1 /*-
2 ***********************************************************************
3 * *
4 * Copyright (c) David L. Mills 1993-2001 *
5 * *
6 * Permission to use, copy, modify, and distribute this software and *
7 * its documentation for any purpose and without fee is hereby *
8 * granted, provided that the above copyright notice appears in all *
9 * copies and that both the copyright notice and this permission *
10 * notice appear in supporting documentation, and that the name *
11 * University of Delaware not be used in advertising or publicity *
12 * pertaining to distribution of the software without specific, *
13 * written prior permission. The University of Delaware makes no *
14 * representations about the suitability this software for any *
15 * purpose. It is provided "as is" without express or implied *
16 * warranty. *
17 * *
18 **********************************************************************/
19
20 /*
21 * Adapted from the original sources for FreeBSD and timecounters by:
22 * Poul-Henning Kamp <phk@FreeBSD.org>.
23 *
24 * The 32bit version of the "LP" macros seems a bit past its "sell by"
25 * date so I have retained only the 64bit version and included it directly
26 * in this file.
27 *
28 * Only minor changes done to interface with the timecounters over in
29 * sys/kern/kern_clock.c. Some of the comments below may be (even more)
30 * confusing and/or plain wrong in that context.
31 */
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD: src/sys/kern/kern_ntptime.c,v 1.54.2.2 2005/04/21 20:33:05 ps Exp $");
35
36 #include "opt_ntp.h"
37
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/sysproto.h>
41 #include <sys/kernel.h>
42 #include <sys/proc.h>
43 #include <sys/lock.h>
44 #include <sys/mutex.h>
45 #include <sys/time.h>
46 #include <sys/timex.h>
47 #include <sys/timetc.h>
48 #include <sys/timepps.h>
49 #include <sys/syscallsubr.h>
50 #include <sys/sysctl.h>
51
52 /*
53 * Single-precision macros for 64-bit machines
54 */
55 typedef int64_t l_fp;
56 #define L_ADD(v, u) ((v) += (u))
57 #define L_SUB(v, u) ((v) -= (u))
58 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32)
59 #define L_NEG(v) ((v) = -(v))
60 #define L_RSHIFT(v, n) \
61 do { \
62 if ((v) < 0) \
63 (v) = -(-(v) >> (n)); \
64 else \
65 (v) = (v) >> (n); \
66 } while (0)
67 #define L_MPY(v, a) ((v) *= (a))
68 #define L_CLR(v) ((v) = 0)
69 #define L_ISNEG(v) ((v) < 0)
70 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32)
71 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
72
73 /*
74 * Generic NTP kernel interface
75 *
76 * These routines constitute the Network Time Protocol (NTP) interfaces
77 * for user and daemon application programs. The ntp_gettime() routine
78 * provides the time, maximum error (synch distance) and estimated error
79 * (dispersion) to client user application programs. The ntp_adjtime()
80 * routine is used by the NTP daemon to adjust the system clock to an
81 * externally derived time. The time offset and related variables set by
82 * this routine are used by other routines in this module to adjust the
83 * phase and frequency of the clock discipline loop which controls the
84 * system clock.
85 *
86 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
87 * defined), the time at each tick interrupt is derived directly from
88 * the kernel time variable. When the kernel time is reckoned in
89 * microseconds, (NTP_NANO undefined), the time is derived from the
90 * kernel time variable together with a variable representing the
91 * leftover nanoseconds at the last tick interrupt. In either case, the
92 * current nanosecond time is reckoned from these values plus an
93 * interpolated value derived by the clock routines in another
94 * architecture-specific module. The interpolation can use either a
95 * dedicated counter or a processor cycle counter (PCC) implemented in
96 * some architectures.
97 *
98 * Note that all routines must run at priority splclock or higher.
