1 /* $NetBSD: kern_tc.c,v 1.77 2024/05/11 06:34:45 andvar Exp $ */
2
3 /*-
4 * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Andrew Doran.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32 /*-
33 * ----------------------------------------------------------------------------
34 * "THE BEER-WARE LICENSE" (Revision 42):
35 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
36 * can do whatever you want with this stuff. If we meet some day, and you think
37 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
38 * ---------------------------------------------------------------------------
39 */
40
41 /*
42 * https://papers.freebsd.org/2002/phk-timecounters.files/timecounter.pdf
43 */
44
45 #include <sys/cdefs.h>
46 /* __FBSDID("$FreeBSD: src/sys/kern/kern_tc.c,v 1.166 2005/09/19 22:16:31 andre Exp $"); */
47 __KERNEL_RCSID(0, "$NetBSD: kern_tc.c,v 1.77 2024/05/11 06:34:45 andvar Exp $");
48
49 #ifdef _KERNEL_OPT
50 #include "opt_ntp.h"
51 #endif
52
53 #include <sys/param.h>
54
55 #include <sys/atomic.h>
56 #include <sys/evcnt.h>
57 #include <sys/kauth.h>
58 #include <sys/kernel.h>
59 #include <sys/lock.h>
60 #include <sys/mutex.h>
61 #include <sys/reboot.h> /* XXX just to get AB_VERBOSE */
62 #include <sys/sysctl.h>
63 #include <sys/syslog.h>
64 #include <sys/systm.h>
65 #include <sys/timepps.h>
66 #include <sys/timetc.h>
67 #include <sys/timex.h>
68 #include <sys/xcall.h>
69
70 /*
71 * A large step happens on boot. This constant detects such steps.
72 * It is relatively small so that ntp_update_second gets called enough
73 * in the typical 'missed a couple of seconds' case, but doesn't loop
74 * forever when the time step is large.
75 */
76 #define LARGE_STEP 200
77
78 /*
79 * Implement a dummy timecounter which we can use until we get a real one
80 * in the air. This allows the console and other early stuff to use
81 * time services.
82 */
83
84 static u_int
dummy_get_timecount(struct timecounter * tc)85 dummy_get_timecount(struct timecounter *tc)
86 {
87 static u_int now;
88
89 return ++now;
90 }
91
92 static struct timecounter dummy_timecounter = {
93 .tc_get_timecount = dummy_get_timecount,
94 .tc_counter_mask = ~0u,
95 .tc_frequency = 1000000,
96 .tc_name = "dummy",
97 .tc_quality = -1000000,
98 .tc_priv = NULL,
99 };
100
101 struct timehands {
102 /* These fields must be initialized by the driver. */
103 struct timecounter *th_counter; /* active timecounter */
104 int64_t th_adjustment; /* frequency adjustment */
105 /* (NTP/adjtime) */
106 uint64_t th_scale; /* scale factor (counter */
107 /* tick->time) */
108 uint64_t th_offset_count; /* offset at last time */
109 /* update (tc_windup()) */
110 struct bintime th_offset; /* bin (up)time at windup */
111 struct timeval th_microtime; /* cached microtime */
112 struct timespec th_nanotime; /* cached nanotime */
113 /* Fields not to be copied in tc_windup start with th_generation. */
114 volatile u_int th_generation; /* current genration */
115 struct timehands *th_next; /* next timehand */
116 };
117
118 static struct timehands th0;
119 static struct timehands th9 = { .th_next = &th0, };
120 static struct timehands th8 = { .th_next = &th9, };
121 static struct timehands th7 = { .th_next = &th8, };
122 static struct timehands th6 = { .th_next = &th7, };
123 static struct timehands th5 = { .th_next = &th6, };
124 static struct timehands th4 = { .th_next = &th5, };
125 static struct timehands th3 = { .th_next = &th4, };
126 static struct timehands th2 = { .th_next = &th3, };
127 static struct timehands th1 = { .th_next = &th2, };
128 static struct timehands th0 = {
129 .th_counter = &dummy_timecounter,
130 .th_scale = (uint64_t)-1 / 1000000,
131 .th_offset = { .sec = 1, .frac = 0 },
132 .th_generation = 1,
133 .th_next = &th1,
134 };
135
136 static struct timehands *volatile timehands = &th0;
137 struct timecounter *timecounter = &dummy_timecounter;
138 static struct timecounter *timecounters = &dummy_timecounter;
139
140 /* used by savecore(8) */
141 time_t time_second_legacy asm("time_second");
142
143 #ifdef __HAVE_ATOMIC64_LOADSTORE
144 volatile time_t time__second __cacheline_aligned = 1;
145 volatile time_t time__uptime __cacheline_aligned = 1;
146 #else
147 static volatile struct {
148 uint32_t lo, hi;
149 } time__uptime32 __cacheline_aligned = {
150 .lo = 1,
151 }, time__second32 __cacheline_aligned = {
152 .lo = 1,
153 };
154 #endif
155
156 static struct {
157 struct bintime bin;
158 volatile unsigned gen; /* even when stable, odd when changing */
159 } timebase __cacheline_aligned;
160
161 static int timestepwarnings;
162
163 kmutex_t timecounter_lock;
164 static u_int timecounter_mods;
165 static volatile int timecounter_removals = 1;
166 static u_int timecounter_bad;
167
168 #ifdef __HAVE_ATOMIC64_LOADSTORE
169
170 static inline void
setrealuptime(time_t second,time_t uptime)171 setrealuptime(time_t second, time_t uptime)
172 {
173
174 time_second_legacy = second;
175
176 atomic_store_relaxed(&time__second, second);
177 atomic_store_relaxed(&time__uptime, uptime);
178 }
179
180 #else
181
182 static inline void
setrealuptime(time_t second,time_t uptime)183 setrealuptime(time_t second, time_t uptime)
184 {
185 uint32_t seclo = second & 0xffffffff, sechi = second >> 32;
186 uint32_t uplo = uptime & 0xffffffff, uphi = uptime >> 32;
187
188 KDASSERT(mutex_owned(&timecounter_lock));
189
190 time_second_legacy = second;
191
192 /*
193 * Fast path -- no wraparound, just updating the low bits, so
194 * no need for seqlocked access.
