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 int tc_min_ticktock_freq = 1;
92 time_t time_second = 1;
93 time_t time_uptime = 1;
95 struct bintime boottimebin;
96 struct timeval boottime;
97 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
98 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
99 NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
101 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
102 SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc, CTLFLAG_RW, 0, "");
104 static int timestepwarnings;
105 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
106 ×tepwarnings, 0, "Log time steps");
108 static void tc_windup(void);
109 static void cpu_tick_calibrate(int);
112 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
117 if (req->flags & SCTL_MASK32) {
118 tv[0] = boottime.tv_sec;
119 tv[1] = boottime.tv_usec;
120 return SYSCTL_OUT(req, tv, sizeof(tv));
123 return SYSCTL_OUT(req, &boottime, sizeof(boottime));
127 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
130 struct timecounter *tc = arg1;
132 ncount = tc->tc_get_timecount(tc);
133 return sysctl_handle_int(oidp, &ncount, 0, req);
137 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
140 struct timecounter *tc = arg1;
142 freq = tc->tc_frequency;
143 return sysctl_handle_64(oidp, &freq, 0, req);
147 * Return the difference between the timehands' counter value now and what
148 * was when we copied it to the timehands' offset_count.
150 static __inline u_int
151 tc_delta(struct timehands *th)
153 struct timecounter *tc;
156 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
157 tc->tc_counter_mask);
161 * Functions for reading the time. We have to loop until we are sure that
162 * the timehands that we operated on was not updated under our feet. See
163 * the comment in <sys/time.h> for a description of these 12 functions.
167 binuptime(struct bintime *bt)
169 struct timehands *th;
174 gen = th->th_generation;
176 bintime_addx(bt, th->th_scale * tc_delta(th));
177 } while (gen == 0 || gen != th->th_generation);
181 nanouptime(struct timespec *tsp)
186 bintime2timespec(&bt, tsp);
190 microuptime(struct timeval *tvp)
195 bintime2timeval(&bt, tvp);
199 bintime(struct bintime *bt)
203 bintime_add(bt, &boottimebin);
207 nanotime(struct timespec *tsp)
212 bintime2timespec(&bt, tsp);
216 microtime(struct timeval *tvp)
221 bintime2timeval(&bt, tvp);
225 getbinuptime(struct bintime *bt)
227 struct timehands *th;
232 gen = th->th_generation;
234 } while (gen == 0 || gen != th->th_generation);
238 getnanouptime(struct timespec *tsp)
240 struct timehands *th;
245 gen = th->th_generation;
246 bintime2timespec(&th->th_offset, tsp);
247 } while (gen == 0 || gen != th->th_generation);
251 getmicrouptime(struct timeval *tvp)
253 struct timehands *th;
258 gen = th->th_generation;
259 bintime2timeval(&th->th_offset, tvp);
260 } while (gen == 0 || gen != th->th_generation);
264 getbintime(struct bintime *bt)
266 struct timehands *th;
271 gen = th->th_generation;
273 } while (gen == 0 || gen != th->th_generation);
274 bintime_add(bt, &boottimebin);
278 getnanotime(struct timespec *tsp)
280 struct timehands *th;
285 gen = th->th_generation;
286 *tsp = th->th_nanotime;
287 } while (gen == 0 || gen != th->th_generation);
291 getmicrotime(struct timeval *tvp)
293 struct timehands *th;
298 gen = th->th_generation;
299 *tvp = th->th_microtime;
300 } while (gen == 0 || gen != th->th_generation);
304 * Initialize a new timecounter and possibly use it.
307 tc_init(struct timecounter *tc)
310 struct sysctl_oid *tc_root;
312 u = tc->tc_frequency / tc->tc_counter_mask;
313 /* XXX: We need some margin here, 10% is a guess */
316 if (u > hz && tc->tc_quality >= 0) {
317 tc->tc_quality = -2000;
319 printf("Timecounter \"%s\" frequency %ju Hz",
320 tc->tc_name, (uintmax_t)tc->tc_frequency);
321 printf(" -- Insufficient hz, needs at least %u\n", u);
323 } else if (tc->tc_quality >= 0 || bootverbose) {
324 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
325 tc->tc_name, (uintmax_t)tc->tc_frequency,
329 tc->tc_next = timecounters;
332 * Set up sysctl tree for this counter.
