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) ((v) = (int64_t)(a) << 32)
77 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
80 * Generic NTP kernel interface
82 * These routines constitute the Network Time Protocol (NTP) interfaces
83 * for user and daemon application programs. The ntp_gettime() routine
84 * provides the time, maximum error (synch distance) and estimated error
85 * (dispersion) to client user application programs. The ntp_adjtime()
86 * routine is used by the NTP daemon to adjust the system clock to an
87 * externally derived time. The time offset and related variables set by
88 * this routine are used by other routines in this module to adjust the
89 * phase and frequency of the clock discipline loop which controls the
92 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
93 * defined), the time at each tick interrupt is derived directly from
94 * the kernel time variable. When the kernel time is reckoned in
95 * microseconds, (NTP_NANO undefined), the time is derived from the
96 * kernel time variable together with a variable representing the
97 * leftover nanoseconds at the last tick interrupt. In either case, the
98 * current nanosecond time is reckoned from these values plus an
99 * interpolated value derived by the clock routines in another
100 * architecture-specific module. The interpolation can use either a
101 * dedicated counter or a processor cycle counter (PCC) implemented in
102 * some architectures.
104 * Note that all routines must run at priority splclock or higher.
107 * Phase/frequency-lock loop (PLL/FLL) definitions
109 * The nanosecond clock discipline uses two variable types, time
110 * variables and frequency variables. Both types are represented as 64-
111 * bit fixed-point quantities with the decimal point between two 32-bit
112 * halves. On a 32-bit machine, each half is represented as a single
113 * word and mathematical operations are done using multiple-precision
114 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
117 * A time variable is a signed 64-bit fixed-point number in ns and
118 * fraction. It represents the remaining time offset to be amortized
119 * over succeeding tick interrupts. The maximum time offset is about
120 * 0.5 s and the resolution is about 2.3e-10 ns.
122 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
123 * 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
124 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
130 * A frequency variable is a signed 64-bit fixed-point number in ns/s
131 * and fraction. It represents the ns and fraction to be added to the
132 * kernel time variable at each second. The maximum frequency offset is
133 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
135 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
136 * 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
137 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
138 * |s s s s s s s s s s s s s| ns/s |
139 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
141 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
144 * The following variables establish the state of the PLL/FLL and the
145 * residual time and frequency offset of the local clock.
147 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
148 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
150 static int time_state = TIME_OK; /* clock state */
151 static int time_status = STA_UNSYNC; /* clock status bits */
152 static long time_tai; /* TAI offset (s) */
153 static long time_monitor; /* last time offset scaled (ns) */
154 static long time_constant; /* poll interval (shift) (s) */
155 static long time_precision = 1; /* clock precision (ns) */
156 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
157 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
158 static long time_reftime; /* time at last adjustment (s) */
159 static l_fp time_offset; /* time offset (ns) */
160 static l_fp time_freq; /* frequency offset (ns/s) */
161 static l_fp time_adj; /* tick adjust (ns/s) */
163 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
167 * The following variables are used when a pulse-per-second (PPS) signal
168 * is available and connected via a modem control lead. They establish
169 * the engineering parameters of the clock discipline loop when
170 * controlled by the PPS signal.
172 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
173 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
174 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
175 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
176 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
177 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
178 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
180 static struct timespec pps_tf[3]; /* phase median filter */
181 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
182 static long pps_fcount; /* frequency accumulator */
183 static long pps_jitter; /* nominal jitter (ns) */
184 static long pps_stabil; /* nominal stability (scaled ns/s) */
185 static long pps_lastsec; /* time at last calibration (s) */
186 static int pps_valid; /* signal watchdog counter */
187 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
188 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
189 static int pps_intcnt; /* wander counter */
192 * PPS signal quality monitors
194 static long pps_calcnt; /* calibration intervals */
195 static long pps_jitcnt; /* jitter limit exceeded */
196 static long pps_stbcnt; /* stability limit exceeded */
197 static long pps_errcnt; /* calibration errors */
198 #endif /* PPS_SYNC */
200 * End of phase/frequency-lock loop (PLL/FLL) definitions
203 static void ntp_init(void);
204 static void hardupdate(long offset);
205 static void ntp_gettime1(struct ntptimeval *ntvp);
206 static int ntp_is_time_error(void);
209 ntp_is_time_error(void)
212 * Status word error decode. If any of these conditions occur,
213 * an error is returned, instead of the status word. Most
214 * applications will care only about the fact the system clock
215 * may not be trusted, not about the details.
