429 ntv.esterror = time_esterror;
430 ntv.status = time_status;
431 ntv.constant = time_constant;
432 if (time_status & STA_NANO)
433 ntv.precision = time_precision;
435 ntv.precision = time_precision / 1000;
436 ntv.tolerance = MAXFREQ * SCALE_PPM;
438 ntv.shift = pps_shift;
439 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
440 if (time_status & STA_NANO)
441 ntv.jitter = pps_jitter;
443 ntv.jitter = pps_jitter / 1000;
444 ntv.stabil = pps_stabil;
445 ntv.calcnt = pps_calcnt;
446 ntv.errcnt = pps_errcnt;
447 ntv.jitcnt = pps_jitcnt;
448 ntv.stbcnt = pps_stbcnt;
449 #endif /* PPS_SYNC */
452 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
456 if (ntp_is_time_error())
457 td->td_retval[0] = TIME_ERROR;
459 td->td_retval[0] = time_state;
467 * second_overflow() - called after ntp_tick_adjust()
469 * This routine is ordinarily called immediately following the above
470 * routine ntp_tick_adjust(). While these two routines are normally
471 * combined, they are separated here only for the purposes of
475 ntp_update_second(int64_t *adjustment, time_t *newsec)
478 l_fp ftemp; /* 32/64-bit temporary */
481 * On rollover of the second both the nanosecond and microsecond
482 * clocks are updated and the state machine cranked as
483 * necessary. The phase adjustment to be used for the next
484 * second is calculated and the maximum error is increased by
487 time_maxerror += MAXFREQ / 1000;
490 * Leap second processing. If in leap-insert state at
491 * the end of the day, the system clock is set back one
492 * second; if in leap-delete state, the system clock is
493 * set ahead one second. The nano_time() routine or
494 * external clock driver will insure that reported time
495 * is always monotonic.
497 switch (time_state) {
503 if (time_status & STA_INS)
504 time_state = TIME_INS;
505 else if (time_status & STA_DEL)
506 time_state = TIME_DEL;
510 * Insert second 23:59:60 following second
514 if (!(time_status & STA_INS))
515 time_state = TIME_OK;
516 else if ((*newsec) % 86400 == 0) {
518 time_state = TIME_OOP;
524 * Delete second 23:59:59.
527 if (!(time_status & STA_DEL))
528 time_state = TIME_OK;
529 else if (((*newsec) + 1) % 86400 == 0) {
532 time_state = TIME_WAIT;
537 * Insert second in progress.
540 time_state = TIME_WAIT;
544 * Wait for status bits to clear.
547 if (!(time_status & (STA_INS | STA_DEL)))
548 time_state = TIME_OK;
552 * Compute the total time adjustment for the next second
553 * in ns. The offset is reduced by a factor depending on
554 * whether the PPS signal is operating. Note that the
555 * value is in effect scaled by the clock frequency,
556 * since the adjustment is added at each tick interrupt.
560 /* XXX even if PPS signal dies we should finish adjustment ? */
561 if (time_status & STA_PPSTIME && time_status &
563 L_RSHIFT(ftemp, pps_shift);
565 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
567 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
568 #endif /* PPS_SYNC */
570 L_SUB(time_offset, ftemp);
571 L_ADD(time_adj, time_freq);
574 * Apply any correction from adjtime(2). If more than one second
575 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
576 * until the last second is slewed the final < 500 usecs.
578 if (time_adjtime != 0) {
579 if (time_adjtime > 1000000)
581 else if (time_adjtime < -1000000)
583 else if (time_adjtime > 500)
585 else if (time_adjtime < -500)
588 tickrate = time_adjtime;
589 time_adjtime -= tickrate;
590 L_LINT(ftemp, tickrate * 1000);
591 L_ADD(time_adj, ftemp);
593 *adjustment = time_adj;
599 time_status &= ~STA_PPSSIGNAL;
600 #endif /* PPS_SYNC */
604 * ntp_init() - initialize variables and structures
606 * This routine must be called after the kernel variables hz and tick
607 * are set or changed and before the next tick interrupt. In this
608 * particular implementation, these values are assumed set elsewhere in
609 * the kernel. The design allows the clock frequency and tick interval
610 * to be changed while the system is running. So, this routine should
611 * probably be integrated with the code that does that.
618 * The following variables are initialized only at startup. Only
619 * those structures not cleared by the compiler need to be
620 * initialized, and these only in the simulator. In the actual
621 * kernel, any nonzero values here will quickly evaporate.
626 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
627 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
628 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
631 #endif /* PPS_SYNC */
634 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL);
637 * hardupdate() - local clock update
639 * This routine is called by ntp_adjtime() to update the local clock
640 * phase and frequency. The implementation is of an adaptive-parameter,
641 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
642 * time and frequency offset estimates for each call. If the kernel PPS
643 * discipline code is configured (PPS_SYNC), the PPS signal itself
644 * determines the new time offset, instead of the calling argument.
645 * Presumably, calls to ntp_adjtime() occur only when the caller
646 * believes the local clock is valid within some bound (+-128 ms with
647 * NTP). If the caller's time is far different than the PPS time, an
648 * argument will ensue, and it's not clear who will lose.
