Initial import from FreeBSD RELENG_4:
[dragonfly.git] / sys / kern / kern_ntptime.c
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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 $
32 */
33
34#include "opt_ntp.h"
35
36#include <sys/param.h>
37#include <sys/systm.h>
38#include <sys/sysproto.h>
39#include <sys/kernel.h>
40#include <sys/proc.h>
41#include <sys/time.h>
42#include <sys/timex.h>
43#include <sys/timepps.h>
44#include <sys/sysctl.h>
45
46/*
47 * Single-precision macros for 64-bit machines
48 */
49typedef long long l_fp;
50#define L_ADD(v, u) ((v) += (u))
51#define L_SUB(v, u) ((v) -= (u))
52#define L_ADDHI(v, a) ((v) += (long long)(a) << 32)
53#define L_NEG(v) ((v) = -(v))
54#define L_RSHIFT(v, n) \
55 do { \
56 if ((v) < 0) \
57 (v) = -(-(v) >> (n)); \
58 else \
59 (v) = (v) >> (n); \
60 } while (0)
61#define L_MPY(v, a) ((v) *= (a))
62#define L_CLR(v) ((v) = 0)
63#define L_ISNEG(v) ((v) < 0)
64#define L_LINT(v, a) ((v) = (long long)(a) << 32)
65#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
66
67/*
68 * Generic NTP kernel interface
69 *
70 * These routines constitute the Network Time Protocol (NTP) interfaces
71 * for user and daemon application programs. The ntp_gettime() routine
72 * provides the time, maximum error (synch distance) and estimated error
73 * (dispersion) to client user application programs. The ntp_adjtime()
74 * routine is used by the NTP daemon to adjust the system clock to an
75 * externally derived time. The time offset and related variables set by
76 * this routine are used by other routines in this module to adjust the
77 * phase and frequency of the clock discipline loop which controls the
78 * system clock.
79 *
80 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
81 * defined), the time at each tick interrupt is derived directly from
82 * the kernel time variable. When the kernel time is reckoned in
83 * microseconds, (NTP_NANO undefined), the time is derived from the
84 * kernel time variable together with a variable representing the
85 * leftover nanoseconds at the last tick interrupt. In either case, the
86 * current nanosecond time is reckoned from these values plus an
87 * interpolated value derived by the clock routines in another
88 * architecture-specific module. The interpolation can use either a
89 * dedicated counter or a processor cycle counter (PCC) implemented in
90 * some architectures.
91 *
92 * Note that all routines must run at priority splclock or higher.
93 */
94/*
95 * Phase/frequency-lock loop (PLL/FLL) definitions
96 *
97 * The nanosecond clock discipline uses two variable types, time
98 * variables and frequency variables. Both types are represented as 64-
99 * bit fixed-point quantities with the decimal point between two 32-bit
100 * halves. On a 32-bit machine, each half is represented as a single
101 * word and mathematical operations are done using multiple-precision
102 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
103 * used.
104 *
105 * A time variable is a signed 64-bit fixed-point number in ns and
106 * fraction. It represents the remaining time offset to be amortized
107 * over succeeding tick interrupts. The maximum time offset is about
108 * 0.5 s and the resolution is about 2.3e-10 ns.
109 *
110 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
111 * 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
112 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
113 * |s s s| ns |
114 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
115 * | fraction |
116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
117 *
118 * A frequency variable is a signed 64-bit fixed-point number in ns/s
119 * and fraction. It represents the ns and fraction to be added to the
120 * kernel time variable at each second. The maximum frequency offset is
121 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
122 *
123 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
124 * 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
125 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
126 * |s s s s s s s s s s s s s| ns/s |
127 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
128 * | fraction |
129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
130 */
131/*
132 * The following variables establish the state of the PLL/FLL and the
133 * residual time and frequency offset of the local clock.
