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: releng/5.1/sys/kern/kern_ntptime.c 108755 2003-01-06 01:01:08Z peter $
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/lock.h>
42 #include <sys/mutex.h>
43 #include <sys/time.h>
44 #include <sys/timex.h>
45 #include <sys/timetc.h>
46 #include <sys/timepps.h>
47 #include <sys/sysctl.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 long time_reftime; /* time at last adjustment (s) */
150 static l_fp time_offset; /* time offset (ns) */
151 static l_fp time_freq; /* frequency offset (ns/s) */
152 static l_fp time_adj; /* tick adjust (ns/s) */
153
154 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
155
156 #ifdef PPS_SYNC
157 /*
158 * The following variables are used when a pulse-per-second (PPS) signal
159 * is available and connected via a modem control lead. They establish
160 * the engineering parameters of the clock discipline loop when
161 * controlled by the PPS signal.
162 */
163 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
164 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
165 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
166 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
167 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
168 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
169 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
170
171 static struct timespec pps_tf[3]; /* phase median filter */
172 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
173 static long pps_fcount; /* frequency accumulator */
174 static long pps_jitter; /* nominal jitter (ns) */
175 static long pps_stabil; /* nominal stability (scaled ns/s) */
176 static long pps_lastsec; /* time at last calibration (s) */
177 static int pps_valid; /* signal watchdog counter */
178 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
179 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
180 static int pps_intcnt; /* wander counter */
181
182 /*
183 * PPS signal quality monitors
184 */
185 static long pps_calcnt; /* calibration intervals */
186 static long pps_jitcnt; /* jitter limit exceeded */
187 static long pps_stbcnt; /* stability limit exceeded */
188 static long pps_errcnt; /* calibration errors */
189 #endif /* PPS_SYNC */
190 /*
191 * End of phase/frequency-lock loop (PLL/FLL) definitions
192 */
193
194 static void ntp_init(void);
195 static void hardupdate(long offset);
196
197 /*
198 * ntp_gettime() - NTP user application interface
199 *
200 * See the timex.h header file for synopsis and API description. Note
201 * that the TAI offset is returned in the ntvtimeval.tai structure
202 * member.
203 */
204 static int
205 ntp_sysctl(SYSCTL_HANDLER_ARGS)
206 {
207 struct ntptimeval ntv; /* temporary structure */
208 struct timespec atv; /* nanosecond time */
209
210 nanotime(&atv);
211 ntv.time.tv_sec = atv.tv_sec;
212 ntv.time.tv_nsec = atv.tv_nsec;
213 ntv.maxerror = time_maxerror;
214 ntv.esterror = time_esterror;
215 ntv.tai = time_tai;
216 ntv.time_state = time_state;
217
218 /*
219 * Status word error decode. If any of these conditions occur,
220 * an error is returned, instead of the status word. Most
221 * applications will care only about the fact the system clock
222 * may not be trusted, not about the details.
223 *
224 * Hardware or software error
225 */
226 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
227
228 /*
229 * PPS signal lost when either time or frequency synchronization
230 * requested
231 */
232 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
233 !(time_status & STA_PPSSIGNAL)) ||
234
235 /*
236 * PPS jitter exceeded when time synchronization requested
237 */
238 (time_status & STA_PPSTIME &&
239 time_status & STA_PPSJITTER) ||
240
241 /*
242 * PPS wander exceeded or calibration error when frequency
243 * synchronization requested
244 */
245 (time_status & STA_PPSFREQ &&
246 time_status & (STA_PPSWANDER | STA_PPSERROR)))
247 ntv.time_state = TIME_ERROR;
248 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
249 }
250
251 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
252 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
253 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
254
255 #ifdef PPS_SYNC
256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
259
260 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
262 #endif
263 /*
264 * ntp_adjtime() - NTP daemon application interface
265 *
266 * See the timex.h header file for synopsis and API description. Note
267 * that the timex.constant structure member has a dual purpose to set
268 * the time constant and to set the TAI offset.
269 */
270 #ifndef _SYS_SYSPROTO_H_
271 struct ntp_adjtime_args {
272 struct timex *tp;
273 };
274 #endif
275
276 /*
277 * MPSAFE
278 */
279 int
280 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
281 {
282 struct timex ntv; /* temporary structure */
283 long freq; /* frequency ns/s) */
284 int modes; /* mode bits from structure */
285 int s; /* caller priority */
286 int error;
287
288 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
289 if (error)
290 return(error);
291
292 /*
293 * Update selected clock variables - only the superuser can
294 * change anything. Note that there is no error checking here on
295 * the assumption the superuser should know what it is doing.
