1 /****************************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993, 1994 * 4 * * 5 * Permission to use, copy, modify, and distribute this software and its * 6 * documentation for any purpose and without fee is hereby granted, provided * 7 * that the above copyright notice appears in all copies and that both the * 8 * copyright notice and this permission notice appear in supporting * 9 * documentation, and that the name University of Delaware not be used in * 10 * advertising or publicity pertaining to distribution of the software * 11 * without specific, written prior permission. The University of Delaware * 12 * makes no representations about the suitability this software for any * 13 * purpose. It is provided "as is" without express or implied warranty. * 14 * * 15 ******************************************************************************/ 16 17 /* 18 * Modification history kern_ntptime.c 19 * 20 * 24 Sep 94 David L. Mills 21 * Tightened code at exits. 22 * 23 * 24 Mar 94 David L. Mills 24 * Revised syscall interface to include new variables for PPS 25 * time discipline. 26 * 27 * 14 Feb 94 David L. Mills 28 * Added code for external clock 29 * 30 * 28 Nov 93 David L. Mills 31 * Revised frequency scaling to conform with adjusted parameters 32 * 33 * 17 Sep 93 David L. Mills 34 * Created file 35 */ 36 /* 37 * ntp_gettime(), ntp_adjtime() - precision time interface for SunOS 38 * V4.1.1 and V4.1.3 39 * 40 * These routines consitute the Network Time Protocol (NTP) interfaces 41 * for user and daemon application programs. The ntp_gettime() routine 42 * provides the time, maximum error (synch distance) and estimated error 43 * (dispersion) to client user application programs. The ntp_adjtime() 44 * routine is used by the NTP daemon to adjust the system clock to an 45 * externally derived time. The time offset and related variables set by 46 * this routine are used by hardclock() to adjust the phase and 47 * frequency of the phase-lock loop which controls the system clock. 48 */ 49 50 #include "opt_ntp.h" 51 52 #include <sys/param.h> 53 #include <sys/systm.h> 54 #include <sys/sysproto.h> 55 #include <sys/kernel.h> 56 #include <sys/proc.h> 57 #include <sys/timex.h> 58 #include <sys/timepps.h> 59 #include <sys/sysctl.h> 60 61 /* 62 * Phase/frequency-lock loop (PLL/FLL) definitions 63 * 64 * The following variables are read and set by the ntp_adjtime() system 65 * call. 66 * 67 * time_state shows the state of the system clock, with values defined 68 * in the timex.h header file. 69 * 70 * time_status shows the status of the system clock, with bits defined 71 * in the timex.h header file. 72 * 73 * time_offset is used by the PLL/FLL to adjust the system time in small 74 * increments. 75 * 76 * time_constant determines the bandwidth or "stiffness" of the PLL. 77 * 78 * time_tolerance determines maximum frequency error or tolerance of the 79 * CPU clock oscillator and is a property of the architecture; however, 80 * in principle it could change as result of the presence of external 81 * discipline signals, for instance. 82 * 83 * time_precision is usually equal to the kernel tick variable; however, 84 * in cases where a precision clock counter or external clock is 85 * available, the resolution can be much less than this and depend on 86 * whether the external clock is working or not. 87 * 88 * time_maxerror is initialized by a ntp_adjtime() call and increased by 89 * the kernel once each second to reflect the maximum error 90 * bound growth. 91 * 92 * time_esterror is set and read by the ntp_adjtime() call, but 93 * otherwise not used by the kernel. 