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/kernel.h>
45 #include <sys/mutex.h>
47 #include <sys/timex.h>
48 #include <sys/timetc.h>
49 #include <sys/timepps.h>
50 #include <sys/syscallsubr.h>
51 #include <sys/sysctl.h>
54 * Single-precision macros for 64-bit machines
57 #define L_ADD(v, u) ((v) += (u))
58 #define L_SUB(v, u) ((v) -= (u))
59 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
60 #define L_NEG(v) ((v) = -(v))
61 #define L_RSHIFT(v, n) \
64 (v) = -(-(v) >> (n)); \
68 #define L_MPY(v, a) ((v) *= (a))
69 #define L_CLR(v) ((v) = 0)
70 #define L_ISNEG(v) ((v) < 0)
71 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32)
72 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
75 * Generic NTP kernel interface
77 * These routines constitute the Network Time Protocol (NTP) interfaces
78 * for user and daemon application programs. The ntp_gettime() routine
79 * provides the time, maximum error (synch distance) and estimated error
80 * (dispersion) to client user application programs. The ntp_adjtime()
81 * routine is used by the NTP daemon to adjust the system clock to an
82 * externally derived time. The time offset and related variables set by
83 * this routine are used by other routines in this module to adjust the
84 * phase and frequency of the clock discipline loop which controls the
87 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
88 * defined), the time at each tick interrupt is derived directly from
89 * the kernel time variable. When the kernel time is reckoned in
90 * microseconds, (NTP_NANO undefined), the time is derived from the
91 * kernel time variable together with a variable representing the
92 * leftover nanoseconds at the last tick interrupt. In either case, the
93 * current nanosecond time is reckoned from these values plus an
94 * interpolated value derived by the clock routines in another
95 * architecture-specific module. The interpolation can use either a
96 * dedicated counter or a processor cycle counter (PCC) implemented in
99 * Note that all routines must run at priority splclock or higher.
102 * Phase/frequency-lock loop (PLL/FLL) definitions
104 * The nanosecond clock discipline uses two variable types, time
105 * variables and frequency variables. Both types are represented as 64-
106 * bit fixed-point quantities with the decimal point between two 32-bit
107 * halves. On a 32-bit machine, each half is represented as a single
108 * word and mathematical operations are done using multiple-precision
109 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
112 * A time variable is a signed 64-bit fixed-point number in ns and
113 * fraction. It represents the remaining time offset to be amortized
114 * over succeeding tick interrupts. The maximum time offset is about
115 * 0.5 s and the resolution is about 2.3e-10 ns.
117 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
118 * 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
119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
121 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
123 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
125 * A frequency variable is a signed 64-bit fixed-point number in ns/s
126 * and fraction. It represents the ns and fraction to be added to the
127 * kernel time variable at each second. The maximum frequency offset is
128 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
130 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
131 * 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
132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
133 * |s s s s s s s s s s s s s| ns/s |
134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
136 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
139 * The following variables establish the state of the PLL/FLL and the
140 * residual time and frequency offset of the local clock.
142 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
143 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
145 static int time_state = TIME_OK; /* clock state */
146 static int time_status = STA_UNSYNC; /* clock status bits */
147 static long time_tai; /* TAI offset (s) */
148 static long time_monitor; /* last time offset scaled (ns) */
149 static long time_constant; /* poll interval (shift) (s) */
150 static long time_precision = 1; /* clock precision (ns) */
151 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
152 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
153 static long time_reftime; /* time at last adjustment (s) */
154 static l_fp time_offset; /* time offset (ns) */
155 static l_fp time_freq; /* frequency offset (ns/s) */
156 static l_fp time_adj; /* tick adjust (ns/s) */
158 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
162 * The following variables are used when a pulse-per-second (PPS) signal
163 * is available and connected via a modem control lead. They establish
164 * the engineering parameters of the clock discipline loop when
165 * controlled by the PPS signal.
