xref: /freebsd/sys/kern/kern_ntptime.c (revision 42c159fe388a3765f69860c84183700af37aca8a)
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  * $FreeBSD$
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 long time_tick;			/* nanoseconds per tick (ns) */
151 static l_fp time_offset;		/* time offset (ns) */
152 static l_fp time_freq;			/* frequency offset (ns/s) */
153 static l_fp time_adj;			/* tick adjust (ns/s) */
154 
155 #ifdef PPS_SYNC
156 /*
157  * The following variables are used when a pulse-per-second (PPS) signal
158  * is available and connected via a modem control lead. They establish
159  * the engineering parameters of the clock discipline loop when
160  * controlled by the PPS signal.
161  */
162 #define PPS_FAVG	2		/* min freq avg interval (s) (shift) */
163 #define PPS_FAVGDEF	8		/* default freq avg int (s) (shift) */
164 #define PPS_FAVGMAX	15		/* max freq avg interval (s) (shift) */
165 #define PPS_PAVG	4		/* phase avg interval (s) (shift) */
166 #define PPS_VALID	120		/* PPS signal watchdog max (s) */
167 #define PPS_MAXWANDER	100000		/* max PPS wander (ns/s) */
168 #define PPS_POPCORN	2		/* popcorn spike threshold (shift) */
169 
170 static struct timespec pps_tf[3];	/* phase median filter */
171 static l_fp pps_freq;			/* scaled frequency offset (ns/s) */
172 static long pps_fcount;			/* frequency accumulator */
173 static long pps_jitter;			/* nominal jitter (ns) */
174 static long pps_stabil;			/* nominal stability (scaled ns/s) */
175 static long pps_lastsec;		/* time at last calibration (s) */
176 static int pps_valid;			/* signal watchdog counter */
177 static int pps_shift = PPS_FAVG;	/* interval duration (s) (shift) */
178 static int pps_shiftmax = PPS_FAVGDEF;	/* max interval duration (s) (shift) */
179 static int pps_intcnt;			/* wander counter */
180 
181 /*
182  * PPS signal quality monitors
183  */
184 static long pps_calcnt;			/* calibration intervals */
185 static long pps_jitcnt;			/* jitter limit exceeded */
186 static long pps_stbcnt;			/* stability limit exceeded */
187 static long pps_errcnt;			/* calibration errors */
188 #endif /* PPS_SYNC */
189 /*
190  * End of phase/frequency-lock loop (PLL/FLL) definitions
191  */
192 
193 static void ntp_init(void);
194 static void hardupdate(long offset);
195 
196 /*
197  * ntp_gettime() - NTP user application interface
198  *
199  * See the timex.h header file for synopsis and API description. Note
200  * that the TAI offset is returned in the ntvtimeval.tai structure
201  * member.
202  */
203 static int
204 ntp_sysctl(SYSCTL_HANDLER_ARGS)
205 {
206 	struct ntptimeval ntv;	/* temporary structure */
207 	struct timespec atv;	/* nanosecond time */
208 
209 	nanotime(&atv);
210 	ntv.time.tv_sec = atv.tv_sec;
211 	ntv.time.tv_nsec = atv.tv_nsec;
212 	ntv.maxerror = time_maxerror;
213 	ntv.esterror = time_esterror;
214 	ntv.tai = time_tai;
215 	ntv.time_state = time_state;
216 
217 	/*
218 	 * Status word error decode. If any of these conditions occur,
219 	 * an error is returned, instead of the status word. Most
220 	 * applications will care only about the fact the system clock
221 	 * may not be trusted, not about the details.