134 */
135#define SHIFT_PLL 4 /* PLL loop gain (shift) */
136#define SHIFT_FLL 2 /* FLL loop gain (shift) */
137
138static int time_state = TIME_OK; /* clock state */
139static int time_status = STA_UNSYNC; /* clock status bits */
140static long time_tai; /* TAI offset (s) */
141static long time_monitor; /* last time offset scaled (ns) */
142static long time_constant; /* poll interval (shift) (s) */
143static long time_precision = 1; /* clock precision (ns) */
144static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
145static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
146static long time_reftime; /* time at last adjustment (s) */
147static long time_tick; /* nanoseconds per tick (ns) */
148static l_fp time_offset; /* time offset (ns) */
149static l_fp time_freq; /* frequency offset (ns/s) */
150static l_fp time_adj; /* tick adjust (ns/s) */
151
152#ifdef PPS_SYNC
153/*
154 * The following variables are used when a pulse-per-second (PPS) signal
155 * is available and connected via a modem control lead. They establish
156 * the engineering parameters of the clock discipline loop when
157 * controlled by the PPS signal.
158 */
159#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
160#define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
161#define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
162#define PPS_PAVG 4 /* phase avg interval (s) (shift) */
163#define PPS_VALID 120 /* PPS signal watchdog max (s) */
164#define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
165#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
166
167static struct timespec pps_tf[3]; /* phase median filter */
168static l_fp pps_freq; /* scaled frequency offset (ns/s) */
169static long pps_fcount; /* frequency accumulator */
170static long pps_jitter; /* nominal jitter (ns) */
171static long pps_stabil; /* nominal stability (scaled ns/s) */
172static long pps_lastsec; /* time at last calibration (s) */
173static int pps_valid; /* signal watchdog counter */
174static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
175static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
176static int pps_intcnt; /* wander counter */
177
178/*
179 * PPS signal quality monitors
180 */
181static long pps_calcnt; /* calibration intervals */
182static long pps_jitcnt; /* jitter limit exceeded */
183static long pps_stbcnt; /* stability limit exceeded */
184static long pps_errcnt; /* calibration errors */
185#endif /* PPS_SYNC */
186/*
187 * End of phase/frequency-lock loop (PLL/FLL) definitions
188 */
189
190static void ntp_init(void);
191static void hardupdate(long offset);
192
193/*
194 * ntp_gettime() - NTP user application interface
195 *
196 * See the timex.h header file for synopsis and API description. Note
197 * that the TAI offset is returned in the ntvtimeval.tai structure
198 * member.
199 */
200static int
201ntp_sysctl(SYSCTL_HANDLER_ARGS)
202{
203 struct ntptimeval ntv; /* temporary structure */
204 struct timespec atv; /* nanosecond time */
205
206 nanotime(&atv);
207 ntv.time.tv_sec = atv.tv_sec;
208 ntv.time.tv_nsec = atv.tv_nsec;
209 ntv.maxerror = time_maxerror;
210 ntv.esterror = time_esterror;
211 ntv.tai = time_tai;
212 ntv.time_state = time_state;
213
214 /*
215 * Status word error decode. If any of these conditions occur,
216 * an error is returned, instead of the status word. Most
217 * applications will care only about the fact the system clock
218 * may not be trusted, not about the details.
219 *
220 * Hardware or software error
221 */
222 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
223
224 /*
225 * PPS signal lost when either time or frequency synchronization
226 * requested
227 */
228 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
229 !(time_status & STA_PPSSIGNAL)) ||
230
231 /*
232 * PPS jitter exceeded when time synchronization requested
233 */
234 (time_status & STA_PPSTIME &&
235 time_status & STA_PPSJITTER) ||
236
237 /*
238 * PPS wander exceeded or calibration error when frequency
239 * synchronization requested
240 */
241 (time_status & STA_PPSFREQ &&
242 time_status & (STA_PPSWANDER | STA_PPSERROR)))
243 ntv.time_state = TIME_ERROR;
244 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
245}
246
247SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
248SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
249 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
250
251#ifdef PPS_SYNC
252SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
253SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
254SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
255
256SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
257SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
258#endif
259/*
260 * ntp_adjtime() - NTP daemon application interface
261 *
262 * See the timex.h header file for synopsis and API description. Note
263 * that the timex.constant structure member has a dual purpose to set
264 * the time constant and to set the TAI offset.
