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kern_tc.c (32444) kern_tc.c (32513)
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 1.51 1998/01/11 00:44:27 phk Exp $
39 * $Id: kern_clock.c,v 1.52 1998/01/11 19:07:58 phk 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
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/signalvar.h>

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157int ticks;
158static int psdiv, pscnt; /* prof => stat divider */
159int psratio; /* ratio: prof / stat */
160
161volatile struct timeval time;
162volatile struct timeval mono_time;
163
164/*
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>
49#include <sys/signalvar.h>

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140int ticks;
141static int psdiv, pscnt; /* prof => stat divider */
142int psratio; /* ratio: prof / stat */
143
144volatile struct timeval time;
145volatile struct timeval mono_time;
146
147/*
165 * Phase/frequency-lock loop (PLL/FLL) definitions
166 *
167 * The following variables are read and set by the ntp_adjtime() system
168 * call.
169 *
170 * time_state shows the state of the system clock, with values defined
171 * in the timex.h header file.
172 *
173 * time_status shows the status of the system clock, with bits defined
174 * in the timex.h header file.
175 *
176 * time_offset is used by the PLL/FLL to adjust the system time in small
177 * increments.
178 *
179 * time_constant determines the bandwidth or "stiffness" of the PLL.
180 *
181 * time_tolerance determines maximum frequency error or tolerance of the
182 * CPU clock oscillator and is a property of the architecture; however,
183 * in principle it could change as result of the presence of external
184 * discipline signals, for instance.
185 *
186 * time_precision is usually equal to the kernel tick variable; however,
187 * in cases where a precision clock counter or external clock is
188 * available, the resolution can be much less than this and depend on
189 * whether the external clock is working or not.
190 *
191 * time_maxerror is initialized by a ntp_adjtime() call and increased by
192 * the kernel once each second to reflect the maximum error
193 * bound growth.
194 *
195 * time_esterror is set and read by the ntp_adjtime() call, but
196 * otherwise not used by the kernel.
197 */
198int time_status = STA_UNSYNC; /* clock status bits */
199int time_state = TIME_OK; /* clock state */
200long time_offset = 0; /* time offset (us) */
201long time_constant = 0; /* pll time constant */
202long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */
203long time_precision = 1; /* clock precision (us) */
204long time_maxerror = MAXPHASE; /* maximum error (us) */
205long time_esterror = MAXPHASE; /* estimated error (us) */
206
207/*
208 * The following variables establish the state of the PLL/FLL and the
209 * residual time and frequency offset of the local clock. The scale
210 * factors are defined in the timex.h header file.
211 *
212 * time_phase and time_freq are the phase increment and the frequency
213 * increment, respectively, of the kernel time variable at each tick of
214 * the clock.
215 *
216 * time_freq is set via ntp_adjtime() from a value stored in a file when
217 * the synchronization daemon is first started. Its value is retrieved
218 * via ntp_adjtime() and written to the file about once per hour by the
219 * daemon.
220 *
221 * time_adj is the adjustment added to the value of tick at each timer
222 * interrupt and is recomputed from time_phase and time_freq at each
223 * seconds rollover.
224 *
225 * time_reftime is the second's portion of the system time on the last
226 * call to ntp_adjtime(). It is used to adjust the time_freq variable
227 * and to increase the time_maxerror as the time since last update
228 * increases.
229 */
230static long time_phase = 0; /* phase offset (scaled us) */
231long time_freq = 0; /* frequency offset (scaled ppm) */
232static long time_adj = 0; /* tick adjust (scaled 1 / hz) */
233static long time_reftime = 0; /* time at last adjustment (s) */
234
235#ifdef PPS_SYNC
236/*
237 * The following variables are used only if the kernel PPS discipline
238 * code is configured (PPS_SYNC). The scale factors are defined in the
239 * timex.h header file.
240 *
241 * pps_time contains the time at each calibration interval, as read by
242 * microtime(). pps_count counts the seconds of the calibration
243 * interval, the duration of which is nominally pps_shift in powers of
244 * two.
245 *
246 * pps_offset is the time offset produced by the time median filter
247 * pps_tf[], while pps_jitter is the dispersion (jitter) measured by
248 * this filter.
