kern_tc.c revision 136404
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: head/sys/kern/kern_tc.c 136404 2004-10-11 22:04:16Z peter $"); 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 38static u_int 39dummy_get_timecount(struct timecounter *tc) 40{ 41 static u_int now; 42 43 return (++now); 44} 45 46static struct timecounter dummy_timecounter = { 47 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000 48}; 49 50struct 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 64extern struct timehands th0; 65static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0}; 66static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9}; 67static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8}; 68static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7}; 69static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6}; 70static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5}; 71static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4}; 72static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3}; 73static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2}; 74static 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 86static struct timehands *volatile timehands = &th0; 87struct timecounter *timecounter = &dummy_timecounter; 88static struct timecounter *timecounters = &dummy_timecounter; 89 90time_t time_second = 1; 91time_t time_uptime = 0; 92 93static struct bintime boottimebin; 94struct timeval boottime; 95static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS); 96SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD, 97 NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime"); 98 99SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, ""); 100 101static int timestepwarnings; 102SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW, 103 ×tepwarnings, 0, ""); 104 105#define TC_STATS(foo) \ 106 static u_int foo; \ 107 SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\ 108 struct __hack 109 110TC_STATS(nbinuptime); TC_STATS(nnanouptime); TC_STATS(nmicrouptime); 111TC_STATS(nbintime); TC_STATS(nnanotime); TC_STATS(nmicrotime); 112TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime); 113TC_STATS(ngetbintime); TC_STATS(ngetnanotime); TC_STATS(ngetmicrotime); 114TC_STATS(nsetclock); 115 116#undef TC_STATS 117 118static void tc_windup(void); 119 120static int 121sysctl_kern_boottime(SYSCTL_HANDLER_ARGS) 122{ 123#ifdef SCTL_MASK32 124 int tv[2]; 125 126 if (req->flags & SCTL_MASK32) { 127 tv[0] = boottime.tv_sec; 128 tv[1] = boottime.tv_usec; 129 return SYSCTL_OUT(req, tv, sizeof(tv)); 130 } else 131#endif 132 return SYSCTL_OUT(req, &boottime, sizeof(boottime)); 133} 134/* 135 * Return the difference between the timehands' counter value now and what 136 * was when we copied it to the timehands' offset_count. 137 */ 138static __inline u_int 139tc_delta(struct timehands *th) 140{ 141 struct timecounter *tc; 142 143 tc = th->th_counter; 144 return ((tc->tc_get_timecount(tc) - th->th_offset_count) & 145 tc->tc_counter_mask); 146} 147 148/* 149 * Functions for reading the time. We have to loop until we are sure that 150 * the timehands that we operated on was not updated under our feet. See 151 * the comment in <sys/time.h> for a description of these 12 functions. 152 */ 153 154void 155binuptime(struct bintime *bt) 156{ 157 struct timehands *th; 158 u_int gen; 159 160 nbinuptime++; 161 do { 162 th = timehands; 163 gen = th->th_generation; 164 *bt = th->th_offset; 165 bintime_addx(bt, th->th_scale * tc_delta(th)); 166 } while (gen == 0 || gen != th->th_generation); 167} 168 169void 170nanouptime(struct timespec *tsp) 171{ 172 struct bintime bt; 173 174 nnanouptime++; 175 binuptime(&bt); 176 bintime2timespec(&bt, tsp); 177} 178 179void 180microuptime(struct timeval *tvp) 181{ 182 struct bintime bt; 183 184 nmicrouptime++; 185 binuptime(&bt); 186 bintime2timeval(&bt, tvp); 187} 188 189void 190bintime(struct bintime *bt) 191{ 192 193 nbintime++; 194 binuptime(bt); 195 bintime_add(bt, &boottimebin); 196} 197 198void 