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/sysmsg.h>
39 #include <sys/kernel.h>
40 #include <sys/proc.h>
41 #include <sys/caps.h>
42 #include <sys/time.h>
43 #include <sys/timex.h>
44 #include <sys/timepps.h>
45 #include <sys/sysctl.h>
46
47 #include <sys/thread2.h>
48
49 /*
50 * Single-precision macros for 64-bit machines
51 */
52 typedef long long l_fp;
53 #define L_ADD(v, u) ((v) += (u))
54 #define L_SUB(v, u) ((v) -= (u))
55 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32)
56 #define L_NEG(v) ((v) = -(v))
57 #define L_RSHIFT(v, n) \
58 do { \
59 if ((v) < 0) \
60 (v) = -(-(v) >> (n)); \
61 else \
62 (v) = (v) >> (n); \
63 } while (0)
64 #define L_MPY(v, a) ((v) *= (a))
65 #define L_CLR(v) ((v) = 0)
66 #define L_ISNEG(v) ((v) < 0)
67 #define L_LINT(v, a) ((v) = (long long)(a) << 32)
68 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
69
70 /*
71 * Generic NTP kernel interface
72 *
73 * These routines constitute the Network Time Protocol (NTP) interfaces
74 * for user and daemon application programs. The ntp_gettime() routine
75 * provides the time, maximum error (synch distance) and estimated error
76 * (dispersion) to client user application programs. The ntp_adjtime()
77 * routine is used by the NTP daemon to adjust the system clock to an
78 * externally derived time. The time offset and related variables set by
79 * this routine are used by other routines in this module to adjust the
80 * phase and frequency of the clock discipline loop which controls the
81 * system clock.
82 *
83 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
84 * defined), the time at each tick interrupt is derived directly from
85 * the kernel time variable. When the kernel time is reckoned in
86 * microseconds, (NTP_NANO undefined), the time is derived from the
87 * kernel time variable together with a variable representing the
88 * leftover nanoseconds at the last tick interrupt. In either case, the
89 * current nanosecond time is reckoned from these values plus an
90 * interpolated value derived by the clock routines in another
91 * architecture-specific module. The interpolation can use either a
92 * dedicated counter or a processor cycle counter (PCC) implemented in
93 * some architectures.
94 *
95 * Note that all routines must run at priority splclock or higher.
96 */
97 /*
98 * Phase/frequency-lock loop (PLL/FLL) definitions
99 *
100 * The nanosecond clock discipline uses two variable types, time
101 * variables and frequency variables. Both types are represented as 64-
102 * bit fixed-point quantities with the decimal point between two 32-bit
103 * halves. On a 32-bit machine, each half is represented as a single
104 * word and mathematical operations are done using multiple-precision
105 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
106 * used.
107 *
108 * A time variable is a signed 64-bit fixed-point number in ns and
109 * fraction. It represents the remaining time offset to be amortized
110 * over succeeding tick interrupts. The maximum time offset is about
111 * 0.5 s and the resolution is about 2.3e-10 ns.
112 *
113 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
114 * 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
115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
116 * |s s s| ns |
117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
118 * | fraction |
119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
120 *
121 * A frequency variable is a signed 64-bit fixed-point number in ns/s
122 * and fraction. It represents the ns and fraction to be added to the
123 * kernel time variable at each second. The maximum frequency offset is
124 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
125 *
126 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
127 * 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
128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
129 * |s s s s s s s s s s s s s| ns/s |
130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
131 * | fraction |
132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
133 */
134 /*
135 * The following variables establish the state of the PLL/FLL and the
136 * residual time and frequency offset of the local clock.