217 * Hardware or software error
219 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
222 * PPS signal lost when either time or frequency synchronization
225 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
226 !(time_status & STA_PPSSIGNAL)) ||
229 * PPS jitter exceeded when time synchronization requested
231 (time_status & STA_PPSTIME &&
232 time_status & STA_PPSJITTER) ||
235 * PPS wander exceeded or calibration error when frequency
236 * synchronization requested
238 (time_status & STA_PPSFREQ &&
239 time_status & (STA_PPSWANDER | STA_PPSERROR)))
246 ntp_gettime1(struct ntptimeval *ntvp)
248 struct timespec atv; /* nanosecond time */
253 ntvp->time.tv_sec = atv.tv_sec;
254 ntvp->time.tv_nsec = atv.tv_nsec;
255 ntvp->maxerror = time_maxerror;
256 ntvp->esterror = time_esterror;
257 ntvp->tai = time_tai;
258 ntvp->time_state = time_state;
260 if (ntp_is_time_error())
261 ntvp->time_state = TIME_ERROR;
265 * ntp_gettime() - NTP user application interface
267 * See the timex.h header file for synopsis and API description. Note that
268 * the TAI offset is returned in the ntvtimeval.tai structure member.
270 #ifndef _SYS_SYSPROTO_H_
271 struct ntp_gettime_args {
272 struct ntptimeval *ntvp;
277 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
279 struct ntptimeval ntv;
285 td->td_retval[0] = ntv.time_state;
286 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
290 ntp_sysctl(SYSCTL_HANDLER_ARGS)
292 struct ntptimeval ntv; /* temporary structure */
296 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
299 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
300 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
301 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
304 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
305 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
306 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD,
307 &time_monitor, 0, "");
309 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
310 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
314 * ntp_adjtime() - NTP daemon application interface
316 * See the timex.h header file for synopsis and API description. Note that
317 * the timex.constant structure member has a dual purpose to set the time
318 * constant and to set the TAI offset.
320 #ifndef _SYS_SYSPROTO_H_
321 struct ntp_adjtime_args {
327 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
329 struct timex ntv; /* temporary structure */
330 long freq; /* frequency ns/s) */
331 int modes; /* mode bits from structure */
332 int s; /* caller priority */
335 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
340 * Update selected clock variables - only the superuser can
341 * change anything. Note that there is no error checking here on
342 * the assumption the superuser should know what it is doing.
343 * Note that either the time constant or TAI offset are loaded
344 * from the ntv.constant member, depending on the mode bits. If
345 * the STA_PLL bit in the status word is cleared, the state and
346 * status words are reset to the initial values at boot.
351 error = priv_check(td, PRIV_NTP_ADJTIME);
355 if (modes & MOD_MAXERROR)
356 time_maxerror = ntv.maxerror;
357 if (modes & MOD_ESTERROR)
358 time_esterror = ntv.esterror;
359 if (modes & MOD_STATUS) {
360 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
361 time_state = TIME_OK;
362 time_status = STA_UNSYNC;
364 pps_shift = PPS_FAVG;
365 #endif /* PPS_SYNC */
367 time_status &= STA_RONLY;
368 time_status |= ntv.status & ~STA_RONLY;
370 if (modes & MOD_TIMECONST) {
371 if (ntv.constant < 0)
373 else if (ntv.constant > MAXTC)
374 time_constant = MAXTC;
376 time_constant = ntv.constant;
378 if (modes & MOD_TAI) {
379 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
380 time_tai = ntv.constant;
383 if (modes & MOD_PPSMAX) {
384 if (ntv.shift < PPS_FAVG)
385 pps_shiftmax = PPS_FAVG;
386 else if (ntv.shift > PPS_FAVGMAX)
387 pps_shiftmax = PPS_FAVGMAX;
389 pps_shiftmax = ntv.shift;
391 #endif /* PPS_SYNC */
392 if (modes & MOD_NANO)
393 time_status |= STA_NANO;
394 if (modes & MOD_MICRO)
395 time_status &= ~STA_NANO;