94 */ 95 static int time_status = STA_UNSYNC; /* clock status bits */ 96 static int time_state = TIME_OK; /* clock state */ 97 static long time_offset = 0; /* time offset (us) */ 98 static long time_constant = 0; /* pll time constant */ 99 static long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */ 100 static long time_precision = 1; /* clock precision (us) */ 101 static long time_maxerror = MAXPHASE; /* maximum error (us) */ 102 static long time_esterror = MAXPHASE; /* estimated error (us) */ 103 static int time_daemon = 0; /* No timedaemon active */ 104 105 /* 106 * The following variables establish the state of the PLL/FLL and the 107 * residual time and frequency offset of the local clock. The scale 108 * factors are defined in the timex.h header file. 109 * 110 * time_phase and time_freq are the phase increment and the frequency 111 * increment, respectively, of the kernel time variable at each tick of 112 * the clock. 113 * 114 * time_freq is set via ntp_adjtime() from a value stored in a file when 115 * the synchronization daemon is first started. Its value is retrieved 116 * via ntp_adjtime() and written to the file about once per hour by the 117 * daemon. 118 * 119 * time_adj is the adjustment added to the value of tick at each timer 120 * interrupt and is recomputed from time_phase and time_freq at each 121 * seconds rollover. 122 * 123 * time_reftime is the second's portion of the system time on the last 124 * call to ntp_adjtime(). It is used to adjust the time_freq variable 125 * and to increase the time_maxerror as the time since last update 126 * increases. 127 */ 128 long time_phase = 0; /* phase offset (scaled us) */ 129 static long time_freq = 0; /* frequency offset (scaled ppm) */ 130 long time_adj = 0; /* tick adjust (scaled 1 / hz) */ 131 static long time_reftime = 0; /* time at last adjustment (s) */ 132 133 #ifdef PPS_SYNC 134 /* 135 * The following variables are used only if the kernel PPS discipline 136 * code is configured (PPS_SYNC). The scale factors are defined in the 137 * timex.h header file. 138 * 139 * pps_time contains the time at each calibration interval, as read by 140 * microtime(). pps_count counts the seconds of the calibration 141 * interval, the duration of which is nominally pps_shift in powers of 142 * two. 143 * 144 * pps_offset is the time offset produced by the time median filter 145 * pps_tf[], while pps_jitter is the dispersion (jitter) measured by 146 * this filter. 147 * 148 * pps_freq is the frequency offset produced by the frequency median 149 * filter pps_ff[], while pps_stabil is the dispersion (wander) measured 150 * by this filter. 151 * 152 * pps_usec is latched from a high resolution counter or external clock 153 * at pps_time. Here we want the hardware counter contents only, not the 154 * contents plus the time_tv.usec as usual. 155 * 156 * pps_valid counts the number of seconds since the last PPS update. It 157 * is used as a watchdog timer to disable the PPS discipline should the 158 * PPS signal be lost. 159 * 160 * pps_glitch counts the number of seconds since the beginning of an 161 * offset burst more than tick/2 from current nominal offset. It is used 162 * mainly to suppress error bursts due to priority conflicts between the 163 * PPS interrupt and timer interrupt. 164 * 165 * pps_intcnt counts the calibration intervals for use in the interval- 166 * adaptation algorithm. It's just too complicated for words. 