FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tc.c
1 /*-
2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
8 */
9
10 #include <sys/cdefs.h>
11 __FBSDID("$FreeBSD: releng/5.3/sys/kern/kern_tc.c 136588 2004-10-16 08:43:07Z cvs2svn $");
12
13 #include "opt_ntp.h"
14
15 #include <sys/param.h>
16 #include <sys/kernel.h>
17 #include <sys/sysctl.h>
18 #include <sys/syslog.h>
19 #include <sys/systm.h>
20 #include <sys/timepps.h>
21 #include <sys/timetc.h>
22 #include <sys/timex.h>
23
24 /*
25 * A large step happens on boot. This constant detects such steps.
26 * It is relatively small so that ntp_update_second gets called enough
27 * in the typical 'missed a couple of seconds' case, but doesn't loop
28 * forever when the time step is large.
29 */
30 #define LARGE_STEP 200
31
32 /*
33 * Implement a dummy timecounter which we can use until we get a real one
34 * in the air. This allows the console and other early stuff to use
35 * time services.
36 */
37
38 static u_int
39 dummy_get_timecount(struct timecounter *tc)
40 {
41 static u_int now;
42
43 return (++now);
44 }
45
46 static struct timecounter dummy_timecounter = {
47 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
48 };
49
50 struct timehands {
51 /* These fields must be initialized by the driver. */
52 struct timecounter *th_counter;
53 int64_t th_adjustment;
54 u_int64_t th_scale;
55 u_int th_offset_count;
56 struct bintime th_offset;
57 struct timeval th_microtime;
58 struct timespec th_nanotime;
59 /* Fields not to be copied in tc_windup start with th_generation. */
60 volatile u_int th_generation;
61 struct timehands *th_next;
62 };
63
64 extern struct timehands th0;
65 static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
66 static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
67 static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
68 static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
69 static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
70 static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
71 static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
72 static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
73 static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
74 static struct timehands th0 = {
75 &dummy_timecounter,
76 0,
77 (uint64_t)-1 / 1000000,
78 0,
79 {1, 0},
80 {0, 0},
81 {0, 0},
82 1,
83 &th1
84 };
85
86 static struct timehands *volatile timehands = &th0;
87 struct timecounter *timecounter = &dummy_timecounter;
88 static struct timecounter *timecounters = &dummy_timecounter;
89
90 time_t time_second = 1;
91 time_t time_uptime = 0;
92
93 static struct bintime boottimebin;
94 struct timeval boottime;
95 SYSCTL_STRUCT(_kern, KERN_BOOTTIME, boottime, CTLFLAG_RD,
96 &boottime, timeval, "System boottime");
97
98 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
99
100 static int timestepwarnings;
101 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
102 ×tepwarnings, 0, "");
103
104 #define TC_STATS(foo) \
105 static u_int foo; \
106 SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\
107 struct __hack
108
109 TC_STATS(nbinuptime); TC_STATS(nnanouptime); TC_STATS(nmicrouptime);
110 TC_STATS(nbintime); TC_STATS(nnanotime); TC_STATS(nmicrotime);
111 TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime);
112 TC_STATS(ngetbintime); TC_STATS(ngetnanotime); TC_STATS(ngetmicrotime);
113 TC_STATS(nsetclock);
114
115 #undef TC_STATS
116
117 static void tc_windup(void);
118
119 /*
120 * Return the difference between the timehands' counter value now and what
121 * was when we copied it to the timehands' offset_count.
122 */
123 static __inline u_int
124 tc_delta(struct timehands *th)
125 {
126 struct timecounter *tc;
127
128 tc = th->th_counter;
129 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
130 tc->tc_counter_mask);
131 }
132
133 /*
134 * Functions for reading the time. We have to loop until we are sure that
135 * the timehands that we operated on was not updated under our feet. See
136 * the comment in <sys/time.h> for a description of these 12 functions.
