kern_ntptime.c revision 55413
1/*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-1999 * 4 * * 5 * Permission to use, copy, modify, and distribute this software and * 6 * its documentation for any purpose and without fee is hereby * 7 * granted, provided that the above copyright notice appears in all * 8 * copies and that both the copyright notice and this permission * 9 * notice appear in supporting documentation, and that the name * 10 * University of Delaware not be used in advertising or publicity * 11 * pertaining to distribution of the software without specific, * 12 * written prior permission. The University of Delaware makes no * 13 * representations about the suitability this software for any * 14 * purpose. It is provided "as is" without express or implied * 15 * warranty. * 16 * * 17 **********************************************************************/ 18 19/* 20 * Adapted from the original sources for FreeBSD and timecounters by: 21 * Poul-Henning Kamp <phk@FreeBSD.org>. 22 * 23 * The 32bit version of the "LP" macros seems a bit past its "sell by" 24 * date so I have retained only the 64bit version and included it directly 25 * in this file. 26 * 27 * Only minor changes done to interface with the timecounters over in 28 * sys/kern/kern_clock.c. Some of the comments below may be (even more) 29 * confusing and/or plain wrong in that context. 30 * 31 * $FreeBSD: head/sys/kern/kern_ntptime.c 55413 2000-01-04 12:04:39Z phk $ 32 */ 33 34#include "opt_ntp.h" 35 36#include <sys/param.h> 37#include <sys/systm.h> 38#include <sys/sysproto.h> 39#include <sys/kernel.h> 40#include <sys/proc.h> 41#include <sys/time.h> 42#include <sys/timex.h> 43#include <sys/timepps.h> 44#include <sys/sysctl.h> 45 46/* 47 * Single-precision macros for 64-bit machines 48 */ 49typedef long long l_fp; 50#define L_ADD(v, u) ((v) += (u)) 51#define L_SUB(v, u) ((v) -= (u)) 52#define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 53#define L_NEG(v) ((v) = -(v)) 54#define L_RSHIFT(v, n) \ 55 do { \ 56 if ((v) < 0) \ 57 (v) = -(-(v) >> (n)); \ 58 else \ 59 (v) = (v) >> (n); \ 60 } while (0) 61#define L_MPY(v, a) ((v) *= (a)) 62#define L_CLR(v) ((v) = 0) 63#define L_ISNEG(v) ((v) < 0) 64#define L_LINT(v, a) ((v) = (long long)(a) << 32) 65#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 66 67/* 68 * Generic NTP kernel interface 69 * 70 * These routines constitute the Network Time Protocol (NTP) interfaces 71 * for user and daemon application programs. The ntp_gettime() routine 72 * provides the time, maximum error (synch distance) and estimated error 73 * (dispersion) to client user application programs. The ntp_adjtime() 74 * routine is used by the NTP daemon to adjust the system clock to an 75 * externally derived time. The time offset and related variables set by 76 * this routine are used by other routines in this module to adjust the 77 * phase and frequency of the clock discipline loop which controls the 78 * system clock. 79 * 80 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 81 * defined), the time at each tick interrupt is derived directly from 82 * the kernel time variable. When the kernel time is reckoned in 83 * microseconds, (NTP_NANO undefined), the time is derived from the 84 * kernel time variable together with a variable representing the 85 * leftover nanoseconds at the last tick interrupt. In either case, the 86 * current nanosecond time is reckoned from these values plus an 87 * interpolated value derived by the clock routines in another 88 * architecture-specific module. The interpolation can use either a 89 * dedicated counter or a processor cycle counter (PCC) implemented in 90 * some architectures. 91 * 92 * Note that all routines must run at priority splclock or higher. 