296 * Note that either the time constant or TAI offset are loaded
297 * from the ntv.constant member, depending on the mode bits. If
298 * the STA_PLL bit in the status word is cleared, the state and
299 * status words are reset to the initial values at boot.
300 */
301 mtx_lock(&Giant);
302 modes = ntv.modes;
303 if (modes)
304 error = suser(td);
305 if (error)
306 goto done2;
307 s = splclock();
308 if (modes & MOD_MAXERROR)
309 time_maxerror = ntv.maxerror;
310 if (modes & MOD_ESTERROR)
311 time_esterror = ntv.esterror;
312 if (modes & MOD_STATUS) {
313 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
314 time_state = TIME_OK;
315 time_status = STA_UNSYNC;
316 #ifdef PPS_SYNC
317 pps_shift = PPS_FAVG;
318 #endif /* PPS_SYNC */
319 }
320 time_status &= STA_RONLY;
321 time_status |= ntv.status & ~STA_RONLY;
322 }
323 if (modes & MOD_TIMECONST) {
324 if (ntv.constant < 0)
325 time_constant = 0;
326 else if (ntv.constant > MAXTC)
327 time_constant = MAXTC;
328 else
329 time_constant = ntv.constant;
330 }
331 if (modes & MOD_TAI) {
332 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
333 time_tai = ntv.constant;
334 }
335 #ifdef PPS_SYNC
336 if (modes & MOD_PPSMAX) {
337 if (ntv.shift < PPS_FAVG)
338 pps_shiftmax = PPS_FAVG;
339 else if (ntv.shift > PPS_FAVGMAX)
340 pps_shiftmax = PPS_FAVGMAX;
341 else
342 pps_shiftmax = ntv.shift;
343 }
344 #endif /* PPS_SYNC */
345 if (modes & MOD_NANO)
346 time_status |= STA_NANO;
347 if (modes & MOD_MICRO)
348 time_status &= ~STA_NANO;
349 if (modes & MOD_CLKB)
350 time_status |= STA_CLK;
351 if (modes & MOD_CLKA)
352 time_status &= ~STA_CLK;
353 if (modes & MOD_OFFSET) {
354 if (time_status & STA_NANO)
355 hardupdate(ntv.offset);
356 else
357 hardupdate(ntv.offset * 1000);
358 }
359 if (modes & MOD_FREQUENCY) {
360 freq = (ntv.freq * 1000LL) >> 16;
361 if (freq > MAXFREQ)
362 L_LINT(time_freq, MAXFREQ);
363 else if (freq < -MAXFREQ)
364 L_LINT(time_freq, -MAXFREQ);
365 else
366 L_LINT(time_freq, freq);
367 #ifdef PPS_SYNC
368 pps_freq = time_freq;
369 #endif /* PPS_SYNC */
370 }
371
372 /*
373 * Retrieve all clock variables. Note that the TAI offset is
374 * returned only by ntp_gettime();
375 */
376 if (time_status & STA_NANO)
377 ntv.offset = L_GINT(time_offset);
378 else
379 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
380 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
381 ntv.maxerror = time_maxerror;
382 ntv.esterror = time_esterror;
383 ntv.status = time_status;
384 ntv.constant = time_constant;
385 if (time_status & STA_NANO)
386 ntv.precision = time_precision;
387 else
388 ntv.precision = time_precision / 1000;
389 ntv.tolerance = MAXFREQ * SCALE_PPM;
390 #ifdef PPS_SYNC
391 ntv.shift = pps_shift;
392 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
393 if (time_status & STA_NANO)
394 ntv.jitter = pps_jitter;
395 else
396 ntv.jitter = pps_jitter / 1000;
397 ntv.stabil = pps_stabil;
398 ntv.calcnt = pps_calcnt;
399 ntv.errcnt = pps_errcnt;
400 ntv.jitcnt = pps_jitcnt;
401 ntv.stbcnt = pps_stbcnt;
402 #endif /* PPS_SYNC */
403 splx(s);
404
405 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
406 if (error)
407 goto done2;
408
409 /*
410 * Status word error decode. See comments in
411 * ntp_gettime() routine.