167 */ 168 static struct timeval pps_time; /* kernel time at last interval */ 169 static long pps_offset = 0; /* pps time offset (us) */ 170 static long pps_jitter = MAXTIME; /* pps time dispersion (jitter) (us) */ 171 static long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */ 172 static long pps_freq = 0; /* frequency offset (scaled ppm) */ 173 static long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */ 174 static long pps_ff[] = {0, 0, 0}; /* frequency offset median filter */ 175 static long pps_usec = 0; /* microsec counter at last interval */ 176 static long pps_valid = PPS_VALID; /* pps signal watchdog counter */ 177 static int pps_glitch = 0; /* pps signal glitch counter */ 178 static int pps_count = 0; /* calibration interval counter (s) */ 179 static int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */ 180 static int pps_intcnt = 0; /* intervals at current duration */ 181 182 /* 183 * PPS signal quality monitors 184 * 185 * pps_jitcnt counts the seconds that have been discarded because the 186 * jitter measured by the time median filter exceeds the limit MAXTIME 187 * (100 us). 188 * 189 * pps_calcnt counts the frequency calibration intervals, which are 190 * variable from 4 s to 256 s. 191 * 192 * pps_errcnt counts the calibration intervals which have been discarded 193 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the 194 * calibration interval jitter exceeds two ticks. 195 * 196 * pps_stbcnt counts the calibration intervals that have been discarded 197 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us). 198 */ 199 static long pps_jitcnt = 0; /* jitter limit exceeded */ 200 static long pps_calcnt = 0; /* calibration intervals */ 201 static long pps_errcnt = 0; /* calibration errors */ 202 static long pps_stbcnt = 0; /* stability limit exceeded */ 203 #endif /* PPS_SYNC */ 204 205 static void hardupdate __P((int64_t offset, int prescaled)); 206 207 /* 208 * hardupdate() - local clock update 209 * 210 * This routine is called by ntp_adjtime() to update the local clock 211 * phase and frequency. The implementation is of an adaptive-parameter, 212 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 213 * time and frequency offset estimates for each call. If the kernel PPS 214 * discipline code is configured (PPS_SYNC), the PPS signal itself 215 * determines the new time offset, instead of the calling argument. 216 * Presumably, calls to ntp_adjtime() occur only when the caller 217 * believes the local clock is valid within some bound (+-128 ms with 218 * NTP). If the caller's time is far different than the PPS time, an 219 * argument will ensue, and it's not clear who will lose. 220 * 221 * For uncompensated quartz crystal oscillatores and nominal update 222 * intervals less than 1024 s, operation should be in phase-lock mode 223 * (STA_FLL = 0), where the loop is disciplined to phase. For update 224 * intervals greater than thiss, operation should be in frequency-lock 225 * mode (STA_FLL = 1), where the loop is disciplined to frequency. 226 * 227 * Note: splclock() is in effect. 228 */ 229 static void 230 hardupdate(offset, prescaled) 231 int64_t offset; 232 int prescaled; 233 { 234 long mtemp; 235 int64_t ltemp; 236 237 if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME)) 238 return; 239 if (prescaled) 240 ltemp = offset; 241 else 242 ltemp = offset << SHIFT_UPDATE; 243 #ifdef PPS_SYNC 244 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 245 ltemp = pps_offset << SHIFT_UPDATE; 246 #endif /* PPS_SYNC */ 247 248 /* 249 * Scale the phase adjustment and clamp to the operating range. 