93 */ 94 95/* 96 * Phase/frequency-lock loop (PLL/FLL) definitions 97 * 98 * The nanosecond clock discipline uses two variable types, time 99 * variables and frequency variables. Both types are represented as 64- 100 * bit fixed-point quantities with the decimal point between two 32-bit 101 * halves. On a 32-bit machine, each half is represented as a single 102 * word and mathematical operations are done using multiple-precision 103 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 104 * used. 105 * 106 * A time variable is a signed 64-bit fixed-point number in ns and 107 * fraction. It represents the remaining time offset to be amortized 108 * over succeeding tick interrupts. The maximum time offset is about 109 * 0.5 s and the resolution is about 2.3e-10 ns. 110 * 111 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 112 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 113 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 114 * |s s s| ns | 115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 116 * | fraction | 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * 119 * A frequency variable is a signed 64-bit fixed-point number in ns/s 120 * and fraction. It represents the ns and fraction to be added to the 121 * kernel time variable at each second. The maximum frequency offset is 122 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 123 * 124 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 125 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 * |s s s s s s s s s s s s s| ns/s | 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * | fraction | 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 */ 132/* 133 * The following variables establish the state of the PLL/FLL and the 134 * residual time and frequency offset of the local clock. 135 */ 136#define SHIFT_PLL 4 /* PLL loop gain (shift) */ 137#define SHIFT_FLL 2 /* FLL loop gain (shift) */ 138 139static int time_state = TIME_OK; /* clock state */ 140static int time_status = STA_UNSYNC; /* clock status bits */ 141static long time_constant; /* poll interval (shift) (s) */ 142static long time_precision = 1; /* clock precision (ns) */ 143static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 144static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 145static long time_reftime; /* time at last adjustment (s) */ 146static long time_tick; /* nanoseconds per tick (ns) */ 147static l_fp time_offset; /* time offset (ns) */ 148static l_fp time_freq; /* frequency offset (ns/s) */ 149 150#ifdef PPS_SYNC 151/* 152 * The following variables are used when a pulse-per-second (PPS) signal 153 * is available and connected via a modem control lead. They establish 154 * the engineering parameters of the clock discipline loop when 155 * controlled by the PPS signal. 156 */ 157#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 158#define PPS_FAVGDEF 7 /* default freq avg int (s) (shift) */ 159#define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 160#define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 161#define PPS_VALID 120 /* PPS signal watchdog max (s) */ 162#define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 163#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 164 165static struct timespec pps_tf[3]; /* phase median filter */ 166static l_fp pps_offset; /* time offset (ns) */ 167static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 168static long pps_fcount; /* frequency accumulator */ 169static long pps_jitter; /* nominal jitter (ns) */ 170static long pps_stabil; /* nominal stability (scaled ns/s) */ 171static long pps_lastsec; /* time at last calibration (s) */ 172static int pps_valid; /* signal watchdog counter */ 173static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 174static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 175static int pps_intcnt; /* wander counter */ 176 177/* 178 * PPS signal quality monitors 179 */ 180static long pps_calcnt; /* calibration intervals */ 181static long pps_jitcnt; /* jitter limit exceeded */ 182static long pps_stbcnt; /* stability limit exceeded */ 183static long pps_errcnt; /* calibration errors */ 184#endif /* PPS_SYNC */ 185/* 186 * End of phase/frequency-lock loop (PLL/FLL) definitions 187 */ 188 189static void ntp_init(void); 190static void hardupdate(long offset); 191 192/* 193 * ntp_gettime() - NTP user application interface 194 * 195 * See the timex.h header file for synopsis and API description. 