kern_ntptime.c revision 65432
1/*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-2000 * 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 65432 2000-09-04 08:19:32Z 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/timetc.h> 44#include <sys/timepps.h> 45#include <sys/sysctl.h> 46 47/* 48 * Single-precision macros for 64-bit machines 49 */ 50typedef long long l_fp; 51#define L_ADD(v, u) ((v) += (u)) 52#define L_SUB(v, u) ((v) -= (u)) 53#define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 54#define L_NEG(v) ((v) = -(v)) 55#define L_RSHIFT(v, n) \ 56 do { \ 57 if ((v) < 0) \ 58 (v) = -(-(v) >> (n)); \ 59 else \ 60 (v) = (v) >> (n); \ 61 } while (0) 62#define L_MPY(v, a) ((v) *= (a)) 63#define L_CLR(v) ((v) = 0) 64#define L_ISNEG(v) ((v) < 0) 65#define L_LINT(v, a) ((v) = (long long)(a) << 32) 66#define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 67 68/* 69 * Generic NTP kernel interface 70 * 71 * These routines constitute the Network Time Protocol (NTP) interfaces 72 * for user and daemon application programs. The ntp_gettime() routine 73 * provides the time, maximum error (synch distance) and estimated error 74 * (dispersion) to client user application programs. The ntp_adjtime() 75 * routine is used by the NTP daemon to adjust the system clock to an 76 * externally derived time. The time offset and related variables set by 77 * this routine are used by other routines in this module to adjust the 78 * phase and frequency of the clock discipline loop which controls the 79 * system clock. 80 * 81 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 82 * defined), the time at each tick interrupt is derived directly from 83 * the kernel time variable. When the kernel time is reckoned in 84 * microseconds, (NTP_NANO undefined), the time is derived from the 85 * kernel time variable together with a variable representing the 86 * leftover nanoseconds at the last tick interrupt. In either case, the 87 * current nanosecond time is reckoned from these values plus an 88 * interpolated value derived by the clock routines in another 89 * architecture-specific module. The interpolation can use either a 90 * dedicated counter or a processor cycle counter (PCC) implemented in 91 * some architectures. 92 * 93 * Note that all routines must run at priority splclock or higher. 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_tai; /* TAI offset (s) */ 142static long time_monitor; /* last time offset scaled (ns) */ 143static long time_constant; /* poll interval (shift) (s) */ 144static long time_precision = 1; /* clock precision (ns) */ 145static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 146static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 147static long time_reftime; /* time at last adjustment (s) */ 148static long time_tick; /* nanoseconds per tick (ns) */ 149static l_fp time_offset; /* time offset (ns) */ 150static l_fp time_freq; /* frequency offset (ns/s) */ 151static l_fp time_adj; /* tick adjust (ns/s) */ 152static l_fp time_phase; /* time phase (ns) */ 153 154#ifdef PPS_SYNC 155/* 156 * The following variables are used when a pulse-per-second (PPS) signal 157 * is available and connected via a modem control lead. They establish 158 * the engineering parameters of the clock discipline loop when 159 * controlled by the PPS signal. 160 */ 161#define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 162#define PPS_FAVGDEF 7 /* default freq avg int (s) (shift) */ 163#define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 164#define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 165#define PPS_VALID 120 /* PPS signal watchdog max (s) */ 166#define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 167#define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 168 169static struct timespec pps_tf[3]; /* phase median filter */ 170static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 171static long pps_lastfreq; /* last scaled freq offset (ns/s) */ 172static long pps_fcount; /* frequency accumulator */ 173static long pps_jitter; /* nominal jitter (ns) */ 174static long pps_stabil; /* nominal stability (scaled ns/s) */ 175static long pps_lastsec; /* time at last calibration (s) */ 176static int pps_valid; /* signal watchdog counter */ 177static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 