250 */ 251 if (ltemp > (MAXPHASE << SHIFT_UPDATE)) 252 time_offset = MAXPHASE << SHIFT_UPDATE; 253 else if (ltemp < -(MAXPHASE << SHIFT_UPDATE)) 254 time_offset = -(MAXPHASE << SHIFT_UPDATE); 255 else 256 time_offset = ltemp; 257 258 /* 259 * Select whether the frequency is to be controlled and in which 260 * mode (PLL or FLL). Clamp to the operating range. Ugly 261 * multiply/divide should be replaced someday. 262 */ 263 if (time_status & STA_FREQHOLD || time_reftime == 0) 264 time_reftime = time_second; 265 mtemp = time_second - time_reftime; 266 time_reftime = time_second; 267 if (time_status & STA_FLL) { 268 if (mtemp >= MINSEC) { 269 ltemp = ((time_offset / mtemp) << (SHIFT_USEC - 270 SHIFT_UPDATE)); 271 if (ltemp < 0) 272 time_freq -= -ltemp >> SHIFT_KH; 273 else 274 time_freq += ltemp >> SHIFT_KH; 275 } 276 } else { 277 if (mtemp < MAXSEC) { 278 ltemp = time_offset * mtemp; 279 if (ltemp < 0) 280 time_freq -= -ltemp >> ((int64_t)time_constant + 281 time_constant + SHIFT_KF - 282 SHIFT_USEC + SHIFT_UPDATE); 283 else 284 time_freq += ltemp >> ((int64_t)time_constant + 285 time_constant + SHIFT_KF - 286 SHIFT_USEC + SHIFT_UPDATE); 287 } 288 } 289 if (time_freq > time_tolerance) 290 time_freq = time_tolerance; 291 else if (time_freq < -time_tolerance) 292 time_freq = -time_tolerance; 293 } 294 295 /* 296 * On rollover of the second the phase adjustment to be used for 297 * the next second is calculated. Also, the maximum error is 298 * increased by the tolerance. If the PPS frequency discipline 299 * code is present, the phase is increased to compensate for the 300 * CPU clock oscillator frequency error. 301 * 302 * On a 32-bit machine and given parameters in the timex.h 303 * header file, the maximum phase adjustment is +-512 ms and 304 * maximum frequency offset is a tad less than) +-512 ppm. On a 305 * 64-bit machine, you shouldn't need to ask. 306 */ 307 void 308 ntp_update_second(struct timecounter *tc) 309 { 310 u_int32_t *newsec; 311 long ltemp; 312 313 if (!time_daemon) 314 return; 315 316 newsec = &tc->tc_offset_sec; 317 time_maxerror += time_tolerance >> SHIFT_USEC; 318 319 /* 320 * Compute the phase adjustment for the next second. In 321 * PLL mode, the offset is reduced by a fixed factor 322 * times the time constant. In FLL mode the offset is 323 * used directly. In either mode, the maximum phase 324 * adjustment for each second is clamped so as to spread 325 * the adjustment over not more than the number of 326 * seconds between updates. 327 */ 328 if (time_offset < 0) { 329 ltemp = -time_offset; 330 if (!(time_status & STA_FLL)) 331 ltemp >>= SHIFT_KG + time_constant; 332 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) 333 ltemp = (MAXPHASE / MINSEC) << SHIFT_UPDATE; 334 time_offset += ltemp; 335 time_adj = -ltemp << (SHIFT_SCALE - SHIFT_UPDATE); 336 } else { 337 ltemp = time_offset; 338 if (!(time_status & STA_FLL)) 339 ltemp >>= SHIFT_KG + time_constant; 340 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE) 341 ltemp = (MAXPHASE / MINSEC) << SHIFT_UPDATE; 342 time_offset -= ltemp; 343 time_adj = ltemp << (SHIFT_SCALE - SHIFT_UPDATE); 344 } 345 346 /* 347 * Compute the frequency estimate and additional phase 348 * adjustment due to frequency error for the next 349 * second. When the PPS signal is engaged, gnaw on the 350 * watchdog counter and update the frequency computed by 351 * the pll and the PPS signal. 