195 */
196 if (__predict_true(sechi == time__second32.hi) &&
197 __predict_true(uphi == time__uptime32.hi)) {
198 atomic_store_relaxed(&time__second32.lo, seclo);
199 atomic_store_relaxed(&time__uptime32.lo, uplo);
200 return;
201 }
202
203 atomic_store_relaxed(&time__second32.hi, 0xffffffff);
204 atomic_store_relaxed(&time__uptime32.hi, 0xffffffff);
205 membar_producer();
206 atomic_store_relaxed(&time__second32.lo, seclo);
207 atomic_store_relaxed(&time__uptime32.lo, uplo);
208 membar_producer();
209 atomic_store_relaxed(&time__second32.hi, sechi);
210 atomic_store_relaxed(&time__uptime32.hi, uphi);
211 }
212
213 time_t
getrealtime(void)214 getrealtime(void)
215 {
216 uint32_t lo, hi;
217
218 do {
219 for (;;) {
220 hi = atomic_load_relaxed(&time__second32.hi);
221 if (__predict_true(hi != 0xffffffff))
222 break;
223 SPINLOCK_BACKOFF_HOOK;
224 }
225 membar_consumer();
226 lo = atomic_load_relaxed(&time__second32.lo);
227 membar_consumer();
228 } while (hi != atomic_load_relaxed(&time__second32.hi));
229
230 return ((time_t)hi << 32) | lo;
231 }
232
233 time_t
getuptime(void)234 getuptime(void)
235 {
236 uint32_t lo, hi;
237
238 do {
239 for (;;) {
240 hi = atomic_load_relaxed(&time__uptime32.hi);
241 if (__predict_true(hi != 0xffffffff))
242 break;
243 SPINLOCK_BACKOFF_HOOK;
244 }
245 membar_consumer();
246 lo = atomic_load_relaxed(&time__uptime32.lo);
247 membar_consumer();
248 } while (hi != atomic_load_relaxed(&time__uptime32.hi));
249
250 return ((time_t)hi << 32) | lo;
251 }
252
253 time_t
getboottime(void)254 getboottime(void)
255 {
256
257 return getrealtime() - getuptime();
258 }
259
260 uint32_t
getuptime32(void)261 getuptime32(void)
262 {
263
264 return atomic_load_relaxed(&time__uptime32.lo);
265 }
266
267 #endif /* !defined(__HAVE_ATOMIC64_LOADSTORE) */
268
269 /*
270 * sysctl helper routine for kern.timercounter.hardware
271 */
272 static int
sysctl_kern_timecounter_hardware(SYSCTLFN_ARGS)273 sysctl_kern_timecounter_hardware(SYSCTLFN_ARGS)
274 {
275 struct sysctlnode node;
276 int error;
277 char newname[MAX_TCNAMELEN];
278 struct timecounter *newtc, *tc;
279
280 tc = timecounter;
281
282 strlcpy(newname, tc->tc_name, sizeof(newname));
283
284 node = *rnode;
285 node.sysctl_data = newname;
286 node.sysctl_size = sizeof(newname);
287
288 error = sysctl_lookup(SYSCTLFN_CALL(&node));
289
290 if (error ||
291 newp == NULL ||
292 strncmp(newname, tc->tc_name, sizeof(newname)) == 0)
293 return error;
294
295 if (l != NULL && (error = kauth_authorize_system(l->l_cred,
296 KAUTH_SYSTEM_TIME, KAUTH_REQ_SYSTEM_TIME_TIMECOUNTERS, newname,
297 NULL, NULL)) != 0)
298 return error;
299
300 if (!cold)
301 mutex_spin_enter(&timecounter_lock);
302 error = EINVAL;
303 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
304 if (strcmp(newname, newtc->tc_name) != 0)
305 continue;
306 /* Warm up new timecounter. */
307 (void)newtc->tc_get_timecount(newtc);
308 (void)newtc->tc_get_timecount(newtc);
309 timecounter = newtc;
310 error = 0;
311 break;
312 }
313 if (!cold)
314 mutex_spin_exit(&timecounter_lock);
315 return error;
316 }
317
318 static int
sysctl_kern_timecounter_choice(SYSCTLFN_ARGS)319 sysctl_kern_timecounter_choice(SYSCTLFN_ARGS)
320 {
321 char buf[MAX_TCNAMELEN+48];
322 char *where;
323 const char *spc;
324 struct timecounter *tc;
325 size_t needed, left, slen;
326 int error, mods;
327
328 if (newp != NULL)
329 return EPERM;
330 if (namelen != 0)
331 return EINVAL;
332
333 mutex_spin_enter(&timecounter_lock);
334 retry:
335 spc = "";
336 error = 0;
337 needed = 0;
338 left = *oldlenp;
339 where = oldp;
340 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
341 if (where == NULL) {
342 needed += sizeof(buf); /* be conservative */
343 } else {
344 slen = snprintf(buf, sizeof(buf), "%s%s(q=%d, f=%" PRId64
345 " Hz)", spc, tc->tc_name, tc->tc_quality,
346 tc->tc_frequency);
347 if (left < slen + 1)
348 break;
349 mods = timecounter_mods;
350 mutex_spin_exit(&timecounter_lock);
351 error = copyout(buf, where, slen + 1);
352 mutex_spin_enter(&timecounter_lock);
353 if (mods != timecounter_mods) {
354 goto retry;
355 }
356 spc = " ";
357 where += slen;
358 needed += slen;
359 left -= slen;
360 }
361 }
362 mutex_spin_exit(&timecounter_lock);
363
364 *oldlenp = needed;
365 return error;
366 }
367
368 SYSCTL_SETUP(sysctl_timecounter_setup, "sysctl timecounter setup")
369 {
370 const struct sysctlnode *node;
371
372 sysctl_createv(clog, 0, NULL, &node,
373 CTLFLAG_PERMANENT,
374 CTLTYPE_NODE, "timecounter",
375 SYSCTL_DESCR("time counter information"),
376 NULL, 0, NULL, 0,
377 CTL_KERN, CTL_CREATE, CTL_EOL);
378
379 if (node != NULL) {
380 sysctl_createv(clog, 0, NULL, NULL,
381 CTLFLAG_PERMANENT,
382 CTLTYPE_STRING, "choice",
383 SYSCTL_DESCR("available counters"),
384 sysctl_kern_timecounter_choice, 0, NULL, 0,
385 CTL_KERN, node->sysctl_num, CTL_CREATE, CTL_EOL);
386
387 sysctl_createv(clog, 0, NULL, NULL,
388 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
389 CTLTYPE_STRING, "hardware",
390 SYSCTL_DESCR("currently active time counter"),
391 sysctl_kern_timecounter_hardware, 0, NULL, MAX_TCNAMELEN,
392 CTL_KERN, node->sysctl_num, CTL_CREATE, CTL_EOL);
393
394 sysctl_createv(clog, 0, NULL, NULL,
395 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
396 CTLTYPE_INT, "timestepwarnings",
397 SYSCTL_DESCR("log time steps"),
398 NULL, 0, ×tepwarnings, 0,
399 CTL_KERN, node->sysctl_num, CTL_CREATE, CTL_EOL);
400 }
401 }
402
403 #ifdef TC_COUNTERS
404 #define TC_STATS(name) \
405 static struct evcnt n##name = \
406 EVCNT_INITIALIZER(EVCNT_TYPE_MISC, NULL, "timecounter", #name); \
407 EVCNT_ATTACH_STATIC(n##name)
408 TC_STATS(binuptime); TC_STATS(nanouptime); TC_STATS(microuptime);
409 TC_STATS(bintime); TC_STATS(nanotime); TC_STATS(microtime);
410 TC_STATS(getbinuptime); TC_STATS(getnanouptime); TC_STATS(getmicrouptime);
411 TC_STATS(getbintime); TC_STATS(getnanotime); TC_STATS(getmicrotime);
412 TC_STATS(setclock);
413 #define TC_COUNT(var) var.ev_count++
414 #undef TC_STATS
415 #else
416 #define TC_COUNT(var) /* nothing */
417 #endif /* TC_COUNTERS */
418
419 static void tc_windup(void);
420
421 /*
422 * Return the difference between the timehands' counter value now and what
423 * was when we copied it to the timehands' offset_count.
