1 /* $NetBSD: kern_clock.c,v 1.92 2004/09/15 04:56:14 tls Exp $ */ 2 3 /*- 4 * Copyright (c) 2000 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /*- 41 * Copyright (c) 1982, 1986, 1991, 1993 42 * The Regents of the University of California. All rights reserved. 43 * (c) UNIX System Laboratories, Inc. 44 * All or some portions of this file are derived from material licensed 45 * to the University of California by American Telephone and Telegraph 46 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 47 * the permission of UNIX System Laboratories, Inc. 48 * 49 * Redistribution and use in source and binary forms, with or without 50 * modification, are permitted provided that the following conditions 51 * are met: 52 * 1. Redistributions of source code must retain the above copyright 53 * notice, this list of conditions and the following disclaimer. 54 * 2. Redistributions in binary form must reproduce the above copyright 55 * notice, this list of conditions and the following disclaimer in the 56 * documentation and/or other materials provided with the distribution. 57 * 3. Neither the name of the University nor the names of its contributors 58 * may be used to endorse or promote products derived from this software 59 * without specific prior written permission. 60 * 61 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 62 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 63 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 64 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 65 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 66 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 67 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 68 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 69 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 70 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 71 * SUCH DAMAGE. 72 * 73 * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94 74 */ 75 76 #include <sys/cdefs.h> 77 __KERNEL_RCSID(0, "$NetBSD: kern_clock.c,v 1.92 2004/09/15 04:56:14 tls Exp $"); 78 79 #include "opt_ntp.h" 80 #include "opt_multiprocessor.h" 81 #include "opt_perfctrs.h" 82 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/callout.h> 86 #include <sys/kernel.h> 87 #include <sys/proc.h> 88 #include <sys/resourcevar.h> 89 #include <sys/signalvar.h> 90 #include <sys/sysctl.h> 91 #include <sys/timex.h> 92 #include <sys/sched.h> 93 #include <sys/time.h> 94 95 #include <machine/cpu.h> 96 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS 97 #include <machine/intr.h> 98 #endif 99 100 #ifdef GPROF 101 #include <sys/gmon.h> 102 #endif 103 104 /* 105 * Clock handling routines. 106 * 107 * This code is written to operate with two timers that run independently of 108 * each other. The main clock, running hz times per second, is used to keep 109 * track of real time. The second timer handles kernel and user profiling, 110 * and does resource use estimation. If the second timer is programmable, 111 * it is randomized to avoid aliasing between the two clocks. For example, 112 * the randomization prevents an adversary from always giving up the CPU 113 * just before its quantum expires. Otherwise, it would never accumulate 114 * CPU ticks. The mean frequency of the second timer is stathz. 115 * 116 * If no second timer exists, stathz will be zero; in this case we drive 117 * profiling and statistics off the main clock. This WILL NOT be accurate; 118 * do not do it unless absolutely necessary. 119 * 120 * The statistics clock may (or may not) be run at a higher rate while 121 * profiling. This profile clock runs at profhz. We require that profhz 122 * be an integral multiple of stathz. 123 * 124 * If the statistics clock is running fast, it must be divided by the ratio 125 * profhz/stathz for statistics. (For profiling, every tick counts.) 126 */ 127 128 #ifdef NTP /* NTP phase-locked loop in kernel */ 129 /* 130 * Phase/frequency-lock loop (PLL/FLL) definitions 131 * 132 * The following variables are read and set by the ntp_adjtime() system 133 * call. 134 * 135 * time_state shows the state of the system clock, with values defined 136 * in the timex.h header file. 137 * 138 * time_status shows the status of the system clock, with bits defined 139 * in the timex.h header file. 140 * 141 * time_offset is used by the PLL/FLL to adjust the system time in small 142 * increments. 143 * 144 * time_constant determines the bandwidth or "stiffness" of the PLL. 145 * 146 * time_tolerance determines maximum frequency error or tolerance of the 147 * CPU clock oscillator and is a property of the architecture; however, 148 * in principle it could change as result of the presence of external 149 * discipline signals, for instance. 150 * 151 * time_precision is usually equal to the kernel tick variable; however, 152 * in cases where a precision clock counter or external clock is 153 * available, the resolution can be much less than this and depend on 154 * whether the external clock is working or not. 155 * 156 * time_maxerror is initialized by a ntp_adjtime() call and increased by 157 * the kernel once each second to reflect the maximum error bound 158 * growth. 159 * 160 * time_esterror is set and read by the ntp_adjtime() call, but 161 * otherwise not used by the kernel. 