Optimize lwkt_rwlock.c a bit
[dragonfly.git] / sys / kern / kern_ntptime.c
CommitLineData
984263bc
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1/***********************************************************************
2 * *
3 * Copyright (c) David L. Mills 1993-2001 *
4 * *
5 * Permission to use, copy, modify, and distribute this software and *
6 * its documentation for any purpose and without fee is hereby *
7 * granted, provided that the above copyright notice appears in all *
8 * copies and that both the copyright notice and this permission *
9 * notice appear in supporting documentation, and that the name *
10 * University of Delaware not be used in advertising or publicity *
11 * pertaining to distribution of the software without specific, *
12 * written prior permission. The University of Delaware makes no *
13 * representations about the suitability this software for any *
14 * purpose. It is provided "as is" without express or implied *
15 * warranty. *
16 * *
17 **********************************************************************/
18
19/*
20 * Adapted from the original sources for FreeBSD and timecounters by:
21 * Poul-Henning Kamp <phk@FreeBSD.org>.
22 *
23 * The 32bit version of the "LP" macros seems a bit past its "sell by"
24 * date so I have retained only the 64bit version and included it directly
25 * in this file.
26 *
27 * Only minor changes done to interface with the timecounters over in
28 * sys/kern/kern_clock.c. Some of the comments below may be (even more)
29 * confusing and/or plain wrong in that context.
30 *
31 * $FreeBSD: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $
1de703da 32 * $DragonFly: src/sys/kern/kern_ntptime.c,v 1.2 2003/06/17 04:28:41 dillon Exp $
984263bc
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33 */
34
35#include "opt_ntp.h"
36
37#include <sys/param.h>
38#include <sys/systm.h>
39#include <sys/sysproto.h>
40#include <sys/kernel.h>
41#include <sys/proc.h>
42#include <sys/time.h>
43#include <sys/timex.h>
44#include <sys/timepps.h>
45#include <sys/sysctl.h>
46
47/*
48 * Single-precision macros for 64-bit machines
49 */
50typedef long long l_fp;
51#define L_ADD(v, u) ((v) += (u))
52#define L_SUB(v, u) ((v) -= (u))
53#define L_ADDHI(v, a) ((v) += (long long)(a) << 32)
54#define L_NEG(v) ((v) = -(v))
55#define L_RSHIFT(v, n) \
56 do { \
57 if ((v) < 0) \
58 (v) = -(-(v) >> (n)); \
59 else \
60 (v) = (v) >> (n); \
61 } while (0)
62#define L_MPY(v, a) ((v) *= (a))
63#define L_CLR(v) ((v) = 0)
64#define L_ISNEG(v) ((v) < 0)
65#define L_LINT(v, a) ((v) = (long long)(a) << 32)
66#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
67
68/*
69 * Generic NTP kernel interface
70 *
71 * These routines constitute the Network Time Protocol (NTP) interfaces
72 * for user and daemon application programs. The ntp_gettime() routine
73 * provides the time, maximum error (synch distance) and estimated error
74 * (dispersion) to client user application programs. The ntp_adjtime()
75 * routine is used by the NTP daemon to adjust the system clock to an
76 * externally derived time. The time offset and related variables set by
77 * this routine are used by other routines in this module to adjust the
78 * phase and frequency of the clock discipline loop which controls the
79 * system clock.
80 *
81 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
82 * defined), the time at each tick interrupt is derived directly from
83 * the kernel time variable. When the kernel time is reckoned in
84 * microseconds, (NTP_NANO undefined), the time is derived from the
85 * kernel time variable together with a variable representing the
86 * leftover nanoseconds at the last tick interrupt. In either case, the
87 * current nanosecond time is reckoned from these values plus an
88 * interpolated value derived by the clock routines in another
89 * architecture-specific module. The interpolation can use either a
90 * dedicated counter or a processor cycle counter (PCC) implemented in
91 * some architectures.
92 *
93 * Note that all routines must run at priority splclock or higher.
94 */
95/*
96 * Phase/frequency-lock loop (PLL/FLL) definitions
97 *
98 * The nanosecond clock discipline uses two variable types, time
99 * variables and frequency variables. Both types are represented as 64-
100 * bit fixed-point quantities with the decimal point between two 32-bit
101 * halves. On a 32-bit machine, each half is represented as a single
102 * word and mathematical operations are done using multiple-precision
103 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
104 * used.