137 */
138 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
139 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
140
141 static int time_state = TIME_OK; /* clock state */
142 static int time_status = STA_UNSYNC; /* clock status bits */
143 static long time_tai; /* TAI offset (s) */
144 static long time_monitor; /* last time offset scaled (ns) */
145 static long time_constant; /* poll interval (shift) (s) */
146 static long time_precision = 1; /* clock precision (ns) */
147 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
148 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
149 static time_t time_reftime; /* time at last adjustment (s) */
150 static long time_tick; /* nanoseconds per tick (ns) */
151 static l_fp time_offset; /* time offset (ns) */
152 static l_fp time_freq; /* frequency offset (ns/s) */
153 static l_fp time_adj; /* tick adjust (ns/s) */
154
155 static struct lock ntp_lock = LOCK_INITIALIZER("ntplk", 0, 0);
156
157 #ifdef PPS_SYNC
158 /*
159 * The following variables are used when a pulse-per-second (PPS) signal
160 * is available and connected via a modem control lead. They establish
161 * the engineering parameters of the clock discipline loop when
162 * controlled by the PPS signal.
163 */
164 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
165 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
166 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
167 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
168 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
169 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
170 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
171
172 static struct timespec pps_tf[3]; /* phase median filter */
173 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
174 static long pps_fcount; /* frequency accumulator */
175 static long pps_jitter; /* nominal jitter (ns) */
176 static long pps_stabil; /* nominal stability (scaled ns/s) */
177 static long pps_lastsec; /* time at last calibration (s) */
178 static int pps_valid; /* signal watchdog counter */
179 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
180 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
181 static int pps_intcnt; /* wander counter */
182
183 /*
184 * PPS signal quality monitors
185 */
186 static long pps_calcnt; /* calibration intervals */
187 static long pps_jitcnt; /* jitter limit exceeded */
188 static long pps_stbcnt; /* stability limit exceeded */
189 static long pps_errcnt; /* calibration errors */
190 #endif /* PPS_SYNC */
191 /*
192 * End of phase/frequency-lock loop (PLL/FLL) definitions
193 */
194
195 static void ntp_init(void);
196 static void hardupdate(long offset);
197
198 /*
199 * ntp_gettime() - NTP user application interface
200 *
201 * See the timex.h header file for synopsis and API description. Note
202 * that the TAI offset is returned in the ntvtimeval.tai structure
203 * member.
204 */
205 static int
ntp_sysctl(SYSCTL_HANDLER_ARGS)206 ntp_sysctl(SYSCTL_HANDLER_ARGS)
207 {
208 struct ntptimeval ntv; /* temporary structure */
209 struct timespec atv; /* nanosecond time */
210 int error;
211
212 lockmgr(&ntp_lock, LK_EXCLUSIVE);
213
214 nanotime(&atv);
215 ntv.time.tv_sec = atv.tv_sec;
216 ntv.time.tv_nsec = atv.tv_nsec;
217 ntv.maxerror = time_maxerror;
218 ntv.esterror = time_esterror;
219 ntv.tai = time_tai;
220 ntv.time_state = time_state;
221
222 /*
223 * Status word error decode. If any of these conditions occur,
224 * an error is returned, instead of the status word. Most
225 * applications will care only about the fact the system clock
226 * may not be trusted, not about the details.
227 *
228 * Hardware or software error
229 */
230 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
231
232 /*
233 * PPS signal lost when either time or frequency synchronization
234 * requested
235 */
236 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
237 !(time_status & STA_PPSSIGNAL)) ||
238
239 /*
240 * PPS jitter exceeded when time synchronization requested
241 */
242 (time_status & STA_PPSTIME &&
243 time_status & STA_PPSJITTER) ||
244
245 /*
246 * PPS wander exceeded or calibration error when frequency
247 * synchronization requested
248 */
249 (time_status & STA_PPSFREQ &&
250 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
251 ntv.time_state = TIME_ERROR;
252 }
253
254 error = sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req);
255 lockmgr(&ntp_lock, LK_RELEASE);
256
257 return error;
258 }
259
260 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
261 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
262 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
263
264 #ifdef PPS_SYNC
265 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
266 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
267 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
268
269 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
270 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
271 #endif
272 /*
273 * ntp_adjtime() - NTP daemon application interface
274 *
275 * See the timex.h header file for synopsis and API description. Note
276 * that the timex.constant structure member has a dual purpose to set
277 * the time constant and to set the TAI offset.