137 */
138
139 void
140 binuptime(struct bintime *bt)
141 {
142 struct timehands *th;
143 u_int gen;
144
145 nbinuptime++;
146 do {
147 th = timehands;
148 gen = th->th_generation;
149 *bt = th->th_offset;
150 bintime_addx(bt, th->th_scale * tc_delta(th));
151 } while (gen == 0 || gen != th->th_generation);
152 }
153
154 void
155 nanouptime(struct timespec *tsp)
156 {
157 struct bintime bt;
158
159 nnanouptime++;
160 binuptime(&bt);
161 bintime2timespec(&bt, tsp);
162 }
163
164 void
165 microuptime(struct timeval *tvp)
166 {
167 struct bintime bt;
168
169 nmicrouptime++;
170 binuptime(&bt);
171 bintime2timeval(&bt, tvp);
172 }
173
174 void
175 bintime(struct bintime *bt)
176 {
177
178 nbintime++;
179 binuptime(bt);
180 bintime_add(bt, &boottimebin);
181 }
182
183 void
184 nanotime(struct timespec *tsp)
185 {
186 struct bintime bt;
187
188 nnanotime++;
189 bintime(&bt);
190 bintime2timespec(&bt, tsp);
191 }
192
193 void
194 microtime(struct timeval *tvp)
195 {
196 struct bintime bt;
197
198 nmicrotime++;
199 bintime(&bt);
200 bintime2timeval(&bt, tvp);
201 }
202
203 void
204 getbinuptime(struct bintime *bt)
205 {
206 struct timehands *th;
207 u_int gen;
208
209 ngetbinuptime++;
210 do {
211 th = timehands;
212 gen = th->th_generation;
213 *bt = th->th_offset;
214 } while (gen == 0 || gen != th->th_generation);
215 }
216
217 void
218 getnanouptime(struct timespec *tsp)
219 {
220 struct timehands *th;
221 u_int gen;
222
223 ngetnanouptime++;
224 do {
225 th = timehands;
226 gen = th->th_generation;
227 bintime2timespec(&th->th_offset, tsp);
228 } while (gen == 0 || gen != th->th_generation);
229 }
230
231 void
232 getmicrouptime(struct timeval *tvp)
233 {
234 struct timehands *th;
235 u_int gen;
236
237 ngetmicrouptime++;
238 do {
239 th = timehands;
240 gen = th->th_generation;
241 bintime2timeval(&th->th_offset, tvp);
242 } while (gen == 0 || gen != th->th_generation);
243 }
244
245 void
246 getbintime(struct bintime *bt)
247 {
248 struct timehands *th;
249 u_int gen;
250
251 ngetbintime++;
252 do {
253 th = timehands;
254 gen = th->th_generation;
255 *bt = th->th_offset;
256 } while (gen == 0 || gen != th->th_generation);
257 bintime_add(bt, &boottimebin);
258 }
259
260 void
261 getnanotime(struct timespec *tsp)
262 {
263 struct timehands *th;
264 u_int gen;
265
266 ngetnanotime++;
267 do {
268 th = timehands;
269 gen = th->th_generation;
270 *tsp = th->th_nanotime;
271 } while (gen == 0 || gen != th->th_generation);
272 }
273
274 void
275 getmicrotime(struct timeval *tvp)
276 {
277 struct timehands *th;
278 u_int gen;
279
280 ngetmicrotime++;
281 do {
282 th = timehands;
283 gen = th->th_generation;
284 *tvp = th->th_microtime;
285 } while (gen == 0 || gen != th->th_generation);
286 }
287
288 /*
289 * Initialize a new timecounter and possibly use it.