105 *
106 * A time variable is a signed 64-bit fixed-point number in ns and
107 * fraction. It represents the remaining time offset to be amortized
108 * over succeeding tick interrupts. The maximum time offset is about
109 * 0.5 s and the resolution is about 2.3e-10 ns.
110 *
111 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
112 * 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
113 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
114 * |s s s| ns |
115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
116 * | fraction |
117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
118 *
119 * A frequency variable is a signed 64-bit fixed-point number in ns/s
120 * and fraction. It represents the ns and fraction to be added to the
121 * kernel time variable at each second. The maximum frequency offset is
122 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
123 *
124 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
125 * 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
126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
127 * |s s s s s s s s s s s s s| ns/s |
128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
129 * | fraction |
130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
131 */
132/*
133 * The following variables establish the state of the PLL/FLL and the
134 * residual time and frequency offset of the local clock.
135 */
136#define SHIFT_PLL 4 /* PLL loop gain (shift) */
137#define SHIFT_FLL 2 /* FLL loop gain (shift) */
138
139static int time_state = TIME_OK; /* clock state */
140static int time_status = STA_UNSYNC; /* clock status bits */
141static long time_tai; /* TAI offset (s) */
142static long time_monitor; /* last time offset scaled (ns) */
143static long time_constant; /* poll interval (shift) (s) */
144static long time_precision = 1; /* clock precision (ns) */
145static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
146static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
147static long time_reftime; /* time at last adjustment (s) */
148static long time_tick; /* nanoseconds per tick (ns) */
149static l_fp time_offset; /* time offset (ns) */
150static l_fp time_freq; /* frequency offset (ns/s) */
151static l_fp time_adj; /* tick adjust (ns/s) */
152
153#ifdef PPS_SYNC
154/*
155 * The following variables are used when a pulse-per-second (PPS) signal
156 * is available and connected via a modem control lead. They establish
157 * the engineering parameters of the clock discipline loop when
158 * controlled by the PPS signal.
159 */
160#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
161#define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
162#define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
163#define PPS_PAVG 4 /* phase avg interval (s) (shift) */
164#define PPS_VALID 120 /* PPS signal watchdog max (s) */
165#define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
166#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
167
168static struct timespec pps_tf[3]; /* phase median filter */
169static l_fp pps_freq; /* scaled frequency offset (ns/s) */
170static long pps_fcount; /* frequency accumulator */
171static long pps_jitter; /* nominal jitter (ns) */
172static long pps_stabil; /* nominal stability (scaled ns/s) */
173static long pps_lastsec; /* time at last calibration (s) */
174static int pps_valid; /* signal watchdog counter */
175static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
176static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
177static int pps_intcnt; /* wander counter */
178
179/*
180 * PPS signal quality monitors
181 */
182static long pps_calcnt; /* calibration intervals */
183static long pps_jitcnt; /* jitter limit exceeded */
184static long pps_stbcnt; /* stability limit exceeded */
185static long pps_errcnt; /* calibration errors */
186#endif /* PPS_SYNC */
187/*
188 * End of phase/frequency-lock loop (PLL/FLL) definitions
189 */
190
191static void ntp_init(void);
192static void hardupdate(long offset);
193
194/*
195 * ntp_gettime() - NTP user application interface
196 *
197 * See the timex.h header file for synopsis and API description. Note
198 * that the TAI offset is returned in the ntvtimeval.tai structure
199 * member.
200 */
201static int
202ntp_sysctl(SYSCTL_HANDLER_ARGS)
203{
204 struct ntptimeval ntv; /* temporary structure */
205 struct timespec atv; /* nanosecond time */
206
207 nanotime(&atv);
208 ntv.time.tv_sec = atv.tv_sec;
209 ntv.time.tv_nsec = atv.tv_nsec;
210 ntv.maxerror = time_maxerror;
211 ntv.esterror = time_esterror;
212 ntv.tai = time_tai;
213 ntv.time_state = time_state;
214
215 /*
216 * Status word error decode. If any of these conditions occur,
217 * an error is returned, instead of the status word. Most
218 * applications will care only about the fact the system clock
219 * may not be trusted, not about the details.