222 	 *
223 	 * Hardware or software error
224 	 */
225 	if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
226 
227 	/*
228 	 * PPS signal lost when either time or frequency synchronization
229 	 * requested
230 	 */
231 	    (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
232 	    !(time_status & STA_PPSSIGNAL)) ||
233 
234 	/*
235 	 * PPS jitter exceeded when time synchronization requested
236 	 */
237 	    (time_status & STA_PPSTIME &&
238 	    time_status & STA_PPSJITTER) ||
239 
240 	/*
241 	 * PPS wander exceeded or calibration error when frequency
242 	 * synchronization requested
243 	 */
244 	    (time_status & STA_PPSFREQ &&
245 	    time_status & (STA_PPSWANDER | STA_PPSERROR)))
246 		ntv.time_state = TIME_ERROR;
247 	return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req));
248 }
249 
250 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
251 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
252 	0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
253 
254 #ifdef PPS_SYNC
255 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
258 
259 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
260 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
261 #endif
262 /*
263  * ntp_adjtime() - NTP daemon application interface
264  *
265  * See the timex.h header file for synopsis and API description. Note
266  * that the timex.constant structure member has a dual purpose to set
267  * the time constant and to set the TAI offset.
268  */
269 #ifndef _SYS_SYSPROTO_H_
270 struct ntp_adjtime_args {
271 	struct timex *tp;
272 };
273 #endif
274 
275 /*
276  * MPSAFE
277  */
278 int
279 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
280 {
281 	struct timex ntv;	/* temporary structure */
282 	long freq;		/* frequency ns/s) */
283 	int modes;		/* mode bits from structure */
284 	int s;			/* caller priority */
285 	int error;
286 
287 	error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
288 	if (error)
289 		return(error);
290 
291 	/*
292 	 * Update selected clock variables - only the superuser can
293 	 * change anything. Note that there is no error checking here on
294 	 * the assumption the superuser should know what it is doing.
295 	 * Note that either the time constant or TAI offset are loaded
296 	 * from the ntv.constant member, depending on the mode bits. If
297 	 * the STA_PLL bit in the status word is cleared, the state and
298 	 * status words are reset to the initial values at boot.
299 	 */
300 	mtx_lock(&Giant);
301 	modes = ntv.modes;
302 	if (modes)
303 		error = suser_td(td);
304 	if (error)
305 		goto done2;
306 	s = splclock();
307 	if (modes & MOD_MAXERROR)
308 		time_maxerror = ntv.maxerror;
309 	if (modes & MOD_ESTERROR)
310 		time_esterror = ntv.esterror;
311 	if (modes & MOD_STATUS) {
312 		if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
313 			time_state = TIME_OK;
314 			time_status = STA_UNSYNC;
315 #ifdef PPS_SYNC
316 			pps_shift = PPS_FAVG;
317 #endif /* PPS_SYNC */
318 		}
319 		time_status &= STA_RONLY;
320 		time_status |= ntv.status & ~STA_RONLY;
321 	}
322 	if (modes & MOD_TIMECONST) {
323 		if (ntv.constant < 0)
324 			time_constant = 0;
325 		else if (ntv.constant > MAXTC)
326 			time_constant = MAXTC;
327 		else
328 			time_constant = ntv.constant;
329 	}
330 	if (modes & MOD_TAI) {
331 		if (ntv.constant > 0) /* XXX zero & negative numbers ? */
332 			time_tai = ntv.constant;
333 	}
334 #ifdef PPS_SYNC
335 	if (modes & MOD_PPSMAX) {
336 		if (ntv.shift < PPS_FAVG)
337 			pps_shiftmax = PPS_FAVG;
338 		else if (ntv.shift > PPS_FAVGMAX)
339 			pps_shiftmax = PPS_FAVGMAX;
340 		else
341 			pps_shiftmax = ntv.shift;
342 	}
343 #endif /* PPS_SYNC */
344 	if (modes & MOD_NANO)
345 		time_status |= STA_NANO;
346 	if (modes & MOD_MICRO)
347 		time_status &= ~STA_NANO;
348 	if (modes & MOD_CLKB)
349 		time_status |= STA_CLK;
350 	if (modes & MOD_CLKA)
351 		time_status &= ~STA_CLK;
