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
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD: releng/5.3/sys/kern/kern_ntptime.c 136588 2004-10-16 08:43:07Z cvs2svn $");
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/lock.h>
43 #include <sys/mutex.h>
44 #include <sys/time.h>
45 #include <sys/timex.h>
46 #include <sys/timetc.h>
47 #include <sys/timepps.h>
48 #include <sys/sysctl.h>
49
50 /*
51 * Single-precision macros for 64-bit machines
52 */
53 typedef int64_t l_fp;
54 #define L_ADD(v, u) ((v) += (u))
55 #define L_SUB(v, u) ((v) -= (u))
56 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
57 #define L_NEG(v) ((v) = -(v))
58 #define L_RSHIFT(v, n) \
59 do { \
60 if ((v) < 0) \
61 (v) = -(-(v) >> (n)); \
62 else \
63 (v) = (v) >> (n); \
64 } while (0)
65 #define L_MPY(v, a) ((v) *= (a))
66 #define L_CLR(v) ((v) = 0)
67 #define L_ISNEG(v) ((v) < 0)
68 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32)
69 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
70
71 /*
72 * Generic NTP kernel interface
73 *
74 * These routines constitute the Network Time Protocol (NTP) interfaces
75 * for user and daemon application programs. The ntp_gettime() routine
76 * provides the time, maximum error (synch distance) and estimated error
77 * (dispersion) to client user application programs. The ntp_adjtime()
78 * routine is used by the NTP daemon to adjust the system clock to an
79 * externally derived time. The time offset and related variables set by
80 * this routine are used by other routines in this module to adjust the
81 * phase and frequency of the clock discipline loop which controls the
82 * system clock.
83 *
84 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
85 * defined), the time at each tick interrupt is derived directly from
86 * the kernel time variable. When the kernel time is reckoned in
87 * microseconds, (NTP_NANO undefined), the time is derived from the
88 * kernel time variable together with a variable representing the
89 * leftover nanoseconds at the last tick interrupt. In either case, the
90 * current nanosecond time is reckoned from these values plus an
91 * interpolated value derived by the clock routines in another
92 * architecture-specific module. The interpolation can use either a
93 * dedicated counter or a processor cycle counter (PCC) implemented in
94 * some architectures.
95 *
96 * Note that all routines must run at priority splclock or higher.
97 */
98 /*
99 * Phase/frequency-lock loop (PLL/FLL) definitions
100 *
101 * The nanosecond clock discipline uses two variable types, time
102 * variables and frequency variables. Both types are represented as 64-
103 * bit fixed-point quantities with the decimal point between two 32-bit
104 * halves. On a 32-bit machine, each half is represented as a single
105 * word and mathematical operations are done using multiple-precision
106 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
107 * used.
108 *
109 * A time variable is a signed 64-bit fixed-point number in ns and
110 * fraction. It represents the remaining time offset to be amortized
111 * over succeeding tick interrupts. The maximum time offset is about
112 * 0.5 s and the resolution is about 2.3e-10 ns.
113 *
114 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
115 * 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
116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
117 * |s s s| ns |
118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
119 * | fraction |
120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
121 *
122 * A frequency variable is a signed 64-bit fixed-point number in ns/s
123 * and fraction. It represents the ns and fraction to be added to the
124 * kernel time variable at each second. The maximum frequency offset is
125 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
126 *
127 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
128 * 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
129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
130 * |s s s s s s s s s s s s s| ns/s |
131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
132 * | fraction |
133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
134 */
135 /*
136 * The following variables establish the state of the PLL/FLL and the
137 * residual time and frequency offset of the local clock.