220 *
221 * Hardware or software error
222 */
223 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
224
225 /*
226 * PPS signal lost when either time or frequency synchronization
227 * requested
228 */
229 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
230 !(time_status & STA_PPSSIGNAL)) ||
231
232 /*
233 * PPS jitter exceeded when time synchronization requested
234 */
235 (time_status & STA_PPSTIME &&
236 time_status & STA_PPSJITTER) ||
237
238 /*
239 * PPS wander exceeded or calibration error when frequency
240 * synchronization requested
241 */
242 (time_status & STA_PPSFREQ &&
243 time_status & (STA_PPSWANDER | STA_PPSERROR)))
244 ntv.time_state = TIME_ERROR;
245 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
246}
247
248SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
249SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
250 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
251
252#ifdef PPS_SYNC
253SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
254SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
255SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
256
257SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
258SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
259#endif
260/*
261 * ntp_adjtime() - NTP daemon application interface
262 *
263 * See the timex.h header file for synopsis and API description. Note
264 * that the timex.constant structure member has a dual purpose to set
265 * the time constant and to set the TAI offset.
266 */
267#ifndef _SYS_SYSPROTO_H_
268struct ntp_adjtime_args {
269 struct timex *tp;
270};
271#endif
272
273int
274ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap)
275{
276 struct timex ntv; /* temporary structure */
277 long freq; /* frequency ns/s) */
278 int modes; /* mode bits from structure */
279 int s; /* caller priority */
280 int error;
281
282 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
283 if (error)
284 return(error);
285
286 /*
287 * Update selected clock variables - only the superuser can
288 * change anything. Note that there is no error checking here on
289 * the assumption the superuser should know what it is doing.
290 * Note that either the time constant or TAI offset are loaded
291 * from the ntv.constant member, depending on the mode bits. If
292 * the STA_PLL bit in the status word is cleared, the state and
293 * status words are reset to the initial values at boot.
294 */
295 modes = ntv.modes;
296 if (modes)
297 error = suser(p);
298 if (error)
299 return (error);
300 s = splclock();
301 if (modes & MOD_MAXERROR)
302 time_maxerror = ntv.maxerror;
303 if (modes & MOD_ESTERROR)
304 time_esterror = ntv.esterror;
305 if (modes & MOD_STATUS) {
306 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
307 time_state = TIME_OK;
308 time_status = STA_UNSYNC;
309#ifdef PPS_SYNC
310 pps_shift = PPS_FAVG;
311#endif /* PPS_SYNC */
312 }
313 time_status &= STA_RONLY;
314 time_status |= ntv.status & ~STA_RONLY;
315 }
316 if (modes & MOD_TIMECONST) {
317 if (ntv.constant < 0)
318 time_constant = 0;
319 else if (ntv.constant > MAXTC)
320 time_constant = MAXTC;
321 else
322 time_constant = ntv.constant;
323 }
324 if (modes & MOD_TAI) {
325 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
326 time_tai = ntv.constant;
327 }
328#ifdef PPS_SYNC
329 if (modes & MOD_PPSMAX) {
330 if (ntv.shift < PPS_FAVG)
331 pps_shiftmax = PPS_FAVG;
332 else if (ntv.shift > PPS_FAVGMAX)
333 pps_shiftmax = PPS_FAVGMAX;
334 else
335 pps_shiftmax = ntv.shift;
336 }
337#endif /* PPS_SYNC */
338 if (modes & MOD_NANO)
339 time_status |= STA_NANO;
340 if (modes & MOD_MICRO)
341 time_status &= ~STA_NANO;
342 if (modes & MOD_CLKB)
343 time_status |= STA_CLK;
344 if (modes & MOD_CLKA)
345 time_status &= ~STA_CLK;
346 if (modes & MOD_OFFSET) {
347 if (time_status & STA_NANO)
348 hardupdate(ntv.offset);
349 else
350 hardupdate(ntv.offset * 1000);
351 }