99 */
100 /*
101 * Phase/frequency-lock loop (PLL/FLL) definitions
102 *
103 * The nanosecond clock discipline uses two variable types, time
104 * variables and frequency variables. Both types are represented as 64-
105 * bit fixed-point quantities with the decimal point between two 32-bit
106 * halves. On a 32-bit machine, each half is represented as a single
107 * word and mathematical operations are done using multiple-precision
108 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
109 * used.
110 *
111 * A time variable is a signed 64-bit fixed-point number in ns and
112 * fraction. It represents the remaining time offset to be amortized
113 * over succeeding tick interrupts. The maximum time offset is about
114 * 0.5 s and the resolution is about 2.3e-10 ns.
115 *
116 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
117 * 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
118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
119 * |s s s| ns |
120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
121 * | fraction |
122 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
123 *
124 * A frequency variable is a signed 64-bit fixed-point number in ns/s
125 * and fraction. It represents the ns and fraction to be added to the
126 * kernel time variable at each second. The maximum frequency offset is
127 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
128 *
129 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
130 * 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
131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
132 * |s s s s s s s s s s s s s| ns/s |
133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
134 * | fraction |
135 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
136 */
137 /*
138 * The following variables establish the state of the PLL/FLL and the
139 * residual time and frequency offset of the local clock.
140 */
141 #define SHIFT_PLL 4 /* PLL loop gain (shift) */
142 #define SHIFT_FLL 2 /* FLL loop gain (shift) */
143
144 static int time_state = TIME_OK; /* clock state */
145 static int time_status = STA_UNSYNC; /* clock status bits */
146 static long time_tai; /* TAI offset (s) */
147 static long time_monitor; /* last time offset scaled (ns) */
148 static long time_constant; /* poll interval (shift) (s) */
149 static long time_precision = 1; /* clock precision (ns) */
150 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
151 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
152 static long time_reftime; /* time at last adjustment (s) */
153 static l_fp time_offset; /* time offset (ns) */
154 static l_fp time_freq; /* frequency offset (ns/s) */
155 static l_fp time_adj; /* tick adjust (ns/s) */
156
157 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */
158
159 #ifdef PPS_SYNC
160 /*
161 * The following variables are used when a pulse-per-second (PPS) signal
162 * is available and connected via a modem control lead. They establish
163 * the engineering parameters of the clock discipline loop when
164 * controlled by the PPS signal.
165 */
166 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
167 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
168 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
169 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */
170 #define PPS_VALID 120 /* PPS signal watchdog max (s) */
171 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
172 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
173
174 static struct timespec pps_tf[3]; /* phase median filter */
175 static l_fp pps_freq; /* scaled frequency offset (ns/s) */
176 static long pps_fcount; /* frequency accumulator */
177 static long pps_jitter; /* nominal jitter (ns) */
178 static long pps_stabil; /* nominal stability (scaled ns/s) */
179 static long pps_lastsec; /* time at last calibration (s) */
180 static int pps_valid; /* signal watchdog counter */
181 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
182 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
183 static int pps_intcnt; /* wander counter */
184
185 /*
186 * PPS signal quality monitors
187 */
188 static long pps_calcnt; /* calibration intervals */
189 static long pps_jitcnt; /* jitter limit exceeded */
190 static long pps_stbcnt; /* stability limit exceeded */
191 static long pps_errcnt; /* calibration errors */
192 #endif /* PPS_SYNC */
193 /*
194 * End of phase/frequency-lock loop (PLL/FLL) definitions
195 */
196
197 static void ntp_init(void);
198 static void hardupdate(long offset);
199
200 /*
201 * ntp_gettime() - NTP user application interface
202 *
203 * See the timex.h header file for synopsis and API description. Note
204 * that the TAI offset is returned in the ntvtimeval.tai structure
205 * member.