196 */ 197static int 198ntp_sysctl SYSCTL_HANDLER_ARGS 199{ 200 struct ntptimeval ntv; /* temporary structure */ 201 struct timespec atv; /* nanosecond time */ 202 203 nanotime(&atv); 204 ntv.time.tv_sec = atv.tv_sec; 205 ntv.time.tv_nsec = atv.tv_nsec; 206 ntv.maxerror = time_maxerror; 207 ntv.esterror = time_esterror; 208 ntv.time_state = time_state; 209 210 /* 211 * Status word error decode. If any of these conditions occur, 212 * an error is returned, instead of the status word. Most 213 * applications will care only about the fact the system clock 214 * may not be trusted, not about the details. 215 * 216 * Hardware or software error 217 */ 218 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 219 220 /* 221 * PPS signal lost when either time or frequency synchronization 222 * requested 223 */ 224 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 225 !(time_status & STA_PPSSIGNAL)) || 226 227 /* 228 * PPS jitter exceeded when time synchronization requested 229 */ 230 (time_status & STA_PPSTIME && 231 time_status & STA_PPSJITTER) || 232 233 /* 234 * PPS wander exceeded or calibration error when frequency 235 * synchronization requested 236 */ 237 (time_status & STA_PPSFREQ && 238 time_status & (STA_PPSWANDER | STA_PPSERROR))) 239 ntv.time_state = TIME_ERROR; 240 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 241} 242 243SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 244SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 245 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 246 247#ifdef PPS_SYNC 248SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 249SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 250#endif 251/* 252 * ntp_adjtime() - NTP daemon application interface 253 * 254 * See the timex.h header file for synopsis and API description. 255 */ 256#ifndef _SYS_SYSPROTO_H_ 257struct ntp_adjtime_args { 258 struct timex *tp; 259}; 260#endif 261 262int 263ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 264{ 265 struct timex ntv; /* temporary structure */ 266 long freq; /* frequency ns/s) */ 267 int modes; /* mode bits from structure */ 268 int s; /* caller priority */ 269 int error; 270 271 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 272 if (error) 273 return(error); 274 275 /* 276 * Update selected clock variables - only the superuser can 277 * change anything. Note that there is no error checking here on 278 * the assumption the superuser should know what it is doing. 279 */ 280 modes = ntv.modes; 281 if (modes) 282 error = suser(p); 283 if (error) 284 return (error); 285 s = splclock(); 286 if (modes & MOD_FREQUENCY) { 287 freq = (ntv.freq * 1000LL) >> 16; 288 if (freq > MAXFREQ) 289 L_LINT(time_freq, MAXFREQ); 290 else if (freq < -MAXFREQ) 291 L_LINT(time_freq, -MAXFREQ); 292 else 293 L_LINT(time_freq, freq); 294 295#ifdef PPS_SYNC 296 pps_freq = time_freq; 297#endif /* PPS_SYNC */ 298 } 299 if (modes & MOD_MAXERROR) 300 time_maxerror = ntv.maxerror; 301 if (modes & MOD_ESTERROR) 302 time_esterror = ntv.esterror; 303 if (modes & MOD_STATUS) { 304 time_status &= STA_RONLY; 305 time_status |= ntv.status & ~STA_RONLY; 306 } 307 if (modes & MOD_TIMECONST) { 308 if (ntv.constant < 0) 309 time_constant = 0; 310 else if (ntv.constant > MAXTC) 311 time_constant = MAXTC; 312 else 313 time_constant = ntv.constant; 314 } 315#ifdef PPS_SYNC 316 if (modes & MOD_PPSMAX) { 317 if (ntv.shift < PPS_FAVG) 318 pps_shiftmax = PPS_FAVG; 319 else if (ntv.shift > PPS_FAVGMAX) 320 pps_shiftmax = PPS_FAVGMAX; 321 else 322 pps_shiftmax = ntv.shift; 323 } 324#endif /* PPS_SYNC */ 325 if (modes & MOD_NANO) 326 time_status |= STA_NANO; 327 if (modes & MOD_MICRO) 328 time_status &= ~STA_NANO; 329 if (modes & MOD_CLKB) 330 time_status |= STA_CLK; 331 if (modes & MOD_CLKA) 332 time_status &= ~STA_CLK; 333 if (modes & MOD_OFFSET) { 334 if (time_status & STA_NANO) 335 hardupdate(ntv.offset); 336 else 337 hardupdate(ntv.offset * 1000); 338 } 339 340 /* 341 * Retrieve all clock variables 342 */ 