278 *
279 * MPALMOSTSAFE
280 */
281 int
sys_ntp_adjtime(struct sysmsg * sysmsg,const struct ntp_adjtime_args * uap)282 sys_ntp_adjtime(struct sysmsg *sysmsg, const struct ntp_adjtime_args *uap)
283 {
284 struct timex ntv; /* temporary structure */
285 long freq; /* frequency ns/s) */
286 int modes; /* mode bits from structure */
287 int error;
288
289 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
290 if (error)
291 return(error);
292
293 /*
294 * Update selected clock variables - only the superuser can
295 * change anything. Note that there is no error checking here on
296 * the assumption the superuser should know what it is doing.
297 * Note that either the time constant or TAI offset are loaded
298 * from the ntv.constant member, depending on the mode bits. If
299 * the STA_PLL bit in the status word is cleared, the state and
300 * status words are reset to the initial values at boot.
301 */
302 modes = ntv.modes;
303 if (modes)
304 error = caps_priv_check_self(SYSCAP_NOSETTIME);
305 if (error)
306 return (error);
307
308 lockmgr(&ntp_lock, LK_EXCLUSIVE);
309 crit_enter();
310 if (modes & MOD_MAXERROR)
311 time_maxerror = ntv.maxerror;
312 if (modes & MOD_ESTERROR)
313 time_esterror = ntv.esterror;
314 if (modes & MOD_STATUS) {
315 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
316 time_state = TIME_OK;
317 time_status = STA_UNSYNC;
318 #ifdef PPS_SYNC
319 pps_shift = PPS_FAVG;
320 #endif /* PPS_SYNC */
321 }
322 time_status &= STA_RONLY;
323 time_status |= ntv.status & ~STA_RONLY;
324 }
325 if (modes & MOD_TIMECONST) {
326 if (ntv.constant < 0)
327 time_constant = 0;
328 else if (ntv.constant > MAXTC)
329 time_constant = MAXTC;
330 else
331 time_constant = ntv.constant;
332 }
333 if (modes & MOD_TAI) {
334 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
335 time_tai = ntv.constant;
336 }
337 #ifdef PPS_SYNC
338 if (modes & MOD_PPSMAX) {
339 if (ntv.shift < PPS_FAVG)
340 pps_shiftmax = PPS_FAVG;
341 else if (ntv.shift > PPS_FAVGMAX)
342 pps_shiftmax = PPS_FAVGMAX;
343 else
344 pps_shiftmax = ntv.shift;
345 }
346 #endif /* PPS_SYNC */
347 if (modes & MOD_NANO)
348 time_status |= STA_NANO;
349 if (modes & MOD_MICRO)
350 time_status &= ~STA_NANO;
351 if (modes & MOD_CLKB)
352 time_status |= STA_CLK;
353 if (modes & MOD_CLKA)
354 time_status &= ~STA_CLK;
355 if (modes & MOD_OFFSET) {
356 if (time_status & STA_NANO)
357 hardupdate(ntv.offset);
358 else
359 hardupdate(ntv.offset * 1000);
360 }
361 /*
362 * Note: the userland specified frequency is in seconds per second
363 * times 65536e+6. Multiply by a thousand and divide by 65336 to
364 * get nanoseconds.
365 */
366 if (modes & MOD_FREQUENCY) {
367 freq = (ntv.freq * 1000LL) >> 16;
368 if (freq > MAXFREQ)
369 L_LINT(time_freq, MAXFREQ);
370 else if (freq < -MAXFREQ)
371 L_LINT(time_freq, -MAXFREQ);
372 else
373 L_LINT(time_freq, freq);
374 #ifdef PPS_SYNC
375 pps_freq = time_freq;
376 #endif /* PPS_SYNC */
377 }
378
379 /*
380 * Retrieve all clock variables. Note that the TAI offset is
381 * returned only by ntp_gettime();
382 */
383 if (time_status & STA_NANO)
384 ntv.offset = time_monitor;
385 else
386 ntv.offset = time_monitor / 1000; /* XXX rounding ? */
387 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
388 ntv.maxerror = time_maxerror;
389 ntv.esterror = time_esterror;
390 ntv.status = time_status;
391 ntv.constant = time_constant;
392 if (time_status & STA_NANO)
393 ntv.precision = time_precision;
394 else
395 ntv.precision = time_precision / 1000;
396 ntv.tolerance = MAXFREQ * SCALE_PPM;
397 #ifdef PPS_SYNC
398 ntv.shift = pps_shift;
399 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
400 if (time_status & STA_NANO)
401 ntv.jitter = pps_jitter;
402 else
403 ntv.jitter = pps_jitter / 1000;
404 ntv.stabil = pps_stabil;
405 ntv.calcnt = pps_calcnt;
406 ntv.errcnt = pps_errcnt;
407 ntv.jitcnt = pps_jitcnt;
408 ntv.stbcnt = pps_stbcnt;
409 #endif /* PPS_SYNC */
410 crit_exit();
411 lockmgr(&ntp_lock, LK_RELEASE);
412
413 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
414 if (error)
415 return (error);
416
417 /*
418 * Status word error decode. See comments in
419 * ntp_gettime() routine.