424 */
425 static inline u_int
tc_delta(struct timehands * th)426 tc_delta(struct timehands *th)
427 {
428 struct timecounter *tc;
429
430 tc = th->th_counter;
431 return (tc->tc_get_timecount(tc) -
432 th->th_offset_count) & tc->tc_counter_mask;
433 }
434
435 /*
436 * Functions for reading the time. We have to loop until we are sure that
437 * the timehands that we operated on was not updated under our feet. See
438 * the comment in <sys/timevar.h> for a description of these 12 functions.
439 */
440
441 void
binuptime(struct bintime * bt)442 binuptime(struct bintime *bt)
443 {
444 struct timehands *th;
445 lwp_t *l;
446 u_int lgen, gen;
447
448 TC_COUNT(nbinuptime);
449
450 /*
451 * Provide exclusion against tc_detach().
452 *
453 * We record the number of timecounter removals before accessing
454 * timecounter state. Note that the LWP can be using multiple
455 * "generations" at once, due to interrupts (interrupted while in
456 * this function). Hardware interrupts will borrow the interrupted
457 * LWP's l_tcgen value for this purpose, and can themselves be
458 * interrupted by higher priority interrupts. In this case we need
459 * to ensure that the oldest generation in use is recorded.
460 *
461 * splsched() is too expensive to use, so we take care to structure
462 * this code in such a way that it is not required. Likewise, we
463 * do not disable preemption.
464 *
465 * Memory barriers are also too expensive to use for such a
466 * performance critical function. The good news is that we do not
467 * need memory barriers for this type of exclusion, as the thread
468 * updating timecounter_removals will issue a broadcast cross call
469 * before inspecting our l_tcgen value (this elides memory ordering
470 * issues).
471 *
472 * XXX If the author of the above comment knows how to make it
473 * safe to avoid memory barriers around the access to
474 * th->th_generation, I'm all ears.
475 */
476 l = curlwp;
477 lgen = l->l_tcgen;
478 if (__predict_true(lgen == 0)) {
479 l->l_tcgen = timecounter_removals;
480 }
481 __insn_barrier();
482
483 do {
484 th = atomic_load_consume(&timehands);
485 gen = th->th_generation;
486 membar_consumer();
487 *bt = th->th_offset;
488 bintime_addx(bt, th->th_scale * tc_delta(th));
489 membar_consumer();
490 } while (gen == 0 || gen != th->th_generation);
491
492 __insn_barrier();
493 l->l_tcgen = lgen;
494 }
495
496 void
nanouptime(struct timespec * tsp)497 nanouptime(struct timespec *tsp)
498 {
499 struct bintime bt;
500
501 TC_COUNT(nnanouptime);
502 binuptime(&bt);
503 bintime2timespec(&bt, tsp);
504 }
505
506 void
microuptime(struct timeval * tvp)507 microuptime(struct timeval *tvp)
508 {
509 struct bintime bt;
510
511 TC_COUNT(nmicrouptime);
512 binuptime(&bt);
513 bintime2timeval(&bt, tvp);
514 }
515
516 void
bintime(struct bintime * bt)517 bintime(struct bintime *bt)
518 {
519 struct bintime boottime;
520
521 TC_COUNT(nbintime);
522 binuptime(bt);
523 getbinboottime(&boottime);
524 bintime_add(bt, &boottime);
525 }
526
527 void
nanotime(struct timespec * tsp)528 nanotime(struct timespec *tsp)
529 {
530 struct bintime bt;
531
532 TC_COUNT(nnanotime);
533 bintime(&bt);
534 bintime2timespec(&bt, tsp);
535 }
536
537 void
microtime(struct timeval * tvp)538 microtime(struct timeval *tvp)
539 {
540 struct bintime bt;
541
542 TC_COUNT(nmicrotime);
543 bintime(&bt);
544 bintime2timeval(&bt, tvp);
545 }
546
547 void
getbinuptime(struct bintime * bt)548 getbinuptime(struct bintime *bt)
549 {
550 struct timehands *th;
551 u_int gen;
552
553 TC_COUNT(ngetbinuptime);
554 do {
555 th = atomic_load_consume(&timehands);
556 gen = th->th_generation;
557 membar_consumer();
558 *bt = th->th_offset;
559 membar_consumer();
560 } while (gen == 0 || gen != th->th_generation);
561 }
562
563 void
getnanouptime(struct timespec * tsp)564 getnanouptime(struct timespec *tsp)
565 {
566 struct timehands *th;
567 u_int gen;
568
569 TC_COUNT(ngetnanouptime);
570 do {
571 th = atomic_load_consume(&timehands);
572 gen = th->th_generation;
573 membar_consumer();
574 bintime2timespec(&th->th_offset, tsp);
575 membar_consumer();
576 } while (gen == 0 || gen != th->th_generation);
577 }
578
579 void
getmicrouptime(struct timeval * tvp)580 getmicrouptime(struct timeval *tvp)
581 {
582 struct timehands *th;
583 u_int gen;
584
585 TC_COUNT(ngetmicrouptime);
586 do {
587 th = atomic_load_consume(&timehands);
588 gen = th->th_generation;
589 membar_consumer();
590 bintime2timeval(&th->th_offset, tvp);
591 membar_consumer();
592 } while (gen == 0 || gen != th->th_generation);
593 }
594
595 void
getbintime(struct bintime * bt)596 getbintime(struct bintime *bt)
597 {
598 struct timehands *th;
599 struct bintime boottime;
600 u_int gen;
601
602 TC_COUNT(ngetbintime);
603 do {
604 th = atomic_load_consume(&timehands);
