1 /***********************************************************************
3 * Copyright (c) David L. Mills 1993-2001 *
5 * Permission to use, copy, modify, and distribute this software and *
6 * its documentation for any purpose and without fee is hereby *
7 * granted, provided that the above copyright notice appears in all *
8 * copies and that both the copyright notice and this permission *
9 * notice appear in supporting documentation, and that the name *
10 * University of Delaware not be used in advertising or publicity *
11 * pertaining to distribution of the software without specific, *
12 * written prior permission. The University of Delaware makes no *
13 * representations about the suitability this software for any *
14 * purpose. It is provided "as is" without express or implied *
17 **********************************************************************/
20 * Adapted from the original sources for FreeBSD and timecounters by:
21 * Poul-Henning Kamp <phk@FreeBSD.org>.
23 * The 32bit version of the "LP" macros seems a bit past its "sell by"
24 * date so I have retained only the 64bit version and included it directly
27 * Only minor changes done to interface with the timecounters over in
28 * sys/kern/kern_clock.c. Some of the comments below may be (even more)
29 * confusing and/or plain wrong in that context.
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/sysproto.h>
40 #include <sys/kernel.h>
43 #include <sys/mutex.h>
45 #include <sys/timex.h>
46 #include <sys/timetc.h>
47 #include <sys/timepps.h>
48 #include <sys/sysctl.h>
51 * Single-precision macros for 64-bit machines
54 #define L_ADD(v, u) ((v) += (u))
55 #define L_SUB(v, u) ((v) -= (u))
56 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
57 #define L_NEG(v) ((v) = -(v))
58 #define L_RSHIFT(v, n) \
61 (v) = -(-(v) >> (n)); \
65 #define L_MPY(v, a) ((v) *= (a))
66 #define L_CLR(v) ((v) = 0)
67 #define L_ISNEG(v) ((v) < 0)
68 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32)
69 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
72 * Generic NTP kernel interface
74 * These routines constitute the Network Time Protocol (NTP) interfaces
75 * for user and daemon application programs. The ntp_gettime() routine
76 * provides the time, maximum error (synch distance) and estimated error
77 * (dispersion) to client user application programs. The ntp_adjtime()
78 * routine is used by the NTP daemon to adjust the system clock to an
79 * externally derived time. The time offset and related variables set by
80 * this routine are used by other routines in this module to adjust the
81 * phase and frequency of the clock discipline loop which controls the
84 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
85 * defined), the time at each tick interrupt is derived directly from
86 * the kernel time variable. When the kernel time is reckoned in
87 * microseconds, (NTP_NANO undefined), the time is derived from the
88 * kernel time variable together with a variable representing the
89 * leftover nanoseconds at the last tick interrupt. In either case, the
90 * current nanosecond time is reckoned from these values plus an
91 * interpolated value derived by the clock routines in another
92 * architecture-specific module. The interpolation can use either a
93 * dedicated counter or a processor cycle counter (PCC) implemented in
96 * Note that all routines must run at priority splclock or higher.
99 * Phase/frequency-lock loop (PLL/FLL) definitions
101 * The nanosecond clock discipline uses two variable types, time
102 * variables and frequency variables. Both types are represented as 64-
103 * bit fixed-point quantities with the decimal point between two 32-bit
104 * halves. On a 32-bit machine, each half is represented as a single
105 * word and mathematical operations are done using multiple-precision
106 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
109 * A time variable is a signed 64-bit fixed-point number in ns and
110 * fraction. It represents the remaining time offset to be amortized
111 * over succeeding tick interrupts. The maximum time offset is about
112 * 0.5 s and the resolution is about 2.3e-10 ns.
114 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
115 * 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
116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
122 * A frequency variable is a signed 64-bit fixed-point number in ns/s
123 * and fraction. It represents the ns and fraction to be added to the
124 * kernel time variable at each second. The maximum frequency offset is
125 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
127 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
128 * 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
129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
130 * |s s s s s s s s s s s s s| ns/s |
131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
136 * The following variables establish the state of the PLL/FLL and the
137 * residual time and frequency offset of the local clock.