343 if (time_status & STA_NANO) 344 ntv.offset = L_GINT(time_offset); 345 else 346 ntv.offset = L_GINT(time_offset) / 1000; 347 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 348 ntv.maxerror = time_maxerror; 349 ntv.esterror = time_esterror; 350 ntv.status = time_status; 351 ntv.constant = time_constant; 352 if (time_status & STA_NANO) 353 ntv.precision = time_precision; 354 else 355 ntv.precision = time_precision / 1000; 356 ntv.tolerance = MAXFREQ * SCALE_PPM; 357#ifdef PPS_SYNC 358 ntv.shift = pps_shift; 359 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 360 if (time_status & STA_NANO) 361 ntv.jitter = pps_jitter; 362 else 363 ntv.jitter = pps_jitter / 1000; 364 ntv.stabil = pps_stabil; 365 ntv.calcnt = pps_calcnt; 366 ntv.errcnt = pps_errcnt; 367 ntv.jitcnt = pps_jitcnt; 368 ntv.stbcnt = pps_stbcnt; 369#endif /* PPS_SYNC */ 370 splx(s); 371 372 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 373 if (error) 374 return (error); 375 376 /* 377 * Status word error decode. See comments in 378 * ntp_gettime() routine. 379 */ 380 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 381 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 382 !(time_status & STA_PPSSIGNAL)) || 383 (time_status & STA_PPSTIME && 384 time_status & STA_PPSJITTER) || 385 (time_status & STA_PPSFREQ && 386 time_status & (STA_PPSWANDER | STA_PPSERROR))) 387 p->p_retval[0] = TIME_ERROR; 388 else 389 p->p_retval[0] = time_state; 390 return (error); 391} 392 393/* 394 * second_overflow() - called after ntp_tick_adjust() 395 * 396 * This routine is ordinarily called immediately following the above 397 * routine ntp_tick_adjust(). While these two routines are normally 398 * combined, they are separated here only for the purposes of 399 * simulation. 400 */ 401void 402ntp_update_second(struct timecounter *tcp) 403{ 404 u_int32_t *newsec; 405 l_fp time_adj; /* 32/64-bit temporaries */ 406 407 newsec = &tcp->tc_offset_sec; 408 /* 409 * On rollover of the second both the nanosecond and microsecond 410 * clocks are updated and the state machine cranked as 411 * necessary. The phase adjustment to be used for the next 412 * second is calculated and the maximum error is increased by 413 * the tolerance. 414 */ 415 time_maxerror += MAXFREQ / 1000; 416 417 /* 418 * Leap second processing. If in leap-insert state at 419 * the end of the day, the system clock is set back one 420 * second; if in leap-delete state, the system clock is 421 * set ahead one second. The nano_time() routine or 422 * external clock driver will insure that reported time 423 * is always monotonic. 424 */ 425 switch (time_state) { 426 427 /* 428 * No warning. 429 */ 430 case TIME_OK: 431 if (time_status & STA_INS) 432 time_state = TIME_INS; 433 else if (time_status & STA_DEL) 434 time_state = TIME_DEL; 435 break; 436 437 /* 438 * Insert second 23:59:60 following second 439 * 23:59:59. 440 */ 441 case TIME_INS: 442 if (!(time_status & STA_INS)) 443 time_state = TIME_OK; 444 else if ((*newsec) % 86400 == 0) { 445 (*newsec)--; 446 time_state = TIME_OOP; 447 } 448 break; 449 450 /* 451 * Delete second 23:59:59. 452 */ 453 case TIME_DEL: 454 if (!(time_status & STA_DEL)) 455 time_state = TIME_OK; 456 else if (((*newsec) + 1) % 86400 == 0) { 457 (*newsec)++; 458 time_state = TIME_WAIT; 459 } 460 break; 461 462 /* 463 * Insert second in progress. 464 */ 465 case TIME_OOP: 466 time_state = TIME_WAIT; 467 break; 468 469 /* 470 * Wait for status bits to clear. 471 */ 472 case TIME_WAIT: 473 if (!(time_status & (STA_INS | STA_DEL))) 474 time_state = TIME_OK; 475 } 476 477 /* 478 * Compute the total time adjustment for the next second 479 * in ns. The offset is reduced by a factor depending on 480 * whether the PPS signal is operating. Note that the 481 * value is in effect scaled by the clock frequency, 482 * since the adjustment is added at each tick interrupt. 