352 if (modes & MOD_FREQUENCY) {
353 freq = (ntv.freq * 1000LL) >> 16;
354 if (freq > MAXFREQ)
355 L_LINT(time_freq, MAXFREQ);
356 else if (freq < -MAXFREQ)
357 L_LINT(time_freq, -MAXFREQ);
358 else
359 L_LINT(time_freq, freq);
360#ifdef PPS_SYNC
361 pps_freq = time_freq;
362#endif /* PPS_SYNC */
363 }
364
365 /*
366 * Retrieve all clock variables. Note that the TAI offset is
367 * returned only by ntp_gettime();
368 */
369 if (time_status & STA_NANO)
370 ntv.offset = time_monitor;
371 else
372 ntv.offset = time_monitor / 1000; /* XXX rounding ? */
373 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
374 ntv.maxerror = time_maxerror;
375 ntv.esterror = time_esterror;
376 ntv.status = time_status;
377 ntv.constant = time_constant;
378 if (time_status & STA_NANO)
379 ntv.precision = time_precision;
380 else
381 ntv.precision = time_precision / 1000;
382 ntv.tolerance = MAXFREQ * SCALE_PPM;
383#ifdef PPS_SYNC
384 ntv.shift = pps_shift;
385 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
386 if (time_status & STA_NANO)
387 ntv.jitter = pps_jitter;
388 else
389 ntv.jitter = pps_jitter / 1000;
390 ntv.stabil = pps_stabil;
391 ntv.calcnt = pps_calcnt;
392 ntv.errcnt = pps_errcnt;
393 ntv.jitcnt = pps_jitcnt;
394 ntv.stbcnt = pps_stbcnt;
395#endif /* PPS_SYNC */
396 splx(s);
397
398 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
399 if (error)
400 return (error);
401
402 /*
403 * Status word error decode. See comments in
404 * ntp_gettime() routine.
405 */
406 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
407 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
408 !(time_status & STA_PPSSIGNAL)) ||
409 (time_status & STA_PPSTIME &&
410 time_status & STA_PPSJITTER) ||
411 (time_status & STA_PPSFREQ &&
412 time_status & (STA_PPSWANDER | STA_PPSERROR)))
413 p->p_retval[0] = TIME_ERROR;
414 else
415 p->p_retval[0] = time_state;
416 return (error);
417}
418
419/*
420 * second_overflow() - called after ntp_tick_adjust()
421 *
422 * This routine is ordinarily called immediately following the above
423 * routine ntp_tick_adjust(). While these two routines are normally
424 * combined, they are separated here only for the purposes of
425 * simulation.
426 */
427void
428ntp_update_second(struct timecounter *tcp)
429{
430 u_int32_t *newsec;
431 l_fp ftemp; /* 32/64-bit temporary */
432
433 newsec = &tcp->tc_offset_sec;
434 /*
435 * On rollover of the second both the nanosecond and microsecond
436 * clocks are updated and the state machine cranked as
437 * necessary. The phase adjustment to be used for the next
438 * second is calculated and the maximum error is increased by
439 * the tolerance.
440 */
441 time_maxerror += MAXFREQ / 1000;
442
443 /*
444 * Leap second processing. If in leap-insert state at
445 * the end of the day, the system clock is set back one
446 * second; if in leap-delete state, the system clock is
447 * set ahead one second. The nano_time() routine or
448 * external clock driver will insure that reported time
449 * is always monotonic.
450 */
451 switch (time_state) {
452
453 /*
454 * No warning.
455 */
456 case TIME_OK:
457 if (time_status & STA_INS)
458 time_state = TIME_INS;
459 else if (time_status & STA_DEL)
460 time_state = TIME_DEL;
461 break;
462
463 /*
464 * Insert second 23:59:60 following second
465 * 23:59:59.
466 */
467 case TIME_INS:
468 if (!(time_status & STA_INS))
469 time_state = TIME_OK;
470 else if ((*newsec) % 86400 == 0) {
471 (*newsec)--;
472 time_state = TIME_OOP;
473 }
474 break;
475
476 /*
477 * Delete second 23:59:59.
478 */
479 case TIME_DEL:
480 if (!(time_status & STA_DEL))
481 time_state = TIME_OK;
482 else if (((*newsec) + 1) % 86400 == 0) {
483 (*newsec)++;
484 time_tai--;
485 time_state = TIME_WAIT;
486 }
487 break;
488
489 /*
490 * Insert second in progress.
491 */
492 case TIME_OOP:
493 time_tai++;
494 time_state = TIME_WAIT;
495 break;
496
497 /*
498 * Wait for status bits to clear.