162 */ 163 int time_state = TIME_OK; /* clock state */ 164 int time_status = STA_UNSYNC; /* clock status bits */ 165 long time_offset = 0; /* time offset (us) */ 166 long time_constant = 0; /* pll time constant */ 167 long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */ 168 long time_precision = 1; /* clock precision (us) */ 169 long time_maxerror = MAXPHASE; /* maximum error (us) */ 170 long time_esterror = MAXPHASE; /* estimated error (us) */ 171 172 /* 173 * The following variables establish the state of the PLL/FLL and the 174 * residual time and frequency offset of the local clock. The scale 175 * factors are defined in the timex.h header file. 176 * 177 * time_phase and time_freq are the phase increment and the frequency 178 * increment, respectively, of the kernel time variable. 179 * 180 * time_freq is set via ntp_adjtime() from a value stored in a file when 181 * the synchronization daemon is first started. Its value is retrieved 182 * via ntp_adjtime() and written to the file about once per hour by the 183 * daemon. 184 * 185 * time_adj is the adjustment added to the value of tick at each timer 186 * interrupt and is recomputed from time_phase and time_freq at each 187 * seconds rollover. 188 * 189 * time_reftime is the second's portion of the system time at the last 190 * call to ntp_adjtime(). It is used to adjust the time_freq variable 191 * and to increase the time_maxerror as the time since last update 192 * increases. 193 */ 194 long time_phase = 0; /* phase offset (scaled us) */ 195 long time_freq = 0; /* frequency offset (scaled ppm) */ 196 long time_adj = 0; /* tick adjust (scaled 1 / hz) */ 197 long time_reftime = 0; /* time at last adjustment (s) */ 198 199 #ifdef PPS_SYNC 200 /* 201 * The following variables are used only if the kernel PPS discipline 202 * code is configured (PPS_SYNC). The scale factors are defined in the 203 * timex.h header file. 204 * 205 * pps_time contains the time at each calibration interval, as read by 206 * microtime(). pps_count counts the seconds of the calibration 207 * interval, the duration of which is nominally pps_shift in powers of 208 * two. 209 * 210 * pps_offset is the time offset produced by the time median filter 211 * pps_tf[], while pps_jitter is the dispersion (jitter) measured by 212 * this filter. 213 * 214 * pps_freq is the frequency offset produced by the frequency median 215 * filter pps_ff[], while pps_stabil is the dispersion (wander) measured 216 * by this filter. 217 * 218 * pps_usec is latched from a high resolution counter or external clock 219 * at pps_time. Here we want the hardware counter contents only, not the 220 * contents plus the time_tv.usec as usual. 221 * 222 * pps_valid counts the number of seconds since the last PPS update. It 223 * is used as a watchdog timer to disable the PPS discipline should the 224 * PPS signal be lost. 225 * 226 * pps_glitch counts the number of seconds since the beginning of an 227 * offset burst more than tick/2 from current nominal offset. It is used 228 * mainly to suppress error bursts due to priority conflicts between the 229 * PPS interrupt and timer interrupt. 230 * 231 * pps_intcnt counts the calibration intervals for use in the interval- 232 * adaptation algorithm. It's just too complicated for words. 233 * 234 * pps_kc_hardpps_source contains an arbitrary value that uniquely 235 * identifies the currently bound source of the PPS signal, or NULL 236 * if no source is bound. 237 * 238 * pps_kc_hardpps_mode indicates which transitions, if any, of the PPS 239 * signal should be reported. 240 */ 241 struct timeval pps_time; /* kernel time at last interval */ 242 long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */ 243 long pps_offset = 0; /* pps time offset (us) */ 244 long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */ 245 long pps_ff[] = {0, 0, 0}; /* pps frequency offset median filter */ 246 long pps_freq = 0; /* frequency offset (scaled ppm) */ 247 long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */ 248 long pps_usec = 0; /* microsec counter at last interval */ 249 long pps_valid = PPS_VALID; /* pps signal watchdog counter */ 250 int pps_glitch = 0; /* pps signal glitch counter */ 251 int pps_count = 0; /* calibration interval counter (s) */ 252 int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */ 253 int pps_intcnt = 0; /* intervals at current duration */ 254 void *pps_kc_hardpps_source = NULL; /* current PPS supplier's identifier */ 255 int pps_kc_hardpps_mode = 0; /* interesting edges of PPS signal */ 256 257 /* 258 * PPS signal quality monitors 259 * 260 * pps_jitcnt counts the seconds that have been discarded because the 261 * jitter measured by the time median filter exceeds the limit MAXTIME 262 * (100 us). 263 * 264 * pps_calcnt counts the frequency calibration intervals, which are 265 * variable from 4 s to 256 s. 266 * 267 * pps_errcnt counts the calibration intervals which have been discarded 268 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the 269 * calibration interval jitter exceeds two ticks. 270 * 271 * pps_stbcnt counts the calibration intervals that have been discarded 272 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us). 273 */ 274 long pps_jitcnt = 0; /* jitter limit exceeded */ 275 long pps_calcnt = 0; /* calibration intervals */ 276 long pps_errcnt = 0; /* calibration errors */ 277 long pps_stbcnt = 0; /* stability limit exceeded */ 278 #endif /* PPS_SYNC */ 279 280 #ifdef EXT_CLOCK 281 /* 282 * External clock definitions 283 * 284 * The following definitions and declarations are used only if an 285 * external clock is configured on the system. 286 */ 287 #define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */ 288 289 /* 290 * The clock_count variable is set to CLOCK_INTERVAL at each PPS 291 * interrupt and decremented once each second. 