178static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 179static int pps_intcnt; /* wander counter */ 180 181/* 182 * PPS signal quality monitors 183 */ 184static long pps_calcnt; /* calibration intervals */ 185static long pps_jitcnt; /* jitter limit exceeded */ 186static long pps_stbcnt; /* stability limit exceeded */ 187static long pps_errcnt; /* calibration errors */ 188#endif /* PPS_SYNC */ 189/* 190 * End of phase/frequency-lock loop (PLL/FLL) definitions 191 */ 192 193static void ntp_init(void); 194static void hardupdate(long offset); 195 196/* 197 * ntp_gettime() - NTP user application interface 198 * 199 * See the timex.h header file for synopsis and API description. Note 200 * that the TAI offset is returned in the ntvtimeval.tai structure 201 * member. 202 */ 203static int 204ntp_sysctl(SYSCTL_HANDLER_ARGS) 205{ 206 struct ntptimeval ntv; /* temporary structure */ 207 struct timespec atv; /* nanosecond time */ 208 209 nanotime(&atv); 210 ntv.time.tv_sec = atv.tv_sec; 211 ntv.time.tv_nsec = atv.tv_nsec; 212 ntv.maxerror = time_maxerror; 213 ntv.esterror = time_esterror; 214 ntv.tai = time_tai; 215 216 /* 217 * Status word error decode. If any of these conditions occur, 218 * an error is returned, instead of the status word. Most 219 * applications will care only about the fact the system clock 220 * may not be trusted, not about the details. 221 * 222 * Hardware or software error 223 */ 224 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 225 226 /* 227 * PPS signal lost when either time or frequency synchronization 228 * requested 229 */ 230 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 231 !(time_status & STA_PPSSIGNAL)) || 232 233 /* 234 * PPS jitter exceeded when time synchronization requested 235 */ 236 (time_status & STA_PPSTIME && 237 time_status & STA_PPSJITTER) || 238 239 /* 240 * PPS wander exceeded or calibration error when frequency 241 * synchronization requested 242 */ 243 (time_status & STA_PPSFREQ && 244 time_status & (STA_PPSWANDER | STA_PPSERROR))) 245 ntv.time_state = TIME_ERROR; 246 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 247} 248 249SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 250SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 251 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 252 253#ifdef PPS_SYNC 254SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 255SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 256 257SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 258SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 259#endif 260/* 261 * ntp_adjtime() - NTP daemon application interface 262 * 263 * See the timex.h header file for synopsis and API description. Note 264 * that the timex.constant structure member has a dual purpose to set 265 * the time constant and to set the TAI offset. 266 */ 267#ifndef _SYS_SYSPROTO_H_ 268struct ntp_adjtime_args { 269 struct timex *tp; 270}; 271#endif 272 273int 274ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 275{ 276 struct timex ntv; /* temporary structure */ 277 long freq; /* frequency ns/s) */ 278 int modes; /* mode bits from structure */ 279 int s; /* caller priority */ 280 int error; 281 282 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 283 if (error) 284 return(error); 285 286 /* 287 * Update selected clock variables - only the superuser can 288 * change anything. Note that there is no error checking here on 289 * the assumption the superuser should know what it is doing. 290 * Note that either the time constant or TAI offset are loaded 291 * from the ntv.constant member, depending on the mode bits. 292 */ 293 modes = ntv.modes; 294 if (modes) 295 error = suser(p); 296 if (error) 297 return (error); 298 s = splclock(); 299 if (modes & MOD_FREQUENCY) { 300 freq = (ntv.freq * 1000LL) >> 16; 301 if (freq > MAXFREQ) 302 L_LINT(time_freq, MAXFREQ); 303 else if (freq < -MAXFREQ) 304 L_LINT(time_freq, -MAXFREQ); 305 else 306 L_LINT(time_freq, freq); 307#ifdef PPS_SYNC 308 pps_freq = time_freq; 309#endif /* PPS_SYNC */ 310 } 311 if (modes & MOD_MAXERROR) 312 time_maxerror = ntv.maxerror; 313 if (modes & MOD_ESTERROR) 314 time_esterror = ntv.esterror; 315 if (modes & MOD_STATUS) { 316 time_status &= STA_RONLY; 317 time_status |= ntv.status & ~STA_RONLY; 318 } 319 if (modes & MOD_TIMECONST) { 