199nanotime(struct timespec *tsp) 200{ 201 struct bintime bt; 202 203 nnanotime++; 204 bintime(&bt); 205 bintime2timespec(&bt, tsp); 206} 207 208void 209microtime(struct timeval *tvp) 210{ 211 struct bintime bt; 212 213 nmicrotime++; 214 bintime(&bt); 215 bintime2timeval(&bt, tvp); 216} 217 218void 219getbinuptime(struct bintime *bt) 220{ 221 struct timehands *th; 222 u_int gen; 223 224 ngetbinuptime++; 225 do { 226 th = timehands; 227 gen = th->th_generation; 228 *bt = th->th_offset; 229 } while (gen == 0 || gen != th->th_generation); 230} 231 232void 233getnanouptime(struct timespec *tsp) 234{ 235 struct timehands *th; 236 u_int gen; 237 238 ngetnanouptime++; 239 do { 240 th = timehands; 241 gen = th->th_generation; 242 bintime2timespec(&th->th_offset, tsp); 243 } while (gen == 0 || gen != th->th_generation); 244} 245 246void 247getmicrouptime(struct timeval *tvp) 248{ 249 struct timehands *th; 250 u_int gen; 251 252 ngetmicrouptime++; 253 do { 254 th = timehands; 255 gen = th->th_generation; 256 bintime2timeval(&th->th_offset, tvp); 257 } while (gen == 0 || gen != th->th_generation); 258} 259 260void 261getbintime(struct bintime *bt) 262{ 263 struct timehands *th; 264 u_int gen; 265 266 ngetbintime++; 267 do { 268 th = timehands; 269 gen = th->th_generation; 270 *bt = th->th_offset; 271 } while (gen == 0 || gen != th->th_generation); 272 bintime_add(bt, &boottimebin); 273} 274 275void 276getnanotime(struct timespec *tsp) 277{ 278 struct timehands *th; 279 u_int gen; 280 281 ngetnanotime++; 282 do { 283 th = timehands; 284 gen = th->th_generation; 285 *tsp = th->th_nanotime; 286 } while (gen == 0 || gen != th->th_generation); 287} 288 289void 290getmicrotime(struct timeval *tvp) 291{ 292 struct timehands *th; 293 u_int gen; 294 295 ngetmicrotime++; 296 do { 297 th = timehands; 298 gen = th->th_generation; 299 *tvp = th->th_microtime; 300 } while (gen == 0 || gen != th->th_generation); 301} 302 303/* 304 * Initialize a new timecounter and possibly use it. 305 */ 306void 307tc_init(struct timecounter *tc) 308{ 309 u_int u; 310 311 u = tc->tc_frequency / tc->tc_counter_mask; 312 /* XXX: We need some margin here, 10% is a guess */ 313 u *= 11; 314 u /= 10; 315 if (u > hz && tc->tc_quality >= 0) { 316 tc->tc_quality = -2000; 317 if (bootverbose) { 318 printf("Timecounter \"%s\" frequency %ju Hz", 319 tc->tc_name, (uintmax_t)tc->tc_frequency); 320 printf(" -- Insufficient hz, needs at least %u\n", u); 321 } 322 } else if (tc->tc_quality >= 0 || bootverbose) { 323 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n", 324 tc->tc_name, (uintmax_t)tc->tc_frequency, 325 tc->tc_quality); 326 } 327 328 tc->tc_next = timecounters; 329 timecounters = tc; 330 /* 331 * Never automatically use a timecounter with negative quality. 332 * Even though we run on the dummy counter, switching here may be 333 * worse since this timecounter may not be monotonous. 334 */ 335 if (tc->tc_quality < 0) 336 return; 337 if (tc->tc_quality < timecounter->tc_quality) 338 return; 339 if (tc->tc_quality == timecounter->tc_quality && 340 tc->tc_frequency < timecounter->tc_frequency) 341 return; 342 (void)tc->tc_get_timecount(tc); 343 (void)tc->tc_get_timecount(tc); 344 timecounter = tc; 345} 346 347/* Report the frequency of the current timecounter. */ 348u_int64_t 349tc_getfrequency(void) 350{ 351 352 return (timehands->th_counter->tc_frequency); 353} 354 355/* 356 * Step our concept of UTC. This is done by modifying our estimate of 357 * when we booted. 358 * XXX: not locked. 359 */ 360void 361tc_setclock(struct timespec *ts) 362{ 363 struct timespec ts2; 364 struct bintime bt, bt2; 365 366 nsetclock++; 367 binuptime(&bt2); 368 timespec2bintime(ts, &bt); 369 bintime_sub(&bt, &bt2); 370 bintime_add(&bt2, &boottimebin); 371 boottimebin = bt; 372 bintime2timeval(&bt, &boottime); 373 374 /* XXX fiddle all the little crinkly bits around the fiords... */ 375 tc_windup(); 376 if (timestepwarnings) { 377 bintime2timespec(&bt2, &ts2); 378 log(LOG_INFO, "Time stepped from %jd.%09ld to %jd.