206 */
207 static int
208 ntp_sysctl(SYSCTL_HANDLER_ARGS)
209 {
210 struct ntptimeval ntv; /* temporary structure */
211 struct timespec atv; /* nanosecond time */
212
213 nanotime(&atv);
214 ntv.time.tv_sec = atv.tv_sec;
215 ntv.time.tv_nsec = atv.tv_nsec;
216 ntv.maxerror = time_maxerror;
217 ntv.esterror = time_esterror;
218 ntv.tai = time_tai;
219 ntv.time_state = time_state;
220
221 /*
222 * Status word error decode. If any of these conditions occur,
223 * an error is returned, instead of the status word. Most
224 * applications will care only about the fact the system clock
225 * may not be trusted, not about the details.
226 *
227 * Hardware or software error
228 */
229 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
230
231 /*
232 * PPS signal lost when either time or frequency synchronization
233 * requested
234 */
235 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
236 !(time_status & STA_PPSSIGNAL)) ||
237
238 /*
239 * PPS jitter exceeded when time synchronization requested
240 */
241 (time_status & STA_PPSTIME &&
242 time_status & STA_PPSJITTER) ||
243
244 /*
245 * PPS wander exceeded or calibration error when frequency
246 * synchronization requested
247 */
248 (time_status & STA_PPSFREQ &&
249 time_status & (STA_PPSWANDER | STA_PPSERROR)))
250 ntv.time_state = TIME_ERROR;
251 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
252 }
253
254 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
255 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
256 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
257
258 #ifdef PPS_SYNC
259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
260 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
261 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
262
263 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
264 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
265 #endif
266 /*
267 * ntp_adjtime() - NTP daemon application interface
268 *
269 * See the timex.h header file for synopsis and API description. Note
270 * that the timex.constant structure member has a dual purpose to set
271 * the time constant and to set the TAI offset.
272 */
273 #ifndef _SYS_SYSPROTO_H_
274 struct ntp_adjtime_args {
275 struct timex *tp;
276 };
277 #endif
278
279 /*
280 * MPSAFE
281 */
282 int
283 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
284 {
285 struct timex ntv; /* temporary structure */
286 long freq; /* frequency ns/s) */
287 int modes; /* mode bits from structure */
288 int s; /* caller priority */
289 int error;
290
291 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
292 if (error)
293 return(error);
294
295 /*
296 * Update selected clock variables - only the superuser can
297 * change anything. Note that there is no error checking here on
298 * the assumption the superuser should know what it is doing.
299 * Note that either the time constant or TAI offset are loaded
300 * from the ntv.constant member, depending on the mode bits. If
301 * the STA_PLL bit in the status word is cleared, the state and
302 * status words are reset to the initial values at boot.
303 */
304 mtx_lock(&Giant);
305 modes = ntv.modes;
306 if (modes)
307 error = suser(td);
308 if (error)
309 goto done2;
310 s = splclock();
311 if (modes & MOD_MAXERROR)
312 time_maxerror = ntv.maxerror;
313 if (modes & MOD_ESTERROR)
314 time_esterror = ntv.esterror;
315 if (modes & MOD_STATUS) {
316 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
317 time_state = TIME_OK;
318 time_status = STA_UNSYNC;
319 #ifdef PPS_SYNC
320 pps_shift = PPS_FAVG;
321 #endif /* PPS_SYNC */
322 }
323 time_status &= STA_RONLY;
324 time_status |= ntv.status & ~STA_RONLY;
325 }
326 if (modes & MOD_TIMECONST) {
327 if (ntv.constant < 0)