249 *
250 * pps_freq is the frequency offset produced by the frequency median
251 * filter pps_ff[], while pps_stabil is the dispersion (wander) measured
252 * by this filter.
253 *
254 * pps_usec is latched from a high resolution counter or external clock
255 * at pps_time. Here we want the hardware counter contents only, not the
256 * contents plus the time_tv.usec as usual.
257 *
258 * pps_valid counts the number of seconds since the last PPS update. It
259 * is used as a watchdog timer to disable the PPS discipline should the
260 * PPS signal be lost.
261 *
262 * pps_glitch counts the number of seconds since the beginning of an
263 * offset burst more than tick/2 from current nominal offset. It is used
264 * mainly to suppress error bursts due to priority conflicts between the
265 * PPS interrupt and timer interrupt.
266 *
267 * pps_intcnt counts the calibration intervals for use in the interval-
268 * adaptation algorithm. It's just too complicated for words.
269 */
270struct timeval pps_time; /* kernel time at last interval */
271long pps_offset = 0; /* pps time offset (us) */
272long pps_jitter = MAXTIME; /* pps time dispersion (jitter) (us) */
273long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */
274long pps_freq = 0; /* frequency offset (scaled ppm) */
275long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
276long pps_ff[] = {0, 0, 0}; /* frequency offset median filter */
277long pps_usec = 0; /* microsec counter at last interval */
278long pps_valid = PPS_VALID; /* pps signal watchdog counter */
279int pps_glitch = 0; /* pps signal glitch counter */
280int pps_count = 0; /* calibration interval counter (s) */
281int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
282int pps_intcnt = 0; /* intervals at current duration */
283
284/*
285 * PPS signal quality monitors
286 *
287 * pps_jitcnt counts the seconds that have been discarded because the
288 * jitter measured by the time median filter exceeds the limit MAXTIME
289 * (100 us).
290 *
291 * pps_calcnt counts the frequency calibration intervals, which are
292 * variable from 4 s to 256 s.
293 *
294 * pps_errcnt counts the calibration intervals which have been discarded
295 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the
296 * calibration interval jitter exceeds two ticks.
297 *
298 * pps_stbcnt counts the calibration intervals that have been discarded
299 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us).
300 */
301long pps_jitcnt = 0; /* jitter limit exceeded */
302long pps_calcnt = 0; /* calibration intervals */
303long pps_errcnt = 0; /* calibration errors */
304long pps_stbcnt = 0; /* stability limit exceeded */
305#endif /* PPS_SYNC */
306
307/* XXX none of this stuff works under FreeBSD */
308
309/*
310 * hardupdate() - local clock update
311 *
312 * This routine is called by ntp_adjtime() to update the local clock
313 * phase and frequency. The implementation is of an adaptive-parameter,
314 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
315 * time and frequency offset estimates for each call. If the kernel PPS
316 * discipline code is configured (PPS_SYNC), the PPS signal itself
317 * determines the new time offset, instead of the calling argument.
318 * Presumably, calls to ntp_adjtime() occur only when the caller
319 * believes the local clock is valid within some bound (+-128 ms with
320 * NTP). If the caller's time is far different than the PPS time, an
321 * argument will ensue, and it's not clear who will lose.
322 *
323 * For uncompensated quartz crystal oscillatores and nominal update
324 * intervals less than 1024 s, operation should be in phase-lock mode
325 * (STA_FLL = 0), where the loop is disciplined to phase. For update
326 * intervals greater than thiss, operation should be in frequency-lock
327 * mode (STA_FLL = 1), where the loop is disciplined to frequency.
328 *
329 * Note: splclock() is in effect.
330 */
331void
332hardupdate(offset)
333 long offset;
334{
335 long ltemp, mtemp;
336
337 if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME))
338 return;
339 ltemp = offset;
340#ifdef PPS_SYNC
341 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
342 ltemp = pps_offset;
343#endif /* PPS_SYNC */
344
345 /*
346 * Scale the phase adjustment and clamp to the operating range.