420 */
421 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
422 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
423 !(time_status & STA_PPSSIGNAL)) ||
424 (time_status & STA_PPSTIME &&
425 time_status & STA_PPSJITTER) ||
426 (time_status & STA_PPSFREQ &&
427 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
428 sysmsg->sysmsg_result = TIME_ERROR;
429 } else {
430 sysmsg->sysmsg_result = time_state;
431 }
432 return (0);
433 }
434
435 /*
436 * second_overflow() - called after ntp_tick_adjust()
437 *
438 * This routine is ordinarily called from hardclock() whenever the seconds
439 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj
440 * to the total adjustment to make over the next second in (ns << 32).
441 *
442 * This routine is only called by cpu #0.
443 */
444 int
ntp_update_second(time_t newsec,int64_t * nsec_adj)445 ntp_update_second(time_t newsec, int64_t *nsec_adj)
446 {
447 l_fp ftemp; /* 32/64-bit temporary */
448 int adjsec = 0;
449
450 /*
451 * On rollover of the second both the nanosecond and microsecond
452 * clocks are updated and the state machine cranked as
453 * necessary. The phase adjustment to be used for the next
454 * second is calculated and the maximum error is increased by
455 * the tolerance.
456 */
457 time_maxerror += MAXFREQ / 1000;
458
459 /*
460 * Leap second processing. If in leap-insert state at
461 * the end of the day, the system clock is set back one
462 * second; if in leap-delete state, the system clock is
463 * set ahead one second. The nano_time() routine or
464 * external clock driver will insure that reported time
465 * is always monotonic.
466 */
467 switch (time_state) {
468
469 /*
470 * No warning.
471 */
472 case TIME_OK:
473 if (time_status & STA_INS)
474 time_state = TIME_INS;
475 else if (time_status & STA_DEL)
476 time_state = TIME_DEL;
477 break;
478
479 /*
480 * Insert second 23:59:60 following second
481 * 23:59:59.
482 */
483 case TIME_INS:
484 if (!(time_status & STA_INS))
485 time_state = TIME_OK;
486 else if ((newsec) % 86400 == 0) {
487 --adjsec;
488 time_state = TIME_OOP;
489 }
490 break;
491
492 /*
493 * Delete second 23:59:59.
494 */
495 case TIME_DEL:
496 if (!(time_status & STA_DEL))
497 time_state = TIME_OK;
498 else if (((newsec) + 1) % 86400 == 0) {
499 ++adjsec;
500 time_tai--;
501 time_state = TIME_WAIT;
502 }
503 break;
504
505 /*
506 * Insert second in progress.
507 */
508 case TIME_OOP:
509 time_tai++;
510 time_state = TIME_WAIT;
511 break;
512
513 /*
514 * Wait for status bits to clear.
515 */
516 case TIME_WAIT:
517 if (!(time_status & (STA_INS | STA_DEL)))
518 time_state = TIME_OK;
519 }
520
521 /*
522 * time_offset represents the total time adjustment we wish to
523 * make (over no particular period of time). time_freq represents
524 * the frequency compensation we wish to apply.
525 *
526 * time_adj represents the total adjustment we wish to make over
527 * one full second. hardclock usually applies this adjustment in
528 * time_adj / hz jumps, hz times a second.
