This commit represents a major revamping of the clock interrupt and timebase
[dragonfly.git] / sys / kern / kern_ntptime.c
CommitLineData
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1/***********************************************************************
2 * *
3 * Copyright (c) David L. Mills 1993-2001 *
4 * *
5 * Permission to use, copy, modify, and distribute this software and *
6 * its documentation for any purpose and without fee is hereby *
7 * granted, provided that the above copyright notice appears in all *
8 * copies and that both the copyright notice and this permission *
9 * notice appear in supporting documentation, and that the name *
10 * University of Delaware not be used in advertising or publicity *
11 * pertaining to distribution of the software without specific, *
12 * written prior permission. The University of Delaware makes no *
13 * representations about the suitability this software for any *
14 * purpose. It is provided "as is" without express or implied *
15 * warranty. *
16 * *
17 **********************************************************************/
18
19/*
20 * Adapted from the original sources for FreeBSD and timecounters by:
21 * Poul-Henning Kamp <phk@FreeBSD.org>.
22 *
23 * The 32bit version of the "LP" macros seems a bit past its "sell by"
24 * date so I have retained only the 64bit version and included it directly
25 * in this file.
26 *
27 * Only minor changes done to interface with the timecounters over in
28 * sys/kern/kern_clock.c. Some of the comments below may be (even more)
29 * confusing and/or plain wrong in that context.
30 *
31 * $FreeBSD: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $
88c4d2f6 32 * $DragonFly: src/sys/kern/kern_ntptime.c,v 1.8 2004/01/30 05:42:17 dillon Exp $
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33 */
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/time.h>
43#include <sys/timex.h>
44#include <sys/timepps.h>
45#include <sys/sysctl.h>
88c4d2f6 46#include <sys/thread2.h>
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47
48/*
49 * Single-precision macros for 64-bit machines
50 */
51typedef long long l_fp;
52#define L_ADD(v, u) ((v) += (u))
53#define L_SUB(v, u) ((v) -= (u))
54#define L_ADDHI(v, a) ((v) += (long long)(a) << 32)
55#define L_NEG(v) ((v) = -(v))
56#define L_RSHIFT(v, n) \
57 do { \
58 if ((v) < 0) \
59 (v) = -(-(v) >> (n)); \
60 else \
61 (v) = (v) >> (n); \
62 } while (0)
63#define L_MPY(v, a) ((v) *= (a))
64#define L_CLR(v) ((v) = 0)
65#define L_ISNEG(v) ((v) < 0)
66#define L_LINT(v, a) ((v) = (long long)(a) << 32)
67#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
68
69/*
70 * Generic NTP kernel interface
71 *
72 * These routines constitute the Network Time Protocol (NTP) interfaces
73 * for user and daemon application programs. The ntp_gettime() routine
74 * provides the time, maximum error (synch distance) and estimated error
75 * (dispersion) to client user application programs. The ntp_adjtime()
76 * routine is used by the NTP daemon to adjust the system clock to an
77 * externally derived time. The time offset and related variables set by
78 * this routine are used by other routines in this module to adjust the
79 * phase and frequency of the clock discipline loop which controls the
80 * system clock.
81 *
82 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
83 * defined), the time at each tick interrupt is derived directly from
84 * the kernel time variable. When the kernel time is reckoned in
85 * microseconds, (NTP_NANO undefined), the time is derived from the
86 * kernel time variable together with a variable representing the
87 * leftover nanoseconds at the last tick interrupt. In either case, the
88 * current nanosecond time is reckoned from these values plus an
89 * interpolated value derived by the clock routines in another
90 * architecture-specific module. The interpolation can use either a
91 * dedicated counter or a processor cycle counter (PCC) implemented in
92 * some architectures.
93 *
94 * Note that all routines must run at priority splclock or higher.
95 */
96/*
97 * Phase/frequency-lock loop (PLL/FLL) definitions
98 *
99 * The nanosecond clock discipline uses two variable types, time
100 * variables and frequency variables. Both types are represented as 64-
101 * bit fixed-point quantities with the decimal point between two 32-bit
102 * halves. On a 32-bit machine, each half is represented as a single
103 * word and mathematical operations are done using multiple-precision
104 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
105 * used.
106 *
107 * A time variable is a signed 64-bit fixed-point number in ns and
108 * fraction. It represents the remaining time offset to be amortized
109 * over succeeding tick interrupts. The maximum time offset is about
110 * 0.5 s and the resolution is about 2.3e-10 ns.