347 */
348 if (ltemp > MAXPHASE)
349 time_offset = MAXPHASE << SHIFT_UPDATE;
350 else if (ltemp < -MAXPHASE)
351 time_offset = -(MAXPHASE << SHIFT_UPDATE);
352 else
353 time_offset = ltemp << SHIFT_UPDATE;
354
355 /*
356 * Select whether the frequency is to be controlled and in which
357 * mode (PLL or FLL). Clamp to the operating range. Ugly
358 * multiply/divide should be replaced someday.
359 */
360 if (time_status & STA_FREQHOLD || time_reftime == 0)
361 time_reftime = time.tv_sec;
362 mtemp = time.tv_sec - time_reftime;
363 time_reftime = time.tv_sec;
364 if (time_status & STA_FLL) {
365 if (mtemp >= MINSEC) {
366 ltemp = ((time_offset / mtemp) << (SHIFT_USEC -
367 SHIFT_UPDATE));
368 if (ltemp < 0)
369 time_freq -= -ltemp >> SHIFT_KH;
370 else
371 time_freq += ltemp >> SHIFT_KH;
372 }
373 } else {
374 if (mtemp < MAXSEC) {
375 ltemp *= mtemp;
376 if (ltemp < 0)
377 time_freq -= -ltemp >> (time_constant +
378 time_constant + SHIFT_KF -
379 SHIFT_USEC);
380 else
381 time_freq += ltemp >> (time_constant +
382 time_constant + SHIFT_KF -
383 SHIFT_USEC);
384 }
385 }
386 if (time_freq > time_tolerance)
387 time_freq = time_tolerance;
388 else if (time_freq < -time_tolerance)
389 time_freq = -time_tolerance;
390}
391
392
393
394/*
395 * Initialize clock frequencies and start both clocks running.
396 */
397/* ARGSUSED*/
398static void
399initclocks(dummy)
400 void *dummy;
401{
402 register int i;

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420/*
421 * The real-time timer, interrupting hz times per second.
422 */
423void
424hardclock(frame)
425 register struct clockframe *frame;
426{
427 register struct proc *p;
148 * Initialize clock frequencies and start both clocks running.
149 */
150/* ARGSUSED*/
151static void
152initclocks(dummy)
153 void *dummy;
154{
155 register int i;

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173/*
174 * The real-time timer, interrupting hz times per second.
175 */
176void
177hardclock(frame)
178 register struct clockframe *frame;
179{
180 register struct proc *p;
181 int time_update;
182 struct timeval newtime = time;
183 long ltemp;
428
429 p = curproc;
430 if (p) {
431 register struct pstats *pstats;
432
433 /*
434 * Run current process's virtual and profile time, as needed.
435 */

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451 */
452 if (stathz == 0)
453 statclock(frame);
454
455 /*
456 * Increment the time-of-day.
457 */
458 ticks++;
184
185 p = curproc;
186 if (p) {
187 register struct pstats *pstats;
188
189 /*
190 * Run current process's virtual and profile time, as needed.
191 */

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207 */
208 if (stathz == 0)
209 statclock(frame);
210
211 /*
212 * Increment the time-of-day.
213 */
214 ticks++;
459 {
460 int time_update;
461 struct timeval newtime = time;
462 long ltemp;
463
215
464 if (timedelta == 0) {
465 time_update = CPU_THISTICKLEN(tick);
466 } else {
467 time_update = CPU_THISTICKLEN(tick) + tickdelta;
468 timedelta -= tickdelta;
469 }
470 BUMPTIME(&mono_time, time_update);
216 if (timedelta == 0) {
217 time_update = CPU_THISTICKLEN(tick);
218 } else {
219 time_update = CPU_THISTICKLEN(tick) + tickdelta;
220 timedelta -= tickdelta;
221 }
222 BUMPTIME(&mono_time, time_update);
471
223
472 /*
473 * Compute the phase adjustment. If the low-order bits
474 * (time_phase) of the update overflow, bump the high-order bits
475 * (time_update).
476 */
477 time_phase += time_adj;
478 if (time_phase <= -FINEUSEC) {
479 ltemp = -time_phase >> SHIFT_SCALE;
480 time_phase += ltemp << SHIFT_SCALE;
481 time_update -= ltemp;
482 }
483 else if (time_phase >= FINEUSEC) {
484 ltemp = time_phase >> SHIFT_SCALE;
485 time_phase -= ltemp << SHIFT_SCALE;
486 time_update += ltemp;
487 }
224 /*
225 * Compute the phase adjustment. If the low-order bits
226 * (time_phase) of the update overflow, bump the high-order bits
227 * (time_update).