605 gen = th->th_generation;
606 membar_consumer();
607 *bt = th->th_offset;
608 membar_consumer();
609 } while (gen == 0 || gen != th->th_generation);
610 getbinboottime(&boottime);
611 bintime_add(bt, &boottime);
612 }
613
614 static inline void
dogetnanotime(struct timespec * tsp)615 dogetnanotime(struct timespec *tsp)
616 {
617 struct timehands *th;
618 u_int gen;
619
620 TC_COUNT(ngetnanotime);
621 do {
622 th = atomic_load_consume(&timehands);
623 gen = th->th_generation;
624 membar_consumer();
625 *tsp = th->th_nanotime;
626 membar_consumer();
627 } while (gen == 0 || gen != th->th_generation);
628 }
629
630 void
getnanotime(struct timespec * tsp)631 getnanotime(struct timespec *tsp)
632 {
633
634 dogetnanotime(tsp);
635 }
636
637 void dtrace_getnanotime(struct timespec *tsp);
638
639 void
dtrace_getnanotime(struct timespec * tsp)640 dtrace_getnanotime(struct timespec *tsp)
641 {
642
643 dogetnanotime(tsp);
644 }
645
646 void
getmicrotime(struct timeval * tvp)647 getmicrotime(struct timeval *tvp)
648 {
649 struct timehands *th;
650 u_int gen;
651
652 TC_COUNT(ngetmicrotime);
653 do {
654 th = atomic_load_consume(&timehands);
655 gen = th->th_generation;
656 membar_consumer();
657 *tvp = th->th_microtime;
658 membar_consumer();
659 } while (gen == 0 || gen != th->th_generation);
660 }
661
662 void
getnanoboottime(struct timespec * tsp)663 getnanoboottime(struct timespec *tsp)
664 {
665 struct bintime bt;
666
667 getbinboottime(&bt);
668 bintime2timespec(&bt, tsp);
669 }
670
671 void
getmicroboottime(struct timeval * tvp)672 getmicroboottime(struct timeval *tvp)
673 {
674 struct bintime bt;
675
676 getbinboottime(&bt);
677 bintime2timeval(&bt, tvp);
678 }
679
680 void
getbinboottime(struct bintime * basep)681 getbinboottime(struct bintime *basep)
682 {
683 struct bintime base;
684 unsigned gen;
685
686 do {
687 /* Spin until the timebase isn't changing. */
688 while ((gen = atomic_load_relaxed(&timebase.gen)) & 1)
689 SPINLOCK_BACKOFF_HOOK;
690
691 /* Read out a snapshot of the timebase. */
692 membar_consumer();
693 base = timebase.bin;
694 membar_consumer();
695
696 /* Restart if it changed while we were reading. */
697 } while (gen != atomic_load_relaxed(&timebase.gen));
698
699 *basep = base;
700 }
701
702 /*
703 * Initialize a new timecounter and possibly use it.
704 */
705 void
tc_init(struct timecounter * tc)706 tc_init(struct timecounter *tc)
707 {
708 u_int u;
709
710 KASSERTMSG(tc->tc_next == NULL, "timecounter %s already initialised",
711 tc->tc_name);
712
713 u = tc->tc_frequency / tc->tc_counter_mask;
714 /* XXX: We need some margin here, 10% is a guess */
715 u *= 11;
716 u /= 10;
717 if (u > hz && tc->tc_quality >= 0) {
718 tc->tc_quality = -2000;
719 aprint_verbose(
720 "timecounter: Timecounter \"%s\" frequency %ju Hz",
721 tc->tc_name, (uintmax_t)tc->tc_frequency);
722 aprint_verbose(" -- Insufficient hz, needs at least %u\n", u);
723 } else if (tc->tc_quality >= 0 || bootverbose) {
724 aprint_verbose(
725 "timecounter: Timecounter \"%s\" frequency %ju Hz "
726 "quality %d\n", tc->tc_name, (uintmax_t)tc->tc_frequency,
727 tc->tc_quality);
728 }
729
730 mutex_spin_enter(&timecounter_lock);
731 tc->tc_next = timecounters;
732 timecounters = tc;
733 timecounter_mods++;
734 /*
735 * Never automatically use a timecounter with negative quality.
736 * Even though we run on the dummy counter, switching here may be
737 * worse since this timecounter may not be monotonous.
738 */
739 if (tc->tc_quality >= 0 && (tc->tc_quality > timecounter->tc_quality ||
740 (tc->tc_quality == timecounter->tc_quality &&
741 tc->tc_frequency > timecounter->tc_frequency))) {
742 (void)tc->tc_get_timecount(tc);
743 (void)tc->tc_get_timecount(tc);
744 timecounter = tc;
745 tc_windup();
746 }
747 mutex_spin_exit(&timecounter_lock);
748 }
749
750 /*
751 * Pick a new timecounter due to the existing counter going bad.
752 */
753 static void
tc_pick(void)754 tc_pick(void)
755 {
756 struct timecounter *best, *tc;
757
758 KASSERT(mutex_owned(&timecounter_lock));
759
760 for (best = tc = timecounters; tc != NULL; tc = tc->tc_next) {
761 if (tc->tc_quality > best->tc_quality)
762 best = tc;
763 else if (tc->tc_quality < best->tc_quality)
764 continue;
765 else if (tc->tc_frequency > best->tc_frequency)
766 best = tc;
767 }
768 (void)best->tc_get_timecount(best);
769 (void)best->tc_get_timecount(best);
770 timecounter = best;
771 }
772
773 /*
774 * A timecounter has gone bad, arrange to pick a new one at the next
775 * clock tick.
776 */
777 void
tc_gonebad(struct timecounter * tc)778 tc_gonebad(struct timecounter *tc)
779 {
780
781 tc->tc_quality = -100;
782 membar_producer();
783 atomic_inc_uint(&timecounter_bad);
784 }
785
786 /*
787 * Stop using a timecounter and remove it from the timecounters list.