111 *
112 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
113 * 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
114 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
115 * |s s s| ns |
116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
117 * | fraction |
118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
119 *
120 * A frequency variable is a signed 64-bit fixed-point number in ns/s
121 * and fraction. It represents the ns and fraction to be added to the
122 * kernel time variable at each second. The maximum frequency offset is
123 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
124 *
125 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
126 * 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
127 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
128 * |s s s s s s s s s s s s s| ns/s |
129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
130 * | fraction |
131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
132 */
133/*
134 * The following variables establish the state of the PLL/FLL and the
135 * residual time and frequency offset of the local clock.
136 */
137#define SHIFT_PLL 4 /* PLL loop gain (shift) */
138#define SHIFT_FLL 2 /* FLL loop gain (shift) */
139
140static int time_state = TIME_OK; /* clock state */
141static int time_status = STA_UNSYNC; /* clock status bits */
142static long time_tai; /* TAI offset (s) */
143static long time_monitor; /* last time offset scaled (ns) */
144static long time_constant; /* poll interval (shift) (s) */
145static long time_precision = 1; /* clock precision (ns) */
146static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
147static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
148static long time_reftime; /* time at last adjustment (s) */
149static long time_tick; /* nanoseconds per tick (ns) */
150static l_fp time_offset; /* time offset (ns) */
151static l_fp time_freq; /* frequency offset (ns/s) */
152static l_fp time_adj; /* tick adjust (ns/s) */
153
154#ifdef PPS_SYNC
155/*
156 * The following variables are used when a pulse-per-second (PPS) signal
157 * is available and connected via a modem control lead. They establish
158 * the engineering parameters of the clock discipline loop when
159 * controlled by the PPS signal.
160 */
161#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */
162#define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */
163#define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */
164#define PPS_PAVG 4 /* phase avg interval (s) (shift) */
165#define PPS_VALID 120 /* PPS signal watchdog max (s) */
166#define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */
167#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */
168
169static struct timespec pps_tf[3]; /* phase median filter */
170static l_fp pps_freq; /* scaled frequency offset (ns/s) */
171static long pps_fcount; /* frequency accumulator */
172static long pps_jitter; /* nominal jitter (ns) */
173static long pps_stabil; /* nominal stability (scaled ns/s) */
174static long pps_lastsec; /* time at last calibration (s) */
175static int pps_valid; /* signal watchdog counter */
176static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */
177static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */
178static int pps_intcnt; /* wander counter */
179
180/*
181 * PPS signal quality monitors
182 */
183static long pps_calcnt; /* calibration intervals */
184static long pps_jitcnt; /* jitter limit exceeded */
185static long pps_stbcnt; /* stability limit exceeded */
186static long pps_errcnt; /* calibration errors */
187#endif /* PPS_SYNC */
188/*
189 * End of phase/frequency-lock loop (PLL/FLL) definitions
190 */
191
192static void ntp_init(void);
193static void hardupdate(long offset);
194
195/*
196 * ntp_gettime() - NTP user application interface
197 *
198 * See the timex.h header file for synopsis and API description. Note
199 * that the TAI offset is returned in the ntvtimeval.tai structure
200 * member.
201 */
202static int
203ntp_sysctl(SYSCTL_HANDLER_ARGS)
204{
205 struct ntptimeval ntv; /* temporary structure */
206 struct timespec atv; /* nanosecond time */
207
208 nanotime(&atv);
209 ntv.time.tv_sec = atv.tv_sec;
210 ntv.time.tv_nsec = atv.tv_nsec;
211 ntv.maxerror = time_maxerror;
212 ntv.esterror = time_esterror;
213 ntv.tai = time_tai;
214 ntv.time_state = time_state;
215
216 /*
217 * Status word error decode. If any of these conditions occur,
218 * an error is returned, instead of the status word. Most
219 * applications will care only about the fact the system clock
220 * may not be trusted, not about the details.