412 */
413 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
414 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
415 !(time_status & STA_PPSSIGNAL)) ||
416 (time_status & STA_PPSTIME &&
417 time_status & STA_PPSJITTER) ||
418 (time_status & STA_PPSFREQ &&
419 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
420 td->td_retval[0] = TIME_ERROR;
421 } else {
422 td->td_retval[0] = time_state;
423 }
424 done2:
425 mtx_unlock(&Giant);
426 return (error);
427 }
428
429 /*
430 * second_overflow() - called after ntp_tick_adjust()
431 *
432 * This routine is ordinarily called immediately following the above
433 * routine ntp_tick_adjust(). While these two routines are normally
434 * combined, they are separated here only for the purposes of
435 * simulation.
436 */
437 void
438 ntp_update_second(int64_t *adjustment, time_t *newsec)
439 {
440 int tickrate;
441 l_fp ftemp; /* 32/64-bit temporary */
442
443 /*
444 * On rollover of the second both the nanosecond and microsecond
445 * clocks are updated and the state machine cranked as
446 * necessary. The phase adjustment to be used for the next
447 * second is calculated and the maximum error is increased by
448 * the tolerance.
449 */
450 time_maxerror += MAXFREQ / 1000;
451
452 /*
453 * Leap second processing. If in leap-insert state at
454 * the end of the day, the system clock is set back one
455 * second; if in leap-delete state, the system clock is
456 * set ahead one second. The nano_time() routine or
457 * external clock driver will insure that reported time
458 * is always monotonic.
459 */
460 switch (time_state) {
461
462 /*
463 * No warning.
464 */
465 case TIME_OK:
466 if (time_status & STA_INS)
467 time_state = TIME_INS;
468 else if (time_status & STA_DEL)
469 time_state = TIME_DEL;
470 break;
471
472 /*
473 * Insert second 23:59:60 following second
474 * 23:59:59.
475 */
476 case TIME_INS:
477 if (!(time_status & STA_INS))
478 time_state = TIME_OK;
479 else if ((*newsec) % 86400 == 0) {
480 (*newsec)--;
481 time_state = TIME_OOP;
482 }
483 break;
484
485 /*
486 * Delete second 23:59:59.
487 */
488 case TIME_DEL:
489 if (!(time_status & STA_DEL))
490 time_state = TIME_OK;
491 else if (((*newsec) + 1) % 86400 == 0) {
492 (*newsec)++;
493 time_tai--;
494 time_state = TIME_WAIT;
495 }
496 break;
497
498 /*
499 * Insert second in progress.
500 */
501 case TIME_OOP:
502 time_tai++;
503 time_state = TIME_WAIT;
504 break;
505
506 /*
507 * Wait for status bits to clear.
508 */
509 case TIME_WAIT:
510 if (!(time_status & (STA_INS | STA_DEL)))
511 time_state = TIME_OK;
512 }
513
514 /*
515 * Compute the total time adjustment for the next second
516 * in ns. The offset is reduced by a factor depending on
517 * whether the PPS signal is operating. Note that the
518 * value is in effect scaled by the clock frequency,
519 * since the adjustment is added at each tick interrupt.
520 */
521 ftemp = time_offset;
522 #ifdef PPS_SYNC
523 /* XXX even if PPS signal dies we should finish adjustment ? */
524 if (time_status & STA_PPSTIME && time_status &
525 STA_PPSSIGNAL)
526 L_RSHIFT(ftemp, pps_shift);
527 else
528 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
529 #else
530 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
531 #endif /* PPS_SYNC */
532 time_adj = ftemp;
533 L_SUB(time_offset, ftemp);
534 L_ADD(time_adj, time_freq);
535
536 /*
537 * Apply any correction from adjtime(2). If more than one second
538 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
539 * until the last second is slewed the final < 500 usecs.