138 */
139 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
140 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
141
142 static int time_state = TIME_OK; /* clock state */
143 static int time_status = STA_UNSYNC; /* clock status bits */
144 static long time_tai; /* TAI offset (s) */
145 static long time_monitor; /* last time offset scaled (ns) */
146 static long time_constant; /* poll interval (shift) (s) */
147 static long time_precision = 1; /* clock precision (ns) */
148 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
149 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
150 static long time_reftime; /* time at last adjustment (s) */
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 int64_t time_adjtime; /* correction from adjtime(2) (usec) */
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
206 ntp_sysctl(SYSCTL_HANDLER_ARGS)
207 {
208 struct ntptimeval ntv; /* temporary structure */
209 struct timespec atv; /* nanosecond time */
210
211 nanotime(&atv);
212 ntv.time.tv_sec = atv.tv_sec;
213 ntv.time.tv_nsec = atv.tv_nsec;
214 ntv.maxerror = time_maxerror;
215 ntv.esterror = time_esterror;
216 ntv.tai = time_tai;
217 ntv.time_state = time_state;
218
219 /*
220 * Status word error decode. If any of these conditions occur,
221 * an error is returned, instead of the status word. Most
222 * applications will care only about the fact the system clock
223 * may not be trusted, not about the details.
224 *
225 * Hardware or software error
226 */
227 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
228
229 /*
230 * PPS signal lost when either time or frequency synchronization
231 * requested
232 */
233 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
234 !(time_status & STA_PPSSIGNAL)) ||
235
236 /*
237 * PPS jitter exceeded when time synchronization requested
238 */
239 (time_status & STA_PPSTIME &&
240 time_status & STA_PPSJITTER) ||
241
242 /*
243 * PPS wander exceeded or calibration error when frequency
244 * synchronization requested
245 */
246 (time_status & STA_PPSFREQ &&
247 time_status & (STA_PPSWANDER | STA_PPSERROR)))
248 ntv.time_state = TIME_ERROR;
249 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
250 }
251
252 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
253 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
254 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
255
256 #ifdef PPS_SYNC
257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
260
261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
262 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
263 #endif
264 /*
265 * ntp_adjtime() - NTP daemon application interface
266 *
267 * See the timex.h header file for synopsis and API description. Note
268 * that the timex.constant structure member has a dual purpose to set
269 * the time constant and to set the TAI offset.
270 */
271 #ifndef _SYS_SYSPROTO_H_
272 struct ntp_adjtime_args {
273 struct timex *tp;
274 };
275 #endif
276
277 /*
278 * MPSAFE
279 */
280 int
281 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
282 {
283 struct timex ntv; /* temporary structure */
284 long freq; /* frequency ns/s) */
285 int modes; /* mode bits from structure */
286 int s; /* caller priority */
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 mtx_lock(&Giant);
303 modes = ntv.modes;
304 if (modes)
305 error = suser(td);
306 if (error)
307 goto done2;
308 s = splclock();
309 if (modes & MOD_MAXERROR)
310 time_maxerror = ntv.maxerror;
311 if (modes & MOD_ESTERROR)
312 time_esterror = ntv.esterror;
313 if (modes & MOD_STATUS) {
314 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
315 time_state = TIME_OK;
316 time_status = STA_UNSYNC;
317 #ifdef PPS_SYNC
318 pps_shift = PPS_FAVG;
319 #endif /* PPS_SYNC */
320 }
321 time_status &= STA_RONLY;
