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kern_clock.c (2320) kern_clock.c (2858)
1/*-
2 * Copyright (c) 1982, 1986, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.

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31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
1/*-
2 * Copyright (c) 1982, 1986, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.

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31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * SUCH DAMAGE.
37 *
38 * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
39 * $Id: kern_clock.c,v 1.4 1994/08/18 22:34:58 wollman Exp $
39 * $Id: kern_clock.c,v 1.5 1994/08/27 16:14:26 davidg Exp $
40 */
41
40 */
41
42/* Portions of this software are covered by the following: */
43/******************************************************************************
44 * *
45 * Copyright (c) David L. Mills 1993, 1994 *
46 * *
47 * Permission to use, copy, modify, and distribute this software and its *
48 * documentation for any purpose and without fee is hereby granted, provided *
49 * that the above copyright notice appears in all copies and that both the *
50 * copyright notice and this permission notice appear in supporting *
51 * documentation, and that the name University of Delaware not be used in *
52 * advertising or publicity pertaining to distribution of the software *
53 * without specific, written prior permission. The University of Delaware *
54 * makes no representations about the suitability this software for any *
55 * purpose. It is provided "as is" without express or implied warranty. *
56 * *
57 *****************************************************************************/
58
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/dkstat.h>
45#include <sys/callout.h>
46#include <sys/kernel.h>
47#include <sys/proc.h>
48#include <sys/resourcevar.h>
59#include <sys/param.h>
60#include <sys/systm.h>
61#include <sys/dkstat.h>
62#include <sys/callout.h>
63#include <sys/kernel.h>
64#include <sys/proc.h>
65#include <sys/resourcevar.h>
66#include <sys/timex.h>
49#include <vm/vm.h>
50
51#include <machine/cpu.h>
67#include <vm/vm.h>
68
69#include <machine/cpu.h>
70#include <machine/clock.h>
52
53#ifdef GPROF
54#include <sys/gmon.h>
55#endif
56
57/* Does anybody else really care about these? */
58struct callout *callfree, *callout, calltodo;
59int ncallout;

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123int ticks;
124static int psdiv, pscnt; /* prof => stat divider */
125int psratio; /* ratio: prof / stat */
126
127volatile struct timeval time;
128volatile struct timeval mono_time;
129
130/*
71
72#ifdef GPROF
73#include <sys/gmon.h>
74#endif
75
76/* Does anybody else really care about these? */
77struct callout *callfree, *callout, calltodo;
78int ncallout;

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142int ticks;
143static int psdiv, pscnt; /* prof => stat divider */
144int psratio; /* ratio: prof / stat */
145
146volatile struct timeval time;
147volatile struct timeval mono_time;
148
149/*
150 * Phase-lock loop (PLL) definitions
151 *
152 * The following variables are read and set by the ntp_adjtime() system
153 * call.
154 *
155 * time_state shows the state of the system clock, with values defined
156 * in the timex.h header file.
157 *
158 * time_status shows the status of the system clock, with bits defined
159 * in the timex.h header file.
160 *
161 * time_offset is used by the PLL to adjust the system time in small
162 * increments.
163 *
164 * time_constant determines the bandwidth or "stiffness" of the PLL.
165 *
166 * time_tolerance determines maximum frequency error or tolerance of the
167 * CPU clock oscillator and is a property of the architecture; however,
168 * in principle it could change as result of the presence of external
169 * discipline signals, for instance.
170 *
171 * time_precision is usually equal to the kernel tick variable; however,
172 * in cases where a precision clock counter or external clock is
173 * available, the resolution can be much less than this and depend on
174 * whether the external clock is working or not.
175 *
176 * time_maxerror is initialized by a ntp_adjtime() call and increased by
177 * the kernel once each second to reflect the maximum error
178 * bound growth.
179 *
180 * time_esterror is set and read by the ntp_adjtime() call, but
181 * otherwise not used by the kernel.
182 */
183int time_status = STA_UNSYNC; /* clock status bits */
184int time_state = TIME_OK; /* clock state */
185long time_offset = 0; /* time offset (us) */
186long time_constant = 0; /* pll time constant */
187long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */
188long time_precision = 1; /* clock precision (us) */
189long time_maxerror = MAXPHASE; /* maximum error (us) */
190long time_esterror = MAXPHASE; /* estimated error (us) */
191
192/*
193 * The following variables establish the state of the PLL and the
194 * residual time and frequency offset of the local clock. The scale
195 * factors are defined in the timex.h header file.