139 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
140 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
142 static int time_state = TIME_OK; /* clock state */
143 static int time_status = STA_UNSYNC; /* clock status bits */
144 static long time_tai; /* TAI offset (s) */
145 static long time_monitor; /* last time offset scaled (ns) */
146 static long time_constant; /* poll interval (shift) (s) */
147 static long time_precision = 1; /* clock precision (ns) */
148 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
149 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
150 static long time_reftime; /* time at last adjustment (s) */
151 static l_fp time_offset; /* time offset (ns) */
152 static l_fp time_freq; /* frequency offset (ns/s) */
153 static l_fp time_adj; /* tick adjust (ns/s) */
155 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
159 * The following variables are used when a pulse-per-second (PPS) signal
160 * is available and connected via a modem control lead. They establish
161 * the engineering parameters of the clock discipline loop when
162 * controlled by the PPS signal.
164 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
165 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
166 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
167 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
168 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
169 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
170 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
172 static struct timespec pps_tf[3]; /* phase median filter */
173 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
174 static long pps_fcount; /* frequency accumulator */
175 static long pps_jitter; /* nominal jitter (ns) */
176 static long pps_stabil; /* nominal stability (scaled ns/s) */
177 static long pps_lastsec; /* time at last calibration (s) */
178 static int pps_valid; /* signal watchdog counter */
179 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
180 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
181 static int pps_intcnt; /* wander counter */
184 * PPS signal quality monitors
186 static long pps_calcnt; /* calibration intervals */
187 static long pps_jitcnt; /* jitter limit exceeded */
188 static long pps_stbcnt; /* stability limit exceeded */
189 static long pps_errcnt; /* calibration errors */
190 #endif /* PPS_SYNC */
192 * End of phase/frequency-lock loop (PLL/FLL) definitions
195 static void ntp_init(void);
196 static void hardupdate(long offset);
197 static void ntp_gettime1(struct ntptimeval *ntvp);
200 ntp_gettime1(struct ntptimeval *ntvp)
202 struct timespec atv; /* nanosecond time */
205 ntvp->time.tv_sec = atv.tv_sec;
206 ntvp->time.tv_nsec = atv.tv_nsec;
207 ntvp->maxerror = time_maxerror;
208 ntvp->esterror = time_esterror;
209 ntvp->tai = time_tai;
210 ntvp->time_state = time_state;
213 * Status word error decode. If any of these conditions occur,
214 * an error is returned, instead of the status word. Most
215 * applications will care only about the fact the system clock
216 * may not be trusted, not about the details.
218 * Hardware or software error
220 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
223 * PPS signal lost when either time or frequency synchronization
226 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
227 !(time_status & STA_PPSSIGNAL)) ||
230 * PPS jitter exceeded when time synchronization requested
232 (time_status & STA_PPSTIME &&
233 time_status & STA_PPSJITTER) ||
236 * PPS wander exceeded or calibration error when frequency
237 * synchronization requested
239 (time_status & STA_PPSFREQ &&
240 time_status & (STA_PPSWANDER | STA_PPSERROR)))
241 ntvp->time_state = TIME_ERROR;
244 #ifndef _SYS_SYSPROTO_H_
245 struct ntp_gettime_args {
246 struct ntptimeval *ntvp;
251 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
253 struct ntptimeval ntv;
257 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
261 * ntp_gettime() - NTP user application interface
263 * See the timex.h header file for synopsis and API description. Note
264 * that the TAI offset is returned in the ntvtimeval.tai structure
268 ntp_sysctl(SYSCTL_HANDLER_ARGS)
270 struct ntptimeval ntv; /* temporary structure */
274 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
277 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
278 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
279 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
282 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
283 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
284 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
286 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
287 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
290 * ntp_adjtime() - NTP daemon application interface
292 * See the timex.h header file for synopsis and API description. Note
293 * that the timex.constant structure member has a dual purpose to set
294 * the time constant and to set the TAI offset.
296 #ifndef _SYS_SYSPROTO_H_
297 struct ntp_adjtime_args {
306 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
308 struct timex ntv; /* temporary structure */
309 long freq; /* frequency ns/s) */
310 int modes; /* mode bits from structure */
311 int s; /* caller priority */
314 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
319 * Update selected clock variables - only the superuser can
320 * change anything. Note that there is no error checking here on
321 * the assumption the superuser should know what it is doing.