292 */ 293 int clock_count = 0; /* CPU clock counter */ 294 295 #ifdef HIGHBALL 296 /* 297 * The clock_offset and clock_cpu variables are used by the HIGHBALL 298 * interface. The clock_offset variable defines the offset between 299 * system time and the HIGBALL counters. The clock_cpu variable contains 300 * the offset between the system clock and the HIGHBALL clock for use in 301 * disciplining the kernel time variable. 302 */ 303 extern struct timeval clock_offset; /* Highball clock offset */ 304 long clock_cpu = 0; /* CPU clock adjust */ 305 #endif /* HIGHBALL */ 306 #endif /* EXT_CLOCK */ 307 #endif /* NTP */ 308 309 310 /* 311 * Bump a timeval by a small number of usec's. 312 */ 313 #define BUMPTIME(t, usec) { \ 314 volatile struct timeval *tp = (t); \ 315 long us; \ 316 \ 317 tp->tv_usec = us = tp->tv_usec + (usec); \ 318 if (us >= 1000000) { \ 319 tp->tv_usec = us - 1000000; \ 320 tp->tv_sec++; \ 321 } \ 322 } 323 324 int stathz; 325 int profhz; 326 int profsrc; 327 int schedhz; 328 int profprocs; 329 int hardclock_ticks; 330 static int statscheddiv; /* stat => sched divider (used if schedhz == 0) */ 331 static int psdiv; /* prof => stat divider */ 332 int psratio; /* ratio: prof / stat */ 333 int tickfix, tickfixinterval; /* used if tick not really integral */ 334 #ifndef NTP 335 static int tickfixcnt; /* accumulated fractional error */ 336 #else 337 int fixtick; /* used by NTP for same */ 338 int shifthz; 339 #endif 340 341 /* 342 * We might want ldd to load the both words from time at once. 343 * To succeed we need to be quadword aligned. 344 * The sparc already does that, and that it has worked so far is a fluke. 345 */ 346 volatile struct timeval time __attribute__((__aligned__(__alignof__(quad_t)))); 347 volatile struct timeval mono_time; 348 349 void *softclock_si; 350 351 /* 352 * Initialize clock frequencies and start both clocks running. 353 */ 354 void 355 initclocks(void) 356 { 357 int i; 358 359 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS 360 softclock_si = softintr_establish(IPL_SOFTCLOCK, softclock, NULL); 361 if (softclock_si == NULL) 362 panic("initclocks: unable to register softclock intr"); 363 #endif 364 365 /* 366 * Set divisors to 1 (normal case) and let the machine-specific 367 * code do its bit. 368 */ 369 psdiv = 1; 370 cpu_initclocks(); 371 372 /* 373 * Compute profhz/stathz/rrticks, and fix profhz if needed. 374 */ 375 i = stathz ? stathz : hz; 376 if (profhz == 0) 377 profhz = i; 378 psratio = profhz / i; 379 rrticks = hz / 10; 380 if (schedhz == 0) { 381 /* 16Hz is best */ 382 statscheddiv = i / 16; 383 if (statscheddiv <= 0) 384 panic("statscheddiv"); 385 } 386 387 #ifdef NTP 388 switch (hz) { 389 case 1: 390 shifthz = SHIFT_SCALE - 0; 391 break; 392 case 2: 393 shifthz = SHIFT_SCALE - 1; 394 break; 395 case 4: 396 shifthz = SHIFT_SCALE - 2; 397 break; 398 case 8: 399 shifthz = SHIFT_SCALE - 3; 400 break; 401 case 16: 402 shifthz = SHIFT_SCALE - 4; 403 break; 404 case 32: 405 shifthz = SHIFT_SCALE - 5; 406 break; 407 case 50: 408 case 60: 409 case 64: 410 shifthz = SHIFT_SCALE - 6; 411 break; 412 case 96: 413 case 100: 414 case 128: 415 shifthz = SHIFT_SCALE - 7; 416 break; 417 case 256: 418 shifthz = SHIFT_SCALE - 8; 419 break; 420 case 512: 421 shifthz = SHIFT_SCALE - 9; 422 break; 423 case 1000: 424 case 1024: 425 shifthz = SHIFT_SCALE - 10; 426 break; 427 case 1200: 428 case 2048: 429 shifthz = SHIFT_SCALE - 11; 430 break; 431 case 4096: 432 shifthz = SHIFT_SCALE - 12; 433 break; 434 case 8192: 435 shifthz = SHIFT_SCALE - 13; 436 break; 437 case 16384: 438 shifthz = SHIFT_SCALE - 14; 439 break; 440 case 32768: 441 shifthz = SHIFT_SCALE - 15; 442 break; 443 case 65536: 444 shifthz = SHIFT_SCALE - 16; 445 break; 446 default: 447 panic("weird hz"); 448 } 449 if (fixtick == 0) { 450 /* 451 * Give MD code a chance to set this to a better 452 * value; but, if it doesn't, we should. 453 */ 454 fixtick = (1000000 - (hz*tick)); 455 } 456 #endif 457 } 458 459 /* 460 * The real-time timer, interrupting hz times per second. 461 */ 462 void 463 hardclock(struct clockframe *frame) 464 { 465 struct lwp *l; 466 struct proc *p; 467 int delta; 468 extern int tickdelta; 469 extern long timedelta; 470 struct cpu_info *ci = curcpu(); 471 struct ptimer *pt; 472 #ifdef NTP 473 int time_update; 474 int ltemp; 475 #endif 476 477 l = curlwp; 478 if (l) { 479 p = l->l_proc; 480 /* 481 * Run current process's virtual and profile time, as needed. 482 */ 483 if (CLKF_USERMODE(frame) && p->p_timers && 484 (pt = LIST_FIRST(&p->p_timers->pts_virtual)) != NULL) 485 if (itimerdecr(pt, tick) == 0) 486 itimerfire(pt); 487 if (p->p_timers && 488 (pt = LIST_FIRST(&p->p_timers->pts_prof)) != NULL) 489 if (itimerdecr(pt, tick) == 0) 490 itimerfire(pt); 491 } 492 493 /* 494 * If no separate statistics clock is available, run it from here. 495 */ 496 if (stathz == 0) 497 statclock(frame); 498 if ((--ci->ci_schedstate.spc_rrticks) <= 0) 499 roundrobin(ci); 500 501 #if defined(MULTIPROCESSOR) 502 /* 503 * If we are not the primary CPU, we're not allowed to do 504 * any more work. 505 */ 506 if (CPU_IS_PRIMARY(ci) == 0) 507 return; 508 #endif 509 510 /* 511 * Increment the time-of-day. The increment is normally just 512 * ``tick''. If the machine is one which has a clock frequency 513 * such that ``hz'' would not divide the second evenly into 514 * milliseconds, a periodic adjustment must be applied. Finally, 515 * if we are still adjusting the time (see adjtime()), 516 * ``tickdelta'' may also be added in. 517 */ 518 hardclock_ticks++; 519 delta = tick; 520 521 #ifndef NTP 522 if (tickfix) { 523 tickfixcnt += tickfix; 524 if (tickfixcnt >= tickfixinterval) { 525 delta++; 526 tickfixcnt -= tickfixinterval; 527 } 528 } 529 #endif /* !NTP */ 530 /* Imprecise 4bsd adjtime() handling */ 531 if (timedelta != 0) { 532 delta += tickdelta; 533 timedelta -= tickdelta; 534 } 535 536 #ifdef notyet 537 microset(); 538 #endif 539 540 #ifndef NTP 541 BUMPTIME(&time, delta); /* XXX Now done using NTP code below */ 542 #endif 543 BUMPTIME(&mono_time, delta); 544 545 #ifdef NTP 546 time_update = delta; 547 548 /* 549 * Compute the phase adjustment. If the low-order bits 550 * (time_phase) of the update overflow, bump the high-order bits 551 * (time_update). 552 */ 553 time_phase += time_adj; 554 if (time_phase <= -FINEUSEC) { 555 ltemp = -time_phase >> SHIFT_SCALE; 556 time_phase += ltemp << SHIFT_SCALE; 557 time_update -= ltemp; 558 } else if (time_phase >= FINEUSEC) { 559 ltemp = time_phase >> SHIFT_SCALE; 560 time_phase -= ltemp << SHIFT_SCALE; 561 time_update += ltemp; 562 } 563 564 #ifdef HIGHBALL 565 /* 566 * If the HIGHBALL board is installed, we need to adjust the 567 * external clock offset in order to close the hardware feedback 568 * loop. This will adjust the external clock phase and frequency 569 * in small amounts. The additional phase noise and frequency 570 * wander this causes should be minimal. We also need to 571 * discipline the kernel time variable, since the PLL is used to 572 * discipline the external clock. If the Highball board is not 573 * present, we discipline kernel time with the PLL as usual. We 574 * assume that the external clock phase adjustment (time_update) 575 * and kernel phase adjustment (clock_cpu) are less than the 576 * value of tick. 577 */ 578 clock_offset.tv_usec += time_update; 579 if (clock_offset.tv_usec >= 1000000) { 580 clock_offset.tv_sec++; 581 clock_offset.tv_usec -= 1000000; 582 } 583 if (clock_offset.tv_usec < 0) { 584 clock_offset.tv_sec--; 585 clock_offset.tv_usec += 1000000; 586 } 587 time.tv_usec += clock_cpu; 588 clock_cpu = 0; 589 #else 590 time.tv_usec += time_update; 591 #endif /* HIGHBALL */ 592 593 /* 594 * On rollover of the second the phase adjustment to be used for 595 * the next second is calculated. Also, the maximum error is 596 * increased by the tolerance. If the PPS frequency discipline 597 * code is present, the phase is increased to compensate for the 598 * CPU clock oscillator frequency error. 599 * 600 * On a 32-bit machine and given parameters in the timex.h 601 * header file, the maximum phase adjustment is +-512 ms and 602 * maximum frequency offset is a tad less than) +-512 ppm. On a 603 * 64-bit machine, you shouldn't need to ask. 604 */ 605 if (time.tv_usec >= 1000000) { 606 time.tv_usec -= 1000000; 607 time.tv_sec++; 608 time_maxerror += time_tolerance >> SHIFT_USEC; 609 610 /* 611 * Leap second processing. If in leap-insert state at 612 * the end of the day, the system clock is set back one 613 * second; if in leap-delete state, the system clock is 614 * set ahead one second. The microtime() routine or 615 * external clock driver will insure that reported time 616 * is always monotonic. The ugly divides should be 617 * replaced. 618 */ 619 switch (time_state) { 620 case TIME_OK: 621 if (time_status & STA_INS) 622 time_state = TIME_INS; 623 else if (time_status & STA_DEL) 624 time_state = TIME_DEL; 625 break; 626 627 case TIME_INS: 628 if (time.tv_sec % 86400 == 0) { 629 time.tv_sec--; 630 time_state = TIME_OOP; 631 } 632 break; 633 634 case TIME_DEL: 635 if ((time.tv_sec + 1) % 86400 == 0) { 636 time.tv_sec++; 637 time_state = TIME_WAIT; 638 } 639 break; 640 641 case TIME_OOP: 642 time_state = TIME_WAIT; 643 break; 644 645 case TIME_WAIT: 646 if (!(time_status & (STA_INS | STA_DEL))) 647 time_state = TIME_OK; 648 break; 649 } 650 651 /* 652 * Compute the phase adjustment for the next second. In 653 * PLL mode, the offset is reduced by a fixed factor 654 * times the time constant. In FLL mode the offset is 655 * used directly. In either mode, the maximum phase 656 * adjustment for each second is clamped so as to spread 657 * the adjustment over not more than the number of 658 * seconds between updates. 659 */ 660 if (time_offset < 0) { 661 ltemp = -time_offset; 662 if (!(time_status & STA_FLL)) 663 ltemp >>= SHIFT_KG + time_constant; 664 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) 665 ltemp = (MAXPHASE / MINSEC) << 666 SHIFT_UPDATE; 667 time_offset += ltemp; 668 time_adj = -ltemp << (shifthz - SHIFT_UPDATE); 669 } else if (time_offset > 0) { 670 ltemp = time_offset; 671 if (!(time_status & STA_FLL)) 672 ltemp >>= SHIFT_KG + time_constant; 673 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) 674 ltemp = (MAXPHASE / MINSEC) << 675 SHIFT_UPDATE; 676 time_offset -= ltemp; 677 time_adj = ltemp << (shifthz - SHIFT_UPDATE); 678 } else 679 time_adj = 0; 680 681 /* 682 * Compute the frequency estimate and additional phase 683 * adjustment due to frequency error for the next 684 * second. When the PPS signal is engaged, gnaw on the 685 * watchdog counter and update the frequency computed by 686 * the pll and the PPS signal. 