483 */ 484#ifdef PPS_SYNC 485 /* XXX even if signal dies we should finish adjustment ? */ 486 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) { 487 time_adj = pps_offset; 488 L_RSHIFT(time_adj, pps_shift); 489 L_SUB(pps_offset, time_adj); 490 } else { 491 time_adj = time_offset; 492 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 493 L_SUB(time_offset, time_adj); 494 } 495#else 496 time_adj = time_offset; 497 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 498 L_SUB(time_offset, time_adj); 499#endif /* PPS_SYNC */ 500 L_ADD(time_adj, time_freq); 501 tcp->tc_adjustment = time_adj; 502#ifdef PPS_SYNC 503 if (pps_valid > 0) 504 pps_valid--; 505 else 506 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 507 STA_PPSWANDER | STA_PPSERROR); 508#endif /* PPS_SYNC */ 509} 510 511/* 512 * ntp_init() - initialize variables and structures 513 * 514 * This routine must be called after the kernel variables hz and tick 515 * are set or changed and before the next tick interrupt. In this 516 * particular implementation, these values are assumed set elsewhere in 517 * the kernel. The design allows the clock frequency and tick interval 518 * to be changed while the system is running. So, this routine should 519 * probably be integrated with the code that does that. 520 */ 521static void 522ntp_init() 523{ 524 525 /* 526 * The following variable must be initialized any time the 527 * kernel variable hz is changed. 528 */ 529 time_tick = NANOSECOND / hz; 530 531 /* 532 * The following variables are initialized only at startup. Only 533 * those structures not cleared by the compiler need to be 534 * initialized, and these only in the simulator. In the actual 535 * kernel, any nonzero values here will quickly evaporate. 536 */ 537 L_CLR(time_offset); 538 L_CLR(time_freq); 539#ifdef PPS_SYNC 540 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 541 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 542 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 543 pps_fcount = 0; 544 L_CLR(pps_freq); 545#endif /* PPS_SYNC */ 546} 547 548SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 549 550/* 551 * hardupdate() - local clock update 552 * 553 * This routine is called by ntp_adjtime() to update the local clock 554 * phase and frequency. The implementation is of an adaptive-parameter, 555 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 556 * time and frequency offset estimates for each call. If the kernel PPS 557 * discipline code is configured (PPS_SYNC), the PPS signal itself 558 * determines the new time offset, instead of the calling argument. 559 * Presumably, calls to ntp_adjtime() occur only when the caller 560 * believes the local clock is valid within some bound (+-128 ms with 561 * NTP). If the caller's time is far different than the PPS time, an 562 * argument will ensue, and it's not clear who will lose. 563 * 564 * For uncompensated quartz crystal oscillators and nominal update 565 * intervals less than 256 s, operation should be in phase-lock mode, 566 * where the loop is disciplined to phase. For update intervals greater 567 * than 1024 s, operation should be in frequency-lock mode, where the 568 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 569 * is selected by the STA_MODE status bit. 570 */ 571static void 572hardupdate(offset) 573 long offset; /* clock offset (ns) */ 574{ 575 long ltemp, mtemp; 576 l_fp ftemp; 577 578 /* 579 * Select how the phase is to be controlled and from which 580 * source. If the PPS signal is present and enabled to 581 * discipline the time, the PPS offset is used; otherwise, the 582 * argument offset is used. 583 */ 584 if (!(time_status & STA_PLL)) 585 return; 586 ltemp = offset; 587 if (ltemp > MAXPHASE) 588 ltemp = MAXPHASE; 589 else if (ltemp < -MAXPHASE) 590 ltemp = -MAXPHASE; 591 if (!