352 */ 353 #ifdef PPS_SYNC 354 pps_valid++; 355 if (pps_valid == PPS_VALID) { 356 pps_jitter = MAXTIME; 357 pps_stabil = MAXFREQ; 358 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 359 STA_PPSWANDER | STA_PPSERROR); 360 } 361 ltemp = time_freq + pps_freq; 362 #else 363 ltemp = time_freq; 364 #endif /* PPS_SYNC */ 365 if (ltemp < 0) 366 time_adj -= -ltemp << (SHIFT_SCALE - SHIFT_USEC); 367 else 368 time_adj += ltemp << (SHIFT_SCALE - SHIFT_USEC); 369 370 tc->tc_adjustment = time_adj; 371 372 /* XXX - this is really bogus, but can't be fixed until 373 xntpd's idea of the system clock is fixed to know how 374 the user wants leap seconds handled; in the mean time, 375 we assume that users of NTP are running without proper 376 leap second support (this is now the default anyway) */ 377 /* 378 * Leap second processing. If in leap-insert state at 379 * the end of the day, the system clock is set back one 380 * second; if in leap-delete state, the system clock is 381 * set ahead one second. The microtime() routine or 382 * external clock driver will insure that reported time 383 * is always monotonic. The ugly divides should be 384 * replaced. 385 */ 386 switch (time_state) { 387 388 case TIME_OK: 389 if (time_status & STA_INS) 390 time_state = TIME_INS; 391 else if (time_status & STA_DEL) 392 time_state = TIME_DEL; 393 break; 394 395 case TIME_INS: 396 if ((*newsec) % 86400 == 0) { 397 (*newsec)--; 398 time_state = TIME_OOP; 399 } 400 break; 401 402 case TIME_DEL: 403 if (((*newsec) + 1) % 86400 == 0) { 404 (*newsec)++; 405 time_state = TIME_WAIT; 406 } 407 break; 408 409 case TIME_OOP: 410 time_state = TIME_WAIT; 411 break; 412 413 case TIME_WAIT: 414 if (!(time_status & (STA_INS | STA_DEL))) 415 time_state = TIME_OK; 416 break; 417 } 418 } 419 420 static int 421 ntp_sysctl SYSCTL_HANDLER_ARGS 422 { 423 struct timeval atv; 424 struct ntptimeval ntv; 425 int s; 426 427 s = splclock(); 428 microtime(&atv); 429 ntv.time = atv; 430 ntv.maxerror = time_maxerror; 431 ntv.esterror = time_esterror; 432 splx(s); 433 434 ntv.time_state = time_state; 435 436 /* 437 * Status word error decode. If any of these conditions 438 * occur, an error is returned, instead of the status 439 * word. Most applications will care only about the fact 440 * the system clock may not be trusted, not about the 441 * details. 442 * 443 * Hardware or software error 444 */ 445 if (time_status & (STA_UNSYNC | STA_CLOCKERR)) { 446 ntv.time_state = TIME_ERROR; 447 } 448 449 /* 450 * PPS signal lost when either time or frequency 451 * synchronization requested 452 */ 453 if (time_status & (STA_PPSFREQ | STA_PPSTIME) && 454 !(time_status & STA_PPSSIGNAL)) { 455 ntv.time_state = TIME_ERROR; 456 } 457 458 /* 459 * PPS jitter exceeded when time synchronization 460 * requested 461 */ 462 if (time_status & STA_PPSTIME && 463 time_status & STA_PPSJITTER) { 464 ntv.time_state = TIME_ERROR; 465 } 466 467 /* 468 * PPS wander exceeded or calibration error when 469 * frequency synchronization requested 470 */ 471 if (time_status & STA_PPSFREQ && 472 time_status & (STA_PPSWANDER | STA_PPSERROR)) { 473 ntv.time_state = TIME_ERROR; 474 } 475 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 476 } 477 478 SYSCTL_NODE(_kern, KERN_NTP_PLL, ntp_pll, CTLFLAG_RW, 0, 479 "NTP kernel PLL related stuff"); 480 SYSCTL_PROC(_kern_ntp_pll, NTP_PLL_GETTIME, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 481 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 482 483 /* 484 * ntp_adjtime() - NTP daemon application interface 485 */ 486 #ifndef _SYS_SYSPROTO_H_ 487 struct ntp_adjtime_args { 488 struct timex *tp; 489 }; 490 #endif 491 492 int 493 ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 494 { 495 struct timex ntv; 496 int modes; 497 int s; 498 int error; 499 500 time_daemon = 1; 501 502 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 503 if (error) 504 return error; 505 506 /* 507 * Update selected clock variables - only the superuser can 508 * change anything. Note that there is no error checking here on 509 * the assumption the superuser should know what it is doing. 