540 */
541 if (time_adjtime != 0) {
542 if (time_adjtime > 1000000)
543 tickrate = 5000;
544 else if (time_adjtime < -1000000)
545 tickrate = -5000;
546 else if (time_adjtime > 500)
547 tickrate = 500;
548 else if (time_adjtime < -500)
549 tickrate = -500;
550 else if (time_adjtime != 0)
551 tickrate = time_adjtime;
552 else
553 tickrate = 0; /* GCC sucks! */
554 time_adjtime -= tickrate;
555 L_LINT(ftemp, tickrate * 1000);
556 L_ADD(time_adj, ftemp);
557 }
558 *adjustment = time_adj;
559
560 #ifdef PPS_SYNC
561 if (pps_valid > 0)
562 pps_valid--;
563 else
564 time_status &= ~STA_PPSSIGNAL;
565 #endif /* PPS_SYNC */
566 }
567
568 /*
569 * ntp_init() - initialize variables and structures
570 *
571 * This routine must be called after the kernel variables hz and tick
572 * are set or changed and before the next tick interrupt. In this
573 * particular implementation, these values are assumed set elsewhere in
574 * the kernel. The design allows the clock frequency and tick interval
575 * to be changed while the system is running. So, this routine should
576 * probably be integrated with the code that does that.
577 */
578 static void
579 ntp_init()
580 {
581
582 /*
583 * The following variables are initialized only at startup. Only
584 * those structures not cleared by the compiler need to be
585 * initialized, and these only in the simulator. In the actual
586 * kernel, any nonzero values here will quickly evaporate.
587 */
588 L_CLR(time_offset);
589 L_CLR(time_freq);
590 #ifdef PPS_SYNC
591 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
592 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
593 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
594 pps_fcount = 0;
595 L_CLR(pps_freq);
596 #endif /* PPS_SYNC */
597 }
598
599 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
600
601 /*
602 * hardupdate() - local clock update
603 *
604 * This routine is called by ntp_adjtime() to update the local clock
605 * phase and frequency. The implementation is of an adaptive-parameter,
606 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
607 * time and frequency offset estimates for each call. If the kernel PPS
608 * discipline code is configured (PPS_SYNC), the PPS signal itself
609 * determines the new time offset, instead of the calling argument.
610 * Presumably, calls to ntp_adjtime() occur only when the caller
611 * believes the local clock is valid within some bound (+-128 ms with
612 * NTP). If the caller's time is far different than the PPS time, an
613 * argument will ensue, and it's not clear who will lose.
614 *
615 * For uncompensated quartz crystal oscillators and nominal update
616 * intervals less than 256 s, operation should be in phase-lock mode,
617 * where the loop is disciplined to phase. For update intervals greater
618 * than 1024 s, operation should be in frequency-lock mode, where the
619 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
620 * is selected by the STA_MODE status bit.
621 */
622 static void
623 hardupdate(offset)
624 long offset; /* clock offset (ns) */
625 {
626 long mtemp;
627 l_fp ftemp;
628
629 /*
630 * Select how the phase is to be controlled and from which
631 * source. If the PPS signal is present and enabled to
632 * discipline the time, the PPS offset is used; otherwise, the
633 * argument offset is used.
634 */
635 if (!(time_status & STA_PLL))
636 return;
637 if (!(time_status & STA_PPSTIME && time_status &
638 STA_PPSSIGNAL)) {
639 if (offset > MAXPHASE)
640 time_monitor = MAXPHASE;
641 else if (offset < -MAXPHASE)
642 time_monitor = -MAXPHASE;
643 else
644 time_monitor = offset;
645 L_LINT(time_offset, time_monitor);
646 }
647
648 /*
649 * Select how the frequency is to be controlled and in which
650 * mode (PLL or FLL). If the PPS signal is present and enabled
651 * to discipline the frequency, the PPS frequency is used;
652 * otherwise, the argument offset is used to compute it.