499 */
500 case TIME_WAIT:
501 if (!(time_status & (STA_INS | STA_DEL)))
502 time_state = TIME_OK;
503 }
504
505 /*
506 * Compute the total time adjustment for the next second
507 * in ns. The offset is reduced by a factor depending on
508 * whether the PPS signal is operating. Note that the
509 * value is in effect scaled by the clock frequency,
510 * since the adjustment is added at each tick interrupt.
511 */
512 ftemp = time_offset;
513#ifdef PPS_SYNC
514 /* XXX even if PPS signal dies we should finish adjustment ? */
515 if (time_status & STA_PPSTIME && time_status &
516 STA_PPSSIGNAL)
517 L_RSHIFT(ftemp, pps_shift);
518 else
519 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
520#else
521 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
522#endif /* PPS_SYNC */
523 time_adj = ftemp;
524 L_SUB(time_offset, ftemp);
525 L_ADD(time_adj, time_freq);
526 tcp->tc_adjustment = time_adj;
527#ifdef PPS_SYNC
528 if (pps_valid > 0)
529 pps_valid--;
530 else
531 time_status &= ~STA_PPSSIGNAL;
532#endif /* PPS_SYNC */
533}
534
535/*
536 * ntp_init() - initialize variables and structures
537 *
538 * This routine must be called after the kernel variables hz and tick
539 * are set or changed and before the next tick interrupt. In this
540 * particular implementation, these values are assumed set elsewhere in
541 * the kernel. The design allows the clock frequency and tick interval
542 * to be changed while the system is running. So, this routine should
543 * probably be integrated with the code that does that.
544 */
545static void
546ntp_init()
547{
548
549 /*
550 * The following variable must be initialized any time the
551 * kernel variable hz is changed.
552 */
553 time_tick = NANOSECOND / hz;
554
555 /*
556 * The following variables are initialized only at startup. Only
557 * those structures not cleared by the compiler need to be
558 * initialized, and these only in the simulator. In the actual
559 * kernel, any nonzero values here will quickly evaporate.
560 */
561 L_CLR(time_offset);
562 L_CLR(time_freq);
563#ifdef PPS_SYNC
564 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
565 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
566 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
567 pps_fcount = 0;
568 L_CLR(pps_freq);
569#endif /* PPS_SYNC */
570}
571
572SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL)
573
574/*
575 * hardupdate() - local clock update
576 *
577 * This routine is called by ntp_adjtime() to update the local clock
578 * phase and frequency. The implementation is of an adaptive-parameter,
579 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
580 * time and frequency offset estimates for each call. If the kernel PPS
581 * discipline code is configured (PPS_SYNC), the PPS signal itself
582 * determines the new time offset, instead of the calling argument.
583 * Presumably, calls to ntp_adjtime() occur only when the caller
584 * believes the local clock is valid within some bound (+-128 ms with
585 * NTP). If the caller's time is far different than the PPS time, an
586 * argument will ensue, and it's not clear who will lose.
587 *
588 * For uncompensated quartz crystal oscillators and nominal update
589 * intervals less than 256 s, operation should be in phase-lock mode,
590 * where the loop is disciplined to phase. For update intervals greater
591 * than 1024 s, operation should be in frequency-lock mode, where the
592 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
593 * is selected by the STA_MODE status bit.
594 */
595static void
596hardupdate(offset)
597 long offset; /* clock offset (ns) */
598{
599 long mtemp;
600 l_fp ftemp;
601
602 /*
603 * Select how the phase is to be controlled and from which
604 * source. If the PPS signal is present and enabled to
605 * discipline the time, the PPS offset is used; otherwise, the
606 * argument offset is used.
607 */
608 if (!(time_status & STA_PLL))
609 return;
610 if (!(time_status & STA_PPSTIME && time_status &
611 STA_PPSSIGNAL)) {
612 if (offset > MAXPHASE)
613 time_monitor = MAXPHASE;
614 else if (offset < -MAXPHASE)
615 time_monitor = -MAXPHASE;
616 else
617 time_monitor = offset;
618 L_LINT(time_offset, time_monitor);
619 }
620
621 /*
622 * Select how the frequency is to be controlled and in which
623 * mode (PLL or FLL). If the PPS signal is present and enabled
624 * to discipline the frequency, the PPS frequency is used;
625 * otherwise, the argument offset is used to compute it.