788 */
789 int
tc_detach(struct timecounter * target)790 tc_detach(struct timecounter *target)
791 {
792 struct timecounter *tc;
793 struct timecounter **tcp = NULL;
794 int removals;
795 lwp_t *l;
796
797 /* First, find the timecounter. */
798 mutex_spin_enter(&timecounter_lock);
799 for (tcp = &timecounters, tc = timecounters;
800 tc != NULL;
801 tcp = &tc->tc_next, tc = tc->tc_next) {
802 if (tc == target)
803 break;
804 }
805 if (tc == NULL) {
806 mutex_spin_exit(&timecounter_lock);
807 return ESRCH;
808 }
809
810 /* And now, remove it. */
811 *tcp = tc->tc_next;
812 if (timecounter == target) {
813 tc_pick();
814 tc_windup();
815 }
816 timecounter_mods++;
817 removals = timecounter_removals++;
818 mutex_spin_exit(&timecounter_lock);
819
820 /*
821 * We now have to determine if any threads in the system are still
822 * making use of this timecounter.
823 *
824 * We issue a broadcast cross call to elide memory ordering issues,
825 * then scan all LWPs in the system looking at each's timecounter
826 * generation number. We need to see a value of zero (not actively
827 * using a timecounter) or a value greater than our removal value.
828 *
829 * We may race with threads that read `timecounter_removals' and
830 * and then get preempted before updating `l_tcgen'. This is not
831 * a problem, since it means that these threads have not yet started
832 * accessing timecounter state. All we do need is one clean
833 * snapshot of the system where every thread appears not to be using
834 * old timecounter state.
835 */
836 for (;;) {
837 xc_barrier(0);
838
839 mutex_enter(&proc_lock);
840 LIST_FOREACH(l, &alllwp, l_list) {
841 if (l->l_tcgen == 0 || l->l_tcgen > removals) {
842 /*
843 * Not using timecounter or old timecounter
844 * state at time of our xcall or later.
845 */
846 continue;
847 }
848 break;
849 }
850 mutex_exit(&proc_lock);
851
852 /*
853 * If the timecounter is still in use, wait at least 10ms
854 * before retrying.
855 */
856 if (l == NULL) {
857 break;
858 }
859 (void)kpause("tcdetach", false, mstohz(10), NULL);
860 }
861
862 tc->tc_next = NULL;
863 return 0;
864 }
865
866 /* Report the frequency of the current timecounter. */
867 uint64_t
tc_getfrequency(void)868 tc_getfrequency(void)
869 {
870
871 return atomic_load_consume(&timehands)->th_counter->tc_frequency;
872 }
873
874 /*
875 * Step our concept of UTC. This is done by modifying our estimate of
876 * when we booted.
877 */
878 void
tc_setclock(const struct timespec * ts)879 tc_setclock(const struct timespec *ts)
880 {
881 struct timespec ts2;
882 struct bintime bt, bt2;
883
884 mutex_spin_enter(&timecounter_lock);
885 TC_COUNT(nsetclock);
886 binuptime(&bt2);
887 timespec2bintime(ts, &bt);
888 bintime_sub(&bt, &bt2);
889 bintime_add(&bt2, &timebase.bin);
890 timebase.gen |= 1; /* change in progress */
891 membar_producer();
892 timebase.bin = bt;
893 membar_producer();
894 timebase.gen++; /* commit change */
895 tc_windup();
896 mutex_spin_exit(&timecounter_lock);
897
898 if (timestepwarnings) {
899 bintime2timespec(&bt2, &ts2);
900 log(LOG_INFO,
901 "Time stepped from %lld.%09ld to %lld.%09ld\n",
902 (long long)ts2.tv_sec, ts2.tv_nsec,
903 (long long)ts->tv_sec, ts->tv_nsec);
904 }
905 }
906
907 /*
908 * Initialize the next struct timehands in the ring and make
909 * it the active timehands. Along the way we might switch to a different
910 * timecounter and/or do seconds processing in NTP. Slightly magic.
911 */
912 static void
tc_windup(void)913 tc_windup(void)
914 {
915 struct bintime bt;
916 struct timehands *th, *tho;
917 uint64_t scale;
918 u_int delta, ncount, ogen;
919 int i, s_update;
920 time_t t;
921
922 KASSERT(mutex_owned(&timecounter_lock));
923
924 s_update = 0;
925
926 /*
927 * Make the next timehands a copy of the current one, but do not
928 * overwrite the generation or next pointer. While we update
929 * the contents, the generation must be zero. Ensure global
930 * visibility of the generation before proceeding.
931 */
932 tho = timehands;
933 th = tho->th_next;
934 ogen = th->th_generation;
935 th->th_generation = 0;
936 membar_producer();
937 bcopy(tho, th, offsetof(struct timehands, th_generation));
938
939 /*
940 * Capture a timecounter delta on the current timecounter and if
941 * changing timecounters, a counter value from the new timecounter.
942 * Update the offset fields accordingly.
943 */
944 delta = tc_delta(th);
945 if (th->th_counter != timecounter)
946 ncount = timecounter->tc_get_timecount(timecounter);
947 else
948 ncount = 0;
949 th->th_offset_count += delta;
950 bintime_addx(&th->th_offset, th->th_scale * delta);
951
952 /*
953 * Hardware latching timecounters may not generate interrupts on
954 * PPS events, so instead we poll them. There is a finite risk that
955 * the hardware might capture a count which is later than the one we
956 * got above, and therefore possibly in the next NTP second which might
957 * have a different rate than the current NTP second. It doesn't
958 * matter in practice.
959 */
960 if (tho->th_counter->tc_poll_pps)
961 tho->th_counter->tc_poll_pps(tho->th_counter);
962
963 /*
964 * Deal with NTP second processing. The for loop normally
965 * iterates at most once, but in extreme situations it might
966 * keep NTP sane if timeouts are not run for several seconds.
967 * At boot, the time step can be large when the TOD hardware
968 * has been read, so on really large steps, we call
969 * ntp_update_second only twice. We need to call it twice in
970 * case we missed a leap second.
971 * If NTP is not compiled in ntp_update_second still calculates
972 * the adjustment resulting from adjtime() calls.
973 */
974 bt = th->th_offset;
975 bintime_add(&bt, &timebase.bin);
976 i = bt.sec - tho->th_microtime.tv_sec;
977 if (i > LARGE_STEP)
978 i = 2;
979 for (; i > 0; i--) {
980 t = bt.sec;
981 ntp_update_second(&th->th_adjustment, &bt.sec);
982 s_update = 1;
983 if (bt.sec != t) {
984 timebase.gen |= 1; /* change in progress */
985 membar_producer();
986 timebase.bin.sec += bt.sec - t;
987 membar_producer();
988 timebase.gen++; /* commit change */
989 }
990 }
991
992 /* Update the UTC timestamps used by the get*() functions. */
993 /* XXX shouldn't do this here. Should force non-`get' versions. */
994 bintime2timeval(&bt, &th->th_microtime);
995 bintime2timespec(&bt, &th->th_nanotime);
996 /* Now is a good time to change timecounters. */
997 if (th->th_counter != timecounter) {
998 th->th_counter = timecounter;
999 th->th_offset_count = ncount;
1000 s_update = 1;
1001 }
1002
1003 /*-
1004 * Recalculate the scaling factor. We want the number of 1/2^64
1005 * fractions of a second per period of the hardware counter, taking
1006 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
1007 * processing provides us with.