653 */
654 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
655 time_reftime = time_second;
656 return;
657 }
658 if (time_status & STA_FREQHOLD || time_reftime == 0)
659 time_reftime = time_second;
660 mtemp = time_second - time_reftime;
661 L_LINT(ftemp, time_monitor);
662 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
663 L_MPY(ftemp, mtemp);
664 L_ADD(time_freq, ftemp);
665 time_status &= ~STA_MODE;
666 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
667 MAXSEC)) {
668 L_LINT(ftemp, (time_monitor << 4) / mtemp);
669 L_RSHIFT(ftemp, SHIFT_FLL + 4);
670 L_ADD(time_freq, ftemp);
671 time_status |= STA_MODE;
672 }
673 time_reftime = time_second;
674 if (L_GINT(time_freq) > MAXFREQ)
675 L_LINT(time_freq, MAXFREQ);
676 else if (L_GINT(time_freq) < -MAXFREQ)
677 L_LINT(time_freq, -MAXFREQ);
678 }
679
680 #ifdef PPS_SYNC
681 /*
682 * hardpps() - discipline CPU clock oscillator to external PPS signal
683 *
684 * This routine is called at each PPS interrupt in order to discipline
685 * the CPU clock oscillator to the PPS signal. There are two independent
686 * first-order feedback loops, one for the phase, the other for the
687 * frequency. The phase loop measures and grooms the PPS phase offset
688 * and leaves it in a handy spot for the seconds overflow routine. The
689 * frequency loop averages successive PPS phase differences and
690 * calculates the PPS frequency offset, which is also processed by the
691 * seconds overflow routine. The code requires the caller to capture the
692 * time and architecture-dependent hardware counter values in
693 * nanoseconds at the on-time PPS signal transition.
694 *
695 * Note that, on some Unix systems this routine runs at an interrupt
696 * priority level higher than the timer interrupt routine hardclock().
697 * Therefore, the variables used are distinct from the hardclock()
698 * variables, except for the actual time and frequency variables, which
699 * are determined by this routine and updated atomically.
700 */
701 void
702 hardpps(tsp, nsec)
703 struct timespec *tsp; /* time at PPS */
704 long nsec; /* hardware counter at PPS */
705 {
706 long u_sec, u_nsec, v_nsec; /* temps */
707 l_fp ftemp;
708
709 /*
710 * The signal is first processed by a range gate and frequency
711 * discriminator. The range gate rejects noise spikes outside
712 * the range +-500 us. The frequency discriminator rejects input
713 * signals with apparent frequency outside the range 1 +-500
714 * PPM. If two hits occur in the same second, we ignore the
715 * later hit; if not and a hit occurs outside the range gate,
716 * keep the later hit for later comparison, but do not process
717 * it.
718 */
719 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
720 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
721 pps_valid = PPS_VALID;
722 u_sec = tsp->tv_sec;
723 u_nsec = tsp->tv_nsec;
724 if (u_nsec >= (NANOSECOND >> 1)) {
725 u_nsec -= NANOSECOND;
726 u_sec++;
727 }
728 v_nsec = u_nsec - pps_tf[0].tv_nsec;
729 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
730 MAXFREQ)
731 return;
732 pps_tf[2] = pps_tf[1];
733 pps_tf[1] = pps_tf[0];
734 pps_tf[0].tv_sec = u_sec;
735 pps_tf[0].tv_nsec = u_nsec;
736
737 /*
738 * Compute the difference between the current and previous
739 * counter values. If the difference exceeds 0.5 s, assume it
740 * has wrapped around, so correct 1.0 s. If the result exceeds
741 * the tick interval, the sample point has crossed a tick
742 * boundary during the last second, so correct the tick. Very
743 * intricate.
744 */
745 u_nsec = nsec;
746 if (u_nsec > (NANOSECOND >> 1))
747 u_nsec -= NANOSECOND;
748 else if (u_nsec < -(NANOSECOND >> 1))
749 u_nsec += NANOSECOND;
750 pps_fcount += u_nsec;
751 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
752 return;
753 time_status &= ~STA_PPSJITTER;
754
755 /*
756 * A three-stage median filter is used to help denoise the PPS
757 * time. The median sample becomes the time offset estimate; the
758 * difference between the other two samples becomes the time
759 * dispersion (jitter) estimate.
760 */
761 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
762 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
763 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
764 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
765 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
766 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
767 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
768 } else {
769 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
770 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
771 }
772 } else {
773 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
774 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
775 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
776 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
777 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
778 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
779 } else {
780 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
781 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
782 }
783 }
784
785 /*
786 * Nominal jitter is due to PPS signal noise and interrupt
787 * latency. If it exceeds the popcorn threshold, the sample is
788 * discarded. otherwise, if so enabled, the time offset is
789 * updated. We can tolerate a modest loss of data here without
790 * much degrading time accuracy.