(time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)) 592 L_LINT(time_offset, ltemp); 593 594 /* 595 * Select how the frequency is to be controlled and in which 596 * mode (PLL or FLL). If the PPS signal is present and enabled 597 * to discipline the frequency, the PPS frequency is used; 598 * otherwise, the argument offset is used to compute it. 599 */ 600 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 601 time_reftime = time_second; 602 return; 603 } 604 if (time_status & STA_FREQHOLD || time_reftime == 0) 605 time_reftime = time_second; 606 mtemp = time_second - time_reftime; 607 L_LINT(ftemp, ltemp); 608 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 609 L_MPY(ftemp, mtemp); 610 L_ADD(time_freq, ftemp); 611 time_status &= ~STA_MODE; 612 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 613 L_LINT(ftemp, (ltemp << 4) / mtemp); 614 L_RSHIFT(ftemp, SHIFT_FLL + 4); 615 L_ADD(time_freq, ftemp); 616 time_status |= STA_MODE; 617 } 618 time_reftime = time_second; 619 if (L_GINT(time_freq) > MAXFREQ) 620 L_LINT(time_freq, MAXFREQ); 621 else if (L_GINT(time_freq) < -MAXFREQ) 622 L_LINT(time_freq, -MAXFREQ); 623} 624 625#ifdef PPS_SYNC 626/* 627 * hardpps() - discipline CPU clock oscillator to external PPS signal 628 * 629 * This routine is called at each PPS interrupt in order to discipline 630 * the CPU clock oscillator to the PPS signal. It measures the PPS phase 631 * and leaves it in a handy spot for the hardclock() routine. It 632 * integrates successive PPS phase differences and calculates the 633 * frequency offset. This is used in hardclock() to discipline the CPU 634 * clock oscillator so that the intrinsic frequency error is cancelled 635 * out. The code requires the caller to capture the time and 636 * architecture-dependent hardware counter values in nanoseconds at the 637 * on-time PPS signal transition. 638 * 639 * Note that, on some Unix systems this routine runs at an interrupt 640 * priority level higher than the timer interrupt routine hardclock(). 641 * Therefore, the variables used are distinct from the hardclock() 642 * variables, except for the actual time and frequency variables, which 643 * are determined by this routine and updated atomically. 644 */ 645void 646hardpps(tsp, nsec) 647 struct timespec *tsp; /* time at PPS */ 648 long nsec; /* hardware counter at PPS */ 649{ 650 long u_sec, u_nsec, v_nsec; /* temps */ 651 l_fp ftemp; 652 653 /* 654 * The signal is first processed by a frequency discriminator 655 * which rejects noise and input signals with frequencies 656 * outside the range 1 +-MAXFREQ PPS. If two hits occur in the 657 * same second, we ignore the later hit; if not and a hit occurs 658 * outside the range gate, keep the later hit but do not 659 * process it. 660 */ 661 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 662 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 663 pps_valid = PPS_VALID; 664 u_sec = tsp->tv_sec; 665 u_nsec = tsp->tv_nsec; 666 if (u_nsec >= (NANOSECOND >> 1)) { 667 u_nsec -= NANOSECOND; 668 u_sec++; 669 } 670 v_nsec = u_nsec - pps_tf[0].tv_nsec; 671 if (u_sec == pps_tf[0].tv_sec && v_nsec < -MAXFREQ) { 672 return; 673 } 674 pps_tf[2] = pps_tf[1]; 675 pps_tf[1] = pps_tf[0]; 676 pps_tf[0].tv_sec = u_sec; 677 pps_tf[0].tv_nsec = u_nsec; 678 679 /* 680 * Compute the difference between the current and previous 681 * counter values. If the difference exceeds 0.5 s, assume it 682 * has wrapped around, so correct 1.0 s. If the result exceeds 683 * the tick interval, the sample point has crossed a tick 684 * boundary during the last second, so correct the tick. Very 685 * intricate. 686 */ 687 u_nsec = nsec; 688 if (u_nsec > (NANOSECOND >> 1)) 689 u_nsec -= NANOSECOND; 690 else if (u_nsec < -(NANOSECOND >> 1)) 691 u_nsec += NANOSECOND; 692 pps_fcount += u_nsec; 693 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) { 694 return; 695 } 696 time_status &= ~STA_PPSJITTER; 697 698 /* 699 * A three-stage median filter is used to help denoise the PPS 700 * time. The median sample becomes the time offset estimate; the 701 * difference between the other two samples becomes the time 702 * dispersion (jitter) estimate. 