228 */
229 time_phase += time_adj;
230 if (time_phase <= -FINEUSEC) {
231 ltemp = -time_phase >> SHIFT_SCALE;
232 time_phase += ltemp << SHIFT_SCALE;
233 time_update -= ltemp;
234 }
235 else if (time_phase >= FINEUSEC) {
236 ltemp = time_phase >> SHIFT_SCALE;
237 time_phase -= ltemp << SHIFT_SCALE;
238 time_update += ltemp;
239 }
488
240
489 newtime.tv_usec += time_update;
490 /*
491 * On rollover of the second the phase adjustment to be used for
492 * the next second is calculated. Also, the maximum error is
493 * increased by the tolerance. If the PPS frequency discipline
494 * code is present, the phase is increased to compensate for the
495 * CPU clock oscillator frequency error.
496 *
497 * On a 32-bit machine and given parameters in the timex.h
498 * header file, the maximum phase adjustment is +-512 ms and
499 * maximum frequency offset is a tad less than) +-512 ppm. On a
500 * 64-bit machine, you shouldn't need to ask.
501 */
502 if (newtime.tv_usec >= 1000000) {
503 newtime.tv_usec -= 1000000;
504 newtime.tv_sec++;
505 time_maxerror += time_tolerance >> SHIFT_USEC;
506
507 /*
508 * Compute the phase adjustment for the next second. In
509 * PLL mode, the offset is reduced by a fixed factor
510 * times the time constant. In FLL mode the offset is
511 * used directly. In either mode, the maximum phase
512 * adjustment for each second is clamped so as to spread
513 * the adjustment over not more than the number of
514 * seconds between updates.
515 */
516 if (time_offset < 0) {
517 ltemp = -time_offset;
518 if (!(time_status & STA_FLL))
519 ltemp >>= SHIFT_KG + time_constant;
520 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
521 ltemp = (MAXPHASE / MINSEC) <<
522 SHIFT_UPDATE;
523 time_offset += ltemp;
524 time_adj = -ltemp << (SHIFT_SCALE - SHIFT_HZ -
525 SHIFT_UPDATE);
526 } else {
527 ltemp = time_offset;
528 if (!(time_status & STA_FLL))
529 ltemp >>= SHIFT_KG + time_constant;
530 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
531 ltemp = (MAXPHASE / MINSEC) <<
532 SHIFT_UPDATE;
533 time_offset -= ltemp;
534 time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ -
535 SHIFT_UPDATE);
536 }
537
538 /*
539 * Compute the frequency estimate and additional phase
540 * adjustment due to frequency error for the next
541 * second. When the PPS signal is engaged, gnaw on the
542 * watchdog counter and update the frequency computed by
543 * the pll and the PPS signal.
544 */
545#ifdef PPS_SYNC
546 pps_valid++;
547 if (pps_valid == PPS_VALID) {
548 pps_jitter = MAXTIME;
549 pps_stabil = MAXFREQ;
550 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
551 STA_PPSWANDER | STA_PPSERROR);
552 }
553 ltemp = time_freq + pps_freq;
554#else
555 ltemp = time_freq;
556#endif /* PPS_SYNC */
557 if (ltemp < 0)
558 time_adj -= -ltemp >>
559 (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
560 else
561 time_adj += ltemp >>
562 (SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE);
563
564#if SHIFT_HZ == 7
565 /*
566 * When the CPU clock oscillator frequency is not a
567 * power of two in Hz, the SHIFT_HZ is only an
568 * approximate scale factor. In the SunOS kernel, this
569 * results in a PLL gain factor of 1/1.28 = 0.78 what it
570 * should be. In the following code the overall gain is
571 * increased by a factor of 1.25, which results in a
572 * residual error less than 3 percent.