322 time_status |= ntv.status & ~STA_RONLY;
323 }
324 if (modes & MOD_TIMECONST) {
325 if (ntv.constant < 0)
326 time_constant = 0;
327 else if (ntv.constant > MAXTC)
328 time_constant = MAXTC;
329 else
330 time_constant = ntv.constant;
331 }
332 if (modes & MOD_TAI) {
333 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
334 time_tai = ntv.constant;
335 }
336 #ifdef PPS_SYNC
337 if (modes & MOD_PPSMAX) {
338 if (ntv.shift < PPS_FAVG)
339 pps_shiftmax = PPS_FAVG;
340 else if (ntv.shift > PPS_FAVGMAX)
341 pps_shiftmax = PPS_FAVGMAX;
342 else
343 pps_shiftmax = ntv.shift;
344 }
345 #endif /* PPS_SYNC */
346 if (modes & MOD_NANO)
347 time_status |= STA_NANO;
348 if (modes & MOD_MICRO)
349 time_status &= ~STA_NANO;
350 if (modes & MOD_CLKB)
351 time_status |= STA_CLK;
352 if (modes & MOD_CLKA)
353 time_status &= ~STA_CLK;
354 if (modes & MOD_FREQUENCY) {
355 freq = (ntv.freq * 1000LL) >> 16;
356 if (freq > MAXFREQ)
357 L_LINT(time_freq, MAXFREQ);
358 else if (freq < -MAXFREQ)
359 L_LINT(time_freq, -MAXFREQ);
360 else {
361 /*
362 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
363 * time_freq is [ns/s * 2^32]
364 */
365 time_freq = ntv.freq * 1000LL * 65536LL;
366 }
367 #ifdef PPS_SYNC
368 pps_freq = time_freq;
369 #endif /* PPS_SYNC */
370 }
371 if (modes & MOD_OFFSET) {
372 if (time_status & STA_NANO)
373 hardupdate(ntv.offset);
374 else
375 hardupdate(ntv.offset * 1000);
376 }
377
378 /*
379 * Retrieve all clock variables. Note that the TAI offset is
380 * returned only by ntp_gettime();
381 */
382 if (time_status & STA_NANO)
383 ntv.offset = L_GINT(time_offset);
384 else
385 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
386 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
387 ntv.maxerror = time_maxerror;
388 ntv.esterror = time_esterror;
389 ntv.status = time_status;
390 ntv.constant = time_constant;
391 if (time_status & STA_NANO)
392 ntv.precision = time_precision;
393 else
394 ntv.precision = time_precision / 1000;
395 ntv.tolerance = MAXFREQ * SCALE_PPM;
396 #ifdef PPS_SYNC
397 ntv.shift = pps_shift;
398 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
399 if (time_status & STA_NANO)
400 ntv.jitter = pps_jitter;
401 else
402 ntv.jitter = pps_jitter / 1000;
403 ntv.stabil = pps_stabil;
404 ntv.calcnt = pps_calcnt;
405 ntv.errcnt = pps_errcnt;
406 ntv.jitcnt = pps_jitcnt;
407 ntv.stbcnt = pps_stbcnt;
408 #endif /* PPS_SYNC */
409 splx(s);
410
411 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
412 if (error)
413 goto done2;
414
415 /*
416 * Status word error decode. See comments in
417 * ntp_gettime() routine.
418 */
419 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
420 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
421 !(time_status & STA_PPSSIGNAL)) ||
422 (time_status & STA_PPSTIME &&
423 time_status & STA_PPSJITTER) ||
424 (time_status & STA_PPSFREQ &&
425 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
426 td->td_retval[0] = TIME_ERROR;
427 } else {
428 td->td_retval[0] = time_state;
429 }
430 done2:
431 mtx_unlock(&Giant);
432 return (error);
433 }
434
435 /*
436 * second_overflow() - called after ntp_tick_adjust()
437 *
438 * This routine is ordinarily called immediately following the above
439 * routine ntp_tick_adjust(). While these two routines are normally
440 * combined, they are separated here only for the purposes of
441 * simulation.
442 */
443 void
444 ntp_update_second(int64_t *adjustment, time_t *newsec)
445 {
446 int tickrate;
447 l_fp ftemp; /* 32/64-bit temporary */
448
449 /*
450 * On rollover of the second both the nanosecond and microsecond
451 * clocks are updated and the state machine cranked as
452 * necessary. The phase adjustment to be used for the next
453 * second is calculated and the maximum error is increased by
454 * the tolerance.