529 */
530 ftemp = time_offset;
531 #ifdef PPS_SYNC
532 /* XXX even if PPS signal dies we should finish adjustment ? */
533 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))
534 L_RSHIFT(ftemp, pps_shift);
535 else
536 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
537 #else
538 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
539 #endif /* PPS_SYNC */
540 time_adj = ftemp; /* adjustment for part of the offset */
541 L_SUB(time_offset, ftemp);
542 L_ADD(time_adj, time_freq); /* add frequency correction */
543 *nsec_adj = time_adj;
544 #ifdef PPS_SYNC
545 if (pps_valid > 0)
546 pps_valid--;
547 else
548 time_status &= ~STA_PPSSIGNAL;
549 #endif /* PPS_SYNC */
550 return(adjsec);
551 }
552
553 /*
554 * ntp_init() - initialize variables and structures
555 *
556 * This routine must be called after the kernel variables hz and tick
557 * are set or changed and before the next tick interrupt. In this
558 * particular implementation, these values are assumed set elsewhere in
559 * the kernel. The design allows the clock frequency and tick interval
560 * to be changed while the system is running. So, this routine should
561 * probably be integrated with the code that does that.
562 */
563 static void
ntp_init(void)564 ntp_init(void)
565 {
566
567 /*
568 * The following variable must be initialized any time the
569 * kernel variable hz is changed.
570 */
571 time_tick = NANOSECOND / hz;
572
573 /*
574 * The following variables are initialized only at startup. Only
575 * those structures not cleared by the compiler need to be
576 * initialized, and these only in the simulator. In the actual
577 * kernel, any nonzero values here will quickly evaporate.
578 */
579 L_CLR(time_offset);
580 L_CLR(time_freq);
581 #ifdef PPS_SYNC
582 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
583 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
584 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
585 pps_fcount = 0;
586 L_CLR(pps_freq);
587 #endif /* PPS_SYNC */
588 }
589
590 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL);
591
592 /*
593 * hardupdate() - local clock update
594 *
595 * This routine is called by ntp_adjtime() to update the local clock
596 * phase and frequency. The implementation is of an adaptive-parameter,
597 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
598 * time and frequency offset estimates for each call. If the kernel PPS
599 * discipline code is configured (PPS_SYNC), the PPS signal itself
600 * determines the new time offset, instead of the calling argument.
601 * Presumably, calls to ntp_adjtime() occur only when the caller
602 * believes the local clock is valid within some bound (+-128 ms with
603 * NTP). If the caller's time is far different than the PPS time, an
604 * argument will ensue, and it's not clear who will lose.
605 *
606 * For uncompensated quartz crystal oscillators and nominal update
607 * intervals less than 256 s, operation should be in phase-lock mode,
608 * where the loop is disciplined to phase. For update intervals greater
609 * than 1024 s, operation should be in frequency-lock mode, where the
610 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
611 * is selected by the STA_MODE status bit.
612 */
613 static void
hardupdate(long offset)614 hardupdate(long offset)
615 {
616 long mtemp;
617 l_fp ftemp;
618
619 /*
620 * Select how the phase is to be controlled and from which
621 * source. If the PPS signal is present and enabled to
622 * discipline the time, the PPS offset is used; otherwise, the
623 * argument offset is used.
624 */
625 if (!(time_status & STA_PLL))
626 return;
627 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) {
628 if (offset > MAXPHASE)
629 time_monitor = MAXPHASE;
630 else if (offset < -MAXPHASE)
631 time_monitor = -MAXPHASE;
632 else
633 time_monitor = offset;
634 L_LINT(time_offset, time_monitor);
635 }
636
637 /*
638 * Select how the frequency is to be controlled and in which
639 * mode (PLL or FLL). If the PPS signal is present and enabled
640 * to discipline the frequency, the PPS frequency is used;
641 * otherwise, the argument offset is used to compute it.