334 tc_root = SYSCTL_ADD_NODE(NULL,
335 SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
336 CTLFLAG_RW, 0, "timecounter description");
337 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
338 "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
339 "mask for implemented bits");
340 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
341 "counter", CTLTYPE_UINT | CTLFLAG_RD, tc, sizeof(*tc),
342 sysctl_kern_timecounter_get, "IU", "current timecounter value");
343 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
344 "frequency", CTLTYPE_U64 | CTLFLAG_RD, tc, sizeof(*tc),
345 sysctl_kern_timecounter_freq, "QU", "timecounter frequency");
346 SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
347 "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
348 "goodness of time counter");
350 * Never automatically use a timecounter with negative quality.
351 * Even though we run on the dummy counter, switching here may be
352 * worse since this timecounter may not be monotonous.
354 if (tc->tc_quality < 0)
356 if (tc->tc_quality < timecounter->tc_quality)
358 if (tc->tc_quality == timecounter->tc_quality &&
359 tc->tc_frequency < timecounter->tc_frequency)
361 (void)tc->tc_get_timecount(tc);
362 (void)tc->tc_get_timecount(tc);
366 /* Report the frequency of the current timecounter. */
368 tc_getfrequency(void)
371 return (timehands->th_counter->tc_frequency);
375 * Step our concept of UTC. This is done by modifying our estimate of
380 tc_setclock(struct timespec *ts)
382 struct timespec tbef, taft;
383 struct bintime bt, bt2;
385 cpu_tick_calibrate(1);
387 timespec2bintime(ts, &bt);
389 bintime_sub(&bt, &bt2);
390 bintime_add(&bt2, &boottimebin);
392 bintime2timeval(&bt, &boottime);
394 /* XXX fiddle all the little crinkly bits around the fiords... */
397 if (timestepwarnings) {
399 "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
400 (intmax_t)tbef.tv_sec, tbef.tv_nsec,
401 (intmax_t)taft.tv_sec, taft.tv_nsec,
402 (intmax_t)ts->tv_sec, ts->tv_nsec);
404 cpu_tick_calibrate(1);
408 * Initialize the next struct timehands in the ring and make
409 * it the active timehands. Along the way we might switch to a different
410 * timecounter and/or do seconds processing in NTP. Slightly magic.
416 struct timehands *th, *tho;
418 u_int delta, ncount, ogen;
423 * Make the next timehands a copy of the current one, but do not
424 * overwrite the generation or next pointer. While we update
425 * the contents, the generation must be zero.
429 ogen = th->th_generation;
430 th->th_generation = 0;
431 bcopy(tho, th, offsetof(struct timehands, th_generation));
434 * Capture a timecounter delta on the current timecounter and if
435 * changing timecounters, a counter value from the new timecounter.
436 * Update the offset fields accordingly.
438 delta = tc_delta(th);
439 if (th->th_counter != timecounter)
440 ncount = timecounter->tc_get_timecount(timecounter);
443 th->th_offset_count += delta;
444 th->th_offset_count &= th->th_counter->tc_counter_mask;
445 while (delta > th->th_counter->tc_frequency) {
446 /* Eat complete unadjusted seconds. */
447 delta -= th->th_counter->tc_frequency;
450 if ((delta > th->th_counter->tc_frequency / 2) &&
451 (th->th_scale * delta < ((uint64_t)1 << 63))) {
452 /* The product th_scale * delta just barely overflows. */
455 bintime_addx(&th->th_offset, th->th_scale * delta);
458 * Hardware latching timecounters may not generate interrupts on
459 * PPS events, so instead we poll them. There is a finite risk that
460 * the hardware might capture a count which is later than the one we
461 * got above, and therefore possibly in the next NTP second which might
462 * have a different rate than the current NTP second. It doesn't
463 * matter in practice.