1008 *
1009 * The th_adjustment is nanoseconds per second with 32 bit binary
1010 * fraction and we want 64 bit binary fraction of second:
1011 *
1012 * x = a * 2^32 / 10^9 = a * 4.294967296
1013 *
1014 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
1015 * we can only multiply by about 850 without overflowing, but that
1016 * leaves suitably precise fractions for multiply before divide.
1017 *
1018 * Divide before multiply with a fraction of 2199/512 results in a
1019 * systematic undercompensation of 10PPM of th_adjustment. On a
1020 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
1021 *
1022 * We happily sacrifice the lowest of the 64 bits of our result
1023 * to the goddess of code clarity.
1024 *
1025 */
1026 if (s_update) {
1027 scale = (uint64_t)1 << 63;
1028 scale += (th->th_adjustment / 1024) * 2199;
1029 scale /= th->th_counter->tc_frequency;
1030 th->th_scale = scale * 2;
1031 }
1032 /*
1033 * Now that the struct timehands is again consistent, set the new
1034 * generation number, making sure to not make it zero. Ensure
1035 * changes are globally visible before changing.
1036 */
1037 if (++ogen == 0)
1038 ogen = 1;
1039 membar_producer();
1040 th->th_generation = ogen;
1041
1042 /*
1043 * Go live with the new struct timehands. Ensure changes are
1044 * globally visible before changing.
1045 */
1046 setrealuptime(th->th_microtime.tv_sec, th->th_offset.sec);
1047 atomic_store_release(&timehands, th);
1048
1049 /*
1050 * Force users of the old timehand to move on. This is
1051 * necessary for MP systems; we need to ensure that the
1052 * consumers will move away from the old timehand before
1053 * we begin updating it again when we eventually wrap
1054 * around.
1055 */
1056 if (++tho->th_generation == 0)
1057 tho->th_generation = 1;
1058 }
1059
1060 /*
1061 * RFC 2783 PPS-API implementation.
1062 */
1063
1064 int
pps_ioctl(u_long cmd,void * data,struct pps_state * pps)1065 pps_ioctl(u_long cmd, void *data, struct pps_state *pps)
1066 {
1067 pps_params_t *app;
1068 pps_info_t *pipi;
1069 #ifdef PPS_SYNC
1070 int *epi;
1071 #endif
1072
1073 KASSERT(mutex_owned(&timecounter_lock));
1074
1075 KASSERT(pps != NULL);
1076
1077 switch (cmd) {
1078 case PPS_IOC_CREATE:
1079 return 0;
1080 case PPS_IOC_DESTROY:
1081 return 0;
1082 case PPS_IOC_SETPARAMS:
1083 app = (pps_params_t *)data;
1084 if (app->mode & ~pps->ppscap)
1085 return EINVAL;
1086 pps->ppsparam = *app;
1087 return 0;
1088 case PPS_IOC_GETPARAMS:
1089 app = (pps_params_t *)data;
1090 *app = pps->ppsparam;
1091 app->api_version = PPS_API_VERS_1;
1092 return 0;
1093 case PPS_IOC_GETCAP:
1094 *(int*)data = pps->ppscap;
1095 return 0;
1096 case PPS_IOC_FETCH:
1097 pipi = (pps_info_t *)data;
1098 pps->ppsinfo.current_mode = pps->ppsparam.mode;
1099 *pipi = pps->ppsinfo;
1100 return 0;
1101 case PPS_IOC_KCBIND:
1102 #ifdef PPS_SYNC
1103 epi = (int *)data;
1104 /* XXX Only root should be able to do this */
1105 if (*epi & ~pps->ppscap)
1106 return EINVAL;
1107 pps->kcmode = *epi;
1108 return 0;
1109 #else
1110 return EOPNOTSUPP;
1111 #endif
1112 default:
1113 return EPASSTHROUGH;
1114 }
1115 }
1116
1117 void
pps_init(struct pps_state * pps)1118 pps_init(struct pps_state *pps)
1119 {
1120
1121 KASSERT(mutex_owned(&timecounter_lock));
1122
1123 pps->ppscap |= PPS_TSFMT_TSPEC;
1124 if (pps->ppscap & PPS_CAPTUREASSERT)
1125 pps->ppscap |= PPS_OFFSETASSERT;
1126 if (pps->ppscap & PPS_CAPTURECLEAR)
1127 pps->ppscap |= PPS_OFFSETCLEAR;
1128 }
1129
1130 /*
1131 * capture a timestamp in the pps structure
1132 */
1133 void
pps_capture(struct pps_state * pps)1134 pps_capture(struct pps_state *pps)
1135 {
1136 struct timehands *th;
1137
1138 KASSERT(mutex_owned(&timecounter_lock));
1139 KASSERT(pps != NULL);
1140
1141 th = timehands;
1142 pps->capgen = th->th_generation;
1143 pps->capth = th;
1144 pps->capcount = (uint64_t)tc_delta(th) + th->th_offset_count;
1145 if (pps->capgen != th->th_generation)
1146 pps->capgen = 0;
1147 }
1148
1149 #ifdef PPS_DEBUG
1150 int ppsdebug = 0;
1151 #endif
1152
1153 /*
1154 * process a pps_capture()ed event
1155 */
1156 void
pps_event(struct pps_state * pps,int event)1157 pps_event(struct pps_state *pps, int event)
1158 {
1159 pps_ref_event(pps, event, NULL, PPS_REFEVNT_PPS|PPS_REFEVNT_CAPTURE);
1160 }
1161
1162 /*
1163 * extended pps api / kernel pll/fll entry point
1164 *
1165 * feed reference time stamps to PPS engine
1166 *
1167 * will simulate a PPS event and feed
1168 * the NTP PLL/FLL if requested.
1169 *
1170 * the ref time stamps should be roughly once
1171 * a second but do not need to be exactly in phase
1172 * with the UTC second but should be close to it.
1173 * this relaxation of requirements allows callout
1174 * driven timestamping mechanisms to feed to pps
1175 * capture/kernel pll logic.