455 */
456 time_maxerror += MAXFREQ / 1000;
457
458 /*
459 * Leap second processing. If in leap-insert state at
460 * the end of the day, the system clock is set back one
461 * second; if in leap-delete state, the system clock is
462 * set ahead one second. The nano_time() routine or
463 * external clock driver will insure that reported time
464 * is always monotonic.
465 */
466 switch (time_state) {
467
468 /*
469 * No warning.
470 */
471 case TIME_OK:
472 if (time_status & STA_INS)
473 time_state = TIME_INS;
474 else if (time_status & STA_DEL)
475 time_state = TIME_DEL;
476 break;
477
478 /*
479 * Insert second 23:59:60 following second
480 * 23:59:59.
481 */
482 case TIME_INS:
483 if (!(time_status & STA_INS))
484 time_state = TIME_OK;
485 else if ((*newsec) % 86400 == 0) {
486 (*newsec)--;
487 time_state = TIME_OOP;
488 time_tai++;
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 (*newsec)++;
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_state = TIME_WAIT;
510 break;
511
512 /*
513 * Wait for status bits to clear.
514 */
515 case TIME_WAIT:
516 if (!(time_status & (STA_INS | STA_DEL)))
517 time_state = TIME_OK;
518 }
519
520 /*
521 * Compute the total time adjustment for the next second
522 * in ns. The offset is reduced by a factor depending on
523 * whether the PPS signal is operating. Note that the
524 * value is in effect scaled by the clock frequency,
525 * since the adjustment is added at each tick interrupt.
526 */
527 ftemp = time_offset;
528 #ifdef PPS_SYNC
529 /* XXX even if PPS signal dies we should finish adjustment ? */
530 if (time_status & STA_PPSTIME && time_status &
531 STA_PPSSIGNAL)
532 L_RSHIFT(ftemp, pps_shift);
533 else
534 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
535 #else
536 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
537 #endif /* PPS_SYNC */
538 time_adj = ftemp;
539 L_SUB(time_offset, ftemp);
540 L_ADD(time_adj, time_freq);
541
542 /*
543 * Apply any correction from adjtime(2). If more than one second
544 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
545 * until the last second is slewed the final < 500 usecs.
546 */
547 if (time_adjtime != 0) {
548 if (time_adjtime > 1000000)
549 tickrate = 5000;
550 else if (time_adjtime < -1000000)
551 tickrate = -5000;
552 else if (time_adjtime > 500)
553 tickrate = 500;
554 else if (time_adjtime < -500)
555 tickrate = -500;
556 else
557 tickrate = time_adjtime;
558 time_adjtime -= tickrate;
559 L_LINT(ftemp, tickrate * 1000);
560 L_ADD(time_adj, ftemp);
561 }
562 *adjustment = time_adj;
563
564 #ifdef PPS_SYNC
565 if (pps_valid > 0)
566 pps_valid--;
567 else
568 time_status &= ~STA_PPSSIGNAL;
569 #endif /* PPS_SYNC */
570 }
571
572 /*
573 * ntp_init() - initialize variables and structures
574 *
575 * This routine must be called after the kernel variables hz and tick
576 * are set or changed and before the next tick interrupt. In this
577 * particular implementation, these values are assumed set elsewhere in
578 * the kernel. The design allows the clock frequency and tick interval
579 * to be changed while the system is running. So, this routine should
580 * probably be integrated with the code that does that.
581 */
582 static void
583 ntp_init()
584 {
585
586 /*
587 * The following variables are initialized only at startup. Only
588 * those structures not cleared by the compiler need to be
589 * initialized, and these only in the simulator. In the actual
590 * kernel, any nonzero values here will quickly evaporate.