196 *
197 * time_phase and time_freq are the phase increment and the frequency
198 * increment, respectively, of the kernel time variable at each tick of
199 * the clock.
200 *
201 * time_freq is set via ntp_adjtime() from a value stored in a file when
202 * the synchronization daemon is first started. Its value is retrieved
203 * via ntp_adjtime() and written to the file about once per hour by the
204 * daemon.
205 *
206 * time_adj is the adjustment added to the value of tick at each timer
207 * interrupt and is recomputed at each timer interrupt.
208 *
209 * time_reftime is the second's portion of the system time on the last
210 * call to ntp_adjtime(). It is used to adjust the time_freq variable
211 * and to increase the time_maxerror as the time since last update
212 * increases.
213 */
214long time_phase = 0; /* phase offset (scaled us) */
215long time_freq = 0; /* frequency offset (scaled ppm) */
216long time_adj = 0; /* tick adjust (scaled 1 / hz) */
217long time_reftime = 0; /* time at last adjustment (s) */
218
219#ifdef PPS_SYNC
220/*
221 * The following variables are used only if the if the kernel PPS
222 * discipline code is configured (PPS_SYNC). The scale factors are
223 * defined in the timex.h header file.
224 *
225 * pps_time contains the time at each calibration interval, as read by
226 * microtime().
227 *
228 * pps_offset is the time offset produced by the time median filter
229 * pps_tf[], while pps_jitter is the dispersion measured by this
230 * filter.
231 *
232 * pps_freq is the frequency offset produced by the frequency median
233 * filter pps_ff[], while pps_stabil is the dispersion measured by
234 * this filter.
235 *
236 * pps_usec is latched from a high resolution counter or external clock
237 * at pps_time. Here we want the hardware counter contents only, not the
238 * contents plus the time_tv.usec as usual.
239 *
240 * pps_valid counts the number of seconds since the last PPS update. It
241 * is used as a watchdog timer to disable the PPS discipline should the
242 * PPS signal be lost.
243 *
244 * pps_glitch counts the number of seconds since the beginning of an
245 * offset burst more than tick/2 from current nominal offset. It is used
246 * mainly to suppress error bursts due to priority conflicts between the
247 * PPS interrupt and timer interrupt.
248 *
249 * pps_count counts the seconds of the calibration interval, the
250 * duration of which is pps_shift in powers of two.
251 *
252 * pps_intcnt counts the calibration intervals for use in the interval-
253 * adaptation algorithm. It's just too complicated for words.
254 */
255struct timeval pps_time; /* kernel time at last interval */
256long pps_offset = 0; /* pps time offset (us) */
257long pps_jitter = MAXTIME; /* pps time dispersion (jitter) (us) */
258long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */
259long pps_freq = 0; /* frequency offset (scaled ppm) */
260long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
261long pps_ff[] = {0, 0, 0}; /* frequency offset median filter */
262long pps_usec = 0; /* microsec counter at last interval */
263long pps_valid = PPS_VALID; /* pps signal watchdog counter */
264int pps_glitch = 0; /* pps signal glitch counter */
265int pps_count = 0; /* calibration interval counter (s) */
266int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
267int pps_intcnt = 0; /* intervals at current duration */
268
269/*
270 * PPS signal quality monitors
271 *
272 * pps_jitcnt counts the seconds that have been discarded because the
273 * jitter measured by the time median filter exceeds the limit MAXTIME
274 * (100 us).
275 *
276 * pps_calcnt counts the frequency calibration intervals, which are
277 * variable from 4 s to 256 s.
278 *
279 * pps_errcnt counts the calibration intervals which have been discarded
280 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the
281 * calibration interval jitter exceeds two ticks.
282 *
283 * pps_stbcnt counts the calibration intervals that have been discarded
284 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us).
285 */
286long pps_jitcnt = 0; /* jitter limit exceeded */
287long pps_calcnt = 0; /* calibration intervals */
288long pps_errcnt = 0; /* calibration errors */
289long pps_stbcnt = 0; /* stability limit exceeded */
290#endif /* PPS_SYNC */
291
292/* XXX none of this stuff works under FreeBSD */
293#ifdef EXT_CLOCK
294/*
295 * External clock definitions
296 *
297 * The following definitions and declarations are used only if an
298 * external clock (HIGHBALL or TPRO) is configured on the system.
299 */
300#define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */
301
302/*
303 * The clock_count variable is set to CLOCK_INTERVAL at each PPS
304 * interrupt and decremented once each second.