396 if (modes & MOD_CLKB)
397 time_status |= STA_CLK;
398 if (modes & MOD_CLKA)
399 time_status &= ~STA_CLK;
400 if (modes & MOD_FREQUENCY) {
401 freq = (ntv.freq * 1000LL) >> 16;
403 L_LINT(time_freq, MAXFREQ);
404 else if (freq < -MAXFREQ)
405 L_LINT(time_freq, -MAXFREQ);
408 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
409 * time_freq is [ns/s * 2^32]
411 time_freq = ntv.freq * 1000LL * 65536LL;
414 pps_freq = time_freq;
415 #endif /* PPS_SYNC */
417 if (modes & MOD_OFFSET) {
418 if (time_status & STA_NANO)
419 hardupdate(ntv.offset);
421 hardupdate(ntv.offset * 1000);
425 * Retrieve all clock variables. Note that the TAI offset is
426 * returned only by ntp_gettime();
428 if (time_status & STA_NANO)
429 ntv.offset = L_GINT(time_offset);
431 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
432 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
433 ntv.maxerror = time_maxerror;
434 ntv.esterror = time_esterror;
435 ntv.status = time_status;
436 ntv.constant = time_constant;
437 if (time_status & STA_NANO)
438 ntv.precision = time_precision;
440 ntv.precision = time_precision / 1000;
441 ntv.tolerance = MAXFREQ * SCALE_PPM;
443 ntv.shift = pps_shift;
444 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
445 if (time_status & STA_NANO)
446 ntv.jitter = pps_jitter;
448 ntv.jitter = pps_jitter / 1000;
449 ntv.stabil = pps_stabil;
450 ntv.calcnt = pps_calcnt;
451 ntv.errcnt = pps_errcnt;
452 ntv.jitcnt = pps_jitcnt;
453 ntv.stbcnt = pps_stbcnt;
454 #endif /* PPS_SYNC */
457 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
461 if (ntp_is_time_error())
462 td->td_retval[0] = TIME_ERROR;
464 td->td_retval[0] = time_state;
472 * second_overflow() - called after ntp_tick_adjust()
474 * This routine is ordinarily called immediately following the above
475 * routine ntp_tick_adjust(). While these two routines are normally
476 * combined, they are separated here only for the purposes of
480 ntp_update_second(int64_t *adjustment, time_t *newsec)
483 l_fp ftemp; /* 32/64-bit temporary */
486 * On rollover of the second both the nanosecond and microsecond
487 * clocks are updated and the state machine cranked as
488 * necessary. The phase adjustment to be used for the next
489 * second is calculated and the maximum error is increased by
492 time_maxerror += MAXFREQ / 1000;
495 * Leap second processing. If in leap-insert state at
496 * the end of the day, the system clock is set back one
497 * second; if in leap-delete state, the system clock is
498 * set ahead one second. The nano_time() routine or
499 * external clock driver will insure that reported time
500 * is always monotonic.
502 switch (time_state) {
508 if (time_status & STA_INS)
509 time_state = TIME_INS;
510 else if (time_status & STA_DEL)
511 time_state = TIME_DEL;
515 * Insert second 23:59:60 following second
519 if (!(time_status & STA_INS))
520 time_state = TIME_OK;
521 else if ((*newsec) % 86400 == 0) {
523 time_state = TIME_OOP;
529 * Delete second 23:59:59.
532 if (!(time_status & STA_DEL))
533 time_state = TIME_OK;
534 else if (((*newsec) + 1) % 86400 == 0) {
537 time_state = TIME_WAIT;
542 * Insert second in progress.
545 time_state = TIME_WAIT;
549 * Wait for status bits to clear.
552 if (!(time_status & (STA_INS | STA_DEL)))
553 time_state = TIME_OK;
557 * Compute the total time adjustment for the next second
558 * in ns. The offset is reduced by a factor depending on
559 * whether the PPS signal is operating. Note that the
560 * value is in effect scaled by the clock frequency,
561 * since the adjustment is added at each tick interrupt.
565 /* XXX even if PPS signal dies we should finish adjustment ? */
566 if (time_status & STA_PPSTIME && time_status &
568 L_RSHIFT(ftemp, pps_shift);
570 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
572 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
573 #endif /* PPS_SYNC */
575 L_SUB(time_offset, ftemp);
576 L_ADD(time_adj, time_freq);
579 * Apply any correction from adjtime(2). If more than one second
580 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
581 * until the last second is slewed the final < 500 usecs.