290 */
291 void
292 tc_init(struct timecounter *tc)
293 {
294 u_int u;
295
296 u = tc->tc_frequency / tc->tc_counter_mask;
297 /* XXX: We need some margin here, 10% is a guess */
298 u *= 11;
299 u /= 10;
300 if (u > hz && tc->tc_quality >= 0) {
301 tc->tc_quality = -2000;
302 if (bootverbose) {
303 printf("Timecounter \"%s\" frequency %ju Hz",
304 tc->tc_name, (uintmax_t)tc->tc_frequency);
305 printf(" -- Insufficient hz, needs at least %u\n", u);
306 }
307 } else if (tc->tc_quality >= 0 || bootverbose) {
308 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
309 tc->tc_name, (uintmax_t)tc->tc_frequency,
310 tc->tc_quality);
311 }
312
313 tc->tc_next = timecounters;
314 timecounters = tc;
315 /*
316 * Never automatically use a timecounter with negative quality.
317 * Even though we run on the dummy counter, switching here may be
318 * worse since this timecounter may not be monotonous.
319 */
320 if (tc->tc_quality < 0)
321 return;
322 if (tc->tc_quality < timecounter->tc_quality)
323 return;
324 if (tc->tc_quality == timecounter->tc_quality &&
325 tc->tc_frequency < timecounter->tc_frequency)
326 return;
327 (void)tc->tc_get_timecount(tc);
328 (void)tc->tc_get_timecount(tc);
329 timecounter = tc;
330 }
331
332 /* Report the frequency of the current timecounter. */
333 u_int64_t
334 tc_getfrequency(void)
335 {
336
337 return (timehands->th_counter->tc_frequency);
338 }
339
340 /*
341 * Step our concept of UTC. This is done by modifying our estimate of
342 * when we booted.
343 * XXX: not locked.
344 */
345 void
346 tc_setclock(struct timespec *ts)
347 {
348 struct timespec ts2;
349 struct bintime bt, bt2;
350
351 nsetclock++;
352 binuptime(&bt2);
353 timespec2bintime(ts, &bt);
354 bintime_sub(&bt, &bt2);
355 bintime_add(&bt2, &boottimebin);
356 boottimebin = bt;
357 bintime2timeval(&bt, &boottime);
358
359 /* XXX fiddle all the little crinkly bits around the fiords... */
360 tc_windup();
361 if (timestepwarnings) {
362 bintime2timespec(&bt2, &ts2);
363 log(LOG_INFO, "Time stepped from %jd.%09ld to %jd.%09ld\n",
364 (intmax_t)ts2.tv_sec, ts2.tv_nsec,
365 (intmax_t)ts->tv_sec, ts->tv_nsec);
366 }
367 }
368
369 /*
370 * Initialize the next struct timehands in the ring and make
371 * it the active timehands. Along the way we might switch to a different
372 * timecounter and/or do seconds processing in NTP. Slightly magic.
373 */
374 static void
375 tc_windup(void)
376 {
377 struct bintime bt;
378 struct timehands *th, *tho;
379 u_int64_t scale;
380 u_int delta, ncount, ogen;
381 int i;
382 time_t t;
383
384 /*
385 * Make the next timehands a copy of the current one, but do not
386 * overwrite the generation or next pointer. While we update
387 * the contents, the generation must be zero.
388 */
389 tho = timehands;
390 th = tho->th_next;
391 ogen = th->th_generation;
392 th->th_generation = 0;
393 bcopy(tho, th, offsetof(struct timehands, th_generation));
394
395 /*
396 * Capture a timecounter delta on the current timecounter and if
397 * changing timecounters, a counter value from the new timecounter.
398 * Update the offset fields accordingly.
399 */
400 delta = tc_delta(th);
401 if (th->th_counter != timecounter)
402 ncount = timecounter->tc_get_timecount(timecounter);
403 else
404 ncount = 0;
405 th->th_offset_count += delta;
406 th->th_offset_count &= th->th_counter->tc_counter_mask;
407 bintime_addx(&th->th_offset, th->th_scale * delta);
408
409 /*
410 * Hardware latching timecounters may not generate interrupts on
411 * PPS events, so instead we poll them. There is a finite risk that
412 * the hardware might capture a count which is later than the one we
413 * got above, and therefore possibly in the next NTP second which might
414 * have a different rate than the current NTP second. It doesn't
415 * matter in practice.