1176 *
1177 * calling pattern is:
1178 * pps_capture() (for PPS_REFEVNT_{CAPTURE|CAPCUR})
1179 * read timestamp from reference source
1180 * pps_ref_event()
1181 *
1182 * supported refmodes:
1183 * PPS_REFEVNT_CAPTURE
1184 * use system timestamp of pps_capture()
1185 * PPS_REFEVNT_CURRENT
1186 * use system timestamp of this call
1187 * PPS_REFEVNT_CAPCUR
1188 * use average of read capture and current system time stamp
1189 * PPS_REFEVNT_PPS
1190 * assume timestamp on second mark - ref_ts is ignored
1191 *
1192 */
1193
1194 void
pps_ref_event(struct pps_state * pps,int event,struct bintime * ref_ts,int refmode)1195 pps_ref_event(struct pps_state *pps,
1196 int event,
1197 struct bintime *ref_ts,
1198 int refmode
1199 )
1200 {
1201 struct bintime bt; /* current time */
1202 struct bintime btd; /* time difference */
1203 struct bintime bt_ref; /* reference time */
1204 struct timespec ts, *tsp, *osp;
1205 struct timehands *th;
1206 uint64_t tcount, acount, dcount, *pcount;
1207 int foff, gen;
1208 #ifdef PPS_SYNC
1209 int fhard;
1210 #endif
1211 pps_seq_t *pseq;
1212
1213 KASSERT(mutex_owned(&timecounter_lock));
1214
1215 KASSERT(pps != NULL);
1216
1217 /* pick up current time stamp if needed */
1218 if (refmode & (PPS_REFEVNT_CURRENT|PPS_REFEVNT_CAPCUR)) {
1219 /* pick up current time stamp */
1220 th = timehands;
1221 gen = th->th_generation;
1222 tcount = (uint64_t)tc_delta(th) + th->th_offset_count;
1223 if (gen != th->th_generation)
1224 gen = 0;
1225
1226 /* If the timecounter was wound up underneath us, bail out. */
1227 if (pps->capgen == 0 ||
1228 pps->capgen != pps->capth->th_generation ||
1229 gen == 0 ||
1230 gen != pps->capgen) {
1231 #ifdef PPS_DEBUG
1232 if (ppsdebug & 0x1) {
1233 log(LOG_DEBUG,
1234 "pps_ref_event(pps=%p, event=%d, ...): DROP (wind-up)\n",
1235 pps, event);
1236 }
1237 #endif
1238 return;
1239 }
1240 } else {
1241 tcount = 0; /* keep GCC happy */
1242 }
1243
1244 #ifdef PPS_DEBUG
1245 if (ppsdebug & 0x1) {
1246 struct timespec tmsp;
1247
1248 if (ref_ts == NULL) {
1249 tmsp.tv_sec = 0;
1250 tmsp.tv_nsec = 0;
1251 } else {
1252 bintime2timespec(ref_ts, &tmsp);
1253 }
1254
1255 log(LOG_DEBUG,
1256 "pps_ref_event(pps=%p, event=%d, ref_ts=%"PRIi64
1257 ".%09"PRIi32", refmode=0x%1x)\n",
1258 pps, event, tmsp.tv_sec, (int32_t)tmsp.tv_nsec, refmode);
1259 }
1260 #endif
1261
1262 /* setup correct event references */
1263 if (event == PPS_CAPTUREASSERT) {
1264 tsp = &pps->ppsinfo.assert_timestamp;
1265 osp = &pps->ppsparam.assert_offset;
1266 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
1267 #ifdef PPS_SYNC
1268 fhard = pps->kcmode & PPS_CAPTUREASSERT;
1269 #endif
1270 pcount = &pps->ppscount[0];
1271 pseq = &pps->ppsinfo.assert_sequence;
1272 } else {
1273 tsp = &pps->ppsinfo.clear_timestamp;
1274 osp = &pps->ppsparam.clear_offset;
1275 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
1276 #ifdef PPS_SYNC
1277 fhard = pps->kcmode & PPS_CAPTURECLEAR;
1278 #endif
1279 pcount = &pps->ppscount[1];
1280 pseq = &pps->ppsinfo.clear_sequence;
1281 }
1282
1283 /* determine system time stamp according to refmode */
1284 dcount = 0; /* keep GCC happy */
1285 switch (refmode & PPS_REFEVNT_RMASK) {
1286 case PPS_REFEVNT_CAPTURE:
1287 acount = pps->capcount; /* use capture timestamp */
1288 break;
1289
1290 case PPS_REFEVNT_CURRENT:
1291 acount = tcount; /* use current timestamp */
1292 break;
1293
1294 case PPS_REFEVNT_CAPCUR:
1295 /*
1296 * calculate counter value between pps_capture() and
1297 * pps_ref_event()
1298 */
1299 dcount = tcount - pps->capcount;
1300 acount = (dcount / 2) + pps->capcount;
1301 break;
1302
1303 default: /* ignore call error silently */
1304 return;
1305 }
1306
1307 /*
1308 * If the timecounter changed, we cannot compare the count values, so
1309 * we have to drop the rest of the PPS-stuff until the next event.
1310 */
1311 if (pps->ppstc != pps->capth->th_counter) {
1312 pps->ppstc = pps->capth->th_counter;
1313 pps->capcount = acount;
1314 *pcount = acount;
1315 pps->ppscount[2] = acount;
1316 #ifdef PPS_DEBUG
1317 if (ppsdebug & 0x1) {
1318 log(LOG_DEBUG,
1319 "pps_ref_event(pps=%p, event=%d, ...): DROP (time-counter change)\n",
1320 pps, event);
1321 }
1322 #endif
1323 return;
1324 }
1325
1326 pps->capcount = acount;
1327
1328 /* Convert the count to a bintime. */
1329 bt = pps->capth->th_offset;
1330 bintime_addx(&bt, pps->capth->th_scale * (acount - pps->capth->th_offset_count));
1331 bintime_add(&bt, &timebase.bin);
1332
1333 if ((refmode & PPS_REFEVNT_PPS) == 0) {
1334 /* determine difference to reference time stamp */
1335 bt_ref = *ref_ts;
1336
1337 btd = bt;
1338 bintime_sub(&btd, &bt_ref);
1339
1340 /*
1341 * simulate a PPS timestamp by dropping the fraction
1342 * and applying the offset
1343 */
1344 if (bt.frac >= (uint64_t)1<<63) /* skip to nearest second */
1345 bt.sec++;
1346 bt.frac = 0;
1347 bintime_add(&bt, &btd);
1348 } else {
1349 /*
1350 * create ref_ts from current time -
1351 * we are supposed to be called on
1352 * the second mark
1353 */
1354 bt_ref = bt;
1355 if (bt_ref.frac >= (uint64_t)1<<63) /* skip to nearest second */
1356 bt_ref.sec++;
1357 bt_ref.frac = 0;
1358 }
1359
1360 /* convert bintime to timestamp */
1361 bintime2timespec(&bt, &ts);
1362
1363 /* If the timecounter was wound up underneath us, bail out. */
1364 if (pps->capgen != pps->capth->th_generation)
1365 return;
1366
1367 /* store time stamp */
1368 *pcount = pps->capcount;
1369 (*pseq)++;
1370 *tsp = ts;
1371
1372 /* add offset correction */
1373 if (foff) {
1374 timespecadd(tsp, osp, tsp);
1375 if (tsp->tv_nsec < 0) {
1376 tsp->tv_nsec += 1000000000;
1377 tsp->tv_sec -= 1;
1378 }
1379 }
1380
1381 #ifdef PPS_DEBUG
1382 if (ppsdebug & 0x2) {
1383 struct timespec ts2;
1384 struct timespec ts3;
1385
1386 bintime2timespec(&bt_ref, &ts2);
1387
1388 bt.sec = 0;
1389 bt.frac = 0;
1390
1391 if (refmode & PPS_REFEVNT_CAPCUR) {
1392 bintime_addx(&bt, pps->capth->th_scale * dcount);
1393 }
1394 bintime2timespec(&bt, &ts3);
1395
1396 log(LOG_DEBUG, "ref_ts=%"PRIi64".%09"PRIi32
1397 ", ts=%"PRIi64".%09"PRIi32", read latency=%"PRIi64" ns\n",
1398 ts2.tv_sec, (int32_t)ts2.tv_nsec,
1399 tsp->tv_sec, (int32_t)tsp->tv_nsec,
1400 timespec2ns(&ts3));
1401 }
1402 #endif
1403
1404 #ifdef PPS_SYNC
1405 if (fhard) {
1406 uint64_t scale;
1407 uint64_t div;
1408
1409 /*
1410 * Feed the NTP PLL/FLL.