352 	if (modes & MOD_OFFSET) {
353 		if (time_status & STA_NANO)
354 			hardupdate(ntv.offset);
355 		else
356 			hardupdate(ntv.offset * 1000);
357 	}
358 	if (modes & MOD_FREQUENCY) {
359 		freq = (ntv.freq * 1000LL) >> 16;
360 		if (freq > MAXFREQ)
361 			L_LINT(time_freq, MAXFREQ);
362 		else if (freq < -MAXFREQ)
363 			L_LINT(time_freq, -MAXFREQ);
364 		else
365 			L_LINT(time_freq, freq);
366 #ifdef PPS_SYNC
367 		pps_freq = time_freq;
368 #endif /* PPS_SYNC */
369 	}
370 
371 	/*
372 	 * Retrieve all clock variables. Note that the TAI offset is
373 	 * returned only by ntp_gettime();
374 	 */
375 	if (time_status & STA_NANO)
376 		ntv.offset = time_monitor;
377 	else
378 		ntv.offset = time_monitor / 1000; /* XXX rounding ? */
379 	ntv.freq = L_GINT((time_freq / 1000LL) << 16);
380 	ntv.maxerror = time_maxerror;
381 	ntv.esterror = time_esterror;
382 	ntv.status = time_status;
383 	ntv.constant = time_constant;
384 	if (time_status & STA_NANO)
385 		ntv.precision = time_precision;
386 	else
387 		ntv.precision = time_precision / 1000;
388 	ntv.tolerance = MAXFREQ * SCALE_PPM;
389 #ifdef PPS_SYNC
390 	ntv.shift = pps_shift;
391 	ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
392 	if (time_status & STA_NANO)
393 		ntv.jitter = pps_jitter;
394 	else
395 		ntv.jitter = pps_jitter / 1000;
396 	ntv.stabil = pps_stabil;
397 	ntv.calcnt = pps_calcnt;
398 	ntv.errcnt = pps_errcnt;
399 	ntv.jitcnt = pps_jitcnt;
400 	ntv.stbcnt = pps_stbcnt;
401 #endif /* PPS_SYNC */
402 	splx(s);
403 
404 	error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
405 	if (error)
406 		goto done2;
407 
408 	/*
409 	 * Status word error decode. See comments in
410 	 * ntp_gettime() routine.
411 	 */
412 	if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
413 	    (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
414 	    !(time_status & STA_PPSSIGNAL)) ||
415 	    (time_status & STA_PPSTIME &&
416 	    time_status & STA_PPSJITTER) ||
417 	    (time_status & STA_PPSFREQ &&
418 	    time_status & (STA_PPSWANDER | STA_PPSERROR))) {
419 		td->td_retval[0] = TIME_ERROR;
420 	} else {
421 		td->td_retval[0] = time_state;
422 	}
423 done2:
424 	mtx_unlock(&Giant);
425 	return (error);
426 }
427 
428 /*
429  * second_overflow() - called after ntp_tick_adjust()
430  *
431  * This routine is ordinarily called immediately following the above
432  * routine ntp_tick_adjust(). While these two routines are normally
433  * combined, they are separated here only for the purposes of
434  * simulation.
435  */
436 void
437 ntp_update_second(struct timecounter *tcp)
438 {
439 	u_int32_t *newsec;
440 	l_fp ftemp;		/* 32/64-bit temporary */
441 
442 	newsec = &tcp->tc_offset.sec;
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 	tcp->tc_adjustment = time_adj;
536 #ifdef PPS_SYNC
537 	if (pps_valid > 0)
538 		pps_valid--;
539 	else
540 		time_status &= ~STA_PPSSIGNAL;
541 #endif /* PPS_SYNC */
542 }
543 
544 /*
545  * ntp_init() - initialize variables and structures
546  *
547  * This routine must be called after the kernel variables hz and tick
548  * are set or changed and before the next tick interrupt. In this
549  * particular implementation, these values are assumed set elsewhere in
550  * the kernel. The design allows the clock frequency and tick interval
551  * to be changed while the system is running. So, this routine should
552  * probably be integrated with the code that does that.
553  */
554 static void
555 ntp_init()
556 {
557 
558 	/*
559 	 * The following variable must be initialized any time the
560 	 * kernel variable hz is changed.
561 	 */
562 	time_tick = NANOSECOND / hz;
563 
564 	/*
565 	 * The following variables are initialized only at startup. Only
566 	 * those structures not cleared by the compiler need to be
567 	 * initialized, and these only in the simulator. In the actual
568 	 * kernel, any nonzero values here will quickly evaporate.