591 */
592 L_CLR(time_offset);
593 L_CLR(time_freq);
594 #ifdef PPS_SYNC
595 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
596 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
597 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
598 pps_fcount = 0;
599 L_CLR(pps_freq);
600 #endif /* PPS_SYNC */
601 }
602
603 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
604
605 /*
606 * hardupdate() - local clock update
607 *
608 * This routine is called by ntp_adjtime() to update the local clock
609 * phase and frequency. The implementation is of an adaptive-parameter,
610 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
611 * time and frequency offset estimates for each call. If the kernel PPS
612 * discipline code is configured (PPS_SYNC), the PPS signal itself
613 * determines the new time offset, instead of the calling argument.
614 * Presumably, calls to ntp_adjtime() occur only when the caller
615 * believes the local clock is valid within some bound (+-128 ms with
616 * NTP). If the caller's time is far different than the PPS time, an
617 * argument will ensue, and it's not clear who will lose.
618 *
619 * For uncompensated quartz crystal oscillators and nominal update
620 * intervals less than 256 s, operation should be in phase-lock mode,
621 * where the loop is disciplined to phase. For update intervals greater
622 * than 1024 s, operation should be in frequency-lock mode, where the
623 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
624 * is selected by the STA_MODE status bit.
625 */
626 static void
627 hardupdate(offset)
628 long offset; /* clock offset (ns) */
629 {
630 long mtemp;
631 l_fp ftemp;
632
633 /*
634 * Select how the phase is to be controlled and from which
635 * source. If the PPS signal is present and enabled to
636 * discipline the time, the PPS offset is used; otherwise, the
637 * argument offset is used.
638 */
639 if (!(time_status & STA_PLL))
640 return;
641 if (!(time_status & STA_PPSTIME && time_status &
642 STA_PPSSIGNAL)) {
643 if (offset > MAXPHASE)
644 time_monitor = MAXPHASE;
645 else if (offset < -MAXPHASE)
646 time_monitor = -MAXPHASE;
647 else
648 time_monitor = offset;
649 L_LINT(time_offset, time_monitor);
650 }
651
652 /*
653 * Select how the frequency is to be controlled and in which
654 * mode (PLL or FLL). If the PPS signal is present and enabled
655 * to discipline the frequency, the PPS frequency is used;
656 * otherwise, the argument offset is used to compute it.
657 */
658 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
659 time_reftime = time_second;
660 return;
661 }
662 if (time_status & STA_FREQHOLD || time_reftime == 0)
663 time_reftime = time_second;
664 mtemp = time_second - time_reftime;
665 L_LINT(ftemp, time_monitor);
666 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
667 L_MPY(ftemp, mtemp);
668 L_ADD(time_freq, ftemp);
669 time_status &= ~STA_MODE;
670 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
671 MAXSEC)) {
672 L_LINT(ftemp, (time_monitor << 4) / mtemp);
673 L_RSHIFT(ftemp, SHIFT_FLL + 4);
674 L_ADD(time_freq, ftemp);
675 time_status |= STA_MODE;
676 }
677 time_reftime = time_second;
678 if (L_GINT(time_freq) > MAXFREQ)
679 L_LINT(time_freq, MAXFREQ);
680 else if (L_GINT(time_freq) < -MAXFREQ)
681 L_LINT(time_freq, -MAXFREQ);
682 }
683
684 #ifdef PPS_SYNC
685 /*
686 * hardpps() - discipline CPU clock oscillator to external PPS signal
687 *
688 * This routine is called at each PPS interrupt in order to discipline
689 * the CPU clock oscillator to the PPS signal. There are two independent
690 * first-order feedback loops, one for the phase, the other for the
691 * frequency. The phase loop measures and grooms the PPS phase offset
692 * and leaves it in a handy spot for the seconds overflow routine. The
693 * frequency loop averages successive PPS phase differences and
694 * calculates the PPS frequency offset, which is also processed by the
695 * seconds overflow routine. The code requires the caller to capture the
696 * time and architecture-dependent hardware counter values in
697 * nanoseconds at the on-time PPS signal transition.