416 */
417 if (tho->th_counter->tc_poll_pps)
418 tho->th_counter->tc_poll_pps(tho->th_counter);
419
420 /*
421 * Deal with NTP second processing. The for loop normally
422 * iterates at most once, but in extreme situations it might
423 * keep NTP sane if timeouts are not run for several seconds.
424 * At boot, the time step can be large when the TOD hardware
425 * has been read, so on really large steps, we call
426 * ntp_update_second only twice. We need to call it twice in
427 * case we missed a leap second.
428 */
429 bt = th->th_offset;
430 bintime_add(&bt, &boottimebin);
431 i = bt.sec - tho->th_microtime.tv_sec;
432 if (i > LARGE_STEP)
433 i = 2;
434 for (; i > 0; i--) {
435 t = bt.sec;
436 ntp_update_second(&th->th_adjustment, &bt.sec);
437 if (bt.sec != t)
438 boottimebin.sec += bt.sec - t;
439 }
440 /* Update the UTC timestamps used by the get*() functions. */
441 /* XXX shouldn't do this here. Should force non-`get' versions. */
442 bintime2timeval(&bt, &th->th_microtime);
443 bintime2timespec(&bt, &th->th_nanotime);
444
445 /* Now is a good time to change timecounters. */
446 if (th->th_counter != timecounter) {
447 th->th_counter = timecounter;
448 th->th_offset_count = ncount;
449 }
450
451 /*-
452 * Recalculate the scaling factor. We want the number of 1/2^64
453 * fractions of a second per period of the hardware counter, taking
454 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
455 * processing provides us with.
456 *
457 * The th_adjustment is nanoseconds per second with 32 bit binary
458 * fraction and we want 64 bit binary fraction of second:
459 *
460 * x = a * 2^32 / 10^9 = a * 4.294967296
461 *
462 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
463 * we can only multiply by about 850 without overflowing, but that
464 * leaves suitably precise fractions for multiply before divide.
465 *
466 * Divide before multiply with a fraction of 2199/512 results in a
467 * systematic undercompensation of 10PPM of th_adjustment. On a
468 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
469 *
470 * We happily sacrifice the lowest of the 64 bits of our result
471 * to the goddess of code clarity.
472 *
473 */
474 scale = (u_int64_t)1 << 63;
475 scale += (th->th_adjustment / 1024) * 2199;
476 scale /= th->th_counter->tc_frequency;
477 th->th_scale = scale * 2;
478
479 /*
480 * Now that the struct timehands is again consistent, set the new
481 * generation number, making sure to not make it zero.
482 */
483 if (++ogen == 0)
484 ogen = 1;
485 th->th_generation = ogen;
486
487 /* Go live with the new struct timehands. */
488 time_second = th->th_microtime.tv_sec;
489 time_uptime = th->th_offset.sec;
490 timehands = th;
491 }
492
493 /* Report or change the active timecounter hardware. */
494 static int
495 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
496 {
497 char newname[32];
498 struct timecounter *newtc, *tc;
499 int error;
500
501 tc = timecounter;
502 strlcpy(newname, tc->tc_name, sizeof(newname));
503
504 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
505 if (error != 0 || req->newptr == NULL ||
506 strcmp(newname, tc->tc_name) == 0)
507 return (error);
508 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
509 if (strcmp(newname, newtc->tc_name) != 0)
510 continue;
511
512 /* Warm up new timecounter. */
513 (void)newtc->tc_get_timecount(newtc);
514 (void)newtc->tc_get_timecount(newtc);
515
516 timecounter = newtc;
517 return (0);
518 }
519 return (EINVAL);
520 }
521
522 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
523 0, 0, sysctl_kern_timecounter_hardware, "A", "");
524
525
526 /* Report or change the active timecounter hardware. */
527 static int
528 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
529 {
530 char buf[32], *spc;
531 struct timecounter *tc;
532 int error;
533
534 spc = "";
535 error = 0;
536 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
537 sprintf(buf, "%s%s(%d)",
538 spc, tc->tc_name, tc->tc_quality);
539 error = SYSCTL_OUT(req, buf, strlen(buf));
540 spc = " ";
541 }
542 return (error);
543 }
544
545 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
546 0, 0, sysctl_kern_timecounter_choice, "A", "");
547
548 /*
549 * RFC 2783 PPS-API implementation.