642 */
643 if ((time_status & STA_PPSFREQ) && time_status & STA_PPSSIGNAL) {
644 time_reftime = time_uptime;
645 return;
646 }
647 if ((time_status & STA_FREQHOLD) || time_reftime == 0)
648 time_reftime = time_uptime;
649 mtemp = time_uptime - time_reftime;
650 L_LINT(ftemp, time_monitor);
651 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
652 L_MPY(ftemp, mtemp);
653 L_ADD(time_freq, ftemp);
654 time_status &= ~STA_MODE;
655 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
656 L_LINT(ftemp, (time_monitor << 4) / mtemp);
657 L_RSHIFT(ftemp, SHIFT_FLL + 4);
658 L_ADD(time_freq, ftemp);
659 time_status |= STA_MODE;
660 }
661 time_reftime = time_uptime;
662 if (L_GINT(time_freq) > MAXFREQ)
663 L_LINT(time_freq, MAXFREQ);
664 else if (L_GINT(time_freq) < -MAXFREQ)
665 L_LINT(time_freq, -MAXFREQ);
666 }
667
668 #ifdef PPS_SYNC
669 /*
670 * hardpps() - discipline CPU clock oscillator to external PPS signal
671 *
672 * This routine is called at each PPS interrupt in order to discipline
673 * the CPU clock oscillator to the PPS signal. There are two independent
674 * first-order feedback loops, one for the phase, the other for the
675 * frequency. The phase loop measures and grooms the PPS phase offset
676 * and leaves it in a handy spot for the seconds overflow routine. The
677 * frequency loop averages successive PPS phase differences and
678 * calculates the PPS frequency offset, which is also processed by the
679 * seconds overflow routine. The code requires the caller to capture the
680 * time and architecture-dependent hardware counter values in
681 * nanoseconds at the on-time PPS signal transition.
682 *
683 * Note that, on some Unix systems this routine runs at an interrupt
684 * priority level higher than the timer interrupt routine hardclock().
685 * Therefore, the variables used are distinct from the hardclock()
686 * variables, except for the actual time and frequency variables, which
687 * are determined by this routine and updated atomically.
688 */
689 void
hardpps(struct timespec * tsp,long nsec)690 hardpps(struct timespec *tsp, long nsec)
691 {
692 long u_sec, u_nsec, v_nsec; /* temps */
693 l_fp ftemp;
694
695 /*
696 * The signal is first processed by a range gate and frequency
697 * discriminator. The range gate rejects noise spikes outside
698 * the range +-500 us. The frequency discriminator rejects input
699 * signals with apparent frequency outside the range 1 +-500
700 * PPM. If two hits occur in the same second, we ignore the
701 * later hit; if not and a hit occurs outside the range gate,
702 * keep the later hit for later comparison, but do not process
703 * it.
704 */
705 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
706 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
707 pps_valid = PPS_VALID;
708 u_sec = tsp->tv_sec;
709 u_nsec = tsp->tv_nsec;
710 if (u_nsec >= (NANOSECOND >> 1)) {
711 u_nsec -= NANOSECOND;
712 u_sec++;
713 }
714 v_nsec = u_nsec - pps_tf[0].tv_nsec;
715 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
716 MAXFREQ)
717 return;
718 pps_tf[2] = pps_tf[1];
719 pps_tf[1] = pps_tf[0];
720 pps_tf[0].tv_sec = u_sec;
721 pps_tf[0].tv_nsec = u_nsec;
722
723 /*
724 * Compute the difference between the current and previous
725 * counter values. If the difference exceeds 0.5 s, assume it
726 * has wrapped around, so correct 1.0 s. If the result exceeds
727 * the tick interval, the sample point has crossed a tick
728 * boundary during the last second, so correct the tick. Very
729 * intricate.
730 */
731 u_nsec = nsec;
732 if (u_nsec > (NANOSECOND >> 1))
733 u_nsec -= NANOSECOND;
734 else if (u_nsec < -(NANOSECOND >> 1))
735 u_nsec += NANOSECOND;
736 pps_fcount += u_nsec;
737 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
738 return;
739 time_status &= ~STA_PPSJITTER;
740
741 /*
742 * A three-stage median filter is used to help denoise the PPS
743 * time. The median sample becomes the time offset estimate; the
744 * difference between the other two samples becomes the time
745 * dispersion (jitter) estimate.