569 	 */
570 	L_CLR(time_offset);
571 	L_CLR(time_freq);
572 #ifdef PPS_SYNC
573 	pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
574 	pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
575 	pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
576 	pps_fcount = 0;
577 	L_CLR(pps_freq);
578 #endif /* PPS_SYNC */
579 }
580 
581 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL)
582 
583 /*
584  * hardupdate() - local clock update
585  *
586  * This routine is called by ntp_adjtime() to update the local clock
587  * phase and frequency. The implementation is of an adaptive-parameter,
588  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
589  * time and frequency offset estimates for each call. If the kernel PPS
590  * discipline code is configured (PPS_SYNC), the PPS signal itself
591  * determines the new time offset, instead of the calling argument.
592  * Presumably, calls to ntp_adjtime() occur only when the caller
593  * believes the local clock is valid within some bound (+-128 ms with
594  * NTP). If the caller's time is far different than the PPS time, an
595  * argument will ensue, and it's not clear who will lose.
596  *
597  * For uncompensated quartz crystal oscillators and nominal update
598  * intervals less than 256 s, operation should be in phase-lock mode,
599  * where the loop is disciplined to phase. For update intervals greater
600  * than 1024 s, operation should be in frequency-lock mode, where the
601  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
602  * is selected by the STA_MODE status bit.
603  */
604 static void
605 hardupdate(offset)
606 	long offset;		/* clock offset (ns) */
607 {
608 	long mtemp;
609 	l_fp ftemp;
610 
611 	/*
612 	 * Select how the phase is to be controlled and from which
613 	 * source. If the PPS signal is present and enabled to
614 	 * discipline the time, the PPS offset is used; otherwise, the
615 	 * argument offset is used.
616 	 */
617 	if (!(time_status & STA_PLL))
618 		return;
619 	if (!(time_status & STA_PPSTIME && time_status &
620 	    STA_PPSSIGNAL)) {
621 		if (offset > MAXPHASE)
622 			time_monitor = MAXPHASE;
623 		else if (offset < -MAXPHASE)
624 			time_monitor = -MAXPHASE;
625 		else
626 			time_monitor = offset;
627 		L_LINT(time_offset, time_monitor);
628 	}
629 
630 	/*
631 	 * Select how the frequency is to be controlled and in which
632 	 * mode (PLL or FLL). If the PPS signal is present and enabled
633 	 * to discipline the frequency, the PPS frequency is used;
634 	 * otherwise, the argument offset is used to compute it.
635 	 */
636 	if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
637 		time_reftime = time_second;
638 		return;
639 	}
640 	if (time_status & STA_FREQHOLD || time_reftime == 0)
641 		time_reftime = time_second;
642 	mtemp = time_second - time_reftime;
643 	L_LINT(ftemp, time_monitor);
644 	L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
645 	L_MPY(ftemp, mtemp);
646 	L_ADD(time_freq, ftemp);
647 	time_status &= ~STA_MODE;
648 	if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
649 	    MAXSEC)) {
650 		L_LINT(ftemp, (time_monitor << 4) / mtemp);
651 		L_RSHIFT(ftemp, SHIFT_FLL + 4);
652 		L_ADD(time_freq, ftemp);
653 		time_status |= STA_MODE;
654 	}
655 	time_reftime = time_second;
656 	if (L_GINT(time_freq) > MAXFREQ)
657 		L_LINT(time_freq, MAXFREQ);
658 	else if (L_GINT(time_freq) < -MAXFREQ)
659 		L_LINT(time_freq, -MAXFREQ);
660 }
661 
662 #ifdef PPS_SYNC
663 /*
664  * hardpps() - discipline CPU clock oscillator to external PPS signal
665  *
666  * This routine is called at each PPS interrupt in order to discipline
667  * the CPU clock oscillator to the PPS signal. There are two independent
668  * first-order feedback loops, one for the phase, the other for the
669  * frequency. The phase loop measures and grooms the PPS phase offset
670  * and leaves it in a handy spot for the seconds overflow routine. The
671  * frequency loop averages successive PPS phase differences and
672  * calculates the PPS frequency offset, which is also processed by the
673  * seconds overflow routine. The code requires the caller to capture the
674  * time and architecture-dependent hardware counter values in
675  * nanoseconds at the on-time PPS signal transition.