322 * Note that either the time constant or TAI offset are loaded
323 * from the ntv.constant member, depending on the mode bits. If
324 * the STA_PLL bit in the status word is cleared, the state and
325 * status words are reset to the initial values at boot.
334 if (modes & MOD_MAXERROR)
335 time_maxerror = ntv.maxerror;
336 if (modes & MOD_ESTERROR)
337 time_esterror = ntv.esterror;
338 if (modes & MOD_STATUS) {
339 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
340 time_state = TIME_OK;
341 time_status = STA_UNSYNC;
343 pps_shift = PPS_FAVG;
344 #endif /* PPS_SYNC */
346 time_status &= STA_RONLY;
347 time_status |= ntv.status & ~STA_RONLY;
349 if (modes & MOD_TIMECONST) {
350 if (ntv.constant < 0)
352 else if (ntv.constant > MAXTC)
353 time_constant = MAXTC;
355 time_constant = ntv.constant;
357 if (modes & MOD_TAI) {
358 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
359 time_tai = ntv.constant;
362 if (modes & MOD_PPSMAX) {
363 if (ntv.shift < PPS_FAVG)
364 pps_shiftmax = PPS_FAVG;
365 else if (ntv.shift > PPS_FAVGMAX)
366 pps_shiftmax = PPS_FAVGMAX;
368 pps_shiftmax = ntv.shift;
370 #endif /* PPS_SYNC */
371 if (modes & MOD_NANO)
372 time_status |= STA_NANO;
373 if (modes & MOD_MICRO)
374 time_status &= ~STA_NANO;
375 if (modes & MOD_CLKB)
376 time_status |= STA_CLK;
377 if (modes & MOD_CLKA)
378 time_status &= ~STA_CLK;
379 if (modes & MOD_FREQUENCY) {
380 freq = (ntv.freq * 1000LL) >> 16;
382 L_LINT(time_freq, MAXFREQ);
383 else if (freq < -MAXFREQ)
384 L_LINT(time_freq, -MAXFREQ);
387 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
388 * time_freq is [ns/s * 2^32]
390 time_freq = ntv.freq * 1000LL * 65536LL;
393 pps_freq = time_freq;
394 #endif /* PPS_SYNC */
396 if (modes & MOD_OFFSET) {
397 if (time_status & STA_NANO)
398 hardupdate(ntv.offset);
400 hardupdate(ntv.offset * 1000);
404 * Retrieve all clock variables. Note that the TAI offset is
405 * returned only by ntp_gettime();
407 if (time_status & STA_NANO)
408 ntv.offset = L_GINT(time_offset);
410 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
411 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
412 ntv.maxerror = time_maxerror;
413 ntv.esterror = time_esterror;
414 ntv.status = time_status;
415 ntv.constant = time_constant;
416 if (time_status & STA_NANO)
417 ntv.precision = time_precision;
419 ntv.precision = time_precision / 1000;
420 ntv.tolerance = MAXFREQ * SCALE_PPM;
422 ntv.shift = pps_shift;
423 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
424 if (time_status & STA_NANO)
425 ntv.jitter = pps_jitter;
427 ntv.jitter = pps_jitter / 1000;
428 ntv.stabil = pps_stabil;
429 ntv.calcnt = pps_calcnt;
430 ntv.errcnt = pps_errcnt;
431 ntv.jitcnt = pps_jitcnt;
432 ntv.stbcnt = pps_stbcnt;
433 #endif /* PPS_SYNC */
436 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
441 * Status word error decode. See comments in
442 * ntp_gettime() routine.
444 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
445 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
446 !(time_status & STA_PPSSIGNAL)) ||
447 (time_status & STA_PPSTIME &&
448 time_status & STA_PPSJITTER) ||
449 (time_status & STA_PPSFREQ &&
450 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
451 td->td_retval[0] = TIME_ERROR;
453 td->td_retval[0] = time_state;
461 * second_overflow() - called after ntp_tick_adjust()
463 * This routine is ordinarily called immediately following the above
464 * routine ntp_tick_adjust(). While these two routines are normally
465 * combined, they are separated here only for the purposes of
469 ntp_update_second(int64_t *adjustment, time_t *newsec)
472 l_fp ftemp; /* 32/64-bit temporary */
475 * On rollover of the second both the nanosecond and microsecond
476 * clocks are updated and the state machine cranked as
477 * necessary. The phase adjustment to be used for the next
478 * second is calculated and the maximum error is increased by
481 time_maxerror += MAXFREQ / 1000;
484 * Leap second processing. If in leap-insert state at
485 * the end of the day, the system clock is set back one
486 * second; if in leap-delete state, the system clock is
487 * set ahead one second. The nano_time() routine or
488 * external clock driver will insure that reported time
489 * is always monotonic.