550 */
551
552 int
553 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
554 {
555 pps_params_t *app;
556 struct pps_fetch_args *fapi;
557 #ifdef PPS_SYNC
558 struct pps_kcbind_args *kapi;
559 #endif
560
561 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
562 switch (cmd) {
563 case PPS_IOC_CREATE:
564 return (0);
565 case PPS_IOC_DESTROY:
566 return (0);
567 case PPS_IOC_SETPARAMS:
568 app = (pps_params_t *)data;
569 if (app->mode & ~pps->ppscap)
570 return (EINVAL);
571 pps->ppsparam = *app;
572 return (0);
573 case PPS_IOC_GETPARAMS:
574 app = (pps_params_t *)data;
575 *app = pps->ppsparam;
576 app->api_version = PPS_API_VERS_1;
577 return (0);
578 case PPS_IOC_GETCAP:
579 *(int*)data = pps->ppscap;
580 return (0);
581 case PPS_IOC_FETCH:
582 fapi = (struct pps_fetch_args *)data;
583 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
584 return (EINVAL);
585 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
586 return (EOPNOTSUPP);
587 pps->ppsinfo.current_mode = pps->ppsparam.mode;
588 fapi->pps_info_buf = pps->ppsinfo;
589 return (0);
590 case PPS_IOC_KCBIND:
591 #ifdef PPS_SYNC
592 kapi = (struct pps_kcbind_args *)data;
593 /* XXX Only root should be able to do this */
594 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
595 return (EINVAL);
596 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
597 return (EINVAL);
598 if (kapi->edge & ~pps->ppscap)
599 return (EINVAL);
600 pps->kcmode = kapi->edge;
601 return (0);
602 #else
603 return (EOPNOTSUPP);
604 #endif
605 default:
606 return (ENOTTY);
607 }
608 }
609
610 void
611 pps_init(struct pps_state *pps)
612 {
613 pps->ppscap |= PPS_TSFMT_TSPEC;
614 if (pps->ppscap & PPS_CAPTUREASSERT)
615 pps->ppscap |= PPS_OFFSETASSERT;
616 if (pps->ppscap & PPS_CAPTURECLEAR)
617 pps->ppscap |= PPS_OFFSETCLEAR;
618 }
619
620 void
621 pps_capture(struct pps_state *pps)
622 {
623 struct timehands *th;
624
625 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
626 th = timehands;
627 pps->capgen = th->th_generation;
628 pps->capth = th;
629 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
630 if (pps->capgen != th->th_generation)
631 pps->capgen = 0;
632 }
633
634 void
635 pps_event(struct pps_state *pps, int event)
636 {
637 struct bintime bt;
638 struct timespec ts, *tsp, *osp;
639 u_int tcount, *pcount;
640 int foff, fhard;
641 pps_seq_t *pseq;
642
643 KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
644 /* If the timecounter was wound up underneath us, bail out. */
645 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
646 return;
647
648 /* Things would be easier with arrays. */
649 if (event == PPS_CAPTUREASSERT) {
650 tsp = &pps->ppsinfo.assert_timestamp;
651 osp = &pps->ppsparam.assert_offset;
652 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
653 fhard = pps->kcmode & PPS_CAPTUREASSERT;
654 pcount = &pps->ppscount[0];
655 pseq = &pps->ppsinfo.assert_sequence;
656 } else {
657 tsp = &pps->ppsinfo.clear_timestamp;
658 osp = &pps->ppsparam.clear_offset;
659 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
660 fhard = pps->kcmode & PPS_CAPTURECLEAR;
661 pcount = &pps->ppscount[1];
662 pseq = &pps->ppsinfo.clear_sequence;
663 }
664
665 /*
666 * If the timecounter changed, we cannot compare the count values, so
667 * we have to drop the rest of the PPS-stuff until the next event.