328 time_constant = 0;
329 else if (ntv.constant > MAXTC)
330 time_constant = MAXTC;
331 else
332 time_constant = ntv.constant;
333 }
334 if (modes & MOD_TAI) {
335 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
336 time_tai = ntv.constant;
337 }
338 #ifdef PPS_SYNC
339 if (modes & MOD_PPSMAX) {
340 if (ntv.shift < PPS_FAVG)
341 pps_shiftmax = PPS_FAVG;
342 else if (ntv.shift > PPS_FAVGMAX)
343 pps_shiftmax = PPS_FAVGMAX;
344 else
345 pps_shiftmax = ntv.shift;
346 }
347 #endif /* PPS_SYNC */
348 if (modes & MOD_NANO)
349 time_status |= STA_NANO;
350 if (modes & MOD_MICRO)
351 time_status &= ~STA_NANO;
352 if (modes & MOD_CLKB)
353 time_status |= STA_CLK;
354 if (modes & MOD_CLKA)
355 time_status &= ~STA_CLK;
356 if (modes & MOD_FREQUENCY) {
357 freq = (ntv.freq * 1000LL) >> 16;
358 if (freq > MAXFREQ)
359 L_LINT(time_freq, MAXFREQ);
360 else if (freq < -MAXFREQ)
361 L_LINT(time_freq, -MAXFREQ);
362 else {
363 /*
364 * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
365 * time_freq is [ns/s * 2^32]
366 */
367 time_freq = ntv.freq * 1000LL * 65536LL;
368 }
369 #ifdef PPS_SYNC
370 pps_freq = time_freq;
371 #endif /* PPS_SYNC */
372 }
373 if (modes & MOD_OFFSET) {
374 if (time_status & STA_NANO)
375 hardupdate(ntv.offset);
376 else
377 hardupdate(ntv.offset * 1000);
378 }
379
380 /*
381 * Retrieve all clock variables. Note that the TAI offset is
382 * returned only by ntp_gettime();
383 */
384 if (time_status & STA_NANO)
385 ntv.offset = L_GINT(time_offset);
386 else
387 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
388 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
389 ntv.maxerror = time_maxerror;
390 ntv.esterror = time_esterror;
391 ntv.status = time_status;
392 ntv.constant = time_constant;
393 if (time_status & STA_NANO)
394 ntv.precision = time_precision;
395 else
396 ntv.precision = time_precision / 1000;
397 ntv.tolerance = MAXFREQ * SCALE_PPM;
398 #ifdef PPS_SYNC
399 ntv.shift = pps_shift;
400 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
401 if (time_status & STA_NANO)
402 ntv.jitter = pps_jitter;
403 else
404 ntv.jitter = pps_jitter / 1000;
405 ntv.stabil = pps_stabil;
406 ntv.calcnt = pps_calcnt;
407 ntv.errcnt = pps_errcnt;
408 ntv.jitcnt = pps_jitcnt;
409 ntv.stbcnt = pps_stbcnt;
410 #endif /* PPS_SYNC */
411 splx(s);
412
413 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
414 if (error)
415 goto done2;
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 td->td_retval[0] = TIME_ERROR;
429 } else {
430 td->td_retval[0] = time_state;
431 }
432 done2:
433 mtx_unlock(&Giant);
434 return (error);
435 }
436
437 /*
438 * second_overflow() - called after ntp_tick_adjust()
439 *
440 * This routine is ordinarily called immediately following the above
441 * routine ntp_tick_adjust(). While these two routines are normally
442 * combined, they are separated here only for the purposes of
443 * simulation.
444 */
445 void
446 ntp_update_second(int64_t *adjustment, time_t *newsec)
447 {
448 int tickrate;
449 l_fp ftemp; /* 32/64-bit temporary */
450
451 /*
452 * On rollover of the second both the nanosecond and microsecond
453 * clocks are updated and the state machine cranked as
454 * necessary. The phase adjustment to be used for the next
455 * second is calculated and the maximum error is increased by
456 * the tolerance.
457 */
458 time_maxerror += MAXFREQ / 1000;
459
460 /*
461 * Leap second processing. If in leap-insert state at
462 * the end of the day, the system clock is set back one
463 * second; if in leap-delete state, the system clock is
464 * set ahead one second. The nano_time() routine or
465 * external clock driver will insure that reported time
466 * is always monotonic.
467 */
468 switch (time_state) {
469
470 /*
471 * No warning.