676  *
677  * Note that, on some Unix systems this routine runs at an interrupt
678  * priority level higher than the timer interrupt routine hardclock().
679  * Therefore, the variables used are distinct from the hardclock()
680  * variables, except for the actual time and frequency variables, which
681  * are determined by this routine and updated atomically.
682  */
683 void
684 hardpps(tsp, nsec)
685 	struct timespec *tsp;	/* time at PPS */
686 	long nsec;		/* hardware counter at PPS */
687 {
688 	long u_sec, u_nsec, v_nsec; /* temps */
689 	l_fp ftemp;
690 
691 	/*
692 	 * The signal is first processed by a range gate and frequency
693 	 * discriminator. The range gate rejects noise spikes outside
694 	 * the range +-500 us. The frequency discriminator rejects input
695 	 * signals with apparent frequency outside the range 1 +-500
696 	 * PPM. If two hits occur in the same second, we ignore the
697 	 * later hit; if not and a hit occurs outside the range gate,
698 	 * keep the later hit for later comparison, but do not process
699 	 * it.
700 	 */
701 	time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
702 	time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
703 	pps_valid = PPS_VALID;
704 	u_sec = tsp->tv_sec;
705 	u_nsec = tsp->tv_nsec;
706 	if (u_nsec >= (NANOSECOND >> 1)) {
707 		u_nsec -= NANOSECOND;
708 		u_sec++;
709 	}
710 	v_nsec = u_nsec - pps_tf[0].tv_nsec;
711 	if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
712 	    MAXFREQ)
713 		return;
714 	pps_tf[2] = pps_tf[1];
715 	pps_tf[1] = pps_tf[0];
716 	pps_tf[0].tv_sec = u_sec;
717 	pps_tf[0].tv_nsec = u_nsec;
718 
719 	/*
720 	 * Compute the difference between the current and previous
721 	 * counter values. If the difference exceeds 0.5 s, assume it
722 	 * has wrapped around, so correct 1.0 s. If the result exceeds
723 	 * the tick interval, the sample point has crossed a tick
724 	 * boundary during the last second, so correct the tick. Very
725 	 * intricate.
726 	 */
727 	u_nsec = nsec;
728 	if (u_nsec > (NANOSECOND >> 1))
729 		u_nsec -= NANOSECOND;
730 	else if (u_nsec < -(NANOSECOND >> 1))
731 		u_nsec += NANOSECOND;
732 	pps_fcount += u_nsec;
733 	if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
734 		return;
735 	time_status &= ~STA_PPSJITTER;
736 
737 	/*
738 	 * A three-stage median filter is used to help denoise the PPS
739 	 * time. The median sample becomes the time offset estimate; the
740 	 * difference between the other two samples becomes the time
741 	 * dispersion (jitter) estimate.
742 	 */
743 	if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
744 		if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
745 			v_nsec = pps_tf[1].tv_nsec;	/* 0 1 2 */
746 			u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
747 		} else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
748 			v_nsec = pps_tf[0].tv_nsec;	/* 2 0 1 */
749 			u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
750 		} else {
751 			v_nsec = pps_tf[2].tv_nsec;	/* 0 2 1 */
752 			u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
753 		}
754 	} else {
755 		if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
756 			v_nsec = pps_tf[1].tv_nsec;	/* 2 1 0 */
757 			u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
758 		} else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
759 			v_nsec = pps_tf[0].tv_nsec;	/* 1 0 2 */
760 			u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
761 		} else {
762 			v_nsec = pps_tf[2].tv_nsec;	/* 1 2 0 */
763 			u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
764 		}
765 	}
766 
767 	/*
768 	 * Nominal jitter is due to PPS signal noise and interrupt
769 	 * latency. If it exceeds the popcorn threshold, the sample is
770 	 * discarded. otherwise, if so enabled, the time offset is
771 	 * updated. We can tolerate a modest loss of data here without
772 	 * much degrading time accuracy.