465 if (tho->th_counter->tc_poll_pps)
466 tho->th_counter->tc_poll_pps(tho->th_counter);
469 * Deal with NTP second processing. The for loop normally
470 * iterates at most once, but in extreme situations it might
471 * keep NTP sane if timeouts are not run for several seconds.
472 * At boot, the time step can be large when the TOD hardware
473 * has been read, so on really large steps, we call
474 * ntp_update_second only twice. We need to call it twice in
475 * case we missed a leap second.
478 bintime_add(&bt, &boottimebin);
479 i = bt.sec - tho->th_microtime.tv_sec;
484 ntp_update_second(&th->th_adjustment, &bt.sec);
486 boottimebin.sec += bt.sec - t;
488 /* Update the UTC timestamps used by the get*() functions. */
489 /* XXX shouldn't do this here. Should force non-`get' versions. */
490 bintime2timeval(&bt, &th->th_microtime);
491 bintime2timespec(&bt, &th->th_nanotime);
493 /* Now is a good time to change timecounters. */
494 if (th->th_counter != timecounter) {
496 if ((timecounter->tc_flags & TC_FLAGS_C3STOP) != 0)
497 cpu_disable_deep_sleep++;
498 if ((th->th_counter->tc_flags & TC_FLAGS_C3STOP) != 0)
499 cpu_disable_deep_sleep--;
501 th->th_counter = timecounter;
502 th->th_offset_count = ncount;
503 tc_min_ticktock_freq = max(1, timecounter->tc_frequency /
504 (((uint64_t)timecounter->tc_counter_mask + 1) / 3));
508 * Recalculate the scaling factor. We want the number of 1/2^64
509 * fractions of a second per period of the hardware counter, taking
510 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
511 * processing provides us with.
513 * The th_adjustment is nanoseconds per second with 32 bit binary
514 * fraction and we want 64 bit binary fraction of second:
516 * x = a * 2^32 / 10^9 = a * 4.294967296
518 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
519 * we can only multiply by about 850 without overflowing, that
520 * leaves no suitably precise fractions for multiply before divide.
522 * Divide before multiply with a fraction of 2199/512 results in a
523 * systematic undercompensation of 10PPM of th_adjustment. On a
524 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
526 * We happily sacrifice the lowest of the 64 bits of our result
527 * to the goddess of code clarity.
530 scale = (uint64_t)1 << 63;
531 scale += (th->th_adjustment / 1024) * 2199;
532 scale /= th->th_counter->tc_frequency;
533 th->th_scale = scale * 2;
536 * Now that the struct timehands is again consistent, set the new
537 * generation number, making sure to not make it zero.
541 th->th_generation = ogen;
543 /* Go live with the new struct timehands. */
544 time_second = th->th_microtime.tv_sec;
545 time_uptime = th->th_offset.sec;
549 /* Report or change the active timecounter hardware. */
551 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
554 struct timecounter *newtc, *tc;
558 strlcpy(newname, tc->tc_name, sizeof(newname));
560 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
561 if (error != 0 || req->newptr == NULL ||
562 strcmp(newname, tc->tc_name) == 0)
564 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
565 if (strcmp(newname, newtc->tc_name) != 0)
568 /* Warm up new timecounter. */
569 (void)newtc->tc_get_timecount(newtc);
570 (void)newtc->tc_get_timecount(newtc);
578 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
579 0, 0, sysctl_kern_timecounter_hardware, "A",
580 "Timecounter hardware selected");
583 /* Report or change the active timecounter hardware. */
585 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
588 struct timecounter *tc;
593 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
594 sprintf(buf, "%s%s(%d)",
595 spc, tc->tc_name, tc->tc_quality);
596 error = SYSCTL_OUT(req, buf, strlen(buf));
602 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
603 0, 0, sysctl_kern_timecounter_choice, "A", "Timecounter hardware detected");
606 * RFC 2783 PPS-API implementation.