167 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
168 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
169 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
170 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
171 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
172 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
173 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
175 static struct timespec pps_tf[3]; /* phase median filter */
176 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
177 static long pps_fcount; /* frequency accumulator */
178 static long pps_jitter; /* nominal jitter (ns) */
179 static long pps_stabil; /* nominal stability (scaled ns/s) */
180 static long pps_lastsec; /* time at last calibration (s) */
181 static int pps_valid; /* signal watchdog counter */
182 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
183 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
184 static int pps_intcnt; /* wander counter */
187 * PPS signal quality monitors
189 static long pps_calcnt; /* calibration intervals */
190 static long pps_jitcnt; /* jitter limit exceeded */
191 static long pps_stbcnt; /* stability limit exceeded */
192 static long pps_errcnt; /* calibration errors */
193 #endif /* PPS_SYNC */
195 * End of phase/frequency-lock loop (PLL/FLL) definitions
198 static void ntp_init(void);
199 static void hardupdate(long offset);
200 static void ntp_gettime1(struct ntptimeval *ntvp);
203 ntp_gettime1(struct ntptimeval *ntvp)
205 struct timespec atv; /* nanosecond time */
210 ntvp->time.tv_sec = atv.tv_sec;
211 ntvp->time.tv_nsec = atv.tv_nsec;
212 ntvp->maxerror = time_maxerror;
213 ntvp->esterror = time_esterror;
214 ntvp->tai = time_tai;
215 ntvp->time_state = time_state;
218 * Status word error decode. If any of these conditions occur,
219 * an error is returned, instead of the status word. Most
220 * applications will care only about the fact the system clock
221 * may not be trusted, not about the details.
223 * Hardware or software error
225 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
228 * PPS signal lost when either time or frequency synchronization
231 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
232 !(time_status & STA_PPSSIGNAL)) ||
235 * PPS jitter exceeded when time synchronization requested
237 (time_status & STA_PPSTIME &&
238 time_status & STA_PPSJITTER) ||
241 * PPS wander exceeded or calibration error when frequency
242 * synchronization requested
244 (time_status & STA_PPSFREQ &&
245 time_status & (STA_PPSWANDER | STA_PPSERROR)))
246 ntvp->time_state = TIME_ERROR;
250 * ntp_gettime() - NTP user application interface
252 * See the timex.h header file for synopsis and API description. Note
253 * that the TAI offset is returned in the ntvtimeval.tai structure
256 #ifndef _SYS_SYSPROTO_H_
257 struct ntp_gettime_args {
258 struct ntptimeval *ntvp;
263 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
265 struct ntptimeval ntv;
271 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
275 ntp_sysctl(SYSCTL_HANDLER_ARGS)
277 struct ntptimeval ntv; /* temporary structure */
281 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
284 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
285 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
286 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
289 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
290 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
291 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
293 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
294 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
297 * ntp_adjtime() - NTP daemon application interface
299 * See the timex.h header file for synopsis and API description. Note
300 * that the timex.constant structure member has a dual purpose to set
301 * the time constant and to set the TAI offset.
303 #ifndef _SYS_SYSPROTO_H_
304 struct ntp_adjtime_args {
313 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
315 struct timex ntv; /* temporary structure */
316 long freq; /* frequency ns/s) */
317 int modes; /* mode bits from structure */
318 int s; /* caller priority */
321 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
326 * Update selected clock variables - only the superuser can
327 * change anything. Note that there is no error checking here on
328 * the assumption the superuser should know what it is doing.
329 * Note that either the time constant or TAI offset are loaded
330 * from the ntv.constant member, depending on the mode bits. If
331 * the STA_PLL bit in the status word is cleared, the state and
332 * status words are reset to the initial values at boot.