305 */
306int clock_count = 0; /* CPU clock counter */
307
308#ifdef HIGHBALL
309/*
310 * The clock_offset and clock_cpu variables are used by the HIGHBALL
311 * interface. The clock_offset variable defines the offset between
312 * system time and the HIGBALL counters. The clock_cpu variable contains
313 * the offset between the system clock and the HIGHBALL clock for use in
314 * disciplining the kernel time variable.
315 */
316extern struct timeval clock_offset; /* Highball clock offset */
317long clock_cpu = 0; /* CPU clock adjust */
318#endif /* HIGHBALL */
319#endif /* EXT_CLOCK */
320
321/*
322 * hardupdate() - local clock update
323 *
324 * This routine is called by ntp_adjtime() to update the local clock
325 * phase and frequency. This is used to implement an adaptive-parameter,
326 * first-order, type-II phase-lock loop. The code computes new time and
327 * frequency offsets each time it is called. The hardclock() routine
328 * amortizes these offsets at each tick interrupt. If the kernel PPS
329 * discipline code is configured (PPS_SYNC), the PPS signal itself
330 * determines the new time offset, instead of the calling argument.
331 * Presumably, calls to ntp_adjtime() occur only when the caller
332 * believes the local clock is valid within some bound (+-128 ms with
333 * NTP). If the caller's time is far different than the PPS time, an
334 * argument will ensue, and it's not clear who will lose.
335 *
336 * For default SHIFT_UPDATE = 12, the offset is limited to +-512 ms, the
337 * maximum interval between updates is 4096 s and the maximum frequency
338 * offset is +-31.25 ms/s.
339 *
340 * Note: splclock() is in effect.
341 */
342void
343hardupdate(offset)
344 long offset;
345{
346 long ltemp, mtemp;
347
348 if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME))
349 return;
350 ltemp = offset;
351#ifdef PPS_SYNC
352 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
353 ltemp = pps_offset;
354#endif /* PPS_SYNC */
355 if (ltemp > MAXPHASE)
356 time_offset = MAXPHASE << SHIFT_UPDATE;
357 else if (ltemp < -MAXPHASE)
358 time_offset = -(MAXPHASE << SHIFT_UPDATE);
359 else
360 time_offset = ltemp << SHIFT_UPDATE;
361 mtemp = time.tv_sec - time_reftime;
362 time_reftime = time.tv_sec;
363 if (mtemp > MAXSEC)
364 mtemp = 0;
365
366 /* ugly multiply should be replaced */
367 if (ltemp < 0)
368 time_freq -= (-ltemp * mtemp) >> (time_constant +
369 time_constant + SHIFT_KF - SHIFT_USEC);
370 else
371 time_freq += (ltemp * mtemp) >> (time_constant +
372 time_constant + SHIFT_KF - SHIFT_USEC);
373 if (time_freq > time_tolerance)
374 time_freq = time_tolerance;
375 else if (time_freq < -time_tolerance)
376 time_freq = -time_tolerance;
377}
378
379
380
381/*
131 * Initialize clock frequencies and start both clocks running.
132 */
133void
134initclocks()
135{
136 register int i;
137
138 /*

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202
203 /*
204 * If no separate statistics clock is available, run it from here.
205 */
206 if (stathz == 0)
207 statclock(frame);
208
209 /*
382 * Initialize clock frequencies and start both clocks running.
383 */
384void
385initclocks()
386{
387 register int i;
388
389 /*

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453
454 /*
455 * If no separate statistics clock is available, run it from here.
456 */
457 if (stathz == 0)
458 statclock(frame);
459
460 /*
210 * Increment the time-of-day. The increment is just ``tick'' unless
211 * we are still adjusting the clock; see adjtime().
461 * Increment the time-of-day.
212 */
213 ticks++;
462 */
463 ticks++;
214 if (timedelta == 0)
215 delta = tick;
216 else {
217 delta = tick + tickdelta;
218 timedelta -= tickdelta;
464 {
465 int time_update;
466 struct timeval newtime = time;
467 long ltemp;
468
469 if (timedelta == 0) {
470 time_update = tick;
471 } else {
472 if (timedelta < 0) {
473 time_update = tick - tickdelta;
474 timedelta += tickdelta;
475 } else {
476 time_update = tick + tickdelta;
477 timedelta -= tickdelta;
478 }
479 }
480 BUMPTIME(&mono_time, time_update);
481
482 /*
483 * Compute the phase adjustment. If the low-order bits
484 * (time_phase) of the update overflow, bump the high-order bits
485 * (time_update).