472 */
473 case TIME_OK:
474 if (time_status & STA_INS)
475 time_state = TIME_INS;
476 else if (time_status & STA_DEL)
477 time_state = TIME_DEL;
478 break;
479
480 /*
481 * Insert second 23:59:60 following second
482 * 23:59:59.
483 */
484 case TIME_INS:
485 if (!(time_status & STA_INS))
486 time_state = TIME_OK;
487 else if ((*newsec) % 86400 == 0) {
488 (*newsec)--;
489 time_state = TIME_OOP;
490 time_tai++;
491 }
492 break;
493
494 /*
495 * Delete second 23:59:59.
496 */
497 case TIME_DEL:
498 if (!(time_status & STA_DEL))
499 time_state = TIME_OK;
500 else if (((*newsec) + 1) % 86400 == 0) {
501 (*newsec)++;
502 time_tai--;
503 time_state = TIME_WAIT;
504 }
505 break;
506
507 /*
508 * Insert second in progress.
509 */
510 case TIME_OOP:
511 time_state = TIME_WAIT;
512 break;
513
514 /*
515 * Wait for status bits to clear.
516 */
517 case TIME_WAIT:
518 if (!(time_status & (STA_INS | STA_DEL)))
519 time_state = TIME_OK;
520 }
521
522 /*
523 * Compute the total time adjustment for the next second
524 * in ns. The offset is reduced by a factor depending on
525 * whether the PPS signal is operating. Note that the
526 * value is in effect scaled by the clock frequency,
527 * since the adjustment is added at each tick interrupt.
528 */
529 ftemp = time_offset;
530 #ifdef PPS_SYNC
531 /* XXX even if PPS signal dies we should finish adjustment ? */
532 if (time_status & STA_PPSTIME && time_status &
533 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;
541 L_SUB(time_offset, ftemp);
542 L_ADD(time_adj, time_freq);
543
544 /*
545 * Apply any correction from adjtime(2). If more than one second
546 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
547 * until the last second is slewed the final < 500 usecs.
548 */
549 if (time_adjtime != 0) {
550 if (time_adjtime > 1000000)
551 tickrate = 5000;
552 else if (time_adjtime < -1000000)
553 tickrate = -5000;
554 else if (time_adjtime > 500)
555 tickrate = 500;
556 else if (time_adjtime < -500)
557 tickrate = -500;
558 else
559 tickrate = time_adjtime;
560 time_adjtime -= tickrate;
561 L_LINT(ftemp, tickrate * 1000);
562 L_ADD(time_adj, ftemp);
563 }
564 *adjustment = time_adj;
565
566 #ifdef PPS_SYNC
567 if (pps_valid > 0)
568 pps_valid--;
569 else
570 time_status &= ~STA_PPSSIGNAL;
571 #endif /* PPS_SYNC */
572 }
573
574 /*
575 * ntp_init() - initialize variables and structures
576 *
577 * This routine must be called after the kernel variables hz and tick
578 * are set or changed and before the next tick interrupt. In this
579 * particular implementation, these values are assumed set elsewhere in
580 * the kernel. The design allows the clock frequency and tick interval
581 * to be changed while the system is running. So, this routine should
582 * probably be integrated with the code that does that.
583 */
584 static void
585 ntp_init()
586 {
587
588 /*
589 * The following variables are initialized only at startup. Only
590 * those structures not cleared by the compiler need to be
591 * initialized, and these only in the simulator. In the actual
592 * kernel, any nonzero values here will quickly evaporate.
593 */
594 L_CLR(time_offset);
595 L_CLR(time_freq);
596 #ifdef PPS_SYNC
597 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
598 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
599 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
600 pps_fcount = 0;
601 L_CLR(pps_freq);
602 #endif /* PPS_SYNC */
603 }
604
605 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL)
606
607 /*
608 * hardupdate() - local clock update
609 *
610 * This routine is called by ntp_adjtime() to update the local clock
611 * phase and frequency. The implementation is of an adaptive-parameter,
612 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
613 * time and frequency offset estimates for each call. If the kernel PPS
614 * discipline code is configured (PPS_SYNC), the PPS signal itself
615 * determines the new time offset, instead of the calling argument.