337 error = priv_check(td, PRIV_NTP_ADJTIME);
341 if (modes & MOD_MAXERROR)
342 time_maxerror = ntv.maxerror;
343 if (modes & MOD_ESTERROR)
344 time_esterror = ntv.esterror;
345 if (modes & MOD_STATUS) {
346 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
347 time_state = TIME_OK;
348 time_status = STA_UNSYNC;
350 pps_shift = PPS_FAVG;
351 #endif /* PPS_SYNC */
353 time_status &= STA_RONLY;
354 time_status |= ntv.status & ~STA_RONLY;
356 if (modes & MOD_TIMECONST) {
357 if (ntv.constant < 0)
359 else if (ntv.constant > MAXTC)
360 time_constant = MAXTC;
362 time_constant = ntv.constant;
364 if (modes & MOD_TAI) {
365 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
366 time_tai = ntv.constant;
369 if (modes & MOD_PPSMAX) {
370 if (ntv.shift < PPS_FAVG)
371 pps_shiftmax = PPS_FAVG;
372 else if (ntv.shift > PPS_FAVGMAX)
373 pps_shiftmax = PPS_FAVGMAX;
375 pps_shiftmax = ntv.shift;
377 #endif /* PPS_SYNC */
378 if (modes & MOD_NANO)
379 time_status |= STA_NANO;
380 if (modes & MOD_MICRO)
381 time_status &= ~STA_NANO;
382 if (modes & MOD_CLKB)
383 time_status |= STA_CLK;
384 if (modes & MOD_CLKA)
385 time_status &= ~STA_CLK;
386 if (modes & MOD_FREQUENCY) {
387 freq = (ntv.freq * 1000LL) >> 16;
389 L_LINT(time_freq, MAXFREQ);
390 else if (freq < -MAXFREQ)
391 L_LINT(time_freq, -MAXFREQ);
394 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
395 * time_freq is [ns/s * 2^32]
397 time_freq = ntv.freq * 1000LL * 65536LL;
400 pps_freq = time_freq;
401 #endif /* PPS_SYNC */
403 if (modes & MOD_OFFSET) {
404 if (time_status & STA_NANO)
405 hardupdate(ntv.offset);
407 hardupdate(ntv.offset * 1000);
411 * Retrieve all clock variables. Note that the TAI offset is
412 * returned only by ntp_gettime();
414 if (time_status & STA_NANO)
415 ntv.offset = L_GINT(time_offset);
417 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
418 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
419 ntv.maxerror = time_maxerror;
420 ntv.esterror = time_esterror;
421 ntv.status = time_status;
422 ntv.constant = time_constant;
423 if (time_status & STA_NANO)
424 ntv.precision = time_precision;
426 ntv.precision = time_precision / 1000;
427 ntv.tolerance = MAXFREQ * SCALE_PPM;
429 ntv.shift = pps_shift;
430 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
431 if (time_status & STA_NANO)
432 ntv.jitter = pps_jitter;
434 ntv.jitter = pps_jitter / 1000;
435 ntv.stabil = pps_stabil;
436 ntv.calcnt = pps_calcnt;
437 ntv.errcnt = pps_errcnt;
438 ntv.jitcnt = pps_jitcnt;
439 ntv.stbcnt = pps_stbcnt;
440 #endif /* PPS_SYNC */
443 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
448 * Status word error decode. See comments in
449 * ntp_gettime() routine.
451 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
452 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
453 !(time_status & STA_PPSSIGNAL)) ||
454 (time_status & STA_PPSTIME &&
455 time_status & STA_PPSJITTER) ||
456 (time_status & STA_PPSFREQ &&
457 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
458 td->td_retval[0] = TIME_ERROR;
460 td->td_retval[0] = time_state;
468 * second_overflow() - called after ntp_tick_adjust()
470 * This routine is ordinarily called immediately following the above
471 * routine ntp_tick_adjust(). While these two routines are normally
472 * combined, they are separated here only for the purposes of
476 ntp_update_second(int64_t *adjustment, time_t *newsec)
479 l_fp ftemp; /* 32/64-bit temporary */
482 * On rollover of the second both the nanosecond and microsecond
483 * clocks are updated and the state machine cranked as
484 * necessary. The phase adjustment to be used for the next
485 * second is calculated and the maximum error is increased by
488 time_maxerror += MAXFREQ / 1000;
491 * Leap second processing. If in leap-insert state at
492 * the end of the day, the system clock is set back one
493 * second; if in leap-delete state, the system clock is
494 * set ahead one second. The nano_time() routine or
495 * external clock driver will insure that reported time
496 * is always monotonic.