573 */
574 /* Same thing applies for FreeBSD --GAW */
575 if (hz == 100) {
576 if (time_adj < 0)
577 time_adj -= -time_adj >> 2;
578 else
579 time_adj += time_adj >> 2;
580 }
581#endif /* SHIFT_HZ */
582
583 /* XXX - this is really bogus, but can't be fixed until
584 xntpd's idea of the system clock is fixed to know how
585 the user wants leap seconds handled; in the mean time,
586 we assume that users of NTP are running without proper
587 leap second support (this is now the default anyway) */
588 /*
589 * Leap second processing. If in leap-insert state at
590 * the end of the day, the system clock is set back one
591 * second; if in leap-delete state, the system clock is
592 * set ahead one second. The microtime() routine or
593 * external clock driver will insure that reported time
594 * is always monotonic. The ugly divides should be
595 * replaced.
596 */
597 switch (time_state) {
598
599 case TIME_OK:
600 if (time_status & STA_INS)
601 time_state = TIME_INS;
602 else if (time_status & STA_DEL)
603 time_state = TIME_DEL;
604 break;
605
606 case TIME_INS:
607 if (newtime.tv_sec % 86400 == 0) {
608 newtime.tv_sec--;
609 time_state = TIME_OOP;
610 }
611 break;
612
613 case TIME_DEL:
614 if ((newtime.tv_sec + 1) % 86400 == 0) {
615 newtime.tv_sec++;
616 time_state = TIME_WAIT;
617 }
618 break;
619
620 case TIME_OOP:
621 time_state = TIME_WAIT;
622 break;
623
624 case TIME_WAIT:
625 if (!(time_status & (STA_INS | STA_DEL)))
626 time_state = TIME_OK;
627 }
628 }
629 CPU_CLOCKUPDATE(&time, &newtime);
241 newtime.tv_usec += time_update;
242 /*
243 * On rollover of the second the phase adjustment to be used for
244 * the next second is calculated. Also, the maximum error is
245 * increased by the tolerance. If the PPS frequency discipline
246 * code is present, the phase is increased to compensate for the
247 * CPU clock oscillator frequency error.
248 *
249 * On a 32-bit machine and given parameters in the timex.h
250 * header file, the maximum phase adjustment is +-512 ms and
251 * maximum frequency offset is a tad less than) +-512 ppm. On a
252 * 64-bit machine, you shouldn't need to ask.
253 */
254 if (newtime.tv_usec >= 1000000) {
255 newtime.tv_usec -= 1000000;
256 newtime.tv_sec++;
257 ntp_update_second(&newtime.tv_sec);
630 }
258 }
631
632 if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
259 CPU_CLOCKUPDATE(&time, &newtime);
260
261 if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL)
633 setsoftclock();
262 setsoftclock();
634 }
635}
636
637void
638gettime(struct timeval *tvp)
639{
640 int s;
641
642 s = splclock();

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

895 clkinfo.profhz = profhz;
896 clkinfo.stathz = stathz ? stathz : hz;
897 return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
898}
899
900SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
901 0, 0, sysctl_kern_clockrate, "S,clockinfo","");
902
263}
264
265void
266gettime(struct timeval *tvp)
267{
268 int s;
269
270 s = splclock();

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

523 clkinfo.profhz = profhz;
524 clkinfo.stathz = stathz ? stathz : hz;
525 return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
526}
527
528SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
529 0, 0, sysctl_kern_clockrate, "S,clockinfo","");
530
903#ifdef PPS_SYNC
904
905/* We need this ugly monster twice, so lets macroize it... */
906
907#define MEDIAN3(a, m, s) \
908 do { \
909 if (a[0] > a[1]) { \
910 if (a[1] > a[2]) { \
911 /* 0 1 2 */ \
912 m = a[1]; \
913 s = a[0] - a[2]; \
914 } else if (a[2] > a[0]) { \
915 /* 2 0 1 */ \
916 m = a[0]; \
917 s = a[2] - a[1]; \
918 } else { \
919 /* 0 2 1 */ \
920 m = a[2]; \
921 s = a[0] - a[1]; \
922 } \
923 } else { \
924 if (a[1] < a[2]) { \
925 /* 2 1 0 */ \
926 m = a[1]; \
927 s = a[2] - a[0]; \
928 } else if (a[2] < a[0]) { \
929 /* 1 0 2 */ \
930 m = a[0]; \
931 s = a[1] - a[2]; \
932 } else { \
933 /* 1 2 0 */ \
934 m = a[2]; \
935 s = a[1] - a[0]; \
936 } \
937 } \
938 } while (0)
939
940/*
941 * hardpps() - discipline CPU clock oscillator to external PPS signal
942 *
943 * This routine is called at each PPS interrupt in order to discipline
944 * the CPU clock oscillator to the PPS signal. It measures the PPS phase
945 * and leaves it in a handy spot for the hardclock() routine. It
946 * integrates successive PPS phase differences and calculates the
947 * frequency offset. This is used in hardclock() to discipline the CPU
948 * clock oscillator so that intrinsic frequency error is cancelled out.