610 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
613 struct pps_fetch_args *fapi;
615 struct pps_kcbind_args *kapi;
618 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
622 case PPS_IOC_DESTROY:
624 case PPS_IOC_SETPARAMS:
625 app = (pps_params_t *)data;
626 if (app->mode & ~pps->ppscap)
628 pps->ppsparam = *app;
630 case PPS_IOC_GETPARAMS:
631 app = (pps_params_t *)data;
632 *app = pps->ppsparam;
633 app->api_version = PPS_API_VERS_1;
636 *(int*)data = pps->ppscap;
639 fapi = (struct pps_fetch_args *)data;
640 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
642 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
644 pps->ppsinfo.current_mode = pps->ppsparam.mode;
645 fapi->pps_info_buf = pps->ppsinfo;
649 kapi = (struct pps_kcbind_args *)data;
650 /* XXX Only root should be able to do this */
651 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
653 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
655 if (kapi->edge & ~pps->ppscap)
657 pps->kcmode = kapi->edge;
668 pps_init(struct pps_state *pps)
670 pps->ppscap |= PPS_TSFMT_TSPEC;
671 if (pps->ppscap & PPS_CAPTUREASSERT)
672 pps->ppscap |= PPS_OFFSETASSERT;
673 if (pps->ppscap & PPS_CAPTURECLEAR)
674 pps->ppscap |= PPS_OFFSETCLEAR;
678 pps_capture(struct pps_state *pps)
680 struct timehands *th;
682 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
684 pps->capgen = th->th_generation;
686 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
687 if (pps->capgen != th->th_generation)
692 pps_event(struct pps_state *pps, int event)
695 struct timespec ts, *tsp, *osp;
696 u_int tcount, *pcount;
700 KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
701 /* If the timecounter was wound up underneath us, bail out. */
702 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
705 /* Things would be easier with arrays. */
706 if (event == PPS_CAPTUREASSERT) {
707 tsp = &pps->ppsinfo.assert_timestamp;
708 osp = &pps->ppsparam.assert_offset;
709 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
710 fhard = pps->kcmode & PPS_CAPTUREASSERT;
711 pcount = &pps->ppscount[0];
712 pseq = &pps->ppsinfo.assert_sequence;
714 tsp = &pps->ppsinfo.clear_timestamp;
715 osp = &pps->ppsparam.clear_offset;
716 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
717 fhard = pps->kcmode & PPS_CAPTURECLEAR;
718 pcount = &pps->ppscount[1];
719 pseq = &pps->ppsinfo.clear_sequence;
723 * If the timecounter changed, we cannot compare the count values, so
724 * we have to drop the rest of the PPS-stuff until the next event.
726 if (pps->ppstc != pps->capth->th_counter) {
727 pps->ppstc = pps->capth->th_counter;
728 *pcount = pps->capcount;
729 pps->ppscount[2] = pps->capcount;
733 /* Convert the count to a timespec. */
734 tcount = pps->capcount - pps->capth->th_offset_count;
735 tcount &= pps->capth->th_counter->tc_counter_mask;
736 bt = pps->capth->th_offset;
737 bintime_addx(&bt, pps->capth->th_scale * tcount);
738 bintime_add(&bt, &boottimebin);
739 bintime2timespec(&bt, &ts);
741 /* If the timecounter was wound up underneath us, bail out. */
742 if (pps->capgen != pps->capth->th_generation)
745 *pcount = pps->capcount;
750 timespecadd(tsp, osp);
751 if (tsp->tv_nsec < 0) {
752 tsp->tv_nsec += 1000000000;
761 * Feed the NTP PLL/FLL.
762 * The FLL wants to know how many (hardware) nanoseconds
763 * elapsed since the previous event.