687 */ 688 #ifdef PPS_SYNC 689 pps_valid++; 690 if (pps_valid == PPS_VALID) { 691 pps_jitter = MAXTIME; 692 pps_stabil = MAXFREQ; 693 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 694 STA_PPSWANDER | STA_PPSERROR); 695 } 696 ltemp = time_freq + pps_freq; 697 #else 698 ltemp = time_freq; 699 #endif /* PPS_SYNC */ 700 701 if (ltemp < 0) 702 time_adj -= -ltemp >> (SHIFT_USEC - shifthz); 703 else 704 time_adj += ltemp >> (SHIFT_USEC - shifthz); 705 time_adj += (long)fixtick << shifthz; 706 707 /* 708 * When the CPU clock oscillator frequency is not a 709 * power of 2 in Hz, shifthz is only an approximate 710 * scale factor. 711 * 712 * To determine the adjustment, you can do the following: 713 * bc -q 714 * scale=24 715 * obase=2 716 * idealhz/realhz 717 * where `idealhz' is the next higher power of 2, and `realhz' 718 * is the actual value. You may need to factor this result 719 * into a sequence of 2 multipliers to get better precision. 720 * 721 * Likewise, the error can be calculated with (e.g. for 100Hz): 722 * bc -q 723 * scale=24 724 * ((1+2^-2+2^-5)*(1-2^-10)*realhz-idealhz)/idealhz 725 * (and then multiply by 1000000 to get ppm). 726 */ 727 switch (hz) { 728 case 60: 729 /* A factor of 1.000100010001 gives about 15ppm 730 error. */ 731 if (time_adj < 0) { 732 time_adj -= (-time_adj >> 4); 733 time_adj -= (-time_adj >> 8); 734 } else { 735 time_adj += (time_adj >> 4); 736 time_adj += (time_adj >> 8); 737 } 738 break; 739 740 case 96: 741 /* A factor of 1.0101010101 gives about 244ppm error. */ 742 if (time_adj < 0) { 743 time_adj -= (-time_adj >> 2); 744 time_adj -= (-time_adj >> 4) + (-time_adj >> 8); 745 } else { 746 time_adj += (time_adj >> 2); 747 time_adj += (time_adj >> 4) + (time_adj >> 8); 748 } 749 break; 750 751 case 50: 752 case 100: 753 /* A factor of 1.010001111010111 gives about 1ppm 754 error. */ 755 if (time_adj < 0) { 756 time_adj -= (-time_adj >> 2) + (-time_adj >> 5); 757 time_adj += (-time_adj >> 10); 758 } else { 759 time_adj += (time_adj >> 2) + (time_adj >> 5); 760 time_adj -= (time_adj >> 10); 761 } 762 break; 763 764 case 1000: 765 /* A factor of 1.000001100010100001 gives about 50ppm 766 error. */ 767 if (time_adj < 0) { 768 time_adj -= (-time_adj >> 6) + (-time_adj >> 11); 769 time_adj -= (-time_adj >> 7); 770 } else { 771 time_adj += (time_adj >> 6) + (time_adj >> 11); 772 time_adj += (time_adj >> 7); 773 } 774 break; 775 776 case 1200: 777 /* A factor of 1.1011010011100001 gives about 64ppm 778 error. */ 779 if (time_adj < 0) { 780 time_adj -= (-time_adj >> 1) + (-time_adj >> 6); 781 time_adj -= (-time_adj >> 3) + (-time_adj >> 10); 782 } else { 783 time_adj += (time_adj >> 1) + (time_adj >> 6); 784 time_adj += (time_adj >> 3) + (time_adj >> 10); 785 } 786 break; 787 } 788 789 #ifdef EXT_CLOCK 790 /* 791 * If an external clock is present, it is necessary to 792 * discipline the kernel time variable anyway, since not 793 * all system components use the microtime() interface. 794 * Here, the time offset between the external clock and 795 * kernel time variable is computed every so often. 796 */ 797 clock_count++; 798 if (clock_count > CLOCK_INTERVAL) { 799 clock_count = 0; 800 microtime(&clock_ext); 801 delta.tv_sec = clock_ext.tv_sec - time.tv_sec; 802 delta.tv_usec = clock_ext.tv_usec - 803 time.tv_usec; 804 if (delta.tv_usec < 0) 805 delta.tv_sec--; 806 if (delta.tv_usec >= 500000) { 807 delta.tv_usec -= 1000000; 808 delta.tv_sec++; 809 } 810 if (delta.tv_usec < -500000) { 811 delta.tv_usec += 1000000; 812 delta.tv_sec--; 813 } 814 if (delta.tv_sec > 0 || (delta.tv_sec == 0 && 815 delta.tv_usec > MAXPHASE) || 816 delta.tv_sec < -1 || (delta.tv_sec == -1 && 817 delta.tv_usec < -MAXPHASE)) { 818 time = clock_ext; 819 delta.tv_sec = 0; 820 delta.tv_usec = 0; 821 } 822 #ifdef HIGHBALL 823 clock_cpu = delta.tv_usec; 824 #else /* HIGHBALL */ 825 hardupdate(delta.tv_usec); 826 #endif /* HIGHBALL */ 827 } 828 #endif /* EXT_CLOCK */ 829 } 830 831 #endif /* NTP */ 832 833 /* 834 * Update real-time timeout queue. 835 * Process callouts at a very low CPU priority, so we don't keep the 836 * relatively high clock interrupt priority any longer than necessary. 837 */ 838 if (callout_hardclock()) { 839 if (CLKF_BASEPRI(frame)) { 840 /* 841 * Save the overhead of a software interrupt; 842 * it will happen as soon as we return, so do 843 * it now. 844 */ 845 spllowersoftclock(); 846 KERNEL_LOCK(LK_CANRECURSE|LK_EXCLUSIVE); 847 softclock(NULL); 848 KERNEL_UNLOCK(); 849 } else { 850 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS 851 softintr_schedule(softclock_si); 852 #else 853 setsoftclock(); 854 #endif 855 } 856 } 857 } 858 859 /* 860 * Compute number of hz until specified time. Used to compute second 861 * argument to callout_reset() from an absolute time. 862 */ 863 int 864 hzto(struct timeval *tv) 865 { 866 unsigned long ticks; 867 long sec, usec; 868 int s; 869 870 /* 871 * If the number of usecs in the whole seconds part of the time 872 * difference fits in a long, then the total number of usecs will 873 * fit in an unsigned long. Compute the total and convert it to 874 * ticks, rounding up and adding 1 to allow for the current tick 875 * to expire. Rounding also depends on unsigned long arithmetic 876 * to avoid overflow. 877 * 878 * Otherwise, if the number of ticks in the whole seconds part of 879 * the time difference fits in a long, then convert the parts to 880 * ticks separately and add, using similar rounding methods and 881 * overflow avoidance. This method would work in the previous 882 * case, but it is slightly slower and assume that hz is integral. 883 * 884 * Otherwise, round the time difference down to the maximum 885 * representable value. 