791 */
792 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
793 time_status |= STA_PPSJITTER;
794 pps_jitcnt++;
795 } else if (time_status & STA_PPSTIME) {
796 time_monitor = -v_nsec;
797 L_LINT(time_offset, time_monitor);
798 }
799 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
800 u_sec = pps_tf[0].tv_sec - pps_lastsec;
801 if (u_sec < (1 << pps_shift))
802 return;
803
804 /*
805 * At the end of the calibration interval the difference between
806 * the first and last counter values becomes the scaled
807 * frequency. It will later be divided by the length of the
808 * interval to determine the frequency update. If the frequency
809 * exceeds a sanity threshold, or if the actual calibration
810 * interval is not equal to the expected length, the data are
811 * discarded. We can tolerate a modest loss of data here without
812 * much degrading frequency accuracy.
813 */
814 pps_calcnt++;
815 v_nsec = -pps_fcount;
816 pps_lastsec = pps_tf[0].tv_sec;
817 pps_fcount = 0;
818 u_nsec = MAXFREQ << pps_shift;
819 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
820 pps_shift)) {
821 time_status |= STA_PPSERROR;
822 pps_errcnt++;
823 return;
824 }
825
826 /*
827 * Here the raw frequency offset and wander (stability) is
828 * calculated. If the wander is less than the wander threshold
829 * for four consecutive averaging intervals, the interval is
830 * doubled; if it is greater than the threshold for four
831 * consecutive intervals, the interval is halved. The scaled
832 * frequency offset is converted to frequency offset. The
833 * stability metric is calculated as the average of recent
834 * frequency changes, but is used only for performance
835 * monitoring.
836 */
837 L_LINT(ftemp, v_nsec);
838 L_RSHIFT(ftemp, pps_shift);
839 L_SUB(ftemp, pps_freq);
840 u_nsec = L_GINT(ftemp);
841 if (u_nsec > PPS_MAXWANDER) {
842 L_LINT(ftemp, PPS_MAXWANDER);
843 pps_intcnt--;
844 time_status |= STA_PPSWANDER;
845 pps_stbcnt++;
846 } else if (u_nsec < -PPS_MAXWANDER) {
847 L_LINT(ftemp, -PPS_MAXWANDER);
848 pps_intcnt--;
849 time_status |= STA_PPSWANDER;
850 pps_stbcnt++;
851 } else {
852 pps_intcnt++;
853 }
854 if (pps_intcnt >= 4) {
855 pps_intcnt = 4;
856 if (pps_shift < pps_shiftmax) {
857 pps_shift++;
858 pps_intcnt = 0;
859 }
860 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
861 pps_intcnt = -4;
862 if (pps_shift > PPS_FAVG) {
863 pps_shift--;
864 pps_intcnt = 0;
865 }
866 }
867 if (u_nsec < 0)
868 u_nsec = -u_nsec;
869 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
870
871 /*
872 * The PPS frequency is recalculated and clamped to the maximum
873 * MAXFREQ. If enabled, the system clock frequency is updated as
874 * well.
875 */
876 L_ADD(pps_freq, ftemp);
877 u_nsec = L_GINT(pps_freq);
878 if (u_nsec > MAXFREQ)
879 L_LINT(pps_freq, MAXFREQ);
880 else if (u_nsec < -MAXFREQ)
881 L_LINT(pps_freq, -MAXFREQ);
882 if (time_status & STA_PPSFREQ)
883 time_freq = pps_freq;
884 }
885 #endif /* PPS_SYNC */
886
887 #ifndef _SYS_SYSPROTO_H_
888 struct adjtime_args {
889 struct timeval *delta;
890 struct timeval *olddelta;
891 };
892 #endif
893 /*
894 * MPSAFE
895 */
896 /* ARGSUSED */
897 int
898 adjtime(struct thread *td, struct adjtime_args *uap)
899 {
900 struct timeval atv;
901 int error;
902
903 if ((error = suser(td)))
904 return (error);
905
906 mtx_lock(&Giant);
907 if (uap->olddelta) {
908 atv.tv_sec = time_adjtime / 1000000;
909 atv.tv_usec = time_adjtime % 1000000;
910 if (atv.tv_usec < 0) {
911 atv.tv_usec += 1000000;
912 atv.tv_sec--;
913 }
914 error = copyout(&atv, uap->olddelta, sizeof(atv));
915 if (error)
916 goto done2;
917 }
918 if (uap->delta) {
919 error = copyin(uap->delta, &atv, sizeof(atv));
920 if (error)
921 goto done2;
922 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec;
923 }
924 done2:
925 mtx_unlock(&Giant);
926 return (error);
927 }
928
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