221 *
222 * Hardware or software error
223 */
224 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
225
226 /*
227 * PPS signal lost when either time or frequency synchronization
228 * requested
229 */
230 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
231 !(time_status & STA_PPSSIGNAL)) ||
232
233 /*
234 * PPS jitter exceeded when time synchronization requested
235 */
236 (time_status & STA_PPSTIME &&
237 time_status & STA_PPSJITTER) ||
238
239 /*
240 * PPS wander exceeded or calibration error when frequency
241 * synchronization requested
242 */
243 (time_status & STA_PPSFREQ &&
244 time_status & (STA_PPSWANDER | STA_PPSERROR)))
245 ntv.time_state = TIME_ERROR;
246 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
247}
248
249SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
250SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
251 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
252
253#ifdef PPS_SYNC
254SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
255SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
256SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
257
258SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
259SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
260#endif
261/*
262 * ntp_adjtime() - NTP daemon application interface
263 *
264 * See the timex.h header file for synopsis and API description. Note
265 * that the timex.constant structure member has a dual purpose to set
266 * the time constant and to set the TAI offset.
267 */
984263bc 268int
41c20dac 269ntp_adjtime(struct ntp_adjtime_args *uap)
984263bc 270{
dadab5e9 271 struct thread *td = curthread;
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272 struct timex ntv; /* temporary structure */
273 long freq; /* frequency ns/s) */
274 int modes; /* mode bits from structure */
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275 int error;
276
277 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
278 if (error)
279 return(error);
280
281 /*
282 * Update selected clock variables - only the superuser can
283 * change anything. Note that there is no error checking here on
284 * the assumption the superuser should know what it is doing.
285 * Note that either the time constant or TAI offset are loaded
286 * from the ntv.constant member, depending on the mode bits. If
287 * the STA_PLL bit in the status word is cleared, the state and
288 * status words are reset to the initial values at boot.
289 */
290 modes = ntv.modes;
291 if (modes)
dadab5e9 292 error = suser(td);
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293 if (error)
294 return (error);
88c4d2f6 295 crit_enter();
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296 if (modes & MOD_MAXERROR)
297 time_maxerror = ntv.maxerror;
298 if (modes & MOD_ESTERROR)
299 time_esterror = ntv.esterror;
300 if (modes & MOD_STATUS) {
301 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
302 time_state = TIME_OK;
303 time_status = STA_UNSYNC;
304#ifdef PPS_SYNC
305 pps_shift = PPS_FAVG;
306#endif /* PPS_SYNC */
307 }
308 time_status &= STA_RONLY;
309 time_status |= ntv.status & ~STA_RONLY;
310 }
311 if (modes & MOD_TIMECONST) {
312 if (ntv.constant < 0)
313 time_constant = 0;
314 else if (ntv.constant > MAXTC)
315 time_constant = MAXTC;
316 else
317 time_constant = ntv.constant;
318 }
319 if (modes & MOD_TAI) {
320 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
321 time_tai = ntv.constant;
322 }
323#ifdef PPS_SYNC
324 if (modes & MOD_PPSMAX) {
325 if (ntv.shift < PPS_FAVG)
326 pps_shiftmax = PPS_FAVG;
327 else if (ntv.shift > PPS_FAVGMAX)
328 pps_shiftmax = PPS_FAVGMAX;
329 else
330 pps_shiftmax = ntv.shift;
331 }
332#endif /* PPS_SYNC */
333 if (modes & MOD_NANO)
334 time_status |= STA_NANO;
335 if (modes & MOD_MICRO)
336 time_status &= ~STA_NANO;
337 if (modes & MOD_CLKB)
338 time_status |= STA_CLK;
339 if (modes & MOD_CLKA)
340 time_status &= ~STA_CLK;
341 if (modes & MOD_OFFSET) {
342 if (time_status & STA_NANO)
343 hardupdate(ntv.offset);
344 else
345 hardupdate(ntv.offset * 1000);
346 }
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347 /*
348 * Note: the userland specified frequency is in seconds per second
349 * times 65536e+6. Multiply by a thousand and divide by 65336 to
350 * get nanoseconds.