626 */
627 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
628 time_reftime = time_second;
629 return;
630 }
631 if (time_status & STA_FREQHOLD || time_reftime == 0)
632 time_reftime = time_second;
633 mtemp = time_second - time_reftime;
634 L_LINT(ftemp, time_monitor);
635 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
636 L_MPY(ftemp, mtemp);
637 L_ADD(time_freq, ftemp);
638 time_status &= ~STA_MODE;
639 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
640 MAXSEC)) {
641 L_LINT(ftemp, (time_monitor << 4) / mtemp);
642 L_RSHIFT(ftemp, SHIFT_FLL + 4);
643 L_ADD(time_freq, ftemp);
644 time_status |= STA_MODE;
645 }
646 time_reftime = time_second;
647 if (L_GINT(time_freq) > MAXFREQ)
648 L_LINT(time_freq, MAXFREQ);
649 else if (L_GINT(time_freq) < -MAXFREQ)
650 L_LINT(time_freq, -MAXFREQ);
651}
652
653#ifdef PPS_SYNC
654/*
655 * hardpps() - discipline CPU clock oscillator to external PPS signal
656 *
657 * This routine is called at each PPS interrupt in order to discipline
658 * the CPU clock oscillator to the PPS signal. There are two independent
659 * first-order feedback loops, one for the phase, the other for the
660 * frequency. The phase loop measures and grooms the PPS phase offset
661 * and leaves it in a handy spot for the seconds overflow routine. The
662 * frequency loop averages successive PPS phase differences and
663 * calculates the PPS frequency offset, which is also processed by the
664 * seconds overflow routine. The code requires the caller to capture the
665 * time and architecture-dependent hardware counter values in
666 * nanoseconds at the on-time PPS signal transition.
667 *
668 * Note that, on some Unix systems this routine runs at an interrupt
669 * priority level higher than the timer interrupt routine hardclock().
670 * Therefore, the variables used are distinct from the hardclock()
671 * variables, except for the actual time and frequency variables, which
672 * are determined by this routine and updated atomically.
673 */
674void
675hardpps(tsp, nsec)
676 struct timespec *tsp; /* time at PPS */
677 long nsec; /* hardware counter at PPS */
678{
679 long u_sec, u_nsec, v_nsec; /* temps */
680 l_fp ftemp;
681
682 /*
683 * The signal is first processed by a range gate and frequency
684 * discriminator. The range gate rejects noise spikes outside
685 * the range +-500 us. The frequency discriminator rejects input
686 * signals with apparent frequency outside the range 1 +-500
687 * PPM. If two hits occur in the same second, we ignore the
688 * later hit; if not and a hit occurs outside the range gate,
689 * keep the later hit for later comparison, but do not process
690 * it.
691 */
692 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
693 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
694 pps_valid = PPS_VALID;
695 u_sec = tsp->tv_sec;
696 u_nsec = tsp->tv_nsec;
697 if (u_nsec >= (NANOSECOND >> 1)) {
698 u_nsec -= NANOSECOND;
699 u_sec++;
700 }
701 v_nsec = u_nsec - pps_tf[0].tv_nsec;
702 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
703 MAXFREQ)
704 return;
705 pps_tf[2] = pps_tf[1];
706 pps_tf[1] = pps_tf[0];
707 pps_tf[0].tv_sec = u_sec;
708 pps_tf[0].tv_nsec = u_nsec;
709
710 /*
711 * Compute the difference between the current and previous
712 * counter values. If the difference exceeds 0.5 s, assume it
713 * has wrapped around, so correct 1.0 s. If the result exceeds
714 * the tick interval, the sample point has crossed a tick
715 * boundary during the last second, so correct the tick. Very
716 * intricate.
717 */
718 u_nsec = nsec;
719 if (u_nsec > (NANOSECOND >> 1))
720 u_nsec -= NANOSECOND;
721 else if (u_nsec < -(NANOSECOND >> 1))
722 u_nsec += NANOSECOND;
723 pps_fcount += u_nsec;
724 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
725 return;
726 time_status &= ~STA_PPSJITTER;
727
728 /*
729 * A three-stage median filter is used to help denoise the PPS
730 * time. The median sample becomes the time offset estimate; the
731 * difference between the other two samples becomes the time
732 * dispersion (jitter) estimate.