650 * For uncompensated quartz crystal oscillators and nominal update
651 * intervals less than 256 s, operation should be in phase-lock mode,
652 * where the loop is disciplined to phase. For update intervals greater
653 * than 1024 s, operation should be in frequency-lock mode, where the
654 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
655 * is selected by the STA_MODE status bit.
659 long offset; /* clock offset (ns) */
665 * Select how the phase is to be controlled and from which
666 * source. If the PPS signal is present and enabled to
667 * discipline the time, the PPS offset is used; otherwise, the
668 * argument offset is used.
670 if (!(time_status & STA_PLL))
672 if (!(time_status & STA_PPSTIME && time_status &
674 if (offset > MAXPHASE)
675 time_monitor = MAXPHASE;
676 else if (offset < -MAXPHASE)
677 time_monitor = -MAXPHASE;
679 time_monitor = offset;
680 L_LINT(time_offset, time_monitor);
684 * Select how the frequency is to be controlled and in which
685 * mode (PLL or FLL). If the PPS signal is present and enabled
686 * to discipline the frequency, the PPS frequency is used;
687 * otherwise, the argument offset is used to compute it.
689 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
690 time_reftime = time_second;
693 if (time_status & STA_FREQHOLD || time_reftime == 0)
694 time_reftime = time_second;
695 mtemp = time_second - time_reftime;
696 L_LINT(ftemp, time_monitor);
697 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
699 L_ADD(time_freq, ftemp);
700 time_status &= ~STA_MODE;
701 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
703 L_LINT(ftemp, (time_monitor << 4) / mtemp);
704 L_RSHIFT(ftemp, SHIFT_FLL + 4);
705 L_ADD(time_freq, ftemp);
706 time_status |= STA_MODE;
708 time_reftime = time_second;
709 if (L_GINT(time_freq) > MAXFREQ)
710 L_LINT(time_freq, MAXFREQ);
711 else if (L_GINT(time_freq) < -MAXFREQ)
712 L_LINT(time_freq, -MAXFREQ);
717 * hardpps() - discipline CPU clock oscillator to external PPS signal
719 * This routine is called at each PPS interrupt in order to discipline
720 * the CPU clock oscillator to the PPS signal. There are two independent
721 * first-order feedback loops, one for the phase, the other for the
722 * frequency. The phase loop measures and grooms the PPS phase offset
723 * and leaves it in a handy spot for the seconds overflow routine. The
724 * frequency loop averages successive PPS phase differences and
725 * calculates the PPS frequency offset, which is also processed by the
726 * seconds overflow routine. The code requires the caller to capture the
727 * time and architecture-dependent hardware counter values in
728 * nanoseconds at the on-time PPS signal transition.
730 * Note that, on some Unix systems this routine runs at an interrupt
731 * priority level higher than the timer interrupt routine hardclock().
732 * Therefore, the variables used are distinct from the hardclock()
733 * variables, except for the actual time and frequency variables, which
734 * are determined by this routine and updated atomically.
738 struct timespec *tsp; /* time at PPS */
739 long nsec; /* hardware counter at PPS */
741 long u_sec, u_nsec, v_nsec; /* temps */
745 * The signal is first processed by a range gate and frequency
746 * discriminator. The range gate rejects noise spikes outside
747 * the range +-500 us. The frequency discriminator rejects input
748 * signals with apparent frequency outside the range 1 +-500
749 * PPM. If two hits occur in the same second, we ignore the
750 * later hit; if not and a hit occurs outside the range gate,
751 * keep the later hit for later comparison, but do not process
754 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
755 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
756 pps_valid = PPS_VALID;
758 u_nsec = tsp->tv_nsec;
759 if (u_nsec >= (NANOSECOND >> 1)) {
760 u_nsec -= NANOSECOND;
763 v_nsec = u_nsec - pps_tf[0].tv_nsec;
764 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
767 pps_tf[2] = pps_tf[1];
768 pps_tf[1] = pps_tf[0];
769 pps_tf[0].tv_sec = u_sec;
770 pps_tf[0].tv_nsec = u_nsec;
773 * Compute the difference between the current and previous
774 * counter values. If the difference exceeds 0.5 s, assume it
775 * has wrapped around, so correct 1.0 s. If the result exceeds
776 * the tick interval, the sample point has crossed a tick
777 * boundary during the last second, so correct the tick. Very
781 if (u_nsec > (NANOSECOND >> 1))
782 u_nsec -= NANOSECOND;
783 else if (u_nsec < -(NANOSECOND >> 1))
784 u_nsec += NANOSECOND;
785 pps_fcount += u_nsec;
786 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
788 time_status &= ~STA_PPSJITTER;
791 * A three-stage median filter is used to help denoise the PPS
792 * time. The median sample becomes the time offset estimate; the
793 * difference between the other two samples becomes the time
794 * dispersion (jitter) estimate.