265 */
266#ifndef _SYS_SYSPROTO_H_
267struct ntp_adjtime_args {
268 struct timex *tp;
269};
270#endif
271
272int
273ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap)
274{
275 struct timex ntv; /* temporary structure */
276 long freq; /* frequency ns/s) */
277 int modes; /* mode bits from structure */
278 int s; /* caller priority */
279 int error;
280
281 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
282 if (error)
283 return(error);
284
285 /*
286 * Update selected clock variables - only the superuser can
287 * change anything. Note that there is no error checking here on
288 * the assumption the superuser should know what it is doing.
289 * Note that either the time constant or TAI offset are loaded
290 * from the ntv.constant member, depending on the mode bits. If
291 * the STA_PLL bit in the status word is cleared, the state and
292 * status words are reset to the initial values at boot.
293 */
294 modes = ntv.modes;
295 if (modes)
296 error = suser(p);
297 if (error)
298 return (error);
299 s = splclock();
300 if (modes & MOD_MAXERROR)
301 time_maxerror = ntv.maxerror;
302 if (modes & MOD_ESTERROR)
303 time_esterror = ntv.esterror;
304 if (modes & MOD_STATUS) {
305 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
306 time_state = TIME_OK;
307 time_status = STA_UNSYNC;
308#ifdef PPS_SYNC
309 pps_shift = PPS_FAVG;
310#endif /* PPS_SYNC */
311 }
312 time_status &= STA_RONLY;
313 time_status |= ntv.status & ~STA_RONLY;
314 }
315 if (modes & MOD_TIMECONST) {
316 if (ntv.constant < 0)
317 time_constant = 0;
318 else if (ntv.constant > MAXTC)
319 time_constant = MAXTC;
320 else
321 time_constant = ntv.constant;
322 }
323 if (modes & MOD_TAI) {
324 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
325 time_tai = ntv.constant;
326 }
327#ifdef PPS_SYNC
328 if (modes & MOD_PPSMAX) {
329 if (ntv.shift < PPS_FAVG)
330 pps_shiftmax = PPS_FAVG;
331 else if (ntv.shift > PPS_FAVGMAX)
332 pps_shiftmax = PPS_FAVGMAX;
333 else
334 pps_shiftmax = ntv.shift;
335 }
336#endif /* PPS_SYNC */
337 if (modes & MOD_NANO)
338 time_status |= STA_NANO;
339 if (modes & MOD_MICRO)
340 time_status &= ~STA_NANO;
341 if (modes & MOD_CLKB)
342 time_status |= STA_CLK;
343 if (modes & MOD_CLKA)
344 time_status &= ~STA_CLK;
345 if (modes & MOD_OFFSET) {
346 if (time_status & STA_NANO)
347 hardupdate(ntv.offset);
348 else
349 hardupdate(ntv.offset * 1000);
350 }
351 if (modes & MOD_FREQUENCY) {
352 freq = (ntv.freq * 1000LL) >> 16;
353 if (freq > MAXFREQ)
354 L_LINT(time_freq, MAXFREQ);
355 else if (freq < -MAXFREQ)
356 L_LINT(time_freq, -MAXFREQ);
357 else
358 L_LINT(time_freq, freq);
359#ifdef PPS_SYNC
360 pps_freq = time_freq;
361#endif /* PPS_SYNC */
362 }
363
364 /*
365 * Retrieve all clock variables. Note that the TAI offset is
366 * returned only by ntp_gettime();
367 */
368 if (time_status & STA_NANO)
369 ntv.offset = time_monitor;
370 else
371 ntv.offset = time_monitor / 1000; /* XXX rounding ? */
372 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
373 ntv.maxerror = time_maxerror;
374 ntv.esterror = time_esterror;
375 ntv.status = time_status;
376 ntv.constant = time_constant;
377 if (time_status & STA_NANO)
378 ntv.precision = time_precision;
379 else
380 ntv.precision = time_precision / 1000;
381 ntv.tolerance = MAXFREQ * SCALE_PPM;
382#ifdef PPS_SYNC
383 ntv.shift = pps_shift;
384 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
385 if (time_status & STA_NANO)
386 ntv.jitter = pps_jitter;
387 else
388 ntv.jitter = pps_jitter / 1000;
389 ntv.stabil = pps_stabil;
390 ntv.calcnt = pps_calcnt;
391 ntv.errcnt = pps_errcnt;
392 ntv.jitcnt = pps_jitcnt;
393 ntv.stbcnt = pps_stbcnt;
394#endif /* PPS_SYNC */
395 splx(s);
396
397 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
398 if (error)
399 return (error);
400
401 /*
402 * Status word error decode. See comments in
403 * ntp_gettime() routine.