773 	 */
774 	if (u_nsec > (pps_jitter << PPS_POPCORN)) {
775 		time_status |= STA_PPSJITTER;
776 		pps_jitcnt++;
777 	} else if (time_status & STA_PPSTIME) {
778 		time_monitor = -v_nsec;
779 		L_LINT(time_offset, time_monitor);
780 	}
781 	pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
782 	u_sec = pps_tf[0].tv_sec - pps_lastsec;
783 	if (u_sec < (1 << pps_shift))
784 		return;
785 
786 	/*
787 	 * At the end of the calibration interval the difference between
788 	 * the first and last counter values becomes the scaled
789 	 * frequency. It will later be divided by the length of the
790 	 * interval to determine the frequency update. If the frequency
791 	 * exceeds a sanity threshold, or if the actual calibration
792 	 * interval is not equal to the expected length, the data are
793 	 * discarded. We can tolerate a modest loss of data here without
794 	 * much degrading frequency accuracy.
795 	 */
796 	pps_calcnt++;
797 	v_nsec = -pps_fcount;
798 	pps_lastsec = pps_tf[0].tv_sec;
799 	pps_fcount = 0;
800 	u_nsec = MAXFREQ << pps_shift;
801 	if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
802 	    pps_shift)) {
803 		time_status |= STA_PPSERROR;
804 		pps_errcnt++;
805 		return;
806 	}
807 
808 	/*
809 	 * Here the raw frequency offset and wander (stability) is
810 	 * calculated. If the wander is less than the wander threshold
811 	 * for four consecutive averaging intervals, the interval is
812 	 * doubled; if it is greater than the threshold for four
813 	 * consecutive intervals, the interval is halved. The scaled
814 	 * frequency offset is converted to frequency offset. The
815 	 * stability metric is calculated as the average of recent
816 	 * frequency changes, but is used only for performance
817 	 * monitoring.
818 	 */
819 	L_LINT(ftemp, v_nsec);
820 	L_RSHIFT(ftemp, pps_shift);
821 	L_SUB(ftemp, pps_freq);
822 	u_nsec = L_GINT(ftemp);
823 	if (u_nsec > PPS_MAXWANDER) {
824 		L_LINT(ftemp, PPS_MAXWANDER);
825 		pps_intcnt--;
826 		time_status |= STA_PPSWANDER;
827 		pps_stbcnt++;
828 	} else if (u_nsec < -PPS_MAXWANDER) {
829 		L_LINT(ftemp, -PPS_MAXWANDER);
830 		pps_intcnt--;
831 		time_status |= STA_PPSWANDER;
832 		pps_stbcnt++;
833 	} else {
834 		pps_intcnt++;
835 	}
836 	if (pps_intcnt >= 4) {
837 		pps_intcnt = 4;
838 		if (pps_shift < pps_shiftmax) {
839 			pps_shift++;
840 			pps_intcnt = 0;
841 		}
842 	} else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
843 		pps_intcnt = -4;
844 		if (pps_shift > PPS_FAVG) {
845 			pps_shift--;
846 			pps_intcnt = 0;
847 		}
848 	}
849 	if (u_nsec < 0)
850 		u_nsec = -u_nsec;
851 	pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
852 
853 	/*
854 	 * The PPS frequency is recalculated and clamped to the maximum
855 	 * MAXFREQ. If enabled, the system clock frequency is updated as
856 	 * well.
857 	 */
858 	L_ADD(pps_freq, ftemp);
859 	u_nsec = L_GINT(pps_freq);
860 	if (u_nsec > MAXFREQ)
861 		L_LINT(pps_freq, MAXFREQ);
862 	else if (u_nsec < -MAXFREQ)
863 		L_LINT(pps_freq, -MAXFREQ);
864 	if (time_status & STA_PPSFREQ)
865 		time_freq = pps_freq;
866 }
867 #endif /* PPS_SYNC */
868