668 */
669 if (pps->ppstc != pps->capth->th_counter) {
670 pps->ppstc = pps->capth->th_counter;
671 *pcount = pps->capcount;
672 pps->ppscount[2] = pps->capcount;
673 return;
674 }
675
676 /* Convert the count to a timespec. */
677 tcount = pps->capcount - pps->capth->th_offset_count;
678 tcount &= pps->capth->th_counter->tc_counter_mask;
679 bt = pps->capth->th_offset;
680 bintime_addx(&bt, pps->capth->th_scale * tcount);
681 bintime_add(&bt, &boottimebin);
682 bintime2timespec(&bt, &ts);
683
684 /* If the timecounter was wound up underneath us, bail out. */
685 if (pps->capgen != pps->capth->th_generation)
686 return;
687
688 *pcount = pps->capcount;
689 (*pseq)++;
690 *tsp = ts;
691
692 if (foff) {
693 timespecadd(tsp, osp);
694 if (tsp->tv_nsec < 0) {
695 tsp->tv_nsec += 1000000000;
696 tsp->tv_sec -= 1;
697 }
698 }
699 #ifdef PPS_SYNC
700 if (fhard) {
701 u_int64_t scale;
702
703 /*
704 * Feed the NTP PLL/FLL.
705 * The FLL wants to know how many (hardware) nanoseconds
706 * elapsed since the previous event.
707 */
708 tcount = pps->capcount - pps->ppscount[2];
709 pps->ppscount[2] = pps->capcount;
710 tcount &= pps->capth->th_counter->tc_counter_mask;
711 scale = (u_int64_t)1 << 63;
712 scale /= pps->capth->th_counter->tc_frequency;
713 scale *= 2;
714 bt.sec = 0;
715 bt.frac = 0;
716 bintime_addx(&bt, scale * tcount);
717 bintime2timespec(&bt, &ts);
718 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
719 }
720 #endif
721 }
722
723 /*
724 * Timecounters need to be updated every so often to prevent the hardware
725 * counter from overflowing. Updating also recalculates the cached values
726 * used by the get*() family of functions, so their precision depends on
727 * the update frequency.
728 */
729
730 static int tc_tick;
731 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0, "");
732
733 void
734 tc_ticktock(void)
735 {
736 static int count;
737
738 if (++count < tc_tick)
739 return;
740 count = 0;
741 tc_windup();
742 }
743
744 static void
745 inittimecounter(void *dummy)
746 {
747 u_int p;
748
749 /*
750 * Set the initial timeout to
751 * max(1, <approx. number of hardclock ticks in a millisecond>).
752 * People should probably not use the sysctl to set the timeout
753 * to smaller than its inital value, since that value is the
754 * smallest reasonable one. If they want better timestamps they
755 * should use the non-"get"* functions.
756 */
757 if (hz > 1000)
758 tc_tick = (hz + 500) / 1000;
759 else
760 tc_tick = 1;
761 p = (tc_tick * 1000000) / hz;
762 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
763
764 /* warm up new timecounter (again) and get rolling. */
765 (void)timecounter->tc_get_timecount(timecounter);
766 (void)timecounter->tc_get_timecount(timecounter);
767 }
768
769 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL)
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