486 */
487 time_phase += time_adj;
488 if (time_phase <= -FINEUSEC) {
489 ltemp = -time_phase >> SHIFT_SCALE;
490 time_phase += ltemp << SHIFT_SCALE;
491 time_update -= ltemp;
492 }
493 else if (time_phase >= FINEUSEC) {
494 ltemp = time_phase >> SHIFT_SCALE;
495 time_phase -= ltemp << SHIFT_SCALE;
496 time_update += ltemp;
497 }
498
499 newtime.tv_usec += time_update;
500 /*
501 * On rollover of the second the phase adjustment to be used for
502 * the next second is calculated. Also, the maximum error is
503 * increased by the tolerance. If the PPS frequency discipline
504 * code is present, the phase is increased to compensate for the
505 * CPU clock oscillator frequency error.
506 *
507 * With SHIFT_SCALE = 23, the maximum frequency adjustment is
508 * +-256 us per tick, or 25.6 ms/s at a clock frequency of 100
509 * Hz. The time contribution is shifted right a minimum of two
510 * bits, while the frequency contribution is a right shift.
511 * Thus, overflow is prevented if the frequency contribution is
512 * limited to half the maximum or 15.625 ms/s.
513 */
514 if (newtime.tv_usec >= 1000000) {
515 newtime.tv_usec -= 1000000;
516 newtime.tv_sec++;
517 time_maxerror += time_tolerance >> SHIFT_USEC;
518 if (time_offset < 0) {
519 ltemp = -time_offset >>
520 (SHIFT_KG + time_constant);
521 time_offset += ltemp;
522 time_adj = -ltemp <<
523 (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
524 } else {
525 ltemp = time_offset >>
526 (SHIFT_KG + time_constant);
527 time_offset -= ltemp;
528 time_adj = ltemp <<
529 (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
530 }
531#ifdef PPS_SYNC
532 /*
533 * Gnaw on the watchdog counter and update the frequency
534 * computed by the pll and the PPS signal.
535 */
536 pps_valid++;
537 if (pps_valid == PPS_VALID) {
538 pps_jitter = MAXTIME;
539 pps_stabil = MAXFREQ;
540 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
541 STA_PPSWANDER | STA_PPSERROR);
542 }
543 ltemp = time_freq + pps_freq;
544#else
545 ltemp = time_freq;
546#endif /* PPS_SYNC */
547 if (ltemp < 0)
548 time_adj -= -ltemp >>
549 (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
550 else
551 time_adj += ltemp >>
552 (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
553
554 /*
555 * When the CPU clock oscillator frequency is not a
556 * power of two in Hz, the SHIFT_HZ is only an
557 * approximate scale factor. In the SunOS kernel, this
558 * results in a PLL gain factor of 1/1.28 = 0.78 what it
559 * should be. In the following code the overall gain is
560 * increased by a factor of 1.25, which results in a
561 * residual error less than 3 percent.
562 */
563 /* Same thing applies for FreeBSD --GAW */
564 if (hz == 100) {
565 if (time_adj < 0)
566 time_adj -= -time_adj >> 2;
567 else
568 time_adj += time_adj >> 2;
569 }
570
571 /* XXX - this is really bogus, but can't be fixed until
572 xntpd's idea of the system clock is fixed to know how
573 the user wants leap seconds handled; in the mean time,
574 we assume that users of NTP are running without proper
575 leap second support (this is now the default anyway) */
576 /*
577 * Leap second processing. If in leap-insert state at
578 * the end of the day, the system clock is set back one
579 * second; if in leap-delete state, the system clock is
580 * set ahead one second. The microtime() routine or
581 * external clock driver will insure that reported time
582 * is always monotonic. The ugly divides should be
583 * replaced.
584 */
585 switch (time_state) {
586
587 case TIME_OK:
588 if (time_status & STA_INS)
589 time_state = TIME_INS;
590 else if (time_status & STA_DEL)
591 time_state = TIME_DEL;
592 break;
593
594 case TIME_INS:
595 if (newtime.tv_sec % 86400 == 0) {
596 newtime.tv_sec--;
597 time_state = TIME_OOP;
598 }
599 break;
600
601 case TIME_DEL:
602 if ((newtime.tv_sec + 1) % 86400 == 0) {
603 newtime.tv_sec++;
604 time_state = TIME_WAIT;
605 }
606 break;
607
608 case TIME_OOP:
609 time_state = TIME_WAIT;
610 break;
611
612 case TIME_WAIT:
613 if (!(time_status & (STA_INS | STA_DEL)))
614 time_state = TIME_OK;
615 }
616 }
617 CPU_CLOCKUPDATE(&time, &newtime);
219 }
618 }
220 BUMPTIME(&time, delta);
221 BUMPTIME(&mono_time, delta);
222
223 /*
224 * Process callouts at a very low cpu priority, so we don't keep the
225 * relatively high clock interrupt priority any longer than necessary.