886 * 887 * If ints are 32-bit, then the maximum value for any timeout in 888 * 10ms ticks is 248 days. 889 */ 890 s = splclock(); 891 sec = tv->tv_sec - time.tv_sec; 892 usec = tv->tv_usec - time.tv_usec; 893 splx(s); 894 895 if (usec < 0) { 896 sec--; 897 usec += 1000000; 898 } 899 900 if (sec < 0 || (sec == 0 && usec <= 0)) { 901 /* 902 * Would expire now or in the past. Return 0 ticks. 903 * This is different from the legacy hzto() interface, 904 * and callers need to check for it. 905 */ 906 ticks = 0; 907 } else if (sec <= (LONG_MAX / 1000000)) 908 ticks = (((sec * 1000000) + (unsigned long)usec + (tick - 1)) 909 / tick) + 1; 910 else if (sec <= (LONG_MAX / hz)) 911 ticks = (sec * hz) + 912 (((unsigned long)usec + (tick - 1)) / tick) + 1; 913 else 914 ticks = LONG_MAX; 915 916 if (ticks > INT_MAX) 917 ticks = INT_MAX; 918 919 return ((int)ticks); 920 } 921 922 /* 923 * Start profiling on a process. 924 * 925 * Kernel profiling passes proc0 which never exits and hence 926 * keeps the profile clock running constantly. 927 */ 928 void 929 startprofclock(struct proc *p) 930 { 931 932 if ((p->p_flag & P_PROFIL) == 0) { 933 p->p_flag |= P_PROFIL; 934 /* 935 * This is only necessary if using the clock as the 936 * profiling source. 937 */ 938 if (++profprocs == 1 && stathz != 0) 939 psdiv = psratio; 940 } 941 } 942 943 /* 944 * Stop profiling on a process. 945 */ 946 void 947 stopprofclock(struct proc *p) 948 { 949 950 if (p->p_flag & P_PROFIL) { 951 p->p_flag &= ~P_PROFIL; 952 /* 953 * This is only necessary if using the clock as the 954 * profiling source. 955 */ 956 if (--profprocs == 0 && stathz != 0) 957 psdiv = 1; 958 } 959 } 960 961 #if defined(PERFCTRS) 962 /* 963 * Independent profiling "tick" in case we're using a separate 964 * clock or profiling event source. Currently, that's just 965 * performance counters--hence the wrapper. 966 */ 967 void 968 proftick(struct clockframe *frame) 969 { 970 #ifdef GPROF 971 struct gmonparam *g; 972 intptr_t i; 973 #endif 974 struct proc *p; 975 976 p = curproc; 977 if (CLKF_USERMODE(frame)) { 978 if (p->p_flag & P_PROFIL) 979 addupc_intr(p, CLKF_PC(frame)); 980 } else { 981 #ifdef GPROF 982 g = &_gmonparam; 983 if (g->state == GMON_PROF_ON) { 984 i = CLKF_PC(frame) - g->lowpc; 985 if (i < g->textsize) { 986 i /= HISTFRACTION * sizeof(*g->kcount); 987 g->kcount[i]++; 988 } 989 } 990 #endif 991 #ifdef PROC_PC 992 if (p && p->p_flag & P_PROFIL) 993 addupc_intr(p, PROC_PC(p)); 994 #endif 995 } 996 } 997 #endif 998 999 /* 1000 * Statistics clock. Grab profile sample, and if divider reaches 0, 1001 * do process and kernel statistics. 1002 */ 1003 void 1004 statclock(struct clockframe *frame) 1005 { 1006 #ifdef GPROF 1007 struct gmonparam *g; 1008 intptr_t i; 1009 #endif 1010 struct cpu_info *ci = curcpu(); 1011 struct schedstate_percpu *spc = &ci->ci_schedstate; 1012 struct lwp *l; 1013 struct proc *p; 1014 1015 /* 1016 * Notice changes in divisor frequency, and adjust clock 1017 * frequency accordingly. 1018 */ 1019 if (spc->spc_psdiv != psdiv) { 1020 spc->spc_psdiv = psdiv; 1021 spc->spc_pscnt = psdiv; 1022 if (psdiv == 1) { 1023 setstatclockrate(stathz); 1024 } else { 1025 setstatclockrate(profhz); 1026 } 1027 } 1028 l = curlwp; 1029 p = (l ? l->l_proc : 0); 1030 if (CLKF_USERMODE(frame)) { 1031 if (p->p_flag & P_PROFIL && profsrc == PROFSRC_CLOCK) 1032 addupc_intr(p, CLKF_PC(frame)); 1033 if (--spc->spc_pscnt > 0) 1034 return; 1035 /* 1036 * Came from user mode; CPU was in user state. 1037 * If this process is being profiled record the tick. 1038 */ 1039 p->p_uticks++; 1040 if (p->p_nice > NZERO) 1041 spc->spc_cp_time[CP_NICE]++; 1042 else 1043 spc->spc_cp_time[CP_USER]++; 1044 } else { 1045 #ifdef GPROF 1046 /* 1047 * Kernel statistics are just like addupc_intr, only easier. 1048 */ 1049 g = &_gmonparam; 1050 if (profsrc == PROFSRC_CLOCK && g->state == GMON_PROF_ON) { 1051 i = CLKF_PC(frame) - g->lowpc; 1052 if (i < g->textsize) { 1053 i /= HISTFRACTION * sizeof(*g->kcount); 1054 g->kcount[i]++; 1055 } 1056 } 1057 #endif 1058 #ifdef LWP_PC 1059 if (p && profsrc == PROFSRC_CLOCK && p->p_flag & P_PROFIL) 1060 addupc_intr(p, LWP_PC(l)); 1061 #endif 1062 if (--spc->spc_pscnt > 0) 1063 return; 1064 /* 1065 * Came from kernel mode, so we were: 1066 * - handling an interrupt, 1067 * - doing syscall or trap work on behalf of the current 1068 * user process, or 1069 * - spinning in the idle loop. 1070 * Whichever it is, charge the time as appropriate. 1071 * Note that we charge interrupts to the current process, 1072 * regardless of whether they are ``for'' that process, 1073 * so that we know how much of its real time was spent 1074 * in ``non-process'' (i.e., interrupt) work. 1075 */ 1076 if (CLKF_INTR(frame)) { 1077 if (p != NULL) 1078 p->p_iticks++; 1079 spc->spc_cp_time[CP_INTR]++; 1080 } else if (p != NULL) { 1081 p->p_sticks++; 1082 spc->spc_cp_time[CP_SYS]++; 1083 } else 1084 spc->spc_cp_time[CP_IDLE]++; 1085 } 1086 spc->spc_pscnt = psdiv; 1087 1088 if (l != NULL) { 1089 ++p->p_cpticks; 1090 /* 1091 * If no separate schedclock is provided, call it here 1092 * at about 16 Hz. 1093 */ 1094 if (schedhz == 0) 1095 if ((int)(--ci->ci_schedstate.spc_schedticks) <= 0) { 1096 schedclock(l); 1097 ci->ci_schedstate.spc_schedticks = statscheddiv; 1098 } 1099 } 1100 } 1101 1102 1103 #ifdef NTP /* NTP phase-locked loop in kernel */ 1104 1105 /* 1106 * hardupdate() - local clock update 1107 * 1108 * This routine is called by ntp_adjtime() to update the local clock 1109 * phase and frequency. The implementation is of an adaptive-parameter, 1110 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 1111 * time and frequency offset estimates for each call. If the kernel PPS 1112 * discipline code is configured (PPS_SYNC), the PPS signal itself 1113 * determines the new time offset, instead of the calling argument. 