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 * ----------------------------------------------------------------------------
10 #include <sys/cdefs.h>
11 __FBSDID("$FreeBSD$");
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>
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.
30 #define LARGE_STEP 200
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
39 dummy_get_timecount(struct timecounter *tc)
46 static struct timecounter dummy_timecounter = {
47 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
51 /* These fields must be initialized by the driver. */
52 struct timecounter *th_counter;
53 int64_t th_adjustment;
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;
64 static 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 = {
77 (uint64_t)-1 / 1000000,
86 static struct timehands *volatile timehands = &th0;
87 struct timecounter *timecounter = &dummy_timecounter;
88 static struct timecounter *timecounters = &dummy_timecounter;
90 volatile time_t time_second = 1;
91 volatile time_t time_uptime = 1;
93 static struct bintime boottimebin;
94 struct timeval boottime;
95 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
96 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
97 NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
99 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
100 SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc, CTLFLAG_RW, 0, "");
102 static int timestepwarnings;
103 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
104 ×tepwarnings, 0, "Log time steps");
106 static void tc_windup(void);
107 static void cpu_tick_calibrate(int);
110 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
115 if (req->flags & SCTL_MASK32) {
116 tv[0] = boottime.tv_sec;
117 tv[1] = boottime.tv_usec;
118 return SYSCTL_OUT(req, tv, sizeof(tv));
121 return SYSCTL_OUT(req, &boottime, sizeof(boottime));
125 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
128 struct timecounter *tc = arg1;
130 ncount = tc->tc_get_timecount(tc);
131 return sysctl_handle_int(oidp, &ncount, 0, req);
135 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
138 struct timecounter *tc = arg1;
140 freq = tc->tc_frequency;
141 return sysctl_handle_quad(oidp, &freq, 0, req);
145 * Return the difference between the timehands' counter value now and what
146 * was when we copied it to the timehands' offset_count.
148 static __inline u_int
149 tc_delta(struct timehands *th)
151 struct timecounter *tc;
154 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
155 tc->tc_counter_mask);
159 * Functions for reading the time. We have to loop until we are sure that
160 * the timehands that we operated on was not updated under our feet. See
161 * the comment in <sys/time.h> for a description of these 12 functions.
165 binuptime(struct bintime *bt)
167 struct timehands *th;
172 gen = th->th_generation;
174 bintime_addx(bt, th->th_scale * tc_delta(th));
175 } while (gen == 0 || gen != th->th_generation);
179 nanouptime(struct timespec *tsp)
184 bintime2timespec(&bt, tsp);
188 microuptime(struct timeval *tvp)
193 bintime2timeval(&bt, tvp);
197 bintime(struct bintime *bt)
201 bintime_add(bt, &boottimebin);
205 nanotime(struct timespec *tsp)
210 bintime2timespec(&bt, tsp);
214 microtime(struct timeval *tvp)
219 bintime2timeval(&bt, tvp);
223 getbinuptime(struct bintime *bt)
225 struct timehands *th;
230 gen = th->th_generation;
232 } while (gen == 0 || gen != th->th_generation);
236 getnanouptime(struct timespec *tsp)
238 struct timehands *th;
243 gen = th->th_generation;
244 bintime2timespec(&th->th_offset, tsp);
245 } while (gen == 0 || gen != th->th_generation);
249 getmicrouptime(struct timeval *tvp)
251 struct timehands *th;
256 gen = th->th_generation;
257 bintime2timeval(&th->th_offset, tvp);
258 } while (gen == 0 || gen != th->th_generation);
262 getbintime(struct bintime *bt)
264 struct timehands *th;
269 gen = th->th_generation;
271 } while (gen == 0 || gen != th->th_generation);
272 bintime_add(bt, &boottimebin);
276 getnanotime(struct timespec *tsp)
278 struct timehands *th;
283 gen = th->th_generation;
284 *tsp = th->th_nanotime;
285 } while (gen == 0 || gen != th->th_generation);
289 getmicrotime(struct timeval *tvp)
291 struct timehands *th;
296 gen = th->th_generation;
297 *tvp = th->th_microtime;
298 } while (gen == 0 || gen != th->th_generation);
302 * Initialize a new timecounter and possibly use it.