616 * Presumably, calls to ntp_adjtime() occur only when the caller
617 * believes the local clock is valid within some bound (+-128 ms with
618 * NTP). If the caller's time is far different than the PPS time, an
619 * argument will ensue, and it's not clear who will lose.
620 *
621 * For uncompensated quartz crystal oscillators and nominal update
622 * intervals less than 256 s, operation should be in phase-lock mode,
623 * where the loop is disciplined to phase. For update intervals greater
624 * than 1024 s, operation should be in frequency-lock mode, where the
625 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
626 * is selected by the STA_MODE status bit.
627 */
628 static void
629 hardupdate(offset)
630 long offset; /* clock offset (ns) */
631 {
632 long mtemp;
633 l_fp ftemp;
634
635 /*
636 * Select how the phase is to be controlled and from which
637 * source. If the PPS signal is present and enabled to
638 * discipline the time, the PPS offset is used; otherwise, the
639 * argument offset is used.
640 */
641 if (!(time_status & STA_PLL))
642 return;
643 if (!(time_status & STA_PPSTIME && time_status &
644 STA_PPSSIGNAL)) {
645 if (offset > MAXPHASE)
646 time_monitor = MAXPHASE;
647 else if (offset < -MAXPHASE)
648 time_monitor = -MAXPHASE;
649 else
650 time_monitor = offset;
651 L_LINT(time_offset, time_monitor);
652 }
653
654 /*
655 * Select how the frequency is to be controlled and in which
656 * mode (PLL or FLL). If the PPS signal is present and enabled
657 * to discipline the frequency, the PPS frequency is used;
658 * otherwise, the argument offset is used to compute it.
659 */
660 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
661 time_reftime = time_second;
662 return;
663 }
664 if (time_status & STA_FREQHOLD || time_reftime == 0)
665 time_reftime = time_second;
666 mtemp = time_second - time_reftime;
667 L_LINT(ftemp, time_monitor);
668 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
669 L_MPY(ftemp, mtemp);
670 L_ADD(time_freq, ftemp);
671 time_status &= ~STA_MODE;
672 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
673 MAXSEC)) {
674 L_LINT(ftemp, (time_monitor << 4) / mtemp);
675 L_RSHIFT(ftemp, SHIFT_FLL + 4);
676 L_ADD(time_freq, ftemp);
677 time_status |= STA_MODE;
678 }
679 time_reftime = time_second;
680 if (L_GINT(time_freq) > MAXFREQ)
681 L_LINT(time_freq, MAXFREQ);
682 else if (L_GINT(time_freq) < -MAXFREQ)
683 L_LINT(time_freq, -MAXFREQ);
684 }
685
686 #ifdef PPS_SYNC
687 /*
688 * hardpps() - discipline CPU clock oscillator to external PPS signal
689 *
690 * This routine is called at each PPS interrupt in order to discipline
691 * the CPU clock oscillator to the PPS signal. There are two independent
692 * first-order feedback loops, one for the phase, the other for the
693 * frequency. The phase loop measures and grooms the PPS phase offset
694 * and leaves it in a handy spot for the seconds overflow routine. The
695 * frequency loop averages successive PPS phase differences and
696 * calculates the PPS frequency offset, which is also processed by the
697 * seconds overflow routine. The code requires the caller to capture the
698 * time and architecture-dependent hardware counter values in
699 * nanoseconds at the on-time PPS signal transition.
700 *
701 * Note that, on some Unix systems this routine runs at an interrupt
702 * priority level higher than the timer interrupt routine hardclock().
703 * Therefore, the variables used are distinct from the hardclock()
704 * variables, except for the actual time and frequency variables, which
705 * are determined by this routine and updated atomically.