583 if (time_adjtime != 0) {
584 if (time_adjtime > 1000000)
586 else if (time_adjtime < -1000000)
588 else if (time_adjtime > 500)
590 else if (time_adjtime < -500)
593 tickrate = time_adjtime;
594 time_adjtime -= tickrate;
595 L_LINT(ftemp, tickrate * 1000);
596 L_ADD(time_adj, ftemp);
598 *adjustment = time_adj;
604 time_status &= ~STA_PPSSIGNAL;
605 #endif /* PPS_SYNC */
609 * ntp_init() - initialize variables and structures
611 * This routine must be called after the kernel variables hz and tick
612 * are set or changed and before the next tick interrupt. In this
613 * particular implementation, these values are assumed set elsewhere in
614 * the kernel. The design allows the clock frequency and tick interval
615 * to be changed while the system is running. So, this routine should
616 * probably be integrated with the code that does that.
623 * The following variables are initialized only at startup. Only
624 * those structures not cleared by the compiler need to be
625 * initialized, and these only in the simulator. In the actual
626 * kernel, any nonzero values here will quickly evaporate.
631 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
632 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
633 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
636 #endif /* PPS_SYNC */
639 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL);
642 * hardupdate() - local clock update
644 * This routine is called by ntp_adjtime() to update the local clock
645 * phase and frequency. The implementation is of an adaptive-parameter,
646 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
647 * time and frequency offset estimates for each call. If the kernel PPS
648 * discipline code is configured (PPS_SYNC), the PPS signal itself
649 * determines the new time offset, instead of the calling argument.
650 * Presumably, calls to ntp_adjtime() occur only when the caller
651 * believes the local clock is valid within some bound (+-128 ms with
652 * NTP). If the caller's time is far different than the PPS time, an
653 * argument will ensue, and it's not clear who will lose.
655 * For uncompensated quartz crystal oscillators and nominal update
656 * intervals less than 256 s, operation should be in phase-lock mode,
657 * where the loop is disciplined to phase. For update intervals greater
658 * than 1024 s, operation should be in frequency-lock mode, where the
659 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
660 * is selected by the STA_MODE status bit.
664 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_second;
698 if (time_status & STA_FREQHOLD || time_reftime == 0)
699 time_reftime = time_second;
700 mtemp = time_second - 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_second;
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.
743 struct timespec *tsp; /* time at PPS */
744 long nsec; /* hardware counter at PPS */
746 long u_sec, u_nsec, v_nsec; /* temps */
750 * The signal is first processed by a range gate and frequency
751 * discriminator. The range gate rejects noise spikes outside
752 * the range +-500 us. The frequency discriminator rejects input
753 * signals with apparent frequency outside the range 1 +-500
754 * PPM. If two hits occur in the same second, we ignore the
755 * later hit; if not and a hit occurs outside the range gate,
756 * keep the later hit for later comparison, but do not process
759 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
760 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
761 pps_valid = PPS_VALID;
763 u_nsec = tsp->tv_nsec;
764 if (u_nsec >= (NANOSECOND >> 1)) {
765 u_nsec -= NANOSECOND;
768 v_nsec = u_nsec - pps_tf[0].tv_nsec;
769 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
772 pps_tf[2] = pps_tf[1];
773 pps_tf[1] = pps_tf[0];
774 pps_tf[0].tv_sec = u_sec;
775 pps_tf[0].tv_nsec = u_nsec;
778 * Compute the difference between the current and previous
779 * counter values. If the difference exceeds 0.5 s, assume it
780 * has wrapped around, so correct 1.0 s. If the result exceeds
781 * the tick interval, the sample point has crossed a tick
782 * boundary during the last second, so correct the tick. Very
786 if (u_nsec > (NANOSECOND >> 1))
787 u_nsec -= NANOSECOND;
788 else if (u_nsec < -(NANOSECOND >> 1))
789 u_nsec += NANOSECOND;
790 pps_fcount += u_nsec;
791 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
793 time_status &= ~STA_PPSJITTER;
796 * A three-stage median filter is used to help denoise the PPS
797 * time. The median sample becomes the time offset estimate; the
798 * difference between the other two samples becomes the time
799 * dispersion (jitter) estimate.
801 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
802 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
803 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
804 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
805 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
806 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
807 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
809 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
810 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
813 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
814 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
815 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
816 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
817 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
818 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
820 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
821 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
826 * Nominal jitter is due to PPS signal noise and interrupt
827 * latency. If it exceeds the popcorn threshold, the sample is
828 * discarded. otherwise, if so enabled, the time offset is
829 * updated. We can tolerate a modest loss of data here without
830 * much degrading time accuracy.