491 switch (time_state) {
497 if (time_status & STA_INS)
498 time_state = TIME_INS;
499 else if (time_status & STA_DEL)
500 time_state = TIME_DEL;
504 * Insert second 23:59:60 following second
508 if (!(time_status & STA_INS))
509 time_state = TIME_OK;
510 else if ((*newsec) % 86400 == 0) {
512 time_state = TIME_OOP;
518 * Delete second 23:59:59.
521 if (!(time_status & STA_DEL))
522 time_state = TIME_OK;
523 else if (((*newsec) + 1) % 86400 == 0) {
526 time_state = TIME_WAIT;
531 * Insert second in progress.
534 time_state = TIME_WAIT;
538 * Wait for status bits to clear.
541 if (!(time_status & (STA_INS | STA_DEL)))
542 time_state = TIME_OK;
546 * Compute the total time adjustment for the next second
547 * in ns. The offset is reduced by a factor depending on
548 * whether the PPS signal is operating. Note that the
549 * value is in effect scaled by the clock frequency,
550 * since the adjustment is added at each tick interrupt.
554 /* XXX even if PPS signal dies we should finish adjustment ? */
555 if (time_status & STA_PPSTIME && time_status &
557 L_RSHIFT(ftemp, pps_shift);
559 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
561 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
562 #endif /* PPS_SYNC */
564 L_SUB(time_offset, ftemp);
565 L_ADD(time_adj, time_freq);
568 * Apply any correction from adjtime(2). If more than one second
569 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
570 * until the last second is slewed the final < 500 usecs.
572 if (time_adjtime != 0) {
573 if (time_adjtime > 1000000)
575 else if (time_adjtime < -1000000)
577 else if (time_adjtime > 500)
579 else if (time_adjtime < -500)
582 tickrate = time_adjtime;
583 time_adjtime -= tickrate;
584 L_LINT(ftemp, tickrate * 1000);
585 L_ADD(time_adj, ftemp);
587 *adjustment = time_adj;
593 time_status &= ~STA_PPSSIGNAL;
594 #endif /* PPS_SYNC */
598 * ntp_init() - initialize variables and structures
600 * This routine must be called after the kernel variables hz and tick
601 * are set or changed and before the next tick interrupt. In this
602 * particular implementation, these values are assumed set elsewhere in
603 * the kernel. The design allows the clock frequency and tick interval
604 * to be changed while the system is running. So, this routine should
605 * probably be integrated with the code that does that.
612 * The following variables are initialized only at startup. Only
613 * those structures not cleared by the compiler need to be
614 * initialized, and these only in the simulator. In the actual
615 * kernel, any nonzero values here will quickly evaporate.
620 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
621 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
622 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
625 #endif /* PPS_SYNC */
628 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
631 * hardupdate() - local clock update
633 * This routine is called by ntp_adjtime() to update the local clock
634 * phase and frequency. The implementation is of an adaptive-parameter,
635 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
636 * time and frequency offset estimates for each call. If the kernel PPS
637 * discipline code is configured (PPS_SYNC), the PPS signal itself
638 * determines the new time offset, instead of the calling argument.
639 * Presumably, calls to ntp_adjtime() occur only when the caller
640 * believes the local clock is valid within some bound (+-128 ms with
641 * NTP). If the caller's time is far different than the PPS time, an
642 * argument will ensue, and it's not clear who will lose.
644 * For uncompensated quartz crystal oscillators and nominal update
645 * intervals less than 256 s, operation should be in phase-lock mode,
646 * where the loop is disciplined to phase. For update intervals greater
647 * than 1024 s, operation should be in frequency-lock mode, where the
648 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
649 * is selected by the STA_MODE status bit.