305 tc_init(struct timecounter *tc)
308 struct sysctl_oid *tc_root;
310 u = tc->tc_frequency / tc->tc_counter_mask;
311 /* XXX: We need some margin here, 10% is a guess */
314 if (u > hz && tc->tc_quality >= 0) {
315 tc->tc_quality = -2000;
317 printf("Timecounter \"%s\" frequency %ju Hz",
318 tc->tc_name, (uintmax_t)tc->tc_frequency);
319 printf(" -- Insufficient hz, needs at least %u\n", u);
321 } else if (tc->tc_quality >= 0 || bootverbose) {
322 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
323 tc->tc_name, (uintmax_t)tc->tc_frequency,
327 tc->tc_next = timecounters;
330 * Set up sysctl tree for this counter.
332 tc_root = SYSCTL_ADD_NODE(NULL,
333 SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
334 CTLFLAG_RW, 0, "timecounter description");
335 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
336 "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
337 "mask for implemented bits");
338 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
339 "counter", CTLTYPE_UINT | CTLFLAG_RD, tc, sizeof(*tc),
340 sysctl_kern_timecounter_get, "IU", "current timecounter value");
341 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
342 "frequency", CTLTYPE_QUAD | CTLFLAG_RD, tc, sizeof(*tc),
343 sysctl_kern_timecounter_freq, "QU", "timecounter frequency");
344 SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
345 "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
346 "goodness of time counter");
348 * Never automatically use a timecounter with negative quality.
349 * Even though we run on the dummy counter, switching here may be
350 * worse since this timecounter may not be monotonous.
352 if (tc->tc_quality < 0)
354 if (tc->tc_quality < timecounter->tc_quality)
356 if (tc->tc_quality == timecounter->tc_quality &&
357 tc->tc_frequency < timecounter->tc_frequency)
359 (void)tc->tc_get_timecount(tc);
360 (void)tc->tc_get_timecount(tc);
364 /* Report the frequency of the current timecounter. */
366 tc_getfrequency(void)
369 return (timehands->th_counter->tc_frequency);
373 * Step our concept of UTC. This is done by modifying our estimate of
378 tc_setclock(struct timespec *ts)
380 struct timespec tbef, taft;
381 struct bintime bt, bt2;
383 cpu_tick_calibrate(1);
385 timespec2bintime(ts, &bt);
387 bintime_sub(&bt, &bt2);
388 bintime_add(&bt2, &boottimebin);
390 bintime2timeval(&bt, &boottime);
392 /* XXX fiddle all the little crinkly bits around the fiords... */
395 if (timestepwarnings) {
397 "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
398 (intmax_t)tbef.tv_sec, tbef.tv_nsec,
399 (intmax_t)taft.tv_sec, taft.tv_nsec,
400 (intmax_t)ts->tv_sec, ts->tv_nsec);
402 cpu_tick_calibrate(1);
406 * Initialize the next struct timehands in the ring and make
407 * it the active timehands. Along the way we might switch to a different
408 * timecounter and/or do seconds processing in NTP. Slightly magic.
414 struct timehands *th, *tho;
416 u_int delta, ncount, ogen;
421 * Make the next timehands a copy of the current one, but do not
422 * overwrite the generation or next pointer. While we update
423 * the contents, the generation must be zero.
427 ogen = th->th_generation;
428 th->th_generation = 0;
429 bcopy(tho, th, offsetof(struct timehands, th_generation));
432 * Capture a timecounter delta on the current timecounter and if
433 * changing timecounters, a counter value from the new timecounter.
434 * Update the offset fields accordingly.
436 delta = tc_delta(th);
437 if (th->th_counter != timecounter)
438 ncount = timecounter->tc_get_timecount(timecounter);
441 th->th_offset_count += delta;
442 th->th_offset_count &= th->th_counter->tc_counter_mask;
443 while (delta > th->th_counter->tc_frequency) {
444 /* Eat complete unadjusted seconds. */
445 delta -= th->th_counter->tc_frequency;
448 if ((delta > th->th_counter->tc_frequency / 2) &&
449 (th->th_scale * delta < ((uint64_t)1 << 63))) {
450 /* The product th_scale * delta just barely overflows. */
453 bintime_addx(&th->th_offset, th->th_scale * delta);
456 * Hardware latching timecounters may not generate interrupts on
457 * PPS events, so instead we poll them. There is a finite risk that
458 * the hardware might capture a count which is later than the one we
459 * got above, and therefore possibly in the next NTP second which might
460 * have a different rate than the current NTP second. It doesn't
461 * matter in practice.