351 */
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352 if (modes & MOD_FREQUENCY) {
353 freq = (ntv.freq * 1000LL) >> 16;
354 if (freq > MAXFREQ)
355 L_LINT(time_freq, MAXFREQ);
356 else if (freq < -MAXFREQ)
357 L_LINT(time_freq, -MAXFREQ);
358 else
359 L_LINT(time_freq, freq);
360#ifdef PPS_SYNC
361 pps_freq = time_freq;
362#endif /* PPS_SYNC */
363 }
364
365 /*
366 * Retrieve all clock variables. Note that the TAI offset is
367 * returned only by ntp_gettime();
368 */
369 if (time_status & STA_NANO)
370 ntv.offset = time_monitor;
371 else
372 ntv.offset = time_monitor / 1000; /* XXX rounding ? */
373 ntv.freq = L_GINT((time_freq / 1000LL) << 16);
374 ntv.maxerror = time_maxerror;
375 ntv.esterror = time_esterror;
376 ntv.status = time_status;
377 ntv.constant = time_constant;
378 if (time_status & STA_NANO)
379 ntv.precision = time_precision;
380 else
381 ntv.precision = time_precision / 1000;
382 ntv.tolerance = MAXFREQ * SCALE_PPM;
383#ifdef PPS_SYNC
384 ntv.shift = pps_shift;
385 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
386 if (time_status & STA_NANO)
387 ntv.jitter = pps_jitter;
388 else
389 ntv.jitter = pps_jitter / 1000;
390 ntv.stabil = pps_stabil;
391 ntv.calcnt = pps_calcnt;
392 ntv.errcnt = pps_errcnt;
393 ntv.jitcnt = pps_jitcnt;
394 ntv.stbcnt = pps_stbcnt;
395#endif /* PPS_SYNC */
88c4d2f6 396 crit_exit();
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397
398 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
399 if (error)
400 return (error);
401
402 /*
403 * Status word error decode. See comments in
404 * ntp_gettime() routine.
405 */
406 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
407 (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
408 !(time_status & STA_PPSSIGNAL)) ||
409 (time_status & STA_PPSTIME &&
410 time_status & STA_PPSJITTER) ||
411 (time_status & STA_PPSFREQ &&
90b9818c 412 time_status & (STA_PPSWANDER | STA_PPSERROR))) {
c7114eea 413 uap->sysmsg_result = TIME_ERROR;
90b9818c 414 } else {
c7114eea 415 uap->sysmsg_result = time_state;
90b9818c 416 }
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417 return (error);
418}
419
420/*
421 * second_overflow() - called after ntp_tick_adjust()
422 *
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423 * This routine is ordinarily called from hardclock() whenever the seconds
424 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj
425 * to the total adjustment to make over the next second in (ns << 32).
984263bc 426 */
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427int
428ntp_update_second(time_t newsec, int64_t *nsec_adj)
984263bc 429{
984263bc 430 l_fp ftemp; /* 32/64-bit temporary */
88c4d2f6 431 int adjsec = 0;
984263bc 432
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433 /*
434 * On rollover of the second both the nanosecond and microsecond
435 * clocks are updated and the state machine cranked as
436 * necessary. The phase adjustment to be used for the next
437 * second is calculated and the maximum error is increased by
438 * the tolerance.
439 */
440 time_maxerror += MAXFREQ / 1000;
441
442 /*
443 * Leap second processing. If in leap-insert state at
444 * the end of the day, the system clock is set back one
445 * second; if in leap-delete state, the system clock is
446 * set ahead one second. The nano_time() routine or
447 * external clock driver will insure that reported time
448 * is always monotonic.
449 */
450 switch (time_state) {
451
452 /*
453 * No warning.
454 */
455 case TIME_OK:
456 if (time_status & STA_INS)
457 time_state = TIME_INS;
458 else if (time_status & STA_DEL)
459 time_state = TIME_DEL;
460 break;
461
462 /*
463 * Insert second 23:59:60 following second
464 * 23:59:59.
465 */
466 case TIME_INS:
467 if (!(time_status & STA_INS))
468 time_state = TIME_OK;
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469 else if ((newsec) % 86400 == 0) {
470 --adjsec;
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471 time_state = TIME_OOP;
472 }
473 break;
474
475 /*
476 * Delete second 23:59:59.
477 */
478 case TIME_DEL:
479 if (!(time_status & STA_DEL))
480 time_state = TIME_OK;
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481 else if (((newsec) + 1) % 86400 == 0) {
482 ++adjsec;
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483 time_tai--;
484 time_state = TIME_WAIT;
485 }
486 break;
487
488 /*
489 * Insert second in progress.
490 */
491 case TIME_OOP:
492 time_tai++;
493 time_state = TIME_WAIT;
494 break;
495
496 /*
497 * Wait for status bits to clear.