498 switch (time_state) {
504 if (time_status & STA_INS)
505 time_state = TIME_INS;
506 else if (time_status & STA_DEL)
507 time_state = TIME_DEL;
511 * Insert second 23:59:60 following second
515 if (!(time_status & STA_INS))
516 time_state = TIME_OK;
517 else if ((*newsec) % 86400 == 0) {
519 time_state = TIME_OOP;
525 * Delete second 23:59:59.
528 if (!(time_status & STA_DEL))
529 time_state = TIME_OK;
530 else if (((*newsec) + 1) % 86400 == 0) {
533 time_state = TIME_WAIT;
538 * Insert second in progress.
541 time_state = TIME_WAIT;
545 * Wait for status bits to clear.
548 if (!(time_status & (STA_INS | STA_DEL)))
549 time_state = TIME_OK;
553 * Compute the total time adjustment for the next second
554 * in ns. The offset is reduced by a factor depending on
555 * whether the PPS signal is operating. Note that the
556 * value is in effect scaled by the clock frequency,
557 * since the adjustment is added at each tick interrupt.
561 /* XXX even if PPS signal dies we should finish adjustment ? */
562 if (time_status & STA_PPSTIME && time_status &
564 L_RSHIFT(ftemp, pps_shift);
566 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
568 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
569 #endif /* PPS_SYNC */
571 L_SUB(time_offset, ftemp);
572 L_ADD(time_adj, time_freq);
575 * Apply any correction from adjtime(2). If more than one second
576 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
577 * until the last second is slewed the final < 500 usecs.
579 if (time_adjtime != 0) {
580 if (time_adjtime > 1000000)
582 else if (time_adjtime < -1000000)
584 else if (time_adjtime > 500)
586 else if (time_adjtime < -500)
589 tickrate = time_adjtime;
590 time_adjtime -= tickrate;
591 L_LINT(ftemp, tickrate * 1000);
592 L_ADD(time_adj, ftemp);
594 *adjustment = time_adj;
600 time_status &= ~STA_PPSSIGNAL;
601 #endif /* PPS_SYNC */
605 * ntp_init() - initialize variables and structures
607 * This routine must be called after the kernel variables hz and tick
608 * are set or changed and before the next tick interrupt. In this
609 * particular implementation, these values are assumed set elsewhere in
610 * the kernel. The design allows the clock frequency and tick interval
611 * to be changed while the system is running. So, this routine should
612 * probably be integrated with the code that does that.
619 * The following variables are initialized only at startup. Only
620 * those structures not cleared by the compiler need to be
621 * initialized, and these only in the simulator. In the actual
622 * kernel, any nonzero values here will quickly evaporate.
627 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
628 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
629 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
632 #endif /* PPS_SYNC */
635 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
638 * hardupdate() - local clock update
640 * This routine is called by ntp_adjtime() to update the local clock
641 * phase and frequency. The implementation is of an adaptive-parameter,
642 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
643 * time and frequency offset estimates for each call. If the kernel PPS
644 * discipline code is configured (PPS_SYNC), the PPS signal itself
645 * determines the new time offset, instead of the calling argument.
646 * Presumably, calls to ntp_adjtime() occur only when the caller
647 * believes the local clock is valid within some bound (+-128 ms with
648 * NTP). If the caller's time is far different than the PPS time, an
649 * argument will ensue, and it's not clear who will lose.
651 * For uncompensated quartz crystal oscillators and nominal update
652 * intervals less than 256 s, operation should be in phase-lock mode,
653 * where the loop is disciplined to phase. For update intervals greater
654 * than 1024 s, operation should be in frequency-lock mode, where the
655 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
656 * is selected by the STA_MODE status bit.
660 long offset; /* clock offset (ns) */
666 * Select how the phase is to be controlled and from which
667 * source. If the PPS signal is present and enabled to
668 * discipline the time, the PPS offset is used; otherwise, the
669 * argument offset is used.