698 *
699 * Note that, on some Unix systems this routine runs at an interrupt
700 * priority level higher than the timer interrupt routine hardclock().
701 * Therefore, the variables used are distinct from the hardclock()
702 * variables, except for the actual time and frequency variables, which
703 * are determined by this routine and updated atomically.
704 */
705 void
706 hardpps(tsp, nsec)
707 struct timespec *tsp; /* time at PPS */
708 long nsec; /* hardware counter at PPS */
709 {
710 long u_sec, u_nsec, v_nsec; /* temps */
711 l_fp ftemp;
712
713 /*
714 * The signal is first processed by a range gate and frequency
715 * discriminator. The range gate rejects noise spikes outside
716 * the range +-500 us. The frequency discriminator rejects input
717 * signals with apparent frequency outside the range 1 +-500
718 * PPM. If two hits occur in the same second, we ignore the
719 * later hit; if not and a hit occurs outside the range gate,
720 * keep the later hit for later comparison, but do not process
721 * it.
722 */
723 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
724 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
725 pps_valid = PPS_VALID;
726 u_sec = tsp->tv_sec;
727 u_nsec = tsp->tv_nsec;
728 if (u_nsec >= (NANOSECOND >> 1)) {
729 u_nsec -= NANOSECOND;
730 u_sec++;
731 }
732 v_nsec = u_nsec - pps_tf[0].tv_nsec;
733 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
734 MAXFREQ)
735 return;
736 pps_tf[2] = pps_tf[1];
737 pps_tf[1] = pps_tf[0];
738 pps_tf[0].tv_sec = u_sec;
739 pps_tf[0].tv_nsec = u_nsec;
740
741 /*
742 * Compute the difference between the current and previous
743 * counter values. If the difference exceeds 0.5 s, assume it
744 * has wrapped around, so correct 1.0 s. If the result exceeds
745 * the tick interval, the sample point has crossed a tick
746 * boundary during the last second, so correct the tick. Very
747 * intricate.
748 */
749 u_nsec = nsec;
750 if (u_nsec > (NANOSECOND >> 1))
751 u_nsec -= NANOSECOND;
752 else if (u_nsec < -(NANOSECOND >> 1))
753 u_nsec += NANOSECOND;
754 pps_fcount += u_nsec;
755 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
756 return;
757 time_status &= ~STA_PPSJITTER;
758
759 /*
760 * A three-stage median filter is used to help denoise the PPS
761 * time. The median sample becomes the time offset estimate; the
762 * difference between the other two samples becomes the time
763 * dispersion (jitter) estimate.
764 */
765 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
766 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
767 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
768 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
769 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
770 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
771 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
772 } else {
773 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
774 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
775 }
776 } else {
777 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
778 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
779 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
780 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
781 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
782 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
783 } else {
784 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
785 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
786 }
787 }
788
789 /*
790 * Nominal jitter is due to PPS signal noise and interrupt
791 * latency. If it exceeds the popcorn threshold, the sample is
792 * discarded. otherwise, if so enabled, the time offset is
793 * updated. We can tolerate a modest loss of data here without
794 * much degrading time accuracy.
795 */
796 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
797 time_status |= STA_PPSJITTER;
798 pps_jitcnt++;
799 } else if (time_status & STA_PPSTIME) {
800 time_monitor = -v_nsec;
801 L_LINT(time_offset, time_monitor);
802 }
803 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
804 u_sec = pps_tf[0].tv_sec - pps_lastsec;
805 if (u_sec < (1 << pps_shift))
806 return;
807
808 /*
809 * At the end of the calibration interval the difference between
810 * the first and last counter values becomes the scaled
811 * frequency. It will later be divided by the length of the
812 * interval to determine the frequency update. If the frequency
813 * exceeds a sanity threshold, or if the actual calibration
814 * interval is not equal to the expected length, the data are
815 * discarded. We can tolerate a modest loss of data here without
816 * much degrading frequency accuracy.