1114 * Presumably, calls to ntp_adjtime() occur only when the caller 1115 * believes the local clock is valid within some bound (+-128 ms with 1116 * NTP). If the caller's time is far different than the PPS time, an 1117 * argument will ensue, and it's not clear who will lose. 1118 * 1119 * For uncompensated quartz crystal oscillatores and nominal update 1120 * intervals less than 1024 s, operation should be in phase-lock mode 1121 * (STA_FLL = 0), where the loop is disciplined to phase. For update 1122 * intervals greater than thiss, operation should be in frequency-lock 1123 * mode (STA_FLL = 1), where the loop is disciplined to frequency. 1124 * 1125 * Note: splclock() is in effect. 1126 */ 1127 void 1128 hardupdate(long offset) 1129 { 1130 long ltemp, mtemp; 1131 1132 if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME)) 1133 return; 1134 ltemp = offset; 1135 #ifdef PPS_SYNC 1136 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 1137 ltemp = pps_offset; 1138 #endif /* PPS_SYNC */ 1139 1140 /* 1141 * Scale the phase adjustment and clamp to the operating range. 1142 */ 1143 if (ltemp > MAXPHASE) 1144 time_offset = MAXPHASE << SHIFT_UPDATE; 1145 else if (ltemp < -MAXPHASE) 1146 time_offset = -(MAXPHASE << SHIFT_UPDATE); 1147 else 1148 time_offset = ltemp << SHIFT_UPDATE; 1149 1150 /* 1151 * Select whether the frequency is to be controlled and in which 1152 * mode (PLL or FLL). Clamp to the operating range. Ugly 1153 * multiply/divide should be replaced someday. 1154 */ 1155 if (time_status & STA_FREQHOLD || time_reftime == 0) 1156 time_reftime = time.tv_sec; 1157 mtemp = time.tv_sec - time_reftime; 1158 time_reftime = time.tv_sec; 1159 if (time_status & STA_FLL) { 1160 if (mtemp >= MINSEC) { 1161 ltemp = ((time_offset / mtemp) << (SHIFT_USEC - 1162 SHIFT_UPDATE)); 1163 if (ltemp < 0) 1164 time_freq -= -ltemp >> SHIFT_KH; 1165 else 1166 time_freq += ltemp >> SHIFT_KH; 1167 } 1168 } else { 1169 if (mtemp < MAXSEC) { 1170 ltemp *= mtemp; 1171 if (ltemp < 0) 1172 time_freq -= -ltemp >> (time_constant + 1173 time_constant + SHIFT_KF - 1174 SHIFT_USEC); 1175 else 1176 time_freq += ltemp >> (time_constant + 1177 time_constant + SHIFT_KF - 1178 SHIFT_USEC); 1179 } 1180 } 1181 if (time_freq > time_tolerance) 1182 time_freq = time_tolerance; 1183 else if (time_freq < -time_tolerance) 1184 time_freq = -time_tolerance; 1185 } 1186 1187 #ifdef PPS_SYNC 1188 /* 1189 * hardpps() - discipline CPU clock oscillator to external PPS signal 1190 * 1191 * This routine is called at each PPS interrupt in order to discipline 1192 * the CPU clock oscillator to the PPS signal. It measures the PPS phase 1193 * and leaves it in a handy spot for the hardclock() routine. It 1194 * integrates successive PPS phase differences and calculates the 1195 * frequency offset. This is used in hardclock() to discipline the CPU 1196 * clock oscillator so that intrinsic frequency error is cancelled out. 1197 * The code requires the caller to capture the time and hardware counter 1198 * value at the on-time PPS signal transition. 1199 * 1200 * Note that, on some Unix systems, this routine runs at an interrupt 1201 * priority level higher than the timer interrupt routine hardclock(). 1202 * Therefore, the variables used are distinct from the hardclock() 1203 * variables, except for certain exceptions: The PPS frequency pps_freq 1204 * and phase pps_offset variables are determined by this routine and 1205 * updated atomically. The time_tolerance variable can be considered a 1206 * constant, since it is infrequently changed, and then only when the 1207 * PPS signal is disabled. The watchdog counter pps_valid is updated 1208 * once per second by hardclock() and is atomically cleared in this 1209 * routine. 1210 */ 1211 void 1212 hardpps(struct timeval *tvp, /* time at PPS */ 1213 long usec /* hardware counter at PPS */) 1214 { 1215 long u_usec, v_usec, bigtick; 1216 long cal_sec, cal_usec; 1217 1218 /* 1219 * An occasional glitch can be produced when the PPS interrupt 1220 * occurs in the hardclock() routine before the time variable is 1221 * updated. Here the offset is discarded when the difference 1222 * between it and the last one is greater than tick/2, but not 1223 * if the interval since the first discard exceeds 30 s. 1224 */ 1225 time_status |= STA_PPSSIGNAL; 1226 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 1227 pps_valid = 0; 1228 u_usec = -tvp->tv_usec; 1229 if (u_usec < -500000) 1230 u_usec += 1000000; 1231 v_usec = pps_offset - u_usec; 1232 if (v_usec < 0) 1233 v_usec = -v_usec; 1234 if (v_usec > (tick >> 1)) { 1235 if (pps_glitch > MAXGLITCH) { 1236 pps_glitch = 0; 1237 pps_tf[2] = u_usec; 1238 pps_tf[1] = u_usec; 1239 } else { 1240 pps_glitch++; 1241 u_usec = pps_offset; 1242 } 1243 } else 1244 pps_glitch = 0; 1245 1246 /* 1247 * A three-stage median filter is used to help deglitch the pps 1248 * time. The median sample becomes the time offset estimate; the 1249 * difference between the other two samples becomes the time 1250 * dispersion (jitter) estimate. 