796 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
797 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
798 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
799 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
800 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
801 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
802 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
804 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
805 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
808 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
809 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
810 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
811 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
812 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
813 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
815 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
816 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
821 * Nominal jitter is due to PPS signal noise and interrupt
822 * latency. If it exceeds the popcorn threshold, the sample is
823 * discarded. otherwise, if so enabled, the time offset is
824 * updated. We can tolerate a modest loss of data here without
825 * much degrading time accuracy.
827 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
828 time_status |= STA_PPSJITTER;
830 } else if (time_status & STA_PPSTIME) {
831 time_monitor = -v_nsec;
832 L_LINT(time_offset, time_monitor);
834 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
835 u_sec = pps_tf[0].tv_sec - pps_lastsec;
836 if (u_sec < (1 << pps_shift))
840 * At the end of the calibration interval the difference between
841 * the first and last counter values becomes the scaled
842 * frequency. It will later be divided by the length of the
843 * interval to determine the frequency update. If the frequency
844 * exceeds a sanity threshold, or if the actual calibration
845 * interval is not equal to the expected length, the data are
846 * discarded. We can tolerate a modest loss of data here without
847 * much degrading frequency accuracy.
850 v_nsec = -pps_fcount;
851 pps_lastsec = pps_tf[0].tv_sec;
853 u_nsec = MAXFREQ << pps_shift;
854 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
856 time_status |= STA_PPSERROR;
862 * Here the raw frequency offset and wander (stability) is
863 * calculated. If the wander is less than the wander threshold
864 * for four consecutive averaging intervals, the interval is
865 * doubled; if it is greater than the threshold for four
866 * consecutive intervals, the interval is halved. The scaled
867 * frequency offset is converted to frequency offset. The
868 * stability metric is calculated as the average of recent
869 * frequency changes, but is used only for performance
872 L_LINT(ftemp, v_nsec);
873 L_RSHIFT(ftemp, pps_shift);
874 L_SUB(ftemp, pps_freq);
875 u_nsec = L_GINT(ftemp);
876 if (u_nsec > PPS_MAXWANDER) {
877 L_LINT(ftemp, PPS_MAXWANDER);
879 time_status |= STA_PPSWANDER;
881 } else if (u_nsec < -PPS_MAXWANDER) {
882 L_LINT(ftemp, -PPS_MAXWANDER);
884 time_status |= STA_PPSWANDER;
889 if (pps_intcnt >= 4) {
891 if (pps_shift < pps_shiftmax) {
895 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
897 if (pps_shift > PPS_FAVG) {
904 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
907 * The PPS frequency is recalculated and clamped to the maximum
908 * MAXFREQ. If enabled, the system clock frequency is updated as
911 L_ADD(pps_freq, ftemp);
912 u_nsec = L_GINT(pps_freq);
913 if (u_nsec > MAXFREQ)
914 L_LINT(pps_freq, MAXFREQ);
915 else if (u_nsec < -MAXFREQ)
916 L_LINT(pps_freq, -MAXFREQ);
917 if (time_status & STA_PPSFREQ)
918 time_freq = pps_freq;
920 #endif /* PPS_SYNC */
922 #ifndef _SYS_SYSPROTO_H_
923 struct adjtime_args {
924 struct timeval *delta;
925 struct timeval *olddelta;
930 adjtime(struct thread *td, struct adjtime_args *uap)
932 struct timeval delta, olddelta, *deltap;
936 error = copyin(uap->delta, &delta, sizeof(delta));
942 error = kern_adjtime(td, deltap, &olddelta);
943 if (uap->olddelta && error == 0)
944 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
949 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
956 atv.tv_sec = time_adjtime / 1000000;
957 atv.tv_usec = time_adjtime % 1000000;
958 if (atv.tv_usec < 0) {
959 atv.tv_usec += 1000000;
965 if ((error = priv_check(td, PRIV_ADJTIME))) {
969 time_adjtime = (int64_t)delta->tv_sec * 1000000 +
976 static struct callout resettodr_callout;
977 static int resettodr_period = 1800;
980 periodic_resettodr(void *arg __unused)
983 if (!ntp_is_time_error()) {
988 if (resettodr_period > 0)
989 callout_schedule(&resettodr_callout, resettodr_period * hz);
993 shutdown_resettodr(void *arg __unused, int howto __unused)
996 callout_drain(&resettodr_callout);
997 if (resettodr_period > 0 && !ntp_is_time_error()) {
1005 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
1009 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
1010 if (error || !req->newptr)
1012 if (resettodr_period == 0)
1013 callout_stop(&resettodr_callout);
1015 callout_reset(&resettodr_callout, resettodr_period * hz,
1016 periodic_resettodr, NULL);
1020 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT|CTLFLAG_RW,
1021 &resettodr_period, 1800, sysctl_resettodr_period, "I",
1022 "Save system time to RTC with this period (in seconds)");
1023 TUNABLE_INT("machdep.rtc_save_period", &resettodr_period);
1026 start_periodic_resettodr(void *arg __unused)
1029 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
1030 SHUTDOWN_PRI_FIRST);
1031 callout_init(&resettodr_callout, 1);
1032 if (resettodr_period == 0)
1034 callout_reset(&resettodr_callout, resettodr_period * hz,
1035 periodic_resettodr, NULL);
1038 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE,
1039 start_periodic_resettodr, NULL);