817 */
818 pps_calcnt++;
819 v_nsec = -pps_fcount;
820 pps_lastsec = pps_tf[0].tv_sec;
821 pps_fcount = 0;
822 u_nsec = MAXFREQ << pps_shift;
823 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
824 pps_shift)) {
825 time_status |= STA_PPSERROR;
826 pps_errcnt++;
827 return;
828 }
829
830 /*
831 * Here the raw frequency offset and wander (stability) is
832 * calculated. If the wander is less than the wander threshold
833 * for four consecutive averaging intervals, the interval is
834 * doubled; if it is greater than the threshold for four
835 * consecutive intervals, the interval is halved. The scaled
836 * frequency offset is converted to frequency offset. The
837 * stability metric is calculated as the average of recent
838 * frequency changes, but is used only for performance
839 * monitoring.
840 */
841 L_LINT(ftemp, v_nsec);
842 L_RSHIFT(ftemp, pps_shift);
843 L_SUB(ftemp, pps_freq);
844 u_nsec = L_GINT(ftemp);
845 if (u_nsec > PPS_MAXWANDER) {
846 L_LINT(ftemp, PPS_MAXWANDER);
847 pps_intcnt--;
848 time_status |= STA_PPSWANDER;
849 pps_stbcnt++;
850 } else if (u_nsec < -PPS_MAXWANDER) {
851 L_LINT(ftemp, -PPS_MAXWANDER);
852 pps_intcnt--;
853 time_status |= STA_PPSWANDER;
854 pps_stbcnt++;
855 } else {
856 pps_intcnt++;
857 }
858 if (pps_intcnt >= 4) {
859 pps_intcnt = 4;
860 if (pps_shift < pps_shiftmax) {
861 pps_shift++;
862 pps_intcnt = 0;
863 }
864 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
865 pps_intcnt = -4;
866 if (pps_shift > PPS_FAVG) {
867 pps_shift--;
868 pps_intcnt = 0;
869 }
870 }
871 if (u_nsec < 0)
872 u_nsec = -u_nsec;
873 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
874
875 /*
876 * The PPS frequency is recalculated and clamped to the maximum
877 * MAXFREQ. If enabled, the system clock frequency is updated as
878 * well.
879 */
880 L_ADD(pps_freq, ftemp);
881 u_nsec = L_GINT(pps_freq);
882 if (u_nsec > MAXFREQ)
883 L_LINT(pps_freq, MAXFREQ);
884 else if (u_nsec < -MAXFREQ)
885 L_LINT(pps_freq, -MAXFREQ);
886 if (time_status & STA_PPSFREQ)
887 time_freq = pps_freq;
888 }
889 #endif /* PPS_SYNC */
890
891 #ifndef _SYS_SYSPROTO_H_
892 struct adjtime_args {
893 struct timeval *delta;
894 struct timeval *olddelta;
895 };
896 #endif
897 /*
898 * MPSAFE
899 */
900 /* ARGSUSED */
901 int
902 adjtime(struct thread *td, struct adjtime_args *uap)
903 {
904 struct timeval atv;
905 int error;
906
907 if ((error = suser(td)))
908 return (error);
909
910 mtx_lock(&Giant);
911 if (uap->olddelta) {
912 atv.tv_sec = time_adjtime / 1000000;
913 atv.tv_usec = time_adjtime % 1000000;
914 if (atv.tv_usec < 0) {
915 atv.tv_usec += 1000000;
916 atv.tv_sec--;
917 }
918 error = copyout(&atv, uap->olddelta, sizeof(atv));
919 if (error)
920 goto done2;
921 }
922 if (uap->delta) {
923 error = copyin(uap->delta, &atv, sizeof(atv));
924 if (error)
925 goto done2;
926 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec;
927 }
928 done2:
929 mtx_unlock(&Giant);
930 return (error);
931 }
932
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