226 */
227 if (needsoft) {
228 if (CLKF_BASEPRI(frame)) {
229 /*

--- 328 unchanged lines hidden (view full) ---

558 * Construct clockinfo structure.
559 */
560 clkinfo.hz = hz;
561 clkinfo.tick = tick;
562 clkinfo.profhz = profhz;
563 clkinfo.stathz = stathz ? stathz : hz;
564 return (sysctl_rdstruct(where, sizep, NULL, &clkinfo, sizeof(clkinfo)));
565}
619
620 /*
621 * Process callouts at a very low cpu priority, so we don't keep the
622 * relatively high clock interrupt priority any longer than necessary.
623 */
624 if (needsoft) {
625 if (CLKF_BASEPRI(frame)) {
626 /*

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955 * Construct clockinfo structure.
956 */
957 clkinfo.hz = hz;
958 clkinfo.tick = tick;
959 clkinfo.profhz = profhz;
960 clkinfo.stathz = stathz ? stathz : hz;
961 return (sysctl_rdstruct(where, sizep, NULL, &clkinfo, sizeof(clkinfo)));
962}
963
964/*#ifdef PPS_SYNC*/
965#if 0
966/* This code is completely bogus; if anybody ever wants to use it, get
967 * the current version from Dave Mills. */
968
969/*
970 * hardpps() - discipline CPU clock oscillator to external pps signal
971 *
972 * This routine is called at each PPS interrupt in order to discipline
973 * the CPU clock oscillator to the PPS signal. It integrates successive
974 * phase differences between the two oscillators and calculates the
975 * frequency offset. This is used in hardclock() to discipline the CPU
976 * clock oscillator so that intrinsic frequency error is cancelled out.
977 * The code requires the caller to capture the time and hardware
978 * counter value at the designated PPS signal transition.
979 */
980void
981hardpps(tvp, usec)
982 struct timeval *tvp; /* time at PPS */
983 long usec; /* hardware counter at PPS */
984{
985 long u_usec, v_usec, bigtick;
986 long cal_sec, cal_usec;
987
988 /*
989 * During the calibration interval adjust the starting time when
990 * the tick overflows. At the end of the interval compute the
991 * duration of the interval and the difference of the hardware
992 * counters at the beginning and end of the interval. This code
993 * is deliciously complicated by the fact valid differences may
994 * exceed the value of tick when using long calibration
995 * intervals and small ticks. Note that the counter can be
996 * greater than tick if caught at just the wrong instant, but
997 * the values returned and used here are correct.
998 */
999 bigtick = (long)tick << SHIFT_USEC;
1000 pps_usec -= ntp_pll.ybar;
1001 if (pps_usec >= bigtick)
1002 pps_usec -= bigtick;
1003 if (pps_usec < 0)
1004 pps_usec += bigtick;
1005 pps_time.tv_sec++;
1006 pps_count++;
1007 if (pps_count < (1 << pps_shift))
1008 return;
1009 pps_count = 0;
1010 ntp_pll.calcnt++;
1011 u_usec = usec << SHIFT_USEC;
1012 v_usec = pps_usec - u_usec;
1013 if (v_usec >= bigtick >> 1)
1014 v_usec -= bigtick;
1015 if (v_usec < -(bigtick >> 1))
1016 v_usec += bigtick;
1017 if (v_usec < 0)
1018 v_usec = -(-v_usec >> ntp_pll.shift);
1019 else
1020 v_usec = v_usec >> ntp_pll.shift;
1021 pps_usec = u_usec;
1022 cal_sec = tvp->tv_sec;
1023 cal_usec = tvp->tv_usec;
1024 cal_sec -= pps_time.tv_sec;
1025 cal_usec -= pps_time.tv_usec;
1026 if (cal_usec < 0) {
1027 cal_usec += 1000000;
1028 cal_sec--;
1029 }
1030 pps_time = *tvp;
1031
1032 /*
1033 * Check for lost interrupts, noise, excessive jitter and
1034 * excessive frequency error. The number of timer ticks during
1035 * the interval may vary +-1 tick. Add to this a margin of one
1036 * tick for the PPS signal jitter and maximum frequency
1037 * deviation. If the limits are exceeded, the calibration
1038 * interval is reset to the minimum and we start over.