404 */
405 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
406 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
407 !(time_status & STA_PPSSIGNAL)) ||
408 (time_status & STA_PPSTIME &&
409 time_status & STA_PPSJITTER) ||
410 (time_status & STA_PPSFREQ &&
411 time_status & (STA_PPSWANDER | STA_PPSERROR)))
412 p->p_retval[0] = TIME_ERROR;
413 else
414 p->p_retval[0] = time_state;
415 return (error);
416}
417
418/*
419 * second_overflow() - called after ntp_tick_adjust()
420 *
421 * This routine is ordinarily called immediately following the above
422 * routine ntp_tick_adjust(). While these two routines are normally
423 * combined, they are separated here only for the purposes of
424 * simulation.
425 */
426void
427ntp_update_second(struct timecounter *tcp)
428{
429 u_int32_t *newsec;
430 l_fp ftemp; /* 32/64-bit temporary */
431
432 newsec = &tcp->tc_offset_sec;
433 /*
434 * On rollover of the second both the nanosecond and microsecond
435 * clocks are updated and the state machine cranked as
436 * necessary. The phase adjustment to be used for the next
437 * second is calculated and the maximum error is increased by
438 * the tolerance.
439 */
440 time_maxerror += MAXFREQ / 1000;
441
442 /*
443 * Leap second processing. If in leap-insert state at
444 * the end of the day, the system clock is set back one
445 * second; if in leap-delete state, the system clock is
446 * set ahead one second. The nano_time() routine or
447 * external clock driver will insure that reported time
448 * is always monotonic.
449 */
450 switch (time_state) {
451
452 /*
453 * No warning.
454 */
455 case TIME_OK:
456 if (time_status & STA_INS)
457 time_state = TIME_INS;
458 else if (time_status & STA_DEL)
459 time_state = TIME_DEL;
460 break;
461
462 /*
463 * Insert second 23:59:60 following second
464 * 23:59:59.
465 */
466 case TIME_INS:
467 if (!(time_status & STA_INS))
468 time_state = TIME_OK;
469 else if ((*newsec) % 86400 == 0) {
470 (*newsec)--;
471 time_state = TIME_OOP;
472 }
473 break;
474
475 /*
476 * Delete second 23:59:59.
477 */
478 case TIME_DEL:
479 if (!(time_status & STA_DEL))
480 time_state = TIME_OK;
481 else if (((*newsec) + 1) % 86400 == 0) {
482 (*newsec)++;
483 time_tai--;
484 time_state = TIME_WAIT;
485 }
486 break;
487
488 /*
489 * Insert second in progress.
490 */
491 case TIME_OOP:
492 time_tai++;
493 time_state = TIME_WAIT;
494 break;
495
496 /*
497 * Wait for status bits to clear.
498 */
499 case TIME_WAIT:
500 if (!(time_status & (STA_INS | STA_DEL)))
501 time_state = TIME_OK;
502 }
503
504 /*
505 * Compute the total time adjustment for the next second
506 * in ns. The offset is reduced by a factor depending on
507 * whether the PPS signal is operating. Note that the
508 * value is in effect scaled by the clock frequency,
509 * since the adjustment is added at each tick interrupt.