498 */
499 case TIME_WAIT:
500 if (!(time_status & (STA_INS | STA_DEL)))
501 time_state = TIME_OK;
502 }
503
504 /*
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505 * time_offset represents the total time adjustment we wish to
506 * make (over no particular period of time). time_freq represents
507 * the frequency compensation we wish to apply.
508 *
509 * time_adj represents the total adjustment we wish to make over
510 * one full second. hardclock usually applies this adjustment in
511 * time_adj / hz jumps, hz times a second.
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512 */
513 ftemp = time_offset;
514#ifdef PPS_SYNC
515 /* XXX even if PPS signal dies we should finish adjustment ? */
88c4d2f6 516 if ((time_status & STA_PPSTIME( && (time_status & STA_PPSSIGNAL))
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517 L_RSHIFT(ftemp, pps_shift);
518 else
519 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
520#else
521 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
522#endif /* PPS_SYNC */
88c4d2f6 523 time_adj = ftemp; /* adjustment for part of the offset */
984263bc 524 L_SUB(time_offset, ftemp);
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525 L_ADD(time_adj, time_freq); /* add frequency correction */
526 *nsec_adj = time_adj;
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527#ifdef PPS_SYNC
528 if (pps_valid > 0)
529 pps_valid--;
530 else
531 time_status &= ~STA_PPSSIGNAL;
532#endif /* PPS_SYNC */
88c4d2f6 533 return(adjsec);
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534}
535
536/*
537 * ntp_init() - initialize variables and structures
538 *
539 * This routine must be called after the kernel variables hz and tick
540 * are set or changed and before the next tick interrupt. In this
541 * particular implementation, these values are assumed set elsewhere in
542 * the kernel. The design allows the clock frequency and tick interval
543 * to be changed while the system is running. So, this routine should
544 * probably be integrated with the code that does that.
545 */
546static void
547ntp_init()
548{
549
550 /*
551 * The following variable must be initialized any time the
552 * kernel variable hz is changed.
553 */
554 time_tick = NANOSECOND / hz;
555
556 /*
557 * The following variables are initialized only at startup. Only
558 * those structures not cleared by the compiler need to be
559 * initialized, and these only in the simulator. In the actual
560 * kernel, any nonzero values here will quickly evaporate.
561 */
562 L_CLR(time_offset);
563 L_CLR(time_freq);
564#ifdef PPS_SYNC
565 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
566 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
567 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
568 pps_fcount = 0;
569 L_CLR(pps_freq);
570#endif /* PPS_SYNC */
571}
572
573SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL)
574
575/*
576 * hardupdate() - local clock update
577 *
578 * This routine is called by ntp_adjtime() to update the local clock
579 * phase and frequency. The implementation is of an adaptive-parameter,
580 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
581 * time and frequency offset estimates for each call. If the kernel PPS
582 * discipline code is configured (PPS_SYNC), the PPS signal itself
583 * determines the new time offset, instead of the calling argument.
584 * Presumably, calls to ntp_adjtime() occur only when the caller
585 * believes the local clock is valid within some bound (+-128 ms with
586 * NTP). If the caller's time is far different than the PPS time, an
587 * argument will ensue, and it's not clear who will lose.
588 *
589 * For uncompensated quartz crystal oscillators and nominal update
590 * intervals less than 256 s, operation should be in phase-lock mode,
591 * where the loop is disciplined to phase. For update intervals greater
592 * than 1024 s, operation should be in frequency-lock mode, where the
593 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
594 * is selected by the STA_MODE status bit.
595 */
596static void
597hardupdate(offset)
598 long offset; /* clock offset (ns) */
599{
600 long mtemp;
601 l_fp ftemp;
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602 globaldata_t gd;
603
604 gd = mycpu;
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605
606 /*
607 * Select how the phase is to be controlled and from which
608 * source. If the PPS signal is present and enabled to
609 * discipline the time, the PPS offset is used; otherwise, the
610 * argument offset is used.
611 */
612 if (!(time_status & STA_PLL))
613 return;
88c4d2f6 614 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) {
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615 if (offset > MAXPHASE)
616 time_monitor = MAXPHASE;
617 else if (offset < -MAXPHASE)
618 time_monitor = -MAXPHASE;
619 else
620 time_monitor = offset;
621 L_LINT(time_offset, time_monitor);
622 }
623
624 /*
625 * Select how the frequency is to be controlled and in which
626 * mode (PLL or FLL). If the PPS signal is present and enabled
627 * to discipline the frequency, the PPS frequency is used;
628 * otherwise, the argument offset is used to compute it.