671 if (!(time_status & STA_PLL))
673 if (!(time_status & STA_PPSTIME && time_status &
675 if (offset > MAXPHASE)
676 time_monitor = MAXPHASE;
677 else if (offset < -MAXPHASE)
678 time_monitor = -MAXPHASE;
680 time_monitor = offset;
681 L_LINT(time_offset, time_monitor);
685 * Select how the frequency is to be controlled and in which
686 * mode (PLL or FLL). If the PPS signal is present and enabled
687 * to discipline the frequency, the PPS frequency is used;
688 * otherwise, the argument offset is used to compute it.
690 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
691 time_reftime = time_second;
694 if (time_status & STA_FREQHOLD || time_reftime == 0)
695 time_reftime = time_second;
696 mtemp = time_second - time_reftime;
697 L_LINT(ftemp, time_monitor);
698 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
700 L_ADD(time_freq, ftemp);
701 time_status &= ~STA_MODE;
702 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
704 L_LINT(ftemp, (time_monitor << 4) / mtemp);
705 L_RSHIFT(ftemp, SHIFT_FLL + 4);
706 L_ADD(time_freq, ftemp);
707 time_status |= STA_MODE;
709 time_reftime = time_second;
710 if (L_GINT(time_freq) > MAXFREQ)
711 L_LINT(time_freq, MAXFREQ);
712 else if (L_GINT(time_freq) < -MAXFREQ)
713 L_LINT(time_freq, -MAXFREQ);
718 * hardpps() - discipline CPU clock oscillator to external PPS signal
720 * This routine is called at each PPS interrupt in order to discipline
721 * the CPU clock oscillator to the PPS signal. There are two independent
722 * first-order feedback loops, one for the phase, the other for the
723 * frequency. The phase loop measures and grooms the PPS phase offset
724 * and leaves it in a handy spot for the seconds overflow routine. The
725 * frequency loop averages successive PPS phase differences and
726 * calculates the PPS frequency offset, which is also processed by the
727 * seconds overflow routine. The code requires the caller to capture the
728 * time and architecture-dependent hardware counter values in
729 * nanoseconds at the on-time PPS signal transition.
731 * Note that, on some Unix systems this routine runs at an interrupt
732 * priority level higher than the timer interrupt routine hardclock().
733 * Therefore, the variables used are distinct from the hardclock()
734 * variables, except for the actual time and frequency variables, which
735 * are determined by this routine and updated atomically.
739 struct timespec *tsp; /* time at PPS */
740 long nsec; /* hardware counter at PPS */
742 long u_sec, u_nsec, v_nsec; /* temps */
746 * The signal is first processed by a range gate and frequency
747 * discriminator. The range gate rejects noise spikes outside
748 * the range +-500 us. The frequency discriminator rejects input
749 * signals with apparent frequency outside the range 1 +-500
750 * PPM. If two hits occur in the same second, we ignore the
751 * later hit; if not and a hit occurs outside the range gate,
752 * keep the later hit for later comparison, but do not process
755 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
756 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
757 pps_valid = PPS_VALID;
759 u_nsec = tsp->tv_nsec;
760 if (u_nsec >= (NANOSECOND >> 1)) {
761 u_nsec -= NANOSECOND;
764 v_nsec = u_nsec - pps_tf[0].tv_nsec;
765 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
768 pps_tf[2] = pps_tf[1];
769 pps_tf[1] = pps_tf[0];
770 pps_tf[0].tv_sec = u_sec;
771 pps_tf[0].tv_nsec = u_nsec;
774 * Compute the difference between the current and previous
775 * counter values. If the difference exceeds 0.5 s, assume it
776 * has wrapped around, so correct 1.0 s. If the result exceeds
777 * the tick interval, the sample point has crossed a tick
778 * boundary during the last second, so correct the tick. Very
782 if (u_nsec > (NANOSECOND >> 1))
783 u_nsec -= NANOSECOND;
784 else if (u_nsec < -(NANOSECOND >> 1))
785 u_nsec += NANOSECOND;
786 pps_fcount += u_nsec;
787 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
789 time_status &= ~STA_PPSJITTER;
792 * A three-stage median filter is used to help denoise the PPS
793 * time. The median sample becomes the time offset estimate; the
794 * difference between the other two samples becomes the time
795 * dispersion (jitter) estimate.
797 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
798 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
799 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
800 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
801 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
802 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
803 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
805 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
806 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
809 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
810 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
811 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
812 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
813 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
814 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
816 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
817 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
822 * Nominal jitter is due to PPS signal noise and interrupt
823 * latency. If it exceeds the popcorn threshold, the sample is
824 * discarded. otherwise, if so enabled, the time offset is
825 * updated. We can tolerate a modest loss of data here without
826 * much degrading time accuracy.
828 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
829 time_status |= STA_PPSJITTER;
831 } else if (time_status & STA_PPSTIME) {
832 time_monitor = -v_nsec;
833 L_LINT(time_offset, time_monitor);
835 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
836 u_sec = pps_tf[0].tv_sec - pps_lastsec;
837 if (u_sec < (1 << pps_shift))
841 * At the end of the calibration interval the difference between
842 * the first and last counter values becomes the scaled
843 * frequency. It will later be divided by the length of the
844 * interval to determine the frequency update. If the frequency
845 * exceeds a sanity threshold, or if the actual calibration
846 * interval is not equal to the expected length, the data are
847 * discarded. We can tolerate a modest loss of data here without
848 * much degrading frequency accuracy.
851 v_nsec = -pps_fcount;
852 pps_lastsec = pps_tf[0].tv_sec;
854 u_nsec = MAXFREQ << pps_shift;
855 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
857 time_status |= STA_PPSERROR;
863 * Here the raw frequency offset and wander (stability) is
864 * calculated. If the wander is less than the wander threshold
865 * for four consecutive averaging intervals, the interval is
866 * doubled; if it is greater than the threshold for four
867 * consecutive intervals, the interval is halved. The scaled
868 * frequency offset is converted to frequency offset. The
869 * stability metric is calculated as the average of recent
870 * frequency changes, but is used only for performance
873 L_LINT(ftemp, v_nsec);
874 L_RSHIFT(ftemp, pps_shift);
875 L_SUB(ftemp, pps_freq);
876 u_nsec = L_GINT(ftemp);
877 if (u_nsec > PPS_MAXWANDER) {
878 L_LINT(ftemp, PPS_MAXWANDER);
880 time_status |= STA_PPSWANDER;
882 } else if (u_nsec < -PPS_MAXWANDER) {
883 L_LINT(ftemp, -PPS_MAXWANDER);
885 time_status |= STA_PPSWANDER;
890 if (pps_intcnt >= 4) {
892 if (pps_shift < pps_shiftmax) {
896 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
898 if (pps_shift > PPS_FAVG) {
905 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
908 * The PPS frequency is recalculated and clamped to the maximum
909 * MAXFREQ. If enabled, the system clock frequency is updated as
912 L_ADD(pps_freq, ftemp);
913 u_nsec = L_GINT(pps_freq);
914 if (u_nsec > MAXFREQ)
915 L_LINT(pps_freq, MAXFREQ);
916 else if (u_nsec < -MAXFREQ)
917 L_LINT(pps_freq, -MAXFREQ);
918 if (time_status & STA_PPSFREQ)
919 time_freq = pps_freq;
921 #endif /* PPS_SYNC */
923 #ifndef _SYS_SYSPROTO_H_
924 struct adjtime_args {
925 struct timeval *delta;
926 struct timeval *olddelta;
934 adjtime(struct thread *td, struct adjtime_args *uap)
936 struct timeval delta, olddelta, *deltap;
940 error = copyin(uap->delta, &delta, sizeof(delta));
946 error = kern_adjtime(td, deltap, &olddelta);
947 if (uap->olddelta && error == 0)
948 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
953 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
958 if ((error = priv_check(td, PRIV_ADJTIME)))
963 atv.tv_sec = time_adjtime / 1000000;
964 atv.tv_usec = time_adjtime % 1000000;
965 if (atv.tv_usec < 0) {
966 atv.tv_usec += 1000000;
972 time_adjtime = (int64_t)delta->tv_sec * 1000000 +