Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tc.c
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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: src/sys/kern/kern_tc.c,v 1.162 2004/08/14 08:33:49 phk Exp $"); 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)
Cache object: 0cd37c9a01aee96f03557c32807736c6
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