653 long offset; /* clock offset (ns) */
659 * Select how the phase is to be controlled and from which
660 * source. If the PPS signal is present and enabled to
661 * discipline the time, the PPS offset is used; otherwise, the
662 * argument offset is used.
664 if (!(time_status & STA_PLL))
666 if (!(time_status & STA_PPSTIME && time_status &
668 if (offset > MAXPHASE)
669 time_monitor = MAXPHASE;
670 else if (offset < -MAXPHASE)
671 time_monitor = -MAXPHASE;
673 time_monitor = offset;
674 L_LINT(time_offset, time_monitor);
678 * Select how the frequency is to be controlled and in which
679 * mode (PLL or FLL). If the PPS signal is present and enabled
680 * to discipline the frequency, the PPS frequency is used;
681 * otherwise, the argument offset is used to compute it.
683 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
684 time_reftime = time_second;
687 if (time_status & STA_FREQHOLD || time_reftime == 0)
688 time_reftime = time_second;
689 mtemp = time_second - time_reftime;
690 L_LINT(ftemp, time_monitor);
691 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
693 L_ADD(time_freq, ftemp);
694 time_status &= ~STA_MODE;
695 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
697 L_LINT(ftemp, (time_monitor << 4) / mtemp);
698 L_RSHIFT(ftemp, SHIFT_FLL + 4);
699 L_ADD(time_freq, ftemp);
700 time_status |= STA_MODE;
702 time_reftime = time_second;
703 if (L_GINT(time_freq) > MAXFREQ)
704 L_LINT(time_freq, MAXFREQ);
705 else if (L_GINT(time_freq) < -MAXFREQ)
706 L_LINT(time_freq, -MAXFREQ);
711 * hardpps() - discipline CPU clock oscillator to external PPS signal
713 * This routine is called at each PPS interrupt in order to discipline
714 * the CPU clock oscillator to the PPS signal. There are two independent
715 * first-order feedback loops, one for the phase, the other for the
716 * frequency. The phase loop measures and grooms the PPS phase offset
717 * and leaves it in a handy spot for the seconds overflow routine. The
718 * frequency loop averages successive PPS phase differences and
719 * calculates the PPS frequency offset, which is also processed by the
720 * seconds overflow routine. The code requires the caller to capture the
721 * time and architecture-dependent hardware counter values in
722 * nanoseconds at the on-time PPS signal transition.
724 * Note that, on some Unix systems this routine runs at an interrupt
725 * priority level higher than the timer interrupt routine hardclock().
726 * Therefore, the variables used are distinct from the hardclock()
727 * variables, except for the actual time and frequency variables, which
728 * are determined by this routine and updated atomically.
732 struct timespec *tsp; /* time at PPS */
733 long nsec; /* hardware counter at PPS */
735 long u_sec, u_nsec, v_nsec; /* temps */
739 * The signal is first processed by a range gate and frequency
740 * discriminator. The range gate rejects noise spikes outside
741 * the range +-500 us. The frequency discriminator rejects input
742 * signals with apparent frequency outside the range 1 +-500
743 * PPM. If two hits occur in the same second, we ignore the
744 * later hit; if not and a hit occurs outside the range gate,
745 * keep the later hit for later comparison, but do not process
748 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
749 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
750 pps_valid = PPS_VALID;
752 u_nsec = tsp->tv_nsec;
753 if (u_nsec >= (NANOSECOND >> 1)) {
754 u_nsec -= NANOSECOND;
757 v_nsec = u_nsec - pps_tf[0].tv_nsec;
758 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
761 pps_tf[2] = pps_tf[1];
762 pps_tf[1] = pps_tf[0];
763 pps_tf[0].tv_sec = u_sec;
764 pps_tf[0].tv_nsec = u_nsec;
767 * Compute the difference between the current and previous
768 * counter values. If the difference exceeds 0.5 s, assume it
769 * has wrapped around, so correct 1.0 s. If the result exceeds
770 * the tick interval, the sample point has crossed a tick
771 * boundary during the last second, so correct the tick. Very
775 if (u_nsec > (NANOSECOND >> 1))
776 u_nsec -= NANOSECOND;
777 else if (u_nsec < -(NANOSECOND >> 1))
778 u_nsec += NANOSECOND;
779 pps_fcount += u_nsec;
780 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
782 time_status &= ~STA_PPSJITTER;
785 * A three-stage median filter is used to help denoise the PPS
786 * time. The median sample becomes the time offset estimate; the
787 * difference between the other two samples becomes the time
788 * dispersion (jitter) estimate.