463 if (tho->th_counter->tc_poll_pps)
464 tho->th_counter->tc_poll_pps(tho->th_counter);
467 * Deal with NTP second processing. The for loop normally
468 * iterates at most once, but in extreme situations it might
469 * keep NTP sane if timeouts are not run for several seconds.
470 * At boot, the time step can be large when the TOD hardware
471 * has been read, so on really large steps, we call
472 * ntp_update_second only twice. We need to call it twice in
473 * case we missed a leap second.
476 bintime_add(&bt, &boottimebin);
477 i = bt.sec - tho->th_microtime.tv_sec;
482 ntp_update_second(&th->th_adjustment, &bt.sec);
484 boottimebin.sec += bt.sec - t;
486 /* Update the UTC timestamps used by the get*() functions. */
487 /* XXX shouldn't do this here. Should force non-`get' versions. */
488 bintime2timeval(&bt, &th->th_microtime);
489 bintime2timespec(&bt, &th->th_nanotime);
491 /* Now is a good time to change timecounters. */
492 if (th->th_counter != timecounter) {
493 th->th_counter = timecounter;
494 th->th_offset_count = ncount;
498 * Recalculate the scaling factor. We want the number of 1/2^64
499 * fractions of a second per period of the hardware counter, taking
500 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
501 * processing provides us with.
503 * The th_adjustment is nanoseconds per second with 32 bit binary
504 * fraction and we want 64 bit binary fraction of second:
506 * x = a * 2^32 / 10^9 = a * 4.294967296
508 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
509 * we can only multiply by about 850 without overflowing, that
510 * leaves no suitably precise fractions for multiply before divide.
512 * Divide before multiply with a fraction of 2199/512 results in a
513 * systematic undercompensation of 10PPM of th_adjustment. On a
514 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
516 * We happily sacrifice the lowest of the 64 bits of our result
517 * to the goddess of code clarity.
520 scale = (u_int64_t)1 << 63;
521 scale += (th->th_adjustment / 1024) * 2199;
522 scale /= th->th_counter->tc_frequency;
523 th->th_scale = scale * 2;
526 * Now that the struct timehands is again consistent, set the new
527 * generation number, making sure to not make it zero.
531 th->th_generation = ogen;
533 /* Go live with the new struct timehands. */
534 time_second = th->th_microtime.tv_sec;
535 time_uptime = th->th_offset.sec;
539 /* Report or change the active timecounter hardware. */
541 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
544 struct timecounter *newtc, *tc;
548 strlcpy(newname, tc->tc_name, sizeof(newname));
550 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
551 if (error != 0 || req->newptr == NULL ||
552 strcmp(newname, tc->tc_name) == 0)
554 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
555 if (strcmp(newname, newtc->tc_name) != 0)
558 /* Warm up new timecounter. */
559 (void)newtc->tc_get_timecount(newtc);
560 (void)newtc->tc_get_timecount(newtc);
568 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
569 0, 0, sysctl_kern_timecounter_hardware, "A",
570 "Timecounter hardware selected");
573 /* Report or change the active timecounter hardware. */
575 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
578 struct timecounter *tc;
583 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
584 sprintf(buf, "%s%s(%d)",
585 spc, tc->tc_name, tc->tc_quality);
586 error = SYSCTL_OUT(req, buf, strlen(buf));
592 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
593 0, 0, sysctl_kern_timecounter_choice, "A", "Timecounter hardware detected");
596 * RFC 2783 PPS-API implementation.