%09ld\n", 379 (intmax_t)ts2.tv_sec, ts2.tv_nsec, 380 (intmax_t)ts->tv_sec, ts->tv_nsec); 381 } 382} 383 384/* 385 * Initialize the next struct timehands in the ring and make 386 * it the active timehands. Along the way we might switch to a different 387 * timecounter and/or do seconds processing in NTP. Slightly magic. 388 */ 389static void 390tc_windup(void) 391{ 392 struct bintime bt; 393 struct timehands *th, *tho; 394 u_int64_t scale; 395 u_int delta, ncount, ogen; 396 int i; 397 time_t t; 398 399 /* 400 * Make the next timehands a copy of the current one, but do not 401 * overwrite the generation or next pointer. While we update 402 * the contents, the generation must be zero. 403 */ 404 tho = timehands; 405 th = tho->th_next; 406 ogen = th->th_generation; 407 th->th_generation = 0; 408 bcopy(tho, th, offsetof(struct timehands, th_generation)); 409 410 /* 411 * Capture a timecounter delta on the current timecounter and if 412 * changing timecounters, a counter value from the new timecounter. 413 * Update the offset fields accordingly. 414 */ 415 delta = tc_delta(th); 416 if (th->th_counter != timecounter) 417 ncount = timecounter->tc_get_timecount(timecounter); 418 else 419 ncount = 0; 420 th->th_offset_count += delta; 421 th->th_offset_count &= th->th_counter->tc_counter_mask; 422 bintime_addx(&th->th_offset, th->th_scale * delta); 423 424 /* 425 * Hardware latching timecounters may not generate interrupts on 426 * PPS events, so instead we poll them. There is a finite risk that 427 * the hardware might capture a count which is later than the one we 428 * got above, and therefore possibly in the next NTP second which might 429 * have a different rate than the current NTP second. It doesn't 430 * matter in practice. 431 */ 432 if (tho->th_counter->tc_poll_pps) 433 tho->th_counter->tc_poll_pps(tho->th_counter); 434 435 /* 436 * Deal with NTP second processing. The for loop normally 437 * iterates at most once, but in extreme situations it might 438 * keep NTP sane if timeouts are not run for several seconds. 439 * At boot, the time step can be large when the TOD hardware 440 * has been read, so on really large steps, we call 441 * ntp_update_second only twice. We need to call it twice in 442 * case we missed a leap second. 443 */ 444 bt = th->th_offset; 445 bintime_add(&bt, &boottimebin); 446 i = bt.sec - tho->th_microtime.tv_sec; 447 if (i > LARGE_STEP) 448 i = 2; 449 for (; i > 0; i--) { 450 t = bt.sec; 451 ntp_update_second(&th->th_adjustment, &bt.sec); 452 if (bt.sec != t) 453 boottimebin.sec += bt.sec - t; 454 } 455 /* Update the UTC timestamps used by the get*() functions. */ 456 /* XXX shouldn't do this here. Should force non-`get' versions. */ 457 bintime2timeval(&bt, &th->th_microtime); 458 bintime2timespec(&bt, &th->th_nanotime); 459 460 /* Now is a good time to change timecounters. */ 461 if (th->th_counter != timecounter) { 462 th->th_counter = timecounter; 463 th->th_offset_count = ncount; 464 } 465 466 /*- 467 * Recalculate the scaling factor. We want the number of 1/2^64 468 * fractions of a second per period of the hardware counter, taking 469 * into account the th_adjustment factor which the NTP PLL/adjtime(2) 470 * processing provides us with. 471 * 472 * The th_adjustment is nanoseconds per second with 32 bit binary 473 * fraction and we want 64 bit binary fraction of second: 474 * 475 * x = a * 2^32 / 10^9 = a * 4.294967296 476 * 477 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int 478 * we can only multiply by about 850 without overflowing, but that 479 * leaves suitably precise fractions for multiply before divide. 480 * 481 * Divide before multiply with a fraction of 2199/512 results in a 482 * systematic undercompensation of 10PPM of th_adjustment. On a 483 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable. 484 * 485 * We happily sacrifice the lowest of the 64 bits of our result 486 * to the goddess of code clarity. 