733 */
734 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
735 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
736 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
737 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
738 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
739 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
740 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
741 } else {
742 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
743 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
744 }
745 } else {
746 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
747 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
748 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
749 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
750 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
751 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
752 } else {
753 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
754 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
755 }
756 }
757
758 /*
759 * Nominal jitter is due to PPS signal noise and interrupt
760 * latency. If it exceeds the popcorn threshold, the sample is
761 * discarded. otherwise, if so enabled, the time offset is
762 * updated. We can tolerate a modest loss of data here without
763 * much degrading time accuracy.
764 */
765 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
766 time_status |= STA_PPSJITTER;
767 pps_jitcnt++;
768 } else if (time_status & STA_PPSTIME) {
769 time_monitor = -v_nsec;
770 L_LINT(time_offset, time_monitor);
771 }
772 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
773 u_sec = pps_tf[0].tv_sec - pps_lastsec;
774 if (u_sec < (1 << pps_shift))
775 return;
776
777 /*
778 * At the end of the calibration interval the difference between
779 * the first and last counter values becomes the scaled
780 * frequency. It will later be divided by the length of the
781 * interval to determine the frequency update. If the frequency
782 * exceeds a sanity threshold, or if the actual calibration
783 * interval is not equal to the expected length, the data are
784 * discarded. We can tolerate a modest loss of data here without
785 * much degrading frequency accuracy.
786 */
787 pps_calcnt++;
788 v_nsec = -pps_fcount;
789 pps_lastsec = pps_tf[0].tv_sec;
790 pps_fcount = 0;
791 u_nsec = MAXFREQ << pps_shift;
792 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
793 pps_shift)) {
794 time_status |= STA_PPSERROR;
795 pps_errcnt++;
796 return;
797 }
798
799 /*
800 * Here the raw frequency offset and wander (stability) is
801 * calculated. If the wander is less than the wander threshold
802 * for four consecutive averaging intervals, the interval is
803 * doubled; if it is greater than the threshold for four
804 * consecutive intervals, the interval is halved. The scaled
805 * frequency offset is converted to frequency offset. The
806 * stability metric is calculated as the average of recent
807 * frequency changes, but is used only for performance
808 * monitoring.
809 */
810 L_LINT(ftemp, v_nsec);
811 L_RSHIFT(ftemp, pps_shift);
812 L_SUB(ftemp, pps_freq);
813 u_nsec = L_GINT(ftemp);
814 if (u_nsec > PPS_MAXWANDER) {
815 L_LINT(ftemp, PPS_MAXWANDER);
816 pps_intcnt--;
817 time_status |= STA_PPSWANDER;
818 pps_stbcnt++;
819 } else if (u_nsec < -PPS_MAXWANDER) {
820 L_LINT(ftemp, -PPS_MAXWANDER);
821 pps_intcnt--;
822 time_status |= STA_PPSWANDER;
823 pps_stbcnt++;
824 } else {
825 pps_intcnt++;
826 }
827 if (pps_intcnt >= 4) {
828 pps_intcnt = 4;
829 if (pps_shift < pps_shiftmax) {
830 pps_shift++;
831 pps_intcnt = 0;
832 }
833 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
834 pps_intcnt = -4;
835 if (pps_shift > PPS_FAVG) {
836 pps_shift--;
837 pps_intcnt = 0;
838 }
839 }
840 if (u_nsec < 0)
841 u_nsec = -u_nsec;
842 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
843
844 /*
845 * The PPS frequency is recalculated and clamped to the maximum
846 * MAXFREQ. If enabled, the system clock frequency is updated as
847 * well.
848 */
849 L_ADD(pps_freq, ftemp);
850 u_nsec = L_GINT(pps_freq);
851 if (u_nsec > MAXFREQ)
852 L_LINT(pps_freq, MAXFREQ);
853 else if (u_nsec < -MAXFREQ)
854 L_LINT(pps_freq, -MAXFREQ);
855 if (time_status & STA_PPSFREQ)
856 time_freq = pps_freq;
857}
858#endif /* PPS_SYNC */