1251 */ 1252 pps_tf[2] = pps_tf[1]; 1253 pps_tf[1] = pps_tf[0]; 1254 pps_tf[0] = u_usec; 1255 if (pps_tf[0] > pps_tf[1]) { 1256 if (pps_tf[1] > pps_tf[2]) { 1257 pps_offset = pps_tf[1]; /* 0 1 2 */ 1258 v_usec = pps_tf[0] - pps_tf[2]; 1259 } else if (pps_tf[2] > pps_tf[0]) { 1260 pps_offset = pps_tf[0]; /* 2 0 1 */ 1261 v_usec = pps_tf[2] - pps_tf[1]; 1262 } else { 1263 pps_offset = pps_tf[2]; /* 0 2 1 */ 1264 v_usec = pps_tf[0] - pps_tf[1]; 1265 } 1266 } else { 1267 if (pps_tf[1] < pps_tf[2]) { 1268 pps_offset = pps_tf[1]; /* 2 1 0 */ 1269 v_usec = pps_tf[2] - pps_tf[0]; 1270 } else if (pps_tf[2] < pps_tf[0]) { 1271 pps_offset = pps_tf[0]; /* 1 0 2 */ 1272 v_usec = pps_tf[1] - pps_tf[2]; 1273 } else { 1274 pps_offset = pps_tf[2]; /* 1 2 0 */ 1275 v_usec = pps_tf[1] - pps_tf[0]; 1276 } 1277 } 1278 if (v_usec > MAXTIME) 1279 pps_jitcnt++; 1280 v_usec = (v_usec << PPS_AVG) - pps_jitter; 1281 if (v_usec < 0) 1282 pps_jitter -= -v_usec >> PPS_AVG; 1283 else 1284 pps_jitter += v_usec >> PPS_AVG; 1285 if (pps_jitter > (MAXTIME >> 1)) 1286 time_status |= STA_PPSJITTER; 1287 1288 /* 1289 * During the calibration interval adjust the starting time when 1290 * the tick overflows. At the end of the interval compute the 1291 * duration of the interval and the difference of the hardware 1292 * counters at the beginning and end of the interval. This code 1293 * is deliciously complicated by the fact valid differences may 1294 * exceed the value of tick when using long calibration 1295 * intervals and small ticks. Note that the counter can be 1296 * greater than tick if caught at just the wrong instant, but 1297 * the values returned and used here are correct. 1298 */ 1299 bigtick = (long)tick << SHIFT_USEC; 1300 pps_usec -= pps_freq; 1301 if (pps_usec >= bigtick) 1302 pps_usec -= bigtick; 1303 if (pps_usec < 0) 1304 pps_usec += bigtick; 1305 pps_time.tv_sec++; 1306 pps_count++; 1307 if (pps_count < (1 << pps_shift)) 1308 return; 1309 pps_count = 0; 1310 pps_calcnt++; 1311 u_usec = usec << SHIFT_USEC; 1312 v_usec = pps_usec - u_usec; 1313 if (v_usec >= bigtick >> 1) 1314 v_usec -= bigtick; 1315 if (v_usec < -(bigtick >> 1)) 1316 v_usec += bigtick; 1317 if (v_usec < 0) 1318 v_usec = -(-v_usec >> pps_shift); 1319 else 1320 v_usec = v_usec >> pps_shift; 1321 pps_usec = u_usec; 1322 cal_sec = tvp->tv_sec; 1323 cal_usec = tvp->tv_usec; 1324 cal_sec -= pps_time.tv_sec; 1325 cal_usec -= pps_time.tv_usec; 1326 if (cal_usec < 0) { 1327 cal_usec += 1000000; 1328 cal_sec--; 1329 } 1330 pps_time = *tvp; 1331 1332 /* 1333 * Check for lost interrupts, noise, excessive jitter and 1334 * excessive frequency error. The number of timer ticks during 1335 * the interval may vary +-1 tick. Add to this a margin of one 1336 * tick for the PPS signal jitter and maximum frequency 1337 * deviation. If the limits are exceeded, the calibration 1338 * interval is reset to the minimum and we start over. 1339 */ 1340 u_usec = (long)tick << 1; 1341 if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec)) 1342 || (cal_sec == 0 && cal_usec < u_usec)) 1343 || v_usec > time_tolerance || v_usec < -time_tolerance) { 1344 pps_errcnt++; 1345 pps_shift = PPS_SHIFT; 1346 pps_intcnt = 0; 1347 time_status |= STA_PPSERROR; 1348 return; 1349 } 1350 1351 /* 1352 * A three-stage median filter is used to help deglitch the pps 1353 * frequency. The median sample becomes the frequency offset 1354 * estimate; the difference between the other two samples 1355 * becomes the frequency dispersion (stability) estimate. 1356 */ 1357 pps_ff[2] = pps_ff[1]; 1358 pps_ff[1] = pps_ff[0]; 1359 pps_ff[0] = v_usec; 1360 if (pps_ff[0] > pps_ff[1]) { 1361 if (pps_ff[1] > pps_ff[2]) { 1362 u_usec = pps_ff[1]; /* 0 1 2 */ 1363 v_usec = pps_ff[0] - pps_ff[2]; 1364 } else if (pps_ff[2] > pps_ff[0]) { 1365 u_usec = pps_ff[0]; /* 2 0 1 */ 1366 v_usec = pps_ff[2] - pps_ff[1]; 1367 } else { 1368 u_usec = pps_ff[2]; /* 0 2 1 */ 1369 v_usec = pps_ff[0] - pps_ff[1]; 1370 } 1371 } else { 1372 if (pps_ff[1] < pps_ff[2]) { 1373 u_usec = pps_ff[1]; /* 2 1 0 */ 1374 v_usec = pps_ff[2] - pps_ff[0]; 1375 } else if (pps_ff[2] < pps_ff[0]) { 1376 u_usec = pps_ff[0]; /* 1 0 2 */ 1377 v_usec = pps_ff[1] - pps_ff[2]; 1378 } else { 1379 u_usec = pps_ff[2]; /* 1 2 0 */ 1380 v_usec = pps_ff[1] - pps_ff[0]; 1381 } 1382 } 1383 1384 /* 1385 * Here the frequency dispersion (stability) is updated. If it 1386 * is less than one-fourth the maximum (MAXFREQ), the frequency 1387 * offset is updated as well, but clamped to the tolerance. It 1388 * will be processed later by the hardclock() routine. 1389 */ 1390 v_usec = (v_usec >> 1) - pps_stabil; 1391 if (v_usec < 0) 1392 pps_stabil -= -v_usec >> PPS_AVG; 1393 else 1394 pps_stabil += v_usec >> PPS_AVG; 1395 if (pps_stabil > MAXFREQ >> 2) { 1396 pps_stbcnt++; 1397 time_status |= STA_PPSWANDER; 1398 return; 1399 } 1400 if (time_status & STA_PPSFREQ) { 1401 if (u_usec < 0) { 1402 pps_freq -= -u_usec >> PPS_AVG; 1403 if (pps_freq < -time_tolerance) 1404 pps_freq = -time_tolerance; 1405 u_usec = -u_usec; 1406 } else { 1407 pps_freq += u_usec >> PPS_AVG; 1408 if (pps_freq > time_tolerance) 1409 pps_freq = time_tolerance; 1410 } 1411 } 1412 1413 /* 1414 * Here the calibration interval is adjusted. If the maximum 1415 * time difference is greater than tick / 4, reduce the interval 1416 * by half. If this is not the case for four consecutive 1417 * intervals, double the interval. 1418 */ 1419 if (u_usec << pps_shift > bigtick >> 2) { 1420 pps_intcnt = 0; 1421 if (pps_shift > PPS_SHIFT) 1422 pps_shift--; 1423 } else if (pps_intcnt >= 4) { 1424 pps_intcnt = 0; 1425 if (pps_shift < PPS_SHIFTMAX) 1426 pps_shift++; 1427 } else 1428 pps_intcnt++; 1429 } 1430 #endif /* PPS_SYNC */ 1431 #endif /* NTP */ 1432