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629 *
630 * gd_time_seconds is basically an uncompensated uptime. We use
631 * this for consistency.
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632 */
633 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
634 time_reftime = time_second;
635 return;
636 }
637 if (time_status & STA_FREQHOLD || time_reftime == 0)
638 time_reftime = time_second;
639 mtemp = time_second - time_reftime;
640 L_LINT(ftemp, time_monitor);
641 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
642 L_MPY(ftemp, mtemp);
643 L_ADD(time_freq, ftemp);
644 time_status &= ~STA_MODE;
88c4d2f6 645 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
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646 L_LINT(ftemp, (time_monitor << 4) / mtemp);
647 L_RSHIFT(ftemp, SHIFT_FLL + 4);
648 L_ADD(time_freq, ftemp);
649 time_status |= STA_MODE;
650 }
651 time_reftime = time_second;
652 if (L_GINT(time_freq) > MAXFREQ)
653 L_LINT(time_freq, MAXFREQ);
654 else if (L_GINT(time_freq) < -MAXFREQ)
655 L_LINT(time_freq, -MAXFREQ);
656}
657
658#ifdef PPS_SYNC
659/*
660 * hardpps() - discipline CPU clock oscillator to external PPS signal
661 *
662 * This routine is called at each PPS interrupt in order to discipline
663 * the CPU clock oscillator to the PPS signal. There are two independent
664 * first-order feedback loops, one for the phase, the other for the
665 * frequency. The phase loop measures and grooms the PPS phase offset
666 * and leaves it in a handy spot for the seconds overflow routine. The
667 * frequency loop averages successive PPS phase differences and
668 * calculates the PPS frequency offset, which is also processed by the
669 * seconds overflow routine. The code requires the caller to capture the
670 * time and architecture-dependent hardware counter values in
671 * nanoseconds at the on-time PPS signal transition.
672 *
673 * Note that, on some Unix systems this routine runs at an interrupt
674 * priority level higher than the timer interrupt routine hardclock().
675 * Therefore, the variables used are distinct from the hardclock()
676 * variables, except for the actual time and frequency variables, which
677 * are determined by this routine and updated atomically.
678 */
679void
680hardpps(tsp, nsec)
681 struct timespec *tsp; /* time at PPS */
682 long nsec; /* hardware counter at PPS */
683{
684 long u_sec, u_nsec, v_nsec; /* temps */
685 l_fp ftemp;
686
687 /*
688 * The signal is first processed by a range gate and frequency
689 * discriminator. The range gate rejects noise spikes outside
690 * the range +-500 us. The frequency discriminator rejects input
691 * signals with apparent frequency outside the range 1 +-500
692 * PPM. If two hits occur in the same second, we ignore the
693 * later hit; if not and a hit occurs outside the range gate,
694 * keep the later hit for later comparison, but do not process
695 * it.
696 */
697 time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
698 time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
699 pps_valid = PPS_VALID;
700 u_sec = tsp->tv_sec;
701 u_nsec = tsp->tv_nsec;
702 if (u_nsec >= (NANOSECOND >> 1)) {
703 u_nsec -= NANOSECOND;
704 u_sec++;
705 }
706 v_nsec = u_nsec - pps_tf[0].tv_nsec;
707 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
708 MAXFREQ)
709 return;
710 pps_tf[2] = pps_tf[1];
711 pps_tf[1] = pps_tf[0];
712 pps_tf[0].tv_sec = u_sec;
713 pps_tf[0].tv_nsec = u_nsec;
714
715 /*
716 * Compute the difference between the current and previous
717 * counter values. If the difference exceeds 0.5 s, assume it
718 * has wrapped around, so correct 1.0 s. If the result exceeds
719 * the tick interval, the sample point has crossed a tick
720 * boundary during the last second, so correct the tick. Very
721 * intricate.
722 */
723 u_nsec = nsec;
724 if (u_nsec > (NANOSECOND >> 1))
725 u_nsec -= NANOSECOND;
726 else if (u_nsec < -(NANOSECOND >> 1))
727 u_nsec += NANOSECOND;
728 pps_fcount += u_nsec;
729 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
730 return;
731 time_status &= ~STA_PPSJITTER;
732
733 /*
734 * A three-stage median filter is used to help denoise the PPS
735 * time. The median sample becomes the time offset estimate; the
736 * difference between the other two samples becomes the time
737 * dispersion (jitter) estimate.