510 */ 511 modes = ntv.modes; 512 if ((modes != 0) 513 && (error = suser(p->p_cred->pc_ucred, &p->p_acflag))) 514 return error; 515 516 s = splclock(); 517 if (modes & MOD_FREQUENCY) 518 #ifdef PPS_SYNC 519 time_freq = ntv.freq - pps_freq; 520 #else /* PPS_SYNC */ 521 time_freq = ntv.freq; 522 #endif /* PPS_SYNC */ 523 if (modes & MOD_MAXERROR) 524 time_maxerror = ntv.maxerror; 525 if (modes & MOD_ESTERROR) 526 time_esterror = ntv.esterror; 527 if (modes & MOD_STATUS) { 528 time_status &= STA_RONLY; 529 time_status |= ntv.status & ~STA_RONLY; 530 } 531 if (modes & MOD_TIMECONST) 532 time_constant = ntv.constant; 533 if (modes & MOD_OFFSET) 534 hardupdate(ntv.offset, modes & MOD_DOSCALE); 535 536 ntv.modes |= MOD_CANSCALE; 537 /* 538 * Retrieve all clock variables 539 */ 540 if (modes & MOD_DOSCALE) 541 ntv.offset = time_offset; 542 else if (time_offset < 0) 543 ntv.offset = -(-time_offset >> SHIFT_UPDATE); 544 else 545 ntv.offset = time_offset >> SHIFT_UPDATE; 546 #ifdef PPS_SYNC 547 ntv.freq = time_freq + pps_freq; 548 #else /* PPS_SYNC */ 549 ntv.freq = time_freq; 550 #endif /* PPS_SYNC */ 551 ntv.maxerror = time_maxerror; 552 ntv.esterror = time_esterror; 553 ntv.status = time_status; 554 ntv.constant = time_constant; 555 ntv.precision = time_precision; 556 ntv.tolerance = time_tolerance; 557 #ifdef PPS_SYNC 558 ntv.shift = pps_shift; 559 ntv.ppsfreq = pps_freq; 560 ntv.jitter = pps_jitter >> PPS_AVG; 561 ntv.stabil = pps_stabil; 562 ntv.calcnt = pps_calcnt; 563 ntv.errcnt = pps_errcnt; 564 ntv.jitcnt = pps_jitcnt; 565 ntv.stbcnt = pps_stbcnt; 566 #endif /* PPS_SYNC */ 567 (void)splx(s); 568 569 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 570 if (!error) { 571 /* 572 * Status word error decode. See comments in 573 * ntp_gettime() routine. 574 */ 575 p->p_retval[0] = time_state; 576 if (time_status & (STA_UNSYNC | STA_CLOCKERR)) 577 p->p_retval[0] = TIME_ERROR; 578 if (time_status & (STA_PPSFREQ | STA_PPSTIME) && 579 !(time_status & STA_PPSSIGNAL)) 580 p->p_retval[0] = TIME_ERROR; 581 if (time_status & STA_PPSTIME && 582 time_status & STA_PPSJITTER) 583 p->p_retval[0] = TIME_ERROR; 584 if (time_status & STA_PPSFREQ && 585 time_status & (STA_PPSWANDER | STA_PPSERROR)) 586 p->p_retval[0] = TIME_ERROR; 587 } 588 return error; 589 } 590 591 #ifdef PPS_SYNC 592 593 /* We need this ugly monster twice, so let's macroize it. */ 594 595 #define MEDIAN3X(a, m, s, i1, i2, i3) \ 596 do { \ 597 m = a[i2]; \ 598 s = a[i1] - a[i3]; \ 599 } while (0) 600 601 #define MEDIAN3(a, m, s) \ 602 do { \ 603 if (a[0] > a[1]) { \ 604 if (a[1] > a[2]) \ 605 MEDIAN3X(a, m, s, 0, 1, 2); \ 606 else if (a[2] > a[0]) \ 607 MEDIAN3X(a, m, s, 2, 0, 1); \ 608 else \ 609 MEDIAN3X(a, m, s, 0, 2, 1); \ 610 } else { \ 611 if (a[2] > a[1]) \ 612 MEDIAN3X(a, m, s, 2, 1, 0); \ 613 else if (a[0] > a[2]) \ 614 MEDIAN3X(a, m, s, 1, 0, 2); \ 615 else \ 616 MEDIAN3X(a, m, s, 1, 2, 0); \ 617 } \ 618 } while (0) 619 620 /* 621 * hardpps() - discipline CPU clock oscillator to external PPS signal 622 * 623 * This routine is called at each PPS interrupt in order to discipline 624 * the CPU clock oscillator to the PPS signal. It measures the PPS phase 625 * and leaves it in a handy spot for the hardclock() routine. It 626 * integrates successive PPS phase differences and calculates the 627 * frequency offset. This is used in hardclock() to discipline the CPU 628 * clock oscillator so that intrinsic frequency error is cancelled out. 629 * The code requires the caller to capture the time and hardware counter 630 * value at the on-time PPS signal transition. 