487 * 488 */ 489 scale = (u_int64_t)1 << 63; 490 scale += (th->th_adjustment / 1024) * 2199; 491 scale /= th->th_counter->tc_frequency; 492 th->th_scale = scale * 2; 493 494 /* 495 * Now that the struct timehands is again consistent, set the new 496 * generation number, making sure to not make it zero. 497 */ 498 if (++ogen == 0) 499 ogen = 1; 500 th->th_generation = ogen; 501 502 /* Go live with the new struct timehands. */ 503 time_second = th->th_microtime.tv_sec; 504 time_uptime = th->th_offset.sec; 505 timehands = th; 506} 507 508/* Report or change the active timecounter hardware. */ 509static int 510sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS) 511{ 512 char newname[32]; 513 struct timecounter *newtc, *tc; 514 int error; 515 516 tc = timecounter; 517 strlcpy(newname, tc->tc_name, sizeof(newname)); 518 519 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req); 520 if (error != 0 || req->newptr == NULL || 521 strcmp(newname, tc->tc_name) == 0) 522 return (error); 523 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) { 524 if (strcmp(newname, newtc->tc_name) != 0) 525 continue; 526 527 /* Warm up new timecounter. */ 528 (void)newtc->tc_get_timecount(newtc); 529 (void)newtc->tc_get_timecount(newtc); 530 531 timecounter = newtc; 532 return (0); 533 } 534 return (EINVAL); 535} 536 537SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW, 538 0, 0, sysctl_kern_timecounter_hardware, "A", ""); 539 540 541/* Report or change the active timecounter hardware. */ 542static int 543sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS) 544{ 545 char buf[32], *spc; 546 struct timecounter *tc; 547 int error; 548 549 spc = ""; 550 error = 0; 551 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) { 552 sprintf(buf, "%s%s(%d)", 553 spc, tc->tc_name, tc->tc_quality); 554 error = SYSCTL_OUT(req, buf, strlen(buf)); 555 spc = " "; 556 } 557 return (error); 558} 559 560SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD, 561 0, 0, sysctl_kern_timecounter_choice, "A", ""); 562 563/* 564 * RFC 2783 PPS-API implementation. 565 */ 566 567int 568pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps) 569{ 570 pps_params_t *app; 571 struct pps_fetch_args *fapi; 572#ifdef PPS_SYNC 573 struct pps_kcbind_args *kapi; 574#endif 575 576 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl")); 577 switch (cmd) { 578 case PPS_IOC_CREATE: 579 return (0); 580 case PPS_IOC_DESTROY: 581 return (0); 582 case PPS_IOC_SETPARAMS: 583 app = (pps_params_t *)data; 584 if (app->mode & ~pps->ppscap) 585 return (EINVAL); 586 pps->ppsparam = *app; 587 return (0); 588 case PPS_IOC_GETPARAMS: 589 app = (pps_params_t *)data; 590 *app = pps->ppsparam; 591 app->api_version = PPS_API_VERS_1; 592 return (0); 593 case PPS_IOC_GETCAP: 594 *(int*)data = pps->ppscap; 595 return (0); 596 case PPS_IOC_FETCH: 597 fapi = (struct pps_fetch_args *)data; 598 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC) 599 return (EINVAL); 600 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec) 601 return (EOPNOTSUPP); 602 pps->ppsinfo.current_mode = pps->ppsparam.mode; 603 fapi->pps_info_buf = pps->ppsinfo; 604 return (0); 605 case PPS_IOC_KCBIND: 606#ifdef PPS_SYNC 607 kapi = (struct pps_kcbind_args *)data; 608 /* XXX Only root should be able to do this */ 609 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC) 610 return (EINVAL); 611 if (kapi->kernel_consumer != PPS_KC_HARDPPS) 612 return (EINVAL); 613 if (kapi->edge & ~pps->ppscap) 614 return (EINVAL); 615 pps->kcmode = kapi->edge; 616 return (0); 617#else 618 return (EOPNOTSUPP); 619#endif 620 default: 621 return (ENOTTY); 622 } 623} 624 625void 626pps_init(struct pps_state *pps) 627{ 628 pps->ppscap |= PPS_TSFMT_TSPEC; 629 if (pps->ppscap & PPS_CAPTUREASSERT) 630 pps->ppscap |= PPS_OFFSETASSERT; 631 if (pps->ppscap & PPS_CAPTURECLEAR) 632 pps->ppscap |= PPS_OFFSETCLEAR; 633} 634 635void 636pps_capture(struct pps_state *pps) 637{ 638 struct timehands *th; 639 640 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture")); 641 th = timehands; 642 pps->capgen = th->th_generation; 643 pps->capth = th; 644 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter); 645 if (pps->capgen != th->th_generation) 646 pps->capgen = 0; 647} 648 649void 650pps_event(struct pps_state *pps, int event) 651{ 652 struct bintime bt; 653 struct timespec ts, *tsp, *osp; 654 u_int tcount, *pcount; 655 int foff, fhard; 656 pps_seq_t *pseq; 657 658 KASSERT(pps != NULL, ("NULL pps pointer in pps_event")); 659 /* If the timecounter was wound up underneath us, bail out. */ 660 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation) 661 return; 662 663 /* Things would be easier with arrays. */ 664 if (event == PPS_CAPTUREASSERT) { 665 tsp = &pps->ppsinfo.assert_timestamp; 666 osp = &pps->ppsparam.assert_offset; 667 foff = pps->ppsparam.mode & PPS_OFFSETASSERT; 668 fhard = pps->kcmode & PPS_CAPTUREASSERT; 669 pcount = &pps->ppscount[0]; 670 pseq = &pps->ppsinfo.assert_sequence; 671 } else { 672 tsp = &pps->ppsinfo.clear_timestamp; 673 osp = &pps->ppsparam.clear_offset; 674 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR; 675 fhard = pps->kcmode & PPS_CAPTURECLEAR; 676 pcount = &pps->ppscount[1]; 677 pseq = &pps->ppsinfo.clear_sequence; 678 } 679 680 /* 681 * If the timecounter changed, we cannot compare the count values, so 682 * we have to drop the rest of the PPS-stuff until the next event. 683 */ 684 if (pps->ppstc != pps->capth->th_counter) { 685 pps->ppstc = pps->capth->th_counter; 686 *pcount = pps->capcount; 687 pps->ppscount[2] = pps->capcount; 688 return; 689 } 690 691 /* Convert the count to a timespec. */ 692 tcount = pps->capcount - pps->capth->th_offset_count; 693 tcount &= pps->capth->th_counter->tc_counter_mask; 694 bt = pps->capth->th_offset; 695 bintime_addx(&bt, pps->capth->th_scale * tcount); 696 bintime_add(&bt, &boottimebin); 697 bintime2timespec(&bt, &ts); 698 699 /* If the timecounter was wound up underneath us, bail out. */ 700 if (pps->capgen != pps->capth->th_generation) 701 return; 702 703 *pcount = pps->capcount; 704 (*pseq)++; 705 *tsp = ts; 706 707 if (foff) { 708 timespecadd(tsp, osp); 709 if (tsp->tv_nsec < 0) { 710 tsp->tv_nsec += 1000000000; 711 tsp->tv_sec -= 1; 712 } 713 } 714#ifdef PPS_SYNC 715 if (fhard) { 716 u_int64_t scale; 717 718 /* 719 * Feed the NTP PLL/FLL. 720 * The FLL wants to know how many (hardware) nanoseconds 721 * elapsed since the previous event. 722 */ 723 tcount = pps->capcount - pps->ppscount[2]; 724 pps->ppscount[2] = pps->capcount; 725 tcount &= pps->capth->th_counter->tc_counter_mask; 726 scale = (u_int64_t)1 << 63; 727 scale /= pps->capth->th_counter->tc_frequency; 728 scale *= 2; 729 bt.sec = 0; 730 bt.frac = 0; 731 bintime_addx(&bt, scale * tcount); 732 bintime2timespec(&bt, &ts); 733 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec); 734 } 735#endif 736} 737 738/* 739 * Timecounters need to be updated every so often to prevent the hardware 740 * counter from overflowing. Updating also recalculates the cached values 741 * used by the get*() family of functions, so their precision depends on 742 * the update frequency. 743 */ 744 745static int tc_tick; 746SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0, ""); 747 748void 749tc_ticktock(void) 750{ 751 static int count; 752 753 if (++count < tc_tick) 754 return; 755 count = 0; 756 tc_windup(); 757} 758 759static void 760inittimecounter(void *dummy) 761{ 762 u_int p; 763 764 /* 765 * Set the initial timeout to 766 * max(1, <approx. number of hardclock ticks in a millisecond>). 767 * People should probably not use the sysctl to set the timeout 768 * to smaller than its inital value, since that value is the 769 * smallest reasonable one. If they want better timestamps they 770 * should use the non-"get"* functions. 771 */ 772 if (hz > 1000) 773 tc_tick = (hz + 500) / 1000; 774 else 775 tc_tick = 1; 776 p = (tc_tick * 1000000) / hz; 777 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000); 778 779 /* warm up new timecounter (again) and get rolling. */ 780 (void)timecounter->tc_get_timecount(timecounter); 781 (void)timecounter->tc_get_timecount(timecounter); 782} 783 784SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL) 785