765 tcount = pps->capcount - pps->ppscount[2];
766 pps->ppscount[2] = pps->capcount;
767 tcount &= pps->capth->th_counter->tc_counter_mask;
768 scale = (uint64_t)1 << 63;
769 scale /= pps->capth->th_counter->tc_frequency;
773 bintime_addx(&bt, scale * tcount);
774 bintime2timespec(&bt, &ts);
775 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
781 * Timecounters need to be updated every so often to prevent the hardware
782 * counter from overflowing. Updating also recalculates the cached values
783 * used by the get*() family of functions, so their precision depends on
784 * the update frequency.
788 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0,
789 "Approximate number of hardclock ticks in a millisecond");
804 inittimecounter(void *dummy)
809 * Set the initial timeout to
810 * max(1, <approx. number of hardclock ticks in a millisecond>).
811 * People should probably not use the sysctl to set the timeout
812 * to smaller than its inital value, since that value is the
813 * smallest reasonable one. If they want better timestamps they
814 * should use the non-"get"* functions.
817 tc_tick = (hz + 500) / 1000;
820 p = (tc_tick * 1000000) / hz;
821 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
823 /* warm up new timecounter (again) and get rolling. */
824 (void)timecounter->tc_get_timecount(timecounter);
825 (void)timecounter->tc_get_timecount(timecounter);
829 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
831 /* Cpu tick handling -------------------------------------------------*/
833 static int cpu_tick_variable;
834 static uint64_t cpu_tick_frequency;
839 static uint64_t base;
840 static unsigned last;
842 struct timecounter *tc;
844 tc = timehands->th_counter;
845 u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
847 base += (uint64_t)tc->tc_counter_mask + 1;
853 cpu_tick_calibration(void)
855 static time_t last_calib;
857 if (time_uptime != last_calib && !(time_uptime & 0xf)) {
858 cpu_tick_calibrate(0);
859 last_calib = time_uptime;
864 * This function gets called every 16 seconds on only one designated
865 * CPU in the system from hardclock() via cpu_tick_calibration()().
867 * Whenever the real time clock is stepped we get called with reset=1
868 * to make sure we handle suspend/resume and similar events correctly.
872 cpu_tick_calibrate(int reset)
874 static uint64_t c_last;
875 uint64_t c_this, c_delta;
876 static struct bintime t_last;
877 struct bintime t_this, t_delta;
881 /* The clock was stepped, abort & reset */
886 /* we don't calibrate fixed rate cputicks */
887 if (!cpu_tick_variable)
890 getbinuptime(&t_this);
891 c_this = cpu_ticks();
892 if (t_last.sec != 0) {
893 c_delta = c_this - c_last;
895 bintime_sub(&t_delta, &t_last);
898 * 2^(64-20) / 16[s] =
900 * 17.592.186.044.416 / 16 =
901 * 1.099.511.627.776 [Hz]
903 divi = t_delta.sec << 20;
904 divi |= t_delta.frac >> (64 - 20);
907 if (c_delta > cpu_tick_frequency) {
908 if (0 && bootverbose)
909 printf("cpu_tick increased to %ju Hz\n",
911 cpu_tick_frequency = c_delta;
919 set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
923 cpu_ticks = tc_cpu_ticks;
925 cpu_tick_frequency = freq;
926 cpu_tick_variable = var;
935 if (cpu_ticks == tc_cpu_ticks)
936 return (tc_getfrequency());
937 return (cpu_tick_frequency);
941 * We need to be slightly careful converting cputicks to microseconds.
942 * There is plenty of margin in 64 bits of microseconds (half a million
943 * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
944 * before divide conversion (to retain precision) we find that the
945 * margin shrinks to 1.5 hours (one millionth of 146y).
946 * With a three prong approach we never lose significant bits, no
947 * matter what the cputick rate and length of timeinterval is.
951 cputick2usec(uint64_t tick)
954 if (tick > 18446744073709551LL) /* floor(2^64 / 1000) */
955 return (tick / (cpu_tickrate() / 1000000LL));
956 else if (tick > 18446744073709LL) /* floor(2^64 / 1000000) */
957 return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
959 return ((tick * 1000000LL) / cpu_tickrate());
962 cpu_tick_f *cpu_ticks = tc_cpu_ticks;