1411 * The FLL wants to know how many (hardware) nanoseconds
1412 * elapsed since the previous event (mod 1 second) thus
1413 * we are actually looking at the frequency difference scaled
1414 * in nsec.
1415 * As the counter time stamps are not truly at 1Hz
1416 * we need to scale the count by the elapsed
1417 * reference time.
1418 * valid sampling interval: [0.5..2[ sec
1419 */
1420
1421 /* calculate elapsed raw count */
1422 tcount = pps->capcount - pps->ppscount[2];
1423 pps->ppscount[2] = pps->capcount;
1424 tcount &= pps->capth->th_counter->tc_counter_mask;
1425
1426 /* calculate elapsed ref time */
1427 btd = bt_ref;
1428 bintime_sub(&btd, &pps->ref_time);
1429 pps->ref_time = bt_ref;
1430
1431 /* check that we stay below 2 sec */
1432 if (btd.sec < 0 || btd.sec > 1)
1433 return;
1434
1435 /* we want at least 0.5 sec between samples */
1436 if (btd.sec == 0 && btd.frac < (uint64_t)1<<63)
1437 return;
1438
1439 /*
1440 * calculate cycles per period by multiplying
1441 * the frequency with the elapsed period
1442 * we pick a fraction of 30 bits
1443 * ~1ns resolution for elapsed time
1444 */
1445 div = (uint64_t)btd.sec << 30;
1446 div |= (btd.frac >> 34) & (((uint64_t)1 << 30) - 1);
1447 div *= pps->capth->th_counter->tc_frequency;
1448 div >>= 30;
1449
1450 if (div == 0) /* safeguard */
1451 return;
1452
1453 scale = (uint64_t)1 << 63;
1454 scale /= div;
1455 scale *= 2;
1456
1457 bt.sec = 0;
1458 bt.frac = 0;
1459 bintime_addx(&bt, scale * tcount);
1460 bintime2timespec(&bt, &ts);
1461
1462 #ifdef PPS_DEBUG
1463 if (ppsdebug & 0x4) {
1464 struct timespec ts2;
1465 int64_t df;
1466
1467 bintime2timespec(&bt_ref, &ts2);
1468 df = timespec2ns(&ts);
1469 if (df > 500000000)
1470 df -= 1000000000;
1471 log(LOG_DEBUG, "hardpps: ref_ts=%"PRIi64
1472 ".%09"PRIi32", ts=%"PRIi64".%09"PRIi32
1473 ", freqdiff=%"PRIi64" ns/s\n",
1474 ts2.tv_sec, (int32_t)ts2.tv_nsec,
1475 tsp->tv_sec, (int32_t)tsp->tv_nsec,
1476 df);
1477 }
1478 #endif
1479
1480 hardpps(tsp, timespec2ns(&ts));
1481 }
1482 #endif
1483 }
1484
1485 /*
1486 * Timecounters need to be updated every so often to prevent the hardware
1487 * counter from overflowing. Updating also recalculates the cached values
1488 * used by the get*() family of functions, so their precision depends on
1489 * the update frequency.
1490 */
1491
1492 static int tc_tick;
1493
1494 void
tc_ticktock(void)1495 tc_ticktock(void)
1496 {
1497 static int count;
1498
1499 if (++count < tc_tick)
1500 return;
1501 count = 0;
1502 mutex_spin_enter(&timecounter_lock);
1503 if (__predict_false(timecounter_bad != 0)) {
1504 /* An existing timecounter has gone bad, pick a new one. */
1505 (void)atomic_swap_uint(&timecounter_bad, 0);
1506 if (timecounter->tc_quality < 0) {
1507 tc_pick();
1508 }
1509 }
1510 tc_windup();
1511 mutex_spin_exit(&timecounter_lock);
1512 }
1513
1514 void
inittimecounter(void)1515 inittimecounter(void)
1516 {
1517 u_int p;
1518
1519 mutex_init(&timecounter_lock, MUTEX_DEFAULT, IPL_HIGH);
1520
1521 /*
1522 * Set the initial timeout to
1523 * max(1, <approx. number of hardclock ticks in a millisecond>).
1524 * People should probably not use the sysctl to set the timeout
1525 * to smaller than its initial value, since that value is the
1526 * smallest reasonable one. If they want better timestamps they
1527 * should use the non-"get"* functions.
1528 */
1529 if (hz > 1000)
1530 tc_tick = (hz + 500) / 1000;
1531 else
1532 tc_tick = 1;
1533 p = (tc_tick * 1000000) / hz;
1534 aprint_verbose("timecounter: Timecounters tick every %d.%03u msec\n",
1535 p / 1000, p % 1000);
1536
1537 /* warm up new timecounter (again) and get rolling. */
1538 (void)timecounter->tc_get_timecount(timecounter);
1539 (void)timecounter->tc_get_timecount(timecounter);
1540 }
1541