631 * 632 * Note that, on some Unix systems, this routine runs at an interrupt 633 * priority level higher than the timer interrupt routine hardclock(). 634 * Therefore, the variables used are distinct from the hardclock() 635 * variables, except for certain exceptions: The PPS frequency pps_freq 636 * and phase pps_offset variables are determined by this routine and 637 * updated atomically. The time_tolerance variable can be considered a 638 * constant, since it is infrequently changed, and then only when the 639 * PPS signal is disabled. The watchdog counter pps_valid is updated 640 * once per second by hardclock() and is atomically cleared in this 641 * routine. 642 */ 643 void 644 hardpps(tvp, p_usec) 645 struct timeval *tvp; /* time at PPS */ 646 long p_usec; /* hardware counter at PPS */ 647 { 648 long u_usec, v_usec, bigtick; 649 long cal_sec, cal_usec; 650 651 /* 652 * An occasional glitch can be produced when the PPS interrupt 653 * occurs in the hardclock() routine before the time variable is 654 * updated. Here the offset is discarded when the difference 655 * between it and the last one is greater than tick/2, but not 656 * if the interval since the first discard exceeds 30 s. 657 */ 658 time_status |= STA_PPSSIGNAL; 659 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 660 pps_valid = 0; 661 u_usec = -tvp->tv_usec; 662 if (u_usec < -500000) 663 u_usec += 1000000; 664 v_usec = pps_offset - u_usec; 665 if (v_usec < 0) 666 v_usec = -v_usec; 667 if (v_usec > (tick >> 1)) { 668 if (pps_glitch > MAXGLITCH) { 669 pps_glitch = 0; 670 pps_tf[2] = u_usec; 671 pps_tf[1] = u_usec; 672 } else { 673 pps_glitch++; 674 u_usec = pps_offset; 675 } 676 } else 677 pps_glitch = 0; 678 679 /* 680 * A three-stage median filter is used to help deglitch the pps 681 * time. The median sample becomes the time offset estimate; the 682 * difference between the other two samples becomes the time 683 * dispersion (jitter) estimate. 684 */ 685 pps_tf[2] = pps_tf[1]; 686 pps_tf[1] = pps_tf[0]; 687 pps_tf[0] = u_usec; 688 MEDIAN3(pps_tf, pps_offset, v_usec); 689 if (v_usec > MAXTIME) 690 pps_jitcnt++; 691 v_usec = (v_usec << PPS_AVG) - pps_jitter; 692 if (v_usec < 0) 693 pps_jitter -= -v_usec >> PPS_AVG; 694 else 695 pps_jitter += v_usec >> PPS_AVG; 696 if (pps_jitter > (MAXTIME >> 1)) 697 time_status |= STA_PPSJITTER; 698 699 /* 700 * During the calibration interval adjust the starting time when 701 * the tick overflows. At the end of the interval compute the 702 * duration of the interval and the difference of the hardware 703 * counters at the beginning and end of the interval. This code 704 * is deliciously complicated by the fact valid differences may 705 * exceed the value of tick when using long calibration 706 * intervals and small ticks. Note that the counter can be 707 * greater than tick if caught at just the wrong instant, but 708 * the values returned and used here are correct. 