949 * The code requires the caller to capture the time and hardware counter
950 * value at the on-time PPS signal transition.
951 *
952 * Note that, on some Unix systems, this routine runs at an interrupt
953 * priority level higher than the timer interrupt routine hardclock().
954 * Therefore, the variables used are distinct from the hardclock()
955 * variables, except for certain exceptions: The PPS frequency pps_freq
956 * and phase pps_offset variables are determined by this routine and
957 * updated atomically. The time_tolerance variable can be considered a
958 * constant, since it is infrequently changed, and then only when the
959 * PPS signal is disabled. The watchdog counter pps_valid is updated
960 * once per second by hardclock() and is atomically cleared in this
961 * routine.
962 */
963void
964hardpps(tvp, p_usec)
965 struct timeval *tvp; /* time at PPS */
966 long p_usec; /* hardware counter at PPS */
967{
968 long u_usec, v_usec, bigtick;
969 long cal_sec, cal_usec;
970
971 /*
972 * An occasional glitch can be produced when the PPS interrupt
973 * occurs in the hardclock() routine before the time variable is
974 * updated. Here the offset is discarded when the difference
975 * between it and the last one is greater than tick/2, but not
976 * if the interval since the first discard exceeds 30 s.
977 */
978 time_status |= STA_PPSSIGNAL;
979 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
980 pps_valid = 0;
981 u_usec = -tvp->tv_usec;
982 if (u_usec < -500000)
983 u_usec += 1000000;
984 v_usec = pps_offset - u_usec;
985 if (v_usec < 0)
986 v_usec = -v_usec;
987 if (v_usec > (tick >> 1)) {
988 if (pps_glitch > MAXGLITCH) {
989 pps_glitch = 0;
990 pps_tf[2] = u_usec;
991 pps_tf[1] = u_usec;
992 } else {
993 pps_glitch++;
994 u_usec = pps_offset;
995 }
996 } else
997 pps_glitch = 0;
998
999 /*
1000 * A three-stage median filter is used to help deglitch the pps
1001 * time. The median sample becomes the time offset estimate; the
1002 * difference between the other two samples becomes the time
1003 * dispersion (jitter) estimate.
1004 */
1005 pps_tf[2] = pps_tf[1];
1006 pps_tf[1] = pps_tf[0];
1007 pps_tf[0] = u_usec;
1008
1009 MEDIAN3(pps_tf, pps_offset, v_usec);
1010
1011 if (v_usec > MAXTIME)
1012 pps_jitcnt++;
1013 v_usec = (v_usec << PPS_AVG) - pps_jitter;
1014 if (v_usec < 0)
1015 pps_jitter -= -v_usec >> PPS_AVG;
1016 else
1017 pps_jitter += v_usec >> PPS_AVG;
1018 if (pps_jitter > (MAXTIME >> 1))
1019 time_status |= STA_PPSJITTER;
1020
1021 /*
1022 * During the calibration interval adjust the starting time when
1023 * the tick overflows. At the end of the interval compute the
1024 * duration of the interval and the difference of the hardware
1025 * counters at the beginning and end of the interval. This code
1026 * is deliciously complicated by the fact valid differences may
1027 * exceed the value of tick when using long calibration
1028 * intervals and small ticks. Note that the counter can be
1029 * greater than tick if caught at just the wrong instant, but
1030 * the values returned and used here are correct.