1039 */
1040 u_usec = (long)tick << 1;
1041 if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec))
1042 || (cal_sec == 0 && cal_usec < u_usec))
1043 || v_usec > ntp_pll.tolerance || v_usec < -ntp_pll.tolerance) {
1044 ntp_pll.jitcnt++;
1045 ntp_pll.shift = NTP_PLL.SHIFT;
1046 pps_dispinc = PPS_DISPINC;
1047 ntp_pll.intcnt = 0;
1048 return;
1049 }
1050
1051 /*
1052 * A three-stage median filter is used to help deglitch the pps
1053 * signal. The median sample becomes the offset estimate; the
1054 * difference between the other two samples becomes the
1055 * dispersion estimate.
1056 */
1057 pps_mf[2] = pps_mf[1];
1058 pps_mf[1] = pps_mf[0];
1059 pps_mf[0] = v_usec;
1060 if (pps_mf[0] > pps_mf[1]) {
1061 if (pps_mf[1] > pps_mf[2]) {
1062 u_usec = pps_mf[1]; /* 0 1 2 */
1063 v_usec = pps_mf[0] - pps_mf[2];
1064 } else if (pps_mf[2] > pps_mf[0]) {
1065 u_usec = pps_mf[0]; /* 2 0 1 */
1066 v_usec = pps_mf[2] - pps_mf[1];
1067 } else {
1068 u_usec = pps_mf[2]; /* 0 2 1 */
1069 v_usec = pps_mf[0] - pps_mf[1];
1070 }
1071 } else {
1072 if (pps_mf[1] < pps_mf[2]) {
1073 u_usec = pps_mf[1]; /* 2 1 0 */
1074 v_usec = pps_mf[2] - pps_mf[0];
1075 } else if (pps_mf[2] < pps_mf[0]) {
1076 u_usec = pps_mf[0]; /* 1 0 2 */
1077 v_usec = pps_mf[1] - pps_mf[2];
1078 } else {
1079 u_usec = pps_mf[2]; /* 1 2 0 */
1080 v_usec = pps_mf[1] - pps_mf[0];
1081 }
1082 }
1083
1084 /*
1085 * Here the dispersion average is updated. If it is less than
1086 * the threshold pps_dispmax, the frequency average is updated
1087 * as well, but clamped to the tolerance.
1088 */
1089 v_usec = (v_usec >> 1) - ntp_pll.disp;
1090 if (v_usec < 0)
1091 ntp_pll.disp -= -v_usec >> PPS_AVG;
1092 else
1093 ntp_pll.disp += v_usec >> PPS_AVG;
1094 if (ntp_pll.disp > pps_dispmax) {
1095 ntp_pll.discnt++;
1096 return;
1097 }
1098 if (u_usec < 0) {
1099 ntp_pll.ybar -= -u_usec >> PPS_AVG;
1100 if (ntp_pll.ybar < -ntp_pll.tolerance)
1101 ntp_pll.ybar = -ntp_pll.tolerance;
1102 u_usec = -u_usec;
1103 } else {
1104 ntp_pll.ybar += u_usec >> PPS_AVG;
1105 if (ntp_pll.ybar > ntp_pll.tolerance)
1106 ntp_pll.ybar = ntp_pll.tolerance;
1107 }
1108
1109 /*
1110 * Here the calibration interval is adjusted. If the maximum
1111 * time difference is greater than tick/4, reduce the interval
1112 * by half. If this is not the case for four consecutive
1113 * intervals, double the interval.
1114 */
1115 if (u_usec << ntp_pll.shift > bigtick >> 2) {
1116 ntp_pll.intcnt = 0;
1117 if (ntp_pll.shift > NTP_PLL.SHIFT) {
1118 ntp_pll.shift--;
1119 pps_dispinc <<= 1;
1120 }
1121 } else if (ntp_pll.intcnt >= 4) {
1122 ntp_pll.intcnt = 0;
1123 if (ntp_pll.shift < NTP_PLL.SHIFTMAX) {
1124 ntp_pll.shift++;
1125 pps_dispinc >>= 1;
1126 }
1127 } else
1128 ntp_pll.intcnt++;
1129}
1130#endif /* PPS_SYNC */