709 */ 710 bigtick = (long)tick << SHIFT_USEC; 711 pps_usec -= pps_freq; 712 if (pps_usec >= bigtick) 713 pps_usec -= bigtick; 714 if (pps_usec < 0) 715 pps_usec += bigtick; 716 pps_time.tv_sec++; 717 pps_count++; 718 if (pps_count < (1 << pps_shift)) 719 return; 720 pps_count = 0; 721 pps_calcnt++; 722 u_usec = p_usec << SHIFT_USEC; 723 v_usec = pps_usec - u_usec; 724 if (v_usec >= bigtick >> 1) 725 v_usec -= bigtick; 726 if (v_usec < -(bigtick >> 1)) 727 v_usec += bigtick; 728 if (v_usec < 0) 729 v_usec = -(-v_usec >> pps_shift); 730 else 731 v_usec = v_usec >> pps_shift; 732 pps_usec = u_usec; 733 cal_sec = tvp->tv_sec; 734 cal_usec = tvp->tv_usec; 735 cal_sec -= pps_time.tv_sec; 736 cal_usec -= pps_time.tv_usec; 737 if (cal_usec < 0) { 738 cal_usec += 1000000; 739 cal_sec--; 740 } 741 pps_time = *tvp; 742 743 /* 744 * Check for lost interrupts, noise, excessive jitter and 745 * excessive frequency error. The number of timer ticks during 746 * the interval may vary +-1 tick. Add to this a margin of one 747 * tick for the PPS signal jitter and maximum frequency 748 * deviation. If the limits are exceeded, the calibration 749 * interval is reset to the minimum and we start over. 750 */ 751 u_usec = (long)tick << 1; 752 if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec)) 753 || (cal_sec == 0 && cal_usec < u_usec)) 754 || v_usec > time_tolerance || v_usec < -time_tolerance) { 755 pps_errcnt++; 756 pps_shift = PPS_SHIFT; 757 pps_intcnt = 0; 758 time_status |= STA_PPSERROR; 759 return; 760 } 761 762 /* 763 * A three-stage median filter is used to help deglitch the pps 764 * frequency. The median sample becomes the frequency offset 765 * estimate; the difference between the other two samples 766 * becomes the frequency dispersion (stability) estimate. 767 */ 768 pps_ff[2] = pps_ff[1]; 769 pps_ff[1] = pps_ff[0]; 770 pps_ff[0] = v_usec; 771 MEDIAN3(pps_ff, u_usec, v_usec); 772 773 /* 774 * Here the frequency dispersion (stability) is updated. If it 775 * is less than one-fourth the maximum (MAXFREQ), the frequency 776 * offset is updated as well, but clamped to the tolerance. It 777 * will be processed later by the hardclock() routine. 778 */ 779 v_usec = (v_usec >> 1) - pps_stabil; 780 if (v_usec < 0) 781 pps_stabil -= -v_usec >> PPS_AVG; 782 else 783 pps_stabil += v_usec >> PPS_AVG; 784 if (pps_stabil > MAXFREQ >> 2) { 785 pps_stbcnt++; 786 time_status |= STA_PPSWANDER; 787 return; 788 } 789 if (time_status & STA_PPSFREQ) { 790 if (u_usec < 0) { 791 pps_freq -= -u_usec >> PPS_AVG; 792 if (pps_freq < -time_tolerance) 793 pps_freq = -time_tolerance; 794 u_usec = -u_usec; 795 } else { 796 pps_freq += u_usec >> PPS_AVG; 797 if (pps_freq > time_tolerance) 798 pps_freq = time_tolerance; 799 } 800 } 801 802 /* 803 * Here the calibration interval is adjusted. If the maximum 804 * time difference is greater than tick / 4, reduce the interval 805 * by half. If this is not the case for four consecutive 806 * intervals, double the interval. 807 */ 808 if (u_usec << pps_shift > bigtick >> 2) { 809 pps_intcnt = 0; 810 if (pps_shift > PPS_SHIFT) 811 pps_shift--; 812 } else if (pps_intcnt >= 4) { 813 pps_intcnt = 0; 814 if (pps_shift < PPS_SHIFTMAX) 815 pps_shift++; 816 } else 817 pps_intcnt++; 818 } 819 820 #endif /* PPS_SYNC */ 821 822 int 823 std_pps_ioctl(u_long cmd, caddr_t data, pps_params_t *pp, pps_info_t *pi, int ppscap) 824 { 825 pps_params_t *app; 826 pps_info_t *api; 827 828 switch (cmd) { 829 case PPS_IOC_CREATE: 830 return (0); 831 case PPS_IOC_DESTROY: 832 return (0); 833 case PPS_IOC_SETPARAMS: 834 app = (pps_params_t *)data; 835 if (app->mode & ~ppscap) 836 return (EINVAL); 837 *pp = *app; 838 return (0); 839 case PPS_IOC_GETPARAMS: 840 app = (pps_params_t *)data; 841 *app = *pp; 842 return (0); 843 case PPS_IOC_GETCAP: 844 *(int*)data = ppscap; 845 return (0); 846 case PPS_IOC_FETCH: 847 api = (pps_info_t *)data; 848 *api = *pi; 849 pi->current_mode = pp->mode; 850 return (0); 851 case PPS_IOC_WAIT: 852 return (EOPNOTSUPP); 853 default: 854 return (ENODEV); 855 } 856 } 857