1031 */
1032 bigtick = (long)tick << SHIFT_USEC;
1033 pps_usec -= pps_freq;
1034 if (pps_usec >= bigtick)
1035 pps_usec -= bigtick;
1036 if (pps_usec < 0)
1037 pps_usec += bigtick;
1038 pps_time.tv_sec++;
1039 pps_count++;
1040 if (pps_count < (1 << pps_shift))
1041 return;
1042 pps_count = 0;
1043 pps_calcnt++;
1044 u_usec = p_usec << SHIFT_USEC;
1045 v_usec = pps_usec - u_usec;
1046 if (v_usec >= bigtick >> 1)
1047 v_usec -= bigtick;
1048 if (v_usec < -(bigtick >> 1))
1049 v_usec += bigtick;
1050 if (v_usec < 0)
1051 v_usec = -(-v_usec >> pps_shift);
1052 else
1053 v_usec = v_usec >> pps_shift;
1054 pps_usec = u_usec;
1055 cal_sec = tvp->tv_sec;
1056 cal_usec = tvp->tv_usec;
1057 cal_sec -= pps_time.tv_sec;
1058 cal_usec -= pps_time.tv_usec;
1059 if (cal_usec < 0) {
1060 cal_usec += 1000000;
1061 cal_sec--;
1062 }
1063 pps_time = *tvp;
1064
1065 /*
1066 * Check for lost interrupts, noise, excessive jitter and
1067 * excessive frequency error. The number of timer ticks during
1068 * the interval may vary +-1 tick. Add to this a margin of one
1069 * tick for the PPS signal jitter and maximum frequency
1070 * deviation. If the limits are exceeded, the calibration
1071 * interval is reset to the minimum and we start over.
1072 */
1073 u_usec = (long)tick << 1;
1074 if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec))
1075 || (cal_sec == 0 && cal_usec < u_usec))
1076 || v_usec > time_tolerance || v_usec < -time_tolerance) {
1077 pps_errcnt++;
1078 pps_shift = PPS_SHIFT;
1079 pps_intcnt = 0;
1080 time_status |= STA_PPSERROR;
1081 return;
1082 }
1083
1084 /*
1085 * A three-stage median filter is used to help deglitch the pps
1086 * frequency. The median sample becomes the frequency offset
1087 * estimate; the difference between the other two samples
1088 * becomes the frequency dispersion (stability) estimate.
1089 */
1090 pps_ff[2] = pps_ff[1];
1091 pps_ff[1] = pps_ff[0];
1092 pps_ff[0] = v_usec;
1093
1094 MEDIAN3(pps_ff, u_usec, v_usec);
1095
1096 /*
1097 * Here the frequency dispersion (stability) is updated. If it
1098 * is less than one-fourth the maximum (MAXFREQ), the frequency
1099 * offset is updated as well, but clamped to the tolerance. It
1100 * will be processed later by the hardclock() routine.
1101 */
1102 v_usec = (v_usec >> 1) - pps_stabil;
1103 if (v_usec < 0)
1104 pps_stabil -= -v_usec >> PPS_AVG;
1105 else
1106 pps_stabil += v_usec >> PPS_AVG;
1107 if (pps_stabil > MAXFREQ >> 2) {
1108 pps_stbcnt++;
1109 time_status |= STA_PPSWANDER;
1110 return;
1111 }
1112 if (time_status & STA_PPSFREQ) {
1113 if (u_usec < 0) {
1114 pps_freq -= -u_usec >> PPS_AVG;
1115 if (pps_freq < -time_tolerance)
1116 pps_freq = -time_tolerance;
1117 u_usec = -u_usec;
1118 } else {
1119 pps_freq += u_usec >> PPS_AVG;
1120 if (pps_freq > time_tolerance)
1121 pps_freq = time_tolerance;
1122 }
1123 }
1124
1125 /*
1126 * Here the calibration interval is adjusted. If the maximum
1127 * time difference is greater than tick / 4, reduce the interval
1128 * by half. If this is not the case for four consecutive
1129 * intervals, double the interval.
1130 */
1131 if (u_usec << pps_shift > bigtick >> 2) {
1132 pps_intcnt = 0;
1133 if (pps_shift > PPS_SHIFT)
1134 pps_shift--;
1135 } else if (pps_intcnt >= 4) {
1136 pps_intcnt = 0;
1137 if (pps_shift < PPS_SHIFTMAX)
1138 pps_shift++;
1139 } else
1140 pps_intcnt++;
1141}
1142#endif /* PPS_SYNC */
1143