703 */ 704 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 705 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 706 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 707 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 708 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 709 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 710 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 711 } else { 712 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 713 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 714 } 715 } else { 716 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 717 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 718 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 719 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 720 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 721 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 722 } else { 723 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 724 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 725 } 726 } 727 728 /* 729 * Nominal jitter is due to PPS signal noise and interrupt 730 * latency. If it exceeds the popcorn threshold, 731 * the sample is discarded. otherwise, if so enabled, the time 732 * offset is updated. We can tolerate a modest loss of data here 733 * without degrading time accuracy. 734 */ 735 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 736 time_status |= STA_PPSJITTER; 737 pps_jitcnt++; 738 } else if (time_status & STA_PPSTIME) { 739 L_LINT(time_offset, -v_nsec); 740 L_LINT(pps_offset, -v_nsec); 741 } 742 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 743 u_sec = pps_tf[0].tv_sec - pps_lastsec; 744 if (u_sec < (1 << pps_shift)) 745 return; 746 747 /* 748 * At the end of the calibration interval the difference between 749 * the first and last counter values becomes the scaled 750 * frequency. It will later be divided by the length of the 751 * interval to determine the frequency update. If the frequency 752 * exceeds a sanity threshold, or if the actual calibration 753 * interval is not equal to the expected length, the data are 754 * discarded. We can tolerate a modest loss of data here without 755 * degrading frequency ccuracy. 756 */ 757 pps_calcnt++; 758 v_nsec = -pps_fcount; 759 pps_lastsec = pps_tf[0].tv_sec; 760 pps_fcount = 0; 761 u_nsec = MAXFREQ << pps_shift; 762 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 763 pps_shift)) { 764 time_status |= STA_PPSERROR; 765 pps_errcnt++; 766 return; 767 } 768 769 /* 770 * Here the raw frequency offset and wander (stability) is 771 * calculated. If the wander is less than the wander threshold 772 * for four consecutive averaging intervals, the interval is 773 * doubled; if it is greater than the threshold for four 774 * consecutive intervals, the interval is halved. The scaled 775 * frequency offset is converted to frequency offset. The 776 * stability metric is calculated as the average of recent 777 * frequency changes, but is used only for performance 778 * monitoring. 779 */ 780 L_LINT(ftemp, v_nsec); 781 L_RSHIFT(ftemp, pps_shift); 782 L_SUB(ftemp, pps_freq); 783 u_nsec = L_GINT(ftemp); 784 if (u_nsec > PPS_MAXWANDER) { 785 L_LINT(ftemp, PPS_MAXWANDER); 786 pps_intcnt--; 787 time_status |= STA_PPSWANDER; 788 pps_stbcnt++; 789 } else if (u_nsec < -PPS_MAXWANDER) { 790 L_LINT(ftemp, -PPS_MAXWANDER); 791 pps_intcnt--; 792 time_status |= STA_PPSWANDER; 793 pps_stbcnt++; 794 } else { 795 pps_intcnt++; 796 } 797 if (pps_shift > pps_shiftmax) { 798 /* If we lowered pps_shiftmax */ 799 pps_shift = pps_shiftmax; 800 pps_intcnt = 0; 801 } else if (pps_intcnt >= 4) { 802 pps_intcnt = 4; 803 if (pps_shift < pps_shiftmax) { 804 pps_shift++; 805 pps_intcnt = 0; 806 } 807 } else if (pps_intcnt <= -4) { 808 pps_intcnt = -4; 809 if (pps_shift > PPS_FAVG) { 810 pps_shift--; 811 pps_intcnt = 0; 812 } 813 } 814 if (u_nsec < 0) 815 u_nsec = -u_nsec; 816 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 817 818 /* 819 * The PPS frequency is recalculated and clamped to the maximum 820 * MAXFREQ. If enabled, the system clock frequency is updated as 821 * well. 822 */ 823 L_ADD(pps_freq, ftemp); 824 u_nsec = L_GINT(pps_freq); 825 if (u_nsec > MAXFREQ) 826 L_LINT(pps_freq, MAXFREQ); 827 else if (u_nsec < -MAXFREQ) 828 L_LINT(pps_freq, -MAXFREQ); 829 if (time_status & STA_PPSFREQ) 830 time_freq = pps_freq; 831} 832#endif /* PPS_SYNC */ 833