706 */
707 void
708 hardpps(tsp, nsec)
709 struct timespec *tsp; /* time at PPS */
710 long nsec; /* hardware counter at PPS */
711 {
712 long u_sec, u_nsec, v_nsec; /* temps */
713 l_fp ftemp;
714
715 /*
716 * The signal is first processed by a range gate and frequency
717 * discriminator. The range gate rejects noise spikes outside
718 * the range +-500 us. The frequency discriminator rejects input
719 * signals with apparent frequency outside the range 1 +-500
720 * PPM. If two hits occur in the same second, we ignore the
721 * later hit; if not and a hit occurs outside the range gate,
722 * keep the later hit for later comparison, but do not process
723 * it.
724 */
725 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
726 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
727 pps_valid = PPS_VALID;
728 u_sec = tsp->tv_sec;
729 u_nsec = tsp->tv_nsec;
730 if (u_nsec >= (NANOSECOND >> 1)) {
731 u_nsec -= NANOSECOND;
732 u_sec++;
733 }
734 v_nsec = u_nsec - pps_tf[0].tv_nsec;
735 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
736 MAXFREQ)
737 return;
738 pps_tf[2] = pps_tf[1];
739 pps_tf[1] = pps_tf[0];
740 pps_tf[0].tv_sec = u_sec;
741 pps_tf[0].tv_nsec = u_nsec;
742
743 /*
744 * Compute the difference between the current and previous
745 * counter values. If the difference exceeds 0.5 s, assume it
746 * has wrapped around, so correct 1.0 s. If the result exceeds
747 * the tick interval, the sample point has crossed a tick
748 * boundary during the last second, so correct the tick. Very
749 * intricate.
750 */
751 u_nsec = nsec;
752 if (u_nsec > (NANOSECOND >> 1))
753 u_nsec -= NANOSECOND;
754 else if (u_nsec < -(NANOSECOND >> 1))
755 u_nsec += NANOSECOND;
756 pps_fcount += u_nsec;
757 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
758 return;
759 time_status &= ~STA_PPSJITTER;
760
761 /*
762 * A three-stage median filter is used to help denoise the PPS
763 * time. The median sample becomes the time offset estimate; the
764 * difference between the other two samples becomes the time
765 * dispersion (jitter) estimate.
766 */
767 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
768 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
769 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
770 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
771 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
772 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
773 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
774 } else {
775 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
776 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
777 }
778 } else {
779 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
780 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
781 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
782 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
783 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
784 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
785 } else {
786 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
787 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
788 }
789 }
790
791 /*
792 * Nominal jitter is due to PPS signal noise and interrupt
793 * latency. If it exceeds the popcorn threshold, the sample is
794 * discarded. otherwise, if so enabled, the time offset is
795 * updated. We can tolerate a modest loss of data here without
796 * much degrading time accuracy.
797 */
798 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
799 time_status |= STA_PPSJITTER;
800 pps_jitcnt++;
801 } else if (time_status & STA_PPSTIME) {
802 time_monitor = -v_nsec;
803 L_LINT(time_offset, time_monitor);
804 }
805 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
806 u_sec = pps_tf[0].tv_sec - pps_lastsec;
807 if (u_sec < (1 << pps_shift))
808 return;
809
810 /*
811 * At the end of the calibration interval the difference between
812 * the first and last counter values becomes the scaled
813 * frequency. It will later be divided by the length of the
814 * interval to determine the frequency update. If the frequency
815 * exceeds a sanity threshold, or if the actual calibration
816 * interval is not equal to the expected length, the data are
817 * discarded. We can tolerate a modest loss of data here without
818 * much degrading frequency accuracy.