510 */
511 ftemp = time_offset;
512#ifdef PPS_SYNC
513 /* XXX even if PPS signal dies we should finish adjustment ? */
514 if (time_status & STA_PPSTIME && time_status &
515 STA_PPSSIGNAL)
516 L_RSHIFT(ftemp, pps_shift);
517 else
518 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
519#else
520 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
521#endif /* PPS_SYNC */
522 time_adj = ftemp;
523 L_SUB(time_offset, ftemp);
524 L_ADD(time_adj, time_freq);
525 tcp->tc_adjustment = time_adj;
526#ifdef PPS_SYNC
527 if (pps_valid > 0)
528 pps_valid--;
529 else
530 time_status &= ~STA_PPSSIGNAL;
531#endif /* PPS_SYNC */
532}
533
534/*
535 * ntp_init() - initialize variables and structures
536 *
537 * This routine must be called after the kernel variables hz and tick
538 * are set or changed and before the next tick interrupt. In this
539 * particular implementation, these values are assumed set elsewhere in
540 * the kernel. The design allows the clock frequency and tick interval
541 * to be changed while the system is running. So, this routine should
542 * probably be integrated with the code that does that.
543 */
544static void
545ntp_init()
546{
547
548 /*
549 * The following variable must be initialized any time the
550 * kernel variable hz is changed.
551 */
552 time_tick = NANOSECOND / hz;
553
554 /*
555 * The following variables are initialized only at startup. Only
556 * those structures not cleared by the compiler need to be
557 * initialized, and these only in the simulator. In the actual
558 * kernel, any nonzero values here will quickly evaporate.
559 */
560 L_CLR(time_offset);
561 L_CLR(time_freq);
562#ifdef PPS_SYNC
563 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
564 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
565 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
566 pps_fcount = 0;
567 L_CLR(pps_freq);
568#endif /* PPS_SYNC */
569}
570
571SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL)
572
573/*
574 * hardupdate() - local clock update
575 *
576 * This routine is called by ntp_adjtime() to update the local clock
577 * phase and frequency. The implementation is of an adaptive-parameter,
578 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
579 * time and frequency offset estimates for each call. If the kernel PPS
580 * discipline code is configured (PPS_SYNC), the PPS signal itself
581 * determines the new time offset, instead of the calling argument.
582 * Presumably, calls to ntp_adjtime() occur only when the caller
583 * believes the local clock is valid within some bound (+-128 ms with
584 * NTP). If the caller's time is far different than the PPS time, an
585 * argument will ensue, and it's not clear who will lose.
586 *
587 * For uncompensated quartz crystal oscillators and nominal update
588 * intervals less than 256 s, operation should be in phase-lock mode,
589 * where the loop is disciplined to phase. For update intervals greater
590 * than 1024 s, operation should be in frequency-lock mode, where the
591 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
592 * is selected by the STA_MODE status bit.
593 */
594static void
595hardupdate(offset)
596 long offset; /* clock offset (ns) */
597{
598 long mtemp;
599 l_fp ftemp;
600
601 /*
602 * Select how the phase is to be controlled and from which
603 * source. If the PPS signal is present and enabled to
604 * discipline the time, the PPS offset is used; otherwise, the
605 * argument offset is used.
606 */
607 if (!(time_status & STA_PLL))
608 return;
609 if (!(time_status & STA_PPSTIME && time_status &
610 STA_PPSSIGNAL)) {
611 if (offset > MAXPHASE)
612 time_monitor = MAXPHASE;
613 else if (offset < -MAXPHASE)
614 time_monitor = -MAXPHASE;
615 else
616 time_monitor = offset;
617 L_LINT(time_offset, time_monitor);
618 }
619
620 /*
621 * Select how the frequency is to be controlled and in which
622 * mode (PLL or FLL). If the PPS signal is present and enabled
623 * to discipline the frequency, the PPS frequency is used;
624 * otherwise, the argument offset is used to compute it.