832 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
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 <<
861 time_status |= STA_PPSERROR;
867 * Here the raw frequency offset and wander (stability) is
868 * calculated. If the wander is less than the wander threshold
869 * for four consecutive averaging intervals, the interval is
870 * doubled; if it is greater than the threshold for four
871 * consecutive intervals, the interval is halved. The scaled
872 * frequency offset is converted to frequency offset. The
873 * stability metric is calculated as the average of recent
874 * frequency changes, but is used only for performance
877 L_LINT(ftemp, v_nsec);
878 L_RSHIFT(ftemp, pps_shift);
879 L_SUB(ftemp, pps_freq);
880 u_nsec = L_GINT(ftemp);
881 if (u_nsec > PPS_MAXWANDER) {
882 L_LINT(ftemp, PPS_MAXWANDER);
884 time_status |= STA_PPSWANDER;
886 } else if (u_nsec < -PPS_MAXWANDER) {
887 L_LINT(ftemp, -PPS_MAXWANDER);
889 time_status |= STA_PPSWANDER;
894 if (pps_intcnt >= 4) {
896 if (pps_shift < pps_shiftmax) {
900 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
902 if (pps_shift > PPS_FAVG) {
909 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
912 * The PPS frequency is recalculated and clamped to the maximum
913 * MAXFREQ. If enabled, the system clock frequency is updated as
916 L_ADD(pps_freq, ftemp);
917 u_nsec = L_GINT(pps_freq);
918 if (u_nsec > MAXFREQ)
919 L_LINT(pps_freq, MAXFREQ);
920 else if (u_nsec < -MAXFREQ)
921 L_LINT(pps_freq, -MAXFREQ);
922 if (time_status & STA_PPSFREQ)
923 time_freq = pps_freq;
925 #endif /* PPS_SYNC */
927 #ifndef _SYS_SYSPROTO_H_
928 struct adjtime_args {
929 struct timeval *delta;
930 struct timeval *olddelta;
935 sys_adjtime(struct thread *td, struct adjtime_args *uap)
937 struct timeval delta, olddelta, *deltap;
941 error = copyin(uap->delta, &delta, sizeof(delta));
947 error = kern_adjtime(td, deltap, &olddelta);
948 if (uap->olddelta && error == 0)
949 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
954 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
961 atv.tv_sec = time_adjtime / 1000000;
962 atv.tv_usec = time_adjtime % 1000000;
963 if (atv.tv_usec < 0) {
964 atv.tv_usec += 1000000;
970 if ((error = priv_check(td, PRIV_ADJTIME))) {
974 time_adjtime = (int64_t)delta->tv_sec * 1000000 +
981 static struct callout resettodr_callout;
982 static int resettodr_period = 1800;
985 periodic_resettodr(void *arg __unused)
988 if (!ntp_is_time_error()) {
993 if (resettodr_period > 0)
994 callout_schedule(&resettodr_callout, resettodr_period * hz);
998 shutdown_resettodr(void *arg __unused, int howto __unused)
1001 callout_drain(&resettodr_callout);
1002 if (resettodr_period > 0 && !ntp_is_time_error()) {
1010 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
1014 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
1015 if (error || !req->newptr)
1017 if (resettodr_period == 0)
1018 callout_stop(&resettodr_callout);
1020 callout_reset(&resettodr_callout, resettodr_period * hz,
1021 periodic_resettodr, NULL);
1025 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT|CTLFLAG_RW,
1026 &resettodr_period, 1800, sysctl_resettodr_period, "I",
1027 "Save system time to RTC with this period (in seconds)");
1028 TUNABLE_INT("machdep.rtc_save_period", &resettodr_period);
1031 start_periodic_resettodr(void *arg __unused)
1034 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
1035 SHUTDOWN_PRI_FIRST);
1036 callout_init(&resettodr_callout, 1);
1037 if (resettodr_period == 0)
1039 callout_reset(&resettodr_callout, resettodr_period * hz,
1040 periodic_resettodr, NULL);
1043 SYSINIT(periodic_resettodr, SI_SUB_RUN_SCHEDULER, SI_ORDER_MIDDLE,
1044 start_periodic_resettodr, NULL);