746 */
747 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
748 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
749 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
750 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
751 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
752 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
753 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
754 } else {
755 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
756 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
757 }
758 } else {
759 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
760 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
761 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
762 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
763 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
764 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
765 } else {
766 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
767 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
768 }
769 }
770
771 /*
772 * Nominal jitter is due to PPS signal noise and interrupt
773 * latency. If it exceeds the popcorn threshold, the sample is
774 * discarded. otherwise, if so enabled, the time offset is
775 * updated. We can tolerate a modest loss of data here without
776 * much degrading time accuracy.
777 */
778 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
779 time_status |= STA_PPSJITTER;
780 pps_jitcnt++;
781 } else if (time_status & STA_PPSTIME) {
782 time_monitor = -v_nsec;
783 L_LINT(time_offset, time_monitor);
784 }
785 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
786 u_sec = pps_tf[0].tv_sec - pps_lastsec;
787 if (u_sec < (1 << pps_shift))
788 return;
789
790 /*
791 * At the end of the calibration interval the difference between
792 * the first and last counter values becomes the scaled
793 * frequency. It will later be divided by the length of the
794 * interval to determine the frequency update. If the frequency
795 * exceeds a sanity threshold, or if the actual calibration
796 * interval is not equal to the expected length, the data are
797 * discarded. We can tolerate a modest loss of data here without
798 * much degrading frequency accuracy.
799 */
800 pps_calcnt++;
801 v_nsec = -pps_fcount;
802 pps_lastsec = pps_tf[0].tv_sec;
803 pps_fcount = 0;
804 u_nsec = MAXFREQ << pps_shift;
805 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
806 pps_shift)) {
807 time_status |= STA_PPSERROR;
808 pps_errcnt++;
809 return;
810 }
811
812 /*
813 * Here the raw frequency offset and wander (stability) is
814 * calculated. If the wander is less than the wander threshold
815 * for four consecutive averaging intervals, the interval is
816 * doubled; if it is greater than the threshold for four
817 * consecutive intervals, the interval is halved. The scaled
818 * frequency offset is converted to frequency offset. The
819 * stability metric is calculated as the average of recent
820 * frequency changes, but is used only for performance
821 * monitoring.
822 */
823 L_LINT(ftemp, v_nsec);
824 L_RSHIFT(ftemp, pps_shift);
825 L_SUB(ftemp, pps_freq);
826 u_nsec = L_GINT(ftemp);
827 if (u_nsec > PPS_MAXWANDER) {
828 L_LINT(ftemp, PPS_MAXWANDER);
829 pps_intcnt--;
830 time_status |= STA_PPSWANDER;
831 pps_stbcnt++;
832 } else if (u_nsec < -PPS_MAXWANDER) {
833 L_LINT(ftemp, -PPS_MAXWANDER);
834 pps_intcnt--;
835 time_status |= STA_PPSWANDER;
836 pps_stbcnt++;
837 } else {
838 pps_intcnt++;
839 }
840 if (pps_intcnt >= 4) {
841 pps_intcnt = 4;
842 if (pps_shift < pps_shiftmax) {
843 pps_shift++;
844 pps_intcnt = 0;
845 }
846 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
847 pps_intcnt = -4;
848 if (pps_shift > PPS_FAVG) {
849 pps_shift--;
850 pps_intcnt = 0;
851 }
852 }
853 if (u_nsec < 0)
854 u_nsec = -u_nsec;
855 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
856
857 /*
858 * The PPS frequency is recalculated and clamped to the maximum
859 * MAXFREQ. If enabled, the system clock frequency is updated as
860 * well.
861 */
862 L_ADD(pps_freq, ftemp);
863 u_nsec = L_GINT(pps_freq);
864 if (u_nsec > MAXFREQ)
865 L_LINT(pps_freq, MAXFREQ);
866 else if (u_nsec < -MAXFREQ)
867 L_LINT(pps_freq, -MAXFREQ);
868 if (time_status & STA_PPSFREQ)
869 time_freq = pps_freq;
870 }
871 #endif /* PPS_SYNC */
872