819 */
820 pps_calcnt++;
821 v_nsec = -pps_fcount;
822 pps_lastsec = pps_tf[0].tv_sec;
823 pps_fcount = 0;
824 u_nsec = MAXFREQ << pps_shift;
825 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
826 pps_shift)) {
827 time_status |= STA_PPSERROR;
828 pps_errcnt++;
829 return;
830 }
831
832 /*
833 * Here the raw frequency offset and wander (stability) is
834 * calculated. If the wander is less than the wander threshold
835 * for four consecutive averaging intervals, the interval is
836 * doubled; if it is greater than the threshold for four
837 * consecutive intervals, the interval is halved. The scaled
838 * frequency offset is converted to frequency offset. The
839 * stability metric is calculated as the average of recent
840 * frequency changes, but is used only for performance
841 * monitoring.
842 */
843 L_LINT(ftemp, v_nsec);
844 L_RSHIFT(ftemp, pps_shift);
845 L_SUB(ftemp, pps_freq);
846 u_nsec = L_GINT(ftemp);
847 if (u_nsec > PPS_MAXWANDER) {
848 L_LINT(ftemp, PPS_MAXWANDER);
849 pps_intcnt--;
850 time_status |= STA_PPSWANDER;
851 pps_stbcnt++;
852 } else if (u_nsec < -PPS_MAXWANDER) {
853 L_LINT(ftemp, -PPS_MAXWANDER);
854 pps_intcnt--;
855 time_status |= STA_PPSWANDER;
856 pps_stbcnt++;
857 } else {
858 pps_intcnt++;
859 }
860 if (pps_intcnt >= 4) {
861 pps_intcnt = 4;
862 if (pps_shift < pps_shiftmax) {
863 pps_shift++;
864 pps_intcnt = 0;
865 }
866 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
867 pps_intcnt = -4;
868 if (pps_shift > PPS_FAVG) {
869 pps_shift--;
870 pps_intcnt = 0;
871 }
872 }
873 if (u_nsec < 0)
874 u_nsec = -u_nsec;
875 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
876
877 /*
878 * The PPS frequency is recalculated and clamped to the maximum
879 * MAXFREQ. If enabled, the system clock frequency is updated as
880 * well.
881 */
882 L_ADD(pps_freq, ftemp);
883 u_nsec = L_GINT(pps_freq);
884 if (u_nsec > MAXFREQ)
885 L_LINT(pps_freq, MAXFREQ);
886 else if (u_nsec < -MAXFREQ)
887 L_LINT(pps_freq, -MAXFREQ);
888 if (time_status & STA_PPSFREQ)
889 time_freq = pps_freq;
890 }
891 #endif /* PPS_SYNC */
892
893 #ifndef _SYS_SYSPROTO_H_
894 struct adjtime_args {
895 struct timeval *delta;
896 struct timeval *olddelta;
897 };
898 #endif
899 /*
900 * MPSAFE
901 */
902 /* ARGSUSED */
903 int
904 adjtime(struct thread *td, struct adjtime_args *uap)
905 {
906 struct timeval delta, olddelta, *deltap;
907 int error;
908
909 if (uap->delta) {
910 error = copyin(uap->delta, &delta, sizeof(delta));
911 if (error)
912 return (error);
913 deltap = δ
914 } else
915 deltap = NULL;
916 error = kern_adjtime(td, deltap, &olddelta);
917 if (uap->olddelta && error == 0)
918 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
919 return (error);
920 }
921
922 int
923 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
924 {
925 struct timeval atv;
926 int error;
927
928 if ((error = suser(td)))
929 return (error);
930
931 mtx_lock(&Giant);
932 if (olddelta) {
933 atv.tv_sec = time_adjtime / 1000000;
934 atv.tv_usec = time_adjtime % 1000000;
935 if (atv.tv_usec < 0) {
936 atv.tv_usec += 1000000;
937 atv.tv_sec--;
938 }
939 *olddelta = atv;
940 }
941 if (delta)
942 time_adjtime = (int64_t)delta->tv_sec * 1000000 +
943 delta->tv_usec;
944 mtx_unlock(&Giant);
945 return (error);
946 }
947
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