600 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
603 struct pps_fetch_args *fapi;
605 struct pps_kcbind_args *kapi;
608 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
612 case PPS_IOC_DESTROY:
614 case PPS_IOC_SETPARAMS:
615 app = (pps_params_t *)data;
616 if (app->mode & ~pps->ppscap)
618 pps->ppsparam = *app;
620 case PPS_IOC_GETPARAMS:
621 app = (pps_params_t *)data;
622 *app = pps->ppsparam;
623 app->api_version = PPS_API_VERS_1;
626 *(int*)data = pps->ppscap;
629 fapi = (struct pps_fetch_args *)data;
630 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
632 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
634 pps->ppsinfo.current_mode = pps->ppsparam.mode;
635 fapi->pps_info_buf = pps->ppsinfo;
639 kapi = (struct pps_kcbind_args *)data;
640 /* XXX Only root should be able to do this */
641 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
643 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
645 if (kapi->edge & ~pps->ppscap)
647 pps->kcmode = kapi->edge;
658 pps_init(struct pps_state *pps)
660 pps->ppscap |= PPS_TSFMT_TSPEC;
661 if (pps->ppscap & PPS_CAPTUREASSERT)
662 pps->ppscap |= PPS_OFFSETASSERT;
663 if (pps->ppscap & PPS_CAPTURECLEAR)
664 pps->ppscap |= PPS_OFFSETCLEAR;
668 pps_capture(struct pps_state *pps)
670 struct timehands *th;
672 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
674 pps->capgen = th->th_generation;
676 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
677 if (pps->capgen != th->th_generation)
682 pps_event(struct pps_state *pps, int event)
685 struct timespec ts, *tsp, *osp;
686 u_int tcount, *pcount;
690 KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
691 /* If the timecounter was wound up underneath us, bail out. */
692 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
695 /* Things would be easier with arrays. */
696 if (event == PPS_CAPTUREASSERT) {
697 tsp = &pps->ppsinfo.assert_timestamp;
698 osp = &pps->ppsparam.assert_offset;
699 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
700 fhard = pps->kcmode & PPS_CAPTUREASSERT;
701 pcount = &pps->ppscount[0];
702 pseq = &pps->ppsinfo.assert_sequence;
704 tsp = &pps->ppsinfo.clear_timestamp;
705 osp = &pps->ppsparam.clear_offset;
706 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
707 fhard = pps->kcmode & PPS_CAPTURECLEAR;
708 pcount = &pps->ppscount[1];
709 pseq = &pps->ppsinfo.clear_sequence;
713 * If the timecounter changed, we cannot compare the count values, so
714 * we have to drop the rest of the PPS-stuff until the next event.
716 if (pps->ppstc != pps->capth->th_counter) {
717 pps->ppstc = pps->capth->th_counter;
718 *pcount = pps->capcount;
719 pps->ppscount[2] = pps->capcount;
723 /* Convert the count to a timespec. */
724 tcount = pps->capcount - pps->capth->th_offset_count;
725 tcount &= pps->capth->th_counter->tc_counter_mask;
726 bt = pps->capth->th_offset;
727 bintime_addx(&bt, pps->capth->th_scale * tcount);
728 bintime_add(&bt, &boottimebin);
729 bintime2timespec(&bt, &ts);
731 /* If the timecounter was wound up underneath us, bail out. */
732 if (pps->capgen != pps->capth->th_generation)
735 *pcount = pps->capcount;
740 timespecadd(tsp, osp);
741 if (tsp->tv_nsec < 0) {
742 tsp->tv_nsec += 1000000000;
751 * Feed the NTP PLL/FLL.
752 * The FLL wants to know how many (hardware) nanoseconds
753 * elapsed since the previous event.
755 tcount = pps->capcount - pps->ppscount[2];
756 pps->ppscount[2] = pps->capcount;
757 tcount &= pps->capth->th_counter->tc_counter_mask;
758 scale = (u_int64_t)1 << 63;
759 scale /= pps->capth->th_counter->tc_frequency;
763 bintime_addx(&bt, scale * tcount);
764 bintime2timespec(&bt, &ts);
765 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
771 * Timecounters need to be updated every so often to prevent the hardware
772 * counter from overflowing. Updating also recalculates the cached values
773 * used by the get*() family of functions, so their precision depends on
774 * the update frequency.