790 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
791 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
792 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
793 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
794 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
795 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
796 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
798 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
799 u_nsec = 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; /* 2 1 0 */
804 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
805 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
806 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
807 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
809 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
810 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
815 * Nominal jitter is due to PPS signal noise and interrupt
816 * latency. If it exceeds the popcorn threshold, the sample is
817 * discarded. otherwise, if so enabled, the time offset is
818 * updated. We can tolerate a modest loss of data here without
819 * much degrading time accuracy.
821 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
822 time_status |= STA_PPSJITTER;
824 } else if (time_status & STA_PPSTIME) {
825 time_monitor = -v_nsec;
826 L_LINT(time_offset, time_monitor);
828 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
829 u_sec = pps_tf[0].tv_sec - pps_lastsec;
830 if (u_sec < (1 << pps_shift))
834 * At the end of the calibration interval the difference between
835 * the first and last counter values becomes the scaled
836 * frequency. It will later be divided by the length of the
837 * interval to determine the frequency update. If the frequency
838 * exceeds a sanity threshold, or if the actual calibration
839 * interval is not equal to the expected length, the data are
840 * discarded. We can tolerate a modest loss of data here without
841 * much degrading frequency accuracy.
844 v_nsec = -pps_fcount;
845 pps_lastsec = pps_tf[0].tv_sec;
847 u_nsec = MAXFREQ << pps_shift;
848 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
850 time_status |= STA_PPSERROR;
856 * Here the raw frequency offset and wander (stability) is
857 * calculated. If the wander is less than the wander threshold
858 * for four consecutive averaging intervals, the interval is
859 * doubled; if it is greater than the threshold for four
860 * consecutive intervals, the interval is halved. The scaled
861 * frequency offset is converted to frequency offset. The
862 * stability metric is calculated as the average of recent
863 * frequency changes, but is used only for performance
866 L_LINT(ftemp, v_nsec);
867 L_RSHIFT(ftemp, pps_shift);
868 L_SUB(ftemp, pps_freq);
869 u_nsec = L_GINT(ftemp);
870 if (u_nsec > PPS_MAXWANDER) {
871 L_LINT(ftemp, PPS_MAXWANDER);
873 time_status |= STA_PPSWANDER;
875 } else if (u_nsec < -PPS_MAXWANDER) {
876 L_LINT(ftemp, -PPS_MAXWANDER);
878 time_status |= STA_PPSWANDER;
883 if (pps_intcnt >= 4) {
885 if (pps_shift < pps_shiftmax) {
889 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
891 if (pps_shift > PPS_FAVG) {
898 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
901 * The PPS frequency is recalculated and clamped to the maximum
902 * MAXFREQ. If enabled, the system clock frequency is updated as
905 L_ADD(pps_freq, ftemp);
906 u_nsec = L_GINT(pps_freq);
907 if (u_nsec > MAXFREQ)
908 L_LINT(pps_freq, MAXFREQ);
909 else if (u_nsec < -MAXFREQ)
910 L_LINT(pps_freq, -MAXFREQ);
911 if (time_status & STA_PPSFREQ)
912 time_freq = pps_freq;
914 #endif /* PPS_SYNC */
916 #ifndef _SYS_SYSPROTO_H_
917 struct adjtime_args {
918 struct timeval *delta;
919 struct timeval *olddelta;
927 adjtime(struct thread *td, struct adjtime_args *uap)
932 if ((error = suser(td)))
937 atv.tv_sec = time_adjtime / 1000000;
938 atv.tv_usec = time_adjtime % 1000000;
939 if (atv.tv_usec < 0) {
940 atv.tv_usec += 1000000;
943 error = copyout(&atv, uap->olddelta, sizeof(atv));
948 error = copyin(uap->delta, &atv, sizeof(atv));
951 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec;