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 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 long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
158 static long time_reftime; /* uptime 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) */
165 static struct mtx ntp_lock;
166 MTX_SYSINIT(ntp, &ntp_lock, "ntp", MTX_SPIN);
168 #define NTP_LOCK() mtx_lock_spin(&ntp_lock)
169 #define NTP_UNLOCK() mtx_unlock_spin(&ntp_lock)
170 #define NTP_ASSERT_LOCKED() mtx_assert(&ntp_lock, MA_OWNED)
174 * The following variables are used when a pulse-per-second (PPS) signal
175 * is available and connected via a modem control lead. They establish
176 * the engineering parameters of the clock discipline loop when
177 * controlled by the PPS signal.
179 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
180 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
181 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
182 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
183 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
184 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
185 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
187 static struct timespec pps_tf[3]; /* phase median filter */
188 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
189 static long pps_fcount; /* frequency accumulator */
190 static long pps_jitter; /* nominal jitter (ns) */
191 static long pps_stabil; /* nominal stability (scaled ns/s) */
192 static long pps_lastsec; /* time at last calibration (s) */
193 static int pps_valid; /* signal watchdog counter */
194 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
195 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
196 static int pps_intcnt; /* wander counter */
199 * PPS signal quality monitors
201 static long pps_calcnt; /* calibration intervals */
202 static long pps_jitcnt; /* jitter limit exceeded */
203 static long pps_stbcnt; /* stability limit exceeded */
204 static long pps_errcnt; /* calibration errors */
205 #endif /* PPS_SYNC */
207 * End of phase/frequency-lock loop (PLL/FLL) definitions
210 static void ntp_init(void);
211 static void hardupdate(long offset);
212 static void ntp_gettime1(struct ntptimeval *ntvp);
213 static bool ntp_is_time_error(int tsl);
216 ntp_is_time_error(int tsl)
220 * Status word error decode. If any of these conditions occur,
221 * an error is returned, instead of the status word. Most
222 * applications will care only about the fact the system clock
223 * may not be trusted, not about the details.
225 * Hardware or software error
227 if ((tsl & (STA_UNSYNC | STA_CLOCKERR)) ||
230 * PPS signal lost when either time or frequency synchronization
233 (tsl & (STA_PPSFREQ | STA_PPSTIME) &&
234 !(tsl & STA_PPSSIGNAL)) ||
237 * PPS jitter exceeded when time synchronization requested
239 (tsl & STA_PPSTIME && tsl & STA_PPSJITTER) ||
242 * PPS wander exceeded or calibration error when frequency
243 * synchronization requested
245 (tsl & STA_PPSFREQ &&
246 tsl & (STA_PPSWANDER | STA_PPSERROR)))
253 ntp_gettime1(struct ntptimeval *ntvp)
255 struct timespec atv; /* nanosecond time */
260 ntvp->time.tv_sec = atv.tv_sec;
261 ntvp->time.tv_nsec = atv.tv_nsec;
262 ntvp->maxerror = time_maxerror;
263 ntvp->esterror = time_esterror;
264 ntvp->tai = time_tai;
265 ntvp->time_state = time_state;
267 if (ntp_is_time_error(time_status))
268 ntvp->time_state = TIME_ERROR;
272 * ntp_gettime() - NTP user application interface
274 * See the timex.h header file for synopsis and API description. Note that
275 * the TAI offset is returned in the ntvtimeval.tai structure member.
277 #ifndef _SYS_SYSPROTO_H_
278 struct ntp_gettime_args {
279 struct ntptimeval *ntvp;
284 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
286 struct ntptimeval ntv;
292 td->td_retval[0] = ntv.time_state;
293 return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
297 ntp_sysctl(SYSCTL_HANDLER_ARGS)
299 struct ntptimeval ntv; /* temporary structure */
305 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
308 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
309 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE | CTLFLAG_RD |
310 CTLFLAG_MPSAFE, 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval",
314 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW,
315 &pps_shiftmax, 0, "Max interval duration (sec) (shift)");
316 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW,
317 &pps_shift, 0, "Interval duration (sec) (shift)");
318 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD,
319 &time_monitor, 0, "Last time offset scaled (ns)");
321 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
323 "Scaled frequency offset (ns/sec)");
324 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD | CTLFLAG_MPSAFE,
326 "Frequency offset (ns/sec)");
330 * ntp_adjtime() - NTP daemon application interface
332 * See the timex.h header file for synopsis and API description. Note that
333 * the timex.constant structure member has a dual purpose to set the time
334 * constant and to set the TAI offset.
336 #ifndef _SYS_SYSPROTO_H_
337 struct ntp_adjtime_args {
343 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
345 struct timex ntv; /* temporary structure */
346 long freq; /* frequency ns/s) */
347 int modes; /* mode bits from structure */
350 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
355 * Update selected clock variables - only the superuser can
356 * change anything. Note that there is no error checking here on
357 * the assumption the superuser should know what it is doing.
358 * Note that either the time constant or TAI offset are loaded
359 * from the ntv.constant member, depending on the mode bits. If
360 * the STA_PLL bit in the status word is cleared, the state and
361 * status words are reset to the initial values at boot.
365 error = priv_check(td, PRIV_NTP_ADJTIME);
369 if (modes & MOD_MAXERROR)
370 time_maxerror = ntv.maxerror;
371 if (modes & MOD_ESTERROR)
372 time_esterror = ntv.esterror;
373 if (modes & MOD_STATUS) {
374 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
375 time_state = TIME_OK;
376 time_status = STA_UNSYNC;
378 pps_shift = PPS_FAVG;
379 #endif /* PPS_SYNC */
381 time_status &= STA_RONLY;
382 time_status |= ntv.status & ~STA_RONLY;
384 if (modes & MOD_TIMECONST) {
385 if (ntv.constant < 0)
387 else if (ntv.constant > MAXTC)
388 time_constant = MAXTC;
390 time_constant = ntv.constant;
392 if (modes & MOD_TAI) {
393 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
394 time_tai = ntv.constant;
397 if (modes & MOD_PPSMAX) {
398 if (ntv.shift < PPS_FAVG)
399 pps_shiftmax = PPS_FAVG;
400 else if (ntv.shift > PPS_FAVGMAX)
401 pps_shiftmax = PPS_FAVGMAX;
403 pps_shiftmax = ntv.shift;
405 #endif /* PPS_SYNC */
406 if (modes & MOD_NANO)
407 time_status |= STA_NANO;
408 if (modes & MOD_MICRO)
409 time_status &= ~STA_NANO;
410 if (modes & MOD_CLKB)
411 time_status |= STA_CLK;
412 if (modes & MOD_CLKA)
413 time_status &= ~STA_CLK;
414 if (modes & MOD_FREQUENCY) {
415 freq = (ntv.freq * 1000LL) >> 16;
417 L_LINT(time_freq, MAXFREQ);
418 else if (freq < -MAXFREQ)
419 L_LINT(time_freq, -MAXFREQ);
422 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
423 * time_freq is [ns/s * 2^32]
425 time_freq = ntv.freq * 1000LL * 65536LL;
428 pps_freq = time_freq;
429 #endif /* PPS_SYNC */
431 if (modes & MOD_OFFSET) {
432 if (time_status & STA_NANO)
433 hardupdate(ntv.offset);
435 hardupdate(ntv.offset * 1000);
439 * Retrieve all clock variables. Note that the TAI offset is
440 * returned only by ntp_gettime();
442 if (time_status & STA_NANO)
443 ntv.offset = L_GINT(time_offset);
445 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
446 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
447 ntv.maxerror = time_maxerror;
448 ntv.esterror = time_esterror;
449 ntv.status = time_status;
450 ntv.constant = time_constant;
451 if (time_status & STA_NANO)
452 ntv.precision = time_precision;
454 ntv.precision = time_precision / 1000;
455 ntv.tolerance = MAXFREQ * SCALE_PPM;
457 ntv.shift = pps_shift;
458 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
459 if (time_status & STA_NANO)
460 ntv.jitter = pps_jitter;
462 ntv.jitter = pps_jitter / 1000;
463 ntv.stabil = pps_stabil;
464 ntv.calcnt = pps_calcnt;
465 ntv.errcnt = pps_errcnt;
466 ntv.jitcnt = pps_jitcnt;
467 ntv.stbcnt = pps_stbcnt;
468 #endif /* PPS_SYNC */
469 retval = ntp_is_time_error(time_status) ? TIME_ERROR : time_state;
472 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
474 td->td_retval[0] = retval;
479 * second_overflow() - called after ntp_tick_adjust()
481 * This routine is ordinarily called immediately following the above
482 * routine ntp_tick_adjust(). While these two routines are normally
483 * combined, they are separated here only for the purposes of
487 ntp_update_second(int64_t *adjustment, time_t *newsec)
490 l_fp ftemp; /* 32/64-bit temporary */
495 * On rollover of the second both the nanosecond and microsecond
496 * clocks are updated and the state machine cranked as
497 * necessary. The phase adjustment to be used for the next
498 * second is calculated and the maximum error is increased by
501 time_maxerror += MAXFREQ / 1000;
504 * Leap second processing. If in leap-insert state at
505 * the end of the day, the system clock is set back one
506 * second; if in leap-delete state, the system clock is
507 * set ahead one second. The nano_time() routine or
508 * external clock driver will insure that reported time
509 * is always monotonic.
511 switch (time_state) {
517 if (time_status & STA_INS)
518 time_state = TIME_INS;
519 else if (time_status & STA_DEL)
520 time_state = TIME_DEL;
524 * Insert second 23:59:60 following second
528 if (!(time_status & STA_INS))
529 time_state = TIME_OK;
530 else if ((*newsec) % 86400 == 0) {
532 time_state = TIME_OOP;
538 * Delete second 23:59:59.
541 if (!(time_status & STA_DEL))
542 time_state = TIME_OK;
543 else if (((*newsec) + 1) % 86400 == 0) {
546 time_state = TIME_WAIT;
551 * Insert second in progress.
554 time_state = TIME_WAIT;
558 * Wait for status bits to clear.
561 if (!(time_status & (STA_INS | STA_DEL)))
562 time_state = TIME_OK;
566 * Compute the total time adjustment for the next second
567 * in ns. The offset is reduced by a factor depending on
568 * whether the PPS signal is operating. Note that the
569 * value is in effect scaled by the clock frequency,
570 * since the adjustment is added at each tick interrupt.
574 /* XXX even if PPS signal dies we should finish adjustment ? */
575 if (time_status & STA_PPSTIME && time_status &
577 L_RSHIFT(ftemp, pps_shift);
579 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
581 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
582 #endif /* PPS_SYNC */
584 L_SUB(time_offset, ftemp);
585 L_ADD(time_adj, time_freq);
588 * Apply any correction from adjtime(2). If more than one second
589 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
590 * until the last second is slewed the final < 500 usecs.
592 if (time_adjtime != 0) {
593 if (time_adjtime > 1000000)
595 else if (time_adjtime < -1000000)
597 else if (time_adjtime > 500)
599 else if (time_adjtime < -500)
602 tickrate = time_adjtime;
603 time_adjtime -= tickrate;
604 L_LINT(ftemp, tickrate * 1000);
605 L_ADD(time_adj, ftemp);
607 *adjustment = time_adj;
613 time_status &= ~STA_PPSSIGNAL;
614 #endif /* PPS_SYNC */
620 * ntp_init() - initialize variables and structures
622 * This routine must be called after the kernel variables hz and tick
623 * are set or changed and before the next tick interrupt. In this
624 * particular implementation, these values are assumed set elsewhere in
625 * the kernel. The design allows the clock frequency and tick interval
626 * to be changed while the system is running. So, this routine should
627 * probably be integrated with the code that does that.
634 * The following variables are initialized only at startup. Only
635 * those structures not cleared by the compiler need to be
636 * initialized, and these only in the simulator. In the actual
637 * kernel, any nonzero values here will quickly evaporate.
642 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
643 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
644 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
647 #endif /* PPS_SYNC */
650 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL);
653 * hardupdate() - local clock update
655 * This routine is called by ntp_adjtime() to update the local clock
656 * phase and frequency. The implementation is of an adaptive-parameter,
657 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
658 * time and frequency offset estimates for each call. If the kernel PPS
659 * discipline code is configured (PPS_SYNC), the PPS signal itself
660 * determines the new time offset, instead of the calling argument.
661 * Presumably, calls to ntp_adjtime() occur only when the caller
662 * believes the local clock is valid within some bound (+-128 ms with
663 * NTP). If the caller's time is far different than the PPS time, an
664 * argument will ensue, and it's not clear who will lose.
666 * For uncompensated quartz crystal oscillators and nominal update
667 * intervals less than 256 s, operation should be in phase-lock mode,
668 * where the loop is disciplined to phase. For update intervals greater
669 * than 1024 s, operation should be in frequency-lock mode, where the
670 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
671 * is selected by the STA_MODE status bit.
675 long offset; /* clock offset (ns) */
683 * Select how the phase is to be controlled and from which
684 * source. If the PPS signal is present and enabled to
685 * discipline the time, the PPS offset is used; otherwise, the
686 * argument offset is used.
688 if (!(time_status & STA_PLL))
690 if (!(time_status & STA_PPSTIME && time_status &
692 if (offset > MAXPHASE)
693 time_monitor = MAXPHASE;
694 else if (offset < -MAXPHASE)
695 time_monitor = -MAXPHASE;
697 time_monitor = offset;
698 L_LINT(time_offset, time_monitor);
702 * Select how the frequency is to be controlled and in which
703 * mode (PLL or FLL). If the PPS signal is present and enabled
704 * to discipline the frequency, the PPS frequency is used;
705 * otherwise, the argument offset is used to compute it.
707 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
708 time_reftime = time_uptime;
711 if (time_status & STA_FREQHOLD || time_reftime == 0)
712 time_reftime = time_uptime;
713 mtemp = time_uptime - time_reftime;
714 L_LINT(ftemp, time_monitor);
715 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
717 L_ADD(time_freq, ftemp);
718 time_status &= ~STA_MODE;
719 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
721 L_LINT(ftemp, (time_monitor << 4) / mtemp);
722 L_RSHIFT(ftemp, SHIFT_FLL + 4);
723 L_ADD(time_freq, ftemp);
724 time_status |= STA_MODE;
726 time_reftime = time_uptime;
727 if (L_GINT(time_freq) > MAXFREQ)
728 L_LINT(time_freq, MAXFREQ);
729 else if (L_GINT(time_freq) < -MAXFREQ)
730 L_LINT(time_freq, -MAXFREQ);
735 * hardpps() - discipline CPU clock oscillator to external PPS signal
737 * This routine is called at each PPS interrupt in order to discipline
738 * the CPU clock oscillator to the PPS signal. There are two independent
739 * first-order feedback loops, one for the phase, the other for the
740 * frequency. The phase loop measures and grooms the PPS phase offset
741 * and leaves it in a handy spot for the seconds overflow routine. The
742 * frequency loop averages successive PPS phase differences and
743 * calculates the PPS frequency offset, which is also processed by the
744 * seconds overflow routine. The code requires the caller to capture the
745 * time and architecture-dependent hardware counter values in
746 * nanoseconds at the on-time PPS signal transition.
748 * Note that, on some Unix systems this routine runs at an interrupt
749 * priority level higher than the timer interrupt routine hardclock().
750 * Therefore, the variables used are distinct from the hardclock()
751 * variables, except for the actual time and frequency variables, which
752 * are determined by this routine and updated atomically.
755 * nsec - hardware counter at PPS
758 hardpps(struct timespec *tsp, long nsec)
760 long u_sec, u_nsec, v_nsec; /* temps */
766 * The signal is first processed by a range gate and frequency
767 * discriminator. The range gate rejects noise spikes outside
768 * the range +-500 us. The frequency discriminator rejects input
769 * signals with apparent frequency outside the range 1 +-500
770 * PPM. If two hits occur in the same second, we ignore the
771 * later hit; if not and a hit occurs outside the range gate,
772 * keep the later hit for later comparison, but do not process
775 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
776 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
777 pps_valid = PPS_VALID;
779 u_nsec = tsp->tv_nsec;
780 if (u_nsec >= (NANOSECOND >> 1)) {
781 u_nsec -= NANOSECOND;
784 v_nsec = u_nsec - pps_tf[0].tv_nsec;
785 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - MAXFREQ)
787 pps_tf[2] = pps_tf[1];
788 pps_tf[1] = pps_tf[0];
789 pps_tf[0].tv_sec = u_sec;
790 pps_tf[0].tv_nsec = u_nsec;
793 * Compute the difference between the current and previous
794 * counter values. If the difference exceeds 0.5 s, assume it
795 * has wrapped around, so correct 1.0 s. If the result exceeds
796 * the tick interval, the sample point has crossed a tick
797 * boundary during the last second, so correct the tick. Very
801 if (u_nsec > (NANOSECOND >> 1))
802 u_nsec -= NANOSECOND;
803 else if (u_nsec < -(NANOSECOND >> 1))
804 u_nsec += NANOSECOND;
805 pps_fcount += u_nsec;
806 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
808 time_status &= ~STA_PPSJITTER;
811 * A three-stage median filter is used to help denoise the PPS
812 * time. The median sample becomes the time offset estimate; the
813 * difference between the other two samples becomes the time
814 * dispersion (jitter) estimate.
816 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
817 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
818 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
819 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
820 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
821 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
822 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
824 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
825 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
828 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
829 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
830 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
831 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
832 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
833 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
835 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
836 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
841 * Nominal jitter is due to PPS signal noise and interrupt
842 * latency. If it exceeds the popcorn threshold, the sample is
843 * discarded. otherwise, if so enabled, the time offset is
844 * updated. We can tolerate a modest loss of data here without
845 * much degrading time accuracy.
847 * The measurements being checked here were made with the system
848 * timecounter, so the popcorn threshold is not allowed to fall below
849 * the number of nanoseconds in two ticks of the timecounter. For a
850 * timecounter running faster than 1 GHz the lower bound is 2ns, just
851 * to avoid a nonsensical threshold of zero.
853 if (u_nsec > lmax(pps_jitter << PPS_POPCORN,
854 2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) {
855 time_status |= STA_PPSJITTER;
857 } else if (time_status & STA_PPSTIME) {
858 time_monitor = -v_nsec;
859 L_LINT(time_offset, time_monitor);
861 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
862 u_sec = pps_tf[0].tv_sec - pps_lastsec;
863 if (u_sec < (1 << pps_shift))
867 * At the end of the calibration interval the difference between
868 * the first and last counter values becomes the scaled
869 * frequency. It will later be divided by the length of the
870 * interval to determine the frequency update. If the frequency
871 * exceeds a sanity threshold, or if the actual calibration
872 * interval is not equal to the expected length, the data are
873 * discarded. We can tolerate a modest loss of data here without
874 * much degrading frequency accuracy.
877 v_nsec = -pps_fcount;
878 pps_lastsec = pps_tf[0].tv_sec;
880 u_nsec = MAXFREQ << pps_shift;
881 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << pps_shift)) {
882 time_status |= STA_PPSERROR;
888 * Here the raw frequency offset and wander (stability) is
889 * calculated. If the wander is less than the wander threshold
890 * for four consecutive averaging intervals, the interval is
891 * doubled; if it is greater than the threshold for four
892 * consecutive intervals, the interval is halved. The scaled
893 * frequency offset is converted to frequency offset. The
894 * stability metric is calculated as the average of recent
895 * frequency changes, but is used only for performance
898 L_LINT(ftemp, v_nsec);
899 L_RSHIFT(ftemp, pps_shift);
900 L_SUB(ftemp, pps_freq);
901 u_nsec = L_GINT(ftemp);
902 if (u_nsec > PPS_MAXWANDER) {
903 L_LINT(ftemp, PPS_MAXWANDER);
905 time_status |= STA_PPSWANDER;
907 } else if (u_nsec < -PPS_MAXWANDER) {
908 L_LINT(ftemp, -PPS_MAXWANDER);
910 time_status |= STA_PPSWANDER;
915 if (pps_intcnt >= 4) {
917 if (pps_shift < pps_shiftmax) {
921 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
923 if (pps_shift > PPS_FAVG) {
930 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
933 * The PPS frequency is recalculated and clamped to the maximum
934 * MAXFREQ. If enabled, the system clock frequency is updated as
937 L_ADD(pps_freq, ftemp);
938 u_nsec = L_GINT(pps_freq);
939 if (u_nsec > MAXFREQ)
940 L_LINT(pps_freq, MAXFREQ);
941 else if (u_nsec < -MAXFREQ)
942 L_LINT(pps_freq, -MAXFREQ);
943 if (time_status & STA_PPSFREQ)
944 time_freq = pps_freq;
949 #endif /* PPS_SYNC */
951 #ifndef _SYS_SYSPROTO_H_
952 struct adjtime_args {
953 struct timeval *delta;
954 struct timeval *olddelta;
959 sys_adjtime(struct thread *td, struct adjtime_args *uap)
961 struct timeval delta, olddelta, *deltap;
965 error = copyin(uap->delta, &delta, sizeof(delta));
971 error = kern_adjtime(td, deltap, &olddelta);
972 if (uap->olddelta && error == 0)
973 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
978 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
985 error = priv_check(td, PRIV_ADJTIME);
988 ltw = (int64_t)delta->tv_sec * 1000000 + delta->tv_usec;
995 if (olddelta != NULL) {
996 atv.tv_sec = ltr / 1000000;
997 atv.tv_usec = ltr % 1000000;
998 if (atv.tv_usec < 0) {
999 atv.tv_usec += 1000000;
1007 static struct callout resettodr_callout;
1008 static int resettodr_period = 1800;
1011 periodic_resettodr(void *arg __unused)
1015 * Read of time_status is lock-less, which is fine since
1016 * ntp_is_time_error() operates on the consistent read value.
1018 if (!ntp_is_time_error(time_status))
1020 if (resettodr_period > 0)
1021 callout_schedule(&resettodr_callout, resettodr_period * hz);
1025 shutdown_resettodr(void *arg __unused, int howto __unused)
1028 callout_drain(&resettodr_callout);
1029 /* Another unlocked read of time_status */
1030 if (resettodr_period > 0 && !ntp_is_time_error(time_status))
1035 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
1039 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
1040 if (error || !req->newptr)
1044 if (resettodr_period == 0)
1045 callout_stop(&resettodr_callout);
1047 callout_reset(&resettodr_callout, resettodr_period * hz,
1048 periodic_resettodr, NULL);
1053 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT | CTLFLAG_RWTUN |
1054 CTLFLAG_MPSAFE, &resettodr_period, 1800, sysctl_resettodr_period, "I",
1055 "Save system time to RTC with this period (in seconds)");
1058 start_periodic_resettodr(void *arg __unused)
1061 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
1062 SHUTDOWN_PRI_FIRST);
1063 callout_init(&resettodr_callout, 1);
1064 if (resettodr_period == 0)
1066 callout_reset(&resettodr_callout, resettodr_period * hz,
1067 periodic_resettodr, NULL);
1070 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE,
1071 start_periodic_resettodr, NULL);