738 */
739 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
740 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
741 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */
742 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
743 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
744 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */
745 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
746 } else {
747 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */
748 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
749 }
750 } else {
751 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
752 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */
753 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
754 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
755 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */
756 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
757 } else {
758 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */
759 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
760 }
761 }
762
763 /*
764 * Nominal jitter is due to PPS signal noise and interrupt
765 * latency. If it exceeds the popcorn threshold, the sample is
766 * discarded. otherwise, if so enabled, the time offset is
767 * updated. We can tolerate a modest loss of data here without
768 * much degrading time accuracy.
769 */
770 if (u_nsec > (pps_jitter << PPS_POPCORN)) {
771 time_status |= STA_PPSJITTER;
772 pps_jitcnt++;
773 } else if (time_status & STA_PPSTIME) {
774 time_monitor = -v_nsec;
775 L_LINT(time_offset, time_monitor);
776 }
777 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
778 u_sec = pps_tf[0].tv_sec - pps_lastsec;
779 if (u_sec < (1 << pps_shift))
780 return;
781
782 /*
783 * At the end of the calibration interval the difference between
784 * the first and last counter values becomes the scaled
785 * frequency. It will later be divided by the length of the
786 * interval to determine the frequency update. If the frequency
787 * exceeds a sanity threshold, or if the actual calibration
788 * interval is not equal to the expected length, the data are
789 * discarded. We can tolerate a modest loss of data here without
790 * much degrading frequency accuracy.
791 */
792 pps_calcnt++;
793 v_nsec = -pps_fcount;
794 pps_lastsec = pps_tf[0].tv_sec;
795 pps_fcount = 0;
796 u_nsec = MAXFREQ << pps_shift;
797 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
798 pps_shift)) {
799 time_status |= STA_PPSERROR;
800 pps_errcnt++;
801 return;
802 }
803
804 /*
805 * Here the raw frequency offset and wander (stability) is
806 * calculated. If the wander is less than the wander threshold
807 * for four consecutive averaging intervals, the interval is
808 * doubled; if it is greater than the threshold for four
809 * consecutive intervals, the interval is halved. The scaled
810 * frequency offset is converted to frequency offset. The
811 * stability metric is calculated as the average of recent
812 * frequency changes, but is used only for performance
813 * monitoring.
814 */
815 L_LINT(ftemp, v_nsec);
816 L_RSHIFT(ftemp, pps_shift);
817 L_SUB(ftemp, pps_freq);
818 u_nsec = L_GINT(ftemp);
819 if (u_nsec > PPS_MAXWANDER) {
820 L_LINT(ftemp, PPS_MAXWANDER);
821 pps_intcnt--;
822 time_status |= STA_PPSWANDER;
823 pps_stbcnt++;
824 } else if (u_nsec < -PPS_MAXWANDER) {
825 L_LINT(ftemp, -PPS_MAXWANDER);
826 pps_intcnt--;
827 time_status |= STA_PPSWANDER;
828 pps_stbcnt++;
829 } else {
830 pps_intcnt++;
831 }
832 if (pps_intcnt >= 4) {
833 pps_intcnt = 4;
834 if (pps_shift < pps_shiftmax) {
835 pps_shift++;
836 pps_intcnt = 0;
837 }
838 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
839 pps_intcnt = -4;
840 if (pps_shift > PPS_FAVG) {
841 pps_shift--;
842 pps_intcnt = 0;
843 }
844 }
845 if (u_nsec < 0)
846 u_nsec = -u_nsec;
847 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
848
849 /*
850 * The PPS frequency is recalculated and clamped to the maximum
851 * MAXFREQ. If enabled, the system clock frequency is updated as
852 * well.
853 */
854 L_ADD(pps_freq, ftemp);
855 u_nsec = L_GINT(pps_freq);
856 if (u_nsec > MAXFREQ)
857 L_LINT(pps_freq, MAXFREQ);
858 else if (u_nsec < -MAXFREQ)
859 L_LINT(pps_freq, -MAXFREQ);
860 if (time_status & STA_PPSFREQ)
861 time_freq = pps_freq;
862}
863#endif /* PPS_SYNC */