778 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0,
779 "Approximate number of hardclock ticks in a millisecond");
785 static time_t last_calib;
787 if (++count < tc_tick)
791 if (time_uptime != last_calib && !(time_uptime & 0xf)) {
792 cpu_tick_calibrate(0);
793 last_calib = time_uptime;
798 inittimecounter(void *dummy)
803 * Set the initial timeout to
804 * max(1, <approx. number of hardclock ticks in a millisecond>).
805 * People should probably not use the sysctl to set the timeout
806 * to smaller than its inital value, since that value is the
807 * smallest reasonable one. If they want better timestamps they
808 * should use the non-"get"* functions.
811 tc_tick = (hz + 500) / 1000;
814 p = (tc_tick * 1000000) / hz;
815 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
817 /* warm up new timecounter (again) and get rolling. */
818 (void)timecounter->tc_get_timecount(timecounter);
819 (void)timecounter->tc_get_timecount(timecounter);
822 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
824 /* Cpu tick handling -------------------------------------------------*/
826 static int cpu_tick_variable;
827 static uint64_t cpu_tick_frequency;
832 static uint64_t base;
833 static unsigned last;
835 struct timecounter *tc;
837 tc = timehands->th_counter;
838 u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
840 base += (uint64_t)tc->tc_counter_mask + 1;
846 * This function gets called every 16 seconds on only one designated
847 * CPU in the system from hardclock() via tc_ticktock().
849 * Whenever the real time clock is stepped we get called with reset=1
850 * to make sure we handle suspend/resume and similar events correctly.
854 cpu_tick_calibrate(int reset)
856 static uint64_t c_last;
857 uint64_t c_this, c_delta;
858 static struct bintime t_last;
859 struct bintime t_this, t_delta;
863 /* The clock was stepped, abort & reset */
868 /* we don't calibrate fixed rate cputicks */
869 if (!cpu_tick_variable)
872 getbinuptime(&t_this);
873 c_this = cpu_ticks();
874 if (t_last.sec != 0) {
875 c_delta = c_this - c_last;
877 bintime_sub(&t_delta, &t_last);
879 * Validate that 16 +/- 1/256 seconds passed.
880 * After division by 16 this gives us a precision of
881 * roughly 250PPM which is sufficient
883 if (t_delta.sec > 16 || (
884 t_delta.sec == 16 && t_delta.frac >= (0x01LL << 56))) {
887 printf("t_delta %ju.%016jx too long\n",
888 (uintmax_t)t_delta.sec,
889 (uintmax_t)t_delta.frac);
890 } else if (t_delta.sec < 15 ||
891 (t_delta.sec == 15 && t_delta.frac <= (0xffLL << 56))) {
894 printf("t_delta %ju.%016jx too short\n",
895 (uintmax_t)t_delta.sec,
896 (uintmax_t)t_delta.frac);
901 * 2^(64-20) / 16[s] =
903 * 17.592.186.044.416 / 16 =
904 * 1.099.511.627.776 [Hz]
906 divi = t_delta.sec << 20;
907 divi |= t_delta.frac >> (64 - 20);
910 if (c_delta > cpu_tick_frequency) {
911 if (0 && bootverbose)
912 printf("cpu_tick increased to %ju Hz\n",
914 cpu_tick_frequency = c_delta;
923 set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
927 cpu_ticks = tc_cpu_ticks;
929 cpu_tick_frequency = freq;
930 cpu_tick_variable = var;
939 if (cpu_ticks == tc_cpu_ticks)
940 return (tc_getfrequency());
941 return (cpu_tick_frequency);
945 * We need to be slightly careful converting cputicks to microseconds.
946 * There is plenty of margin in 64 bits of microseconds (half a million
947 * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
948 * before divide conversion (to retain precision) we find that the
949 * margin shrinks to 1.5 hours (one millionth of 146y).
950 * With a three prong approach we never lose significant bits, no
951 * matter what the cputick rate and length of timeinterval is.
955 cputick2usec(uint64_t tick)
958 if (tick > 18446744073709551LL) /* floor(2^64 / 1000) */
959 return (tick / (cpu_tickrate() / 1000000LL));
960 else if (tick > 18446744073709LL) /* floor(2^64 / 1000000) */
961 return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
963 return ((tick * 1000000LL) / cpu_tickrate());
966 cpu_tick_f *cpu_ticks = tc_cpu_ticks;