625 */
626 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
627 time_reftime = time_second;
628 return;
629 }
630 if (time_status & STA_FREQHOLD || time_reftime == 0)
631 time_reftime = time_second;
632 mtemp = time_second - time_reftime;
633 L_LINT(ftemp, time_monitor);
634 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
635 L_MPY(ftemp, mtemp);
636 L_ADD(time_freq, ftemp);
637 time_status &= ~STA_MODE;
638 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
639 MAXSEC)) {
640 L_LINT(ftemp, (time_monitor << 4) / mtemp);
641 L_RSHIFT(ftemp, SHIFT_FLL + 4);
642 L_ADD(time_freq, ftemp);
643 time_status |= STA_MODE;
644 }
645 time_reftime = time_second;
646 if (L_GINT(time_freq) > MAXFREQ)
647 L_LINT(time_freq, MAXFREQ);
648 else if (L_GINT(time_freq) < -MAXFREQ)
649 L_LINT(time_freq, -MAXFREQ);
650}
651
652#ifdef PPS_SYNC
653/*
654 * hardpps() - discipline CPU clock oscillator to external PPS signal
655 *
656 * This routine is called at each PPS interrupt in order to discipline
657 * the CPU clock oscillator to the PPS signal. There are two independent
658 * first-order feedback loops, one for the phase, the other for the
659 * frequency. The phase loop measures and grooms the PPS phase offset
660 * and leaves it in a handy spot for the seconds overflow routine. The
661 * frequency loop averages successive PPS phase differences and
662 * calculates the PPS frequency offset, which is also processed by the
663 * seconds overflow routine. The code requires the caller to capture the
664 * time and architecture-dependent hardware counter values in
665 * nanoseconds at the on-time PPS signal transition.
666 *
667 * Note that, on some Unix systems this routine runs at an interrupt
668 * priority level higher than the timer interrupt routine hardclock().
669 * Therefore, the variables used are distinct from the hardclock()
670 * variables, except for the actual time and frequency variables, which
671 * are determined by this routine and updated atomically.
672 */
673void
674hardpps(tsp, nsec)
675 struct timespec *tsp; /* time at PPS */
676 long nsec; /* hardware counter at PPS */
677{
678 long u_sec, u_nsec, v_nsec; /* temps */
679 l_fp ftemp;
680
681 /*
682 * The signal is first processed by a range gate and frequency
683 * discriminator. The range gate rejects noise spikes outside
684 * the range +-500 us. The frequency discriminator rejects input
685 * signals with apparent frequency outside the range 1 +-500
686 * PPM. If two hits occur in the same second, we ignore the
687 * later hit; if not and a hit occurs outside the range gate,
688 * keep the later hit for later comparison, but do not process
689 * it.
690 */
691 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
692 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
693 pps_valid = PPS_VALID;
694 u_sec = tsp->tv_sec;
695 u_nsec = tsp->tv_nsec;
696 if (u_nsec >= (NANOSECOND >> 1)) {
697 u_nsec -= NANOSECOND;
698 u_sec++;
699 }
700 v_nsec = u_nsec - pps_tf[0].tv_nsec;
701 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
702 MAXFREQ)
703 return;
704 pps_tf[2] = pps_tf[1];
705 pps_tf[1] = pps_tf[0];
706 pps_tf[0].tv_sec = u_sec;
707 pps_tf[0].tv_nsec = u_nsec;
708
709 /*
710 * Compute the difference between the current and previous
711 * counter values. If the difference exceeds 0.5 s, assume it
712 * has wrapped around, so correct 1.0 s. If the result exceeds
713 * the tick interval, the sample point has crossed a tick
714 * boundary during the last second, so correct the tick. Very
715 * intricate.
716 */
717 u_nsec = nsec;
718 if (u_nsec > (NANOSECOND >> 1))
719 u_nsec -= NANOSECOND;
720 else if (u_nsec < -(NANOSECOND >> 1))
721 u_nsec += NANOSECOND;
722 pps_fcount += u_nsec;
723 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
724 return;
725 time_status &= ~STA_PPSJITTER;
726
727 /*
728 * A three-stage median filter is used to help denoise the PPS
729 * time. The median sample becomes the time offset estimate; the
730 * difference between the other two samples becomes the time
731 * dispersion (jitter) estimate.
732 */
733 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
734 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
735 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
736 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
737 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
738 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
739 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
740 } else {
741 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
742 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
743 }
744 } else {
745 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
746 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
747 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
748 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
749 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
750 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
751 } else {
752 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
753 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
754 }
755 }
756
757 /*
758 * Nominal jitter is due to PPS signal noise and interrupt
759 * latency. If it exceeds the popcorn threshold, the sample is
760 * discarded. otherwise, if so enabled, the time offset is
761 * updated. We can tolerate a modest loss of data here without
762 * much degrading time accuracy.
763 */
764 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
765 time_status |= STA_PPSJITTER;
766 pps_jitcnt++;
767 } else if (time_status & STA_PPSTIME) {
768 time_monitor = -v_nsec;
769 L_LINT(time_offset, time_monitor);
770 }
771 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
772 u_sec = pps_tf[0].tv_sec - pps_lastsec;
773 if (u_sec < (1 << pps_shift))
774 return;
775
776 /*
777 * At the end of the calibration interval the difference between
778 * the first and last counter values becomes the scaled
779 * frequency. It will later be divided by the length of the
780 * interval to determine the frequency update. If the frequency
781 * exceeds a sanity threshold, or if the actual calibration
782 * interval is not equal to the expected length, the data are
783 * discarded. We can tolerate a modest loss of data here without
784 * much degrading frequency accuracy.
785 */
786 pps_calcnt++;
787 v_nsec = -pps_fcount;
788 pps_lastsec = pps_tf[0].tv_sec;
789 pps_fcount = 0;
790 u_nsec = MAXFREQ << pps_shift;
791 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
792 pps_shift)) {
793 time_status |= STA_PPSERROR;
794 pps_errcnt++;
795 return;
796 }
797
798 /*
799 * Here the raw frequency offset and wander (stability) is
800 * calculated. If the wander is less than the wander threshold
801 * for four consecutive averaging intervals, the interval is
802 * doubled; if it is greater than the threshold for four
803 * consecutive intervals, the interval is halved. The scaled
804 * frequency offset is converted to frequency offset. The
805 * stability metric is calculated as the average of recent
806 * frequency changes, but is used only for performance
807 * monitoring.
808 */
809 L_LINT(ftemp, v_nsec);
810 L_RSHIFT(ftemp, pps_shift);
811 L_SUB(ftemp, pps_freq);
812 u_nsec = L_GINT(ftemp);
813 if (u_nsec > PPS_MAXWANDER) {
814 L_LINT(ftemp, PPS_MAXWANDER);
815 pps_intcnt--;
816 time_status |= STA_PPSWANDER;
817 pps_stbcnt++;
818 } else if (u_nsec < -PPS_MAXWANDER) {
819 L_LINT(ftemp, -PPS_MAXWANDER);
820 pps_intcnt--;
821 time_status |= STA_PPSWANDER;
822 pps_stbcnt++;
823 } else {
824 pps_intcnt++;
825 }
826 if (pps_intcnt >= 4) {
827 pps_intcnt = 4;
828 if (pps_shift < pps_shiftmax) {
829 pps_shift++;
830 pps_intcnt = 0;
831 }
832 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
833 pps_intcnt = -4;
834 if (pps_shift > PPS_FAVG) {
835 pps_shift--;
836 pps_intcnt = 0;
837 }
838 }
839 if (u_nsec < 0)
840 u_nsec = -u_nsec;
841 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
842
843 /*
844 * The PPS frequency is recalculated and clamped to the maximum
845 * MAXFREQ. If enabled, the system clock frequency is updated as
846 * well.
847 */
848 L_ADD(pps_freq, ftemp);
849 u_nsec = L_GINT(pps_freq);
850 if (u_nsec > MAXFREQ)
851 L_LINT(pps_freq, MAXFREQ);
852 else if (u_nsec < -MAXFREQ)
853 L_LINT(pps_freq, -MAXFREQ);
854 if (time_status & STA_PPSFREQ)
855 time_freq = pps_freq;
856}
857#endif /* PPS_SYNC */