320 if (ntv.constant < 0) 321 time_constant = 0; 322 else if (ntv.constant > MAXTC) 323 time_constant = MAXTC; 324 else 325 time_constant = ntv.constant; 326 } 327 if (modes & MOD_TAI) { 328 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 329 time_tai = ntv.constant; 330 } 331#ifdef PPS_SYNC 332 if (modes & MOD_PPSMAX) { 333 if (ntv.shift < PPS_FAVG) 334 pps_shiftmax = PPS_FAVG; 335 else if (ntv.shift > PPS_FAVGMAX) 336 pps_shiftmax = PPS_FAVGMAX; 337 else 338 pps_shiftmax = ntv.shift; 339 } 340#endif /* PPS_SYNC */ 341 if (modes & MOD_NANO) 342 time_status |= STA_NANO; 343 if (modes & MOD_MICRO) 344 time_status &= ~STA_NANO; 345 if (modes & MOD_CLKB) 346 time_status |= STA_CLK; 347 if (modes & MOD_CLKA) 348 time_status &= ~STA_CLK; 349 if (modes & MOD_OFFSET) { 350 if (time_status & STA_NANO) 351 hardupdate(ntv.offset); 352 else 353 hardupdate(ntv.offset * 1000); 354 } 355 356 /* 357 * Retrieve all clock variables. Note that the TAI offset is 358 * returned only by ntp_gettime(); 359 */ 360 if (time_status & STA_NANO) 361 ntv.offset = time_monitor; 362 else 363 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 364 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 365 ntv.maxerror = time_maxerror; 366 ntv.esterror = time_esterror; 367 ntv.status = time_status; 368 ntv.constant = time_constant; 369 if (time_status & STA_NANO) 370 ntv.precision = time_precision; 371 else 372 ntv.precision = time_precision / 1000; 373 ntv.tolerance = MAXFREQ * SCALE_PPM; 374#ifdef PPS_SYNC 375 ntv.shift = pps_shift; 376 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 377 if (time_status & STA_NANO) 378 ntv.jitter = pps_jitter; 379 else 380 ntv.jitter = pps_jitter / 1000; 381 ntv.stabil = pps_stabil; 382 ntv.calcnt = pps_calcnt; 383 ntv.errcnt = pps_errcnt; 384 ntv.jitcnt = pps_jitcnt; 385 ntv.stbcnt = pps_stbcnt; 386#endif /* PPS_SYNC */ 387 splx(s); 388 389 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 390 if (error) 391 return (error); 392 393 /* 394 * Status word error decode. See comments in 395 * ntp_gettime() routine. 396 */ 397 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 398 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 399 !(time_status & STA_PPSSIGNAL)) || 400 (time_status & STA_PPSTIME && 401 time_status & STA_PPSJITTER) || 402 (time_status & STA_PPSFREQ && 403 time_status & (STA_PPSWANDER | STA_PPSERROR))) 404 p->p_retval[0] = TIME_ERROR; 405 else 406 p->p_retval[0] = time_state; 407 return (error); 408} 409 410/* 411 * second_overflow() - called after ntp_tick_adjust() 412 * 413 * This routine is ordinarily called immediately following the above 414 * routine ntp_tick_adjust(). While these two routines are normally 415 * combined, they are separated here only for the purposes of 416 * simulation. 417 */ 418void 419ntp_update_second(struct timecounter *tcp) 420{ 421 u_int32_t *newsec; 422 l_fp ftemp; /* 32/64-bit temporary */ 423 424 newsec = &tcp->tc_offset_sec; 425 /* 426 * On rollover of the second both the nanosecond and microsecond 427 * clocks are updated and the state machine cranked as 428 * necessary. The phase adjustment to be used for the next 429 * second is calculated and the maximum error is increased by 430 * the tolerance. 431 */ 432 time_maxerror += MAXFREQ / 1000; 433 434 /* 435 * Leap second processing. If in leap-insert state at 436 * the end of the day, the system clock is set back one 437 * second; if in leap-delete state, the system clock is 438 * set ahead one second. The nano_time() routine or 439 * external clock driver will insure that reported time 440 * is always monotonic. 441 */ 442 switch (time_state) { 443 444 /* 445 * No warning. 446 */ 447 case TIME_OK: 448 if (time_status & STA_INS) 449 time_state = TIME_INS; 450 else if (time_status & STA_DEL) 451 time_state = TIME_DEL; 452 break; 453 454 /* 455 * Insert second 23:59:60 following second 456 * 23:59:59. 457 */ 458 case TIME_INS: 459 if (!(time_status & STA_INS)) 460 time_state = TIME_OK; 461 else if ((*newsec) % 86400 == 0) { 462 (*newsec)--; 463 time_state = TIME_OOP; 464 } 465 break; 466 467 /* 468 * Delete second 23:59:59. 469 */ 470 case TIME_DEL: 471 if (!(time_status & STA_DEL)) 472 time_state = TIME_OK; 473 else if (((*newsec) + 1) % 86400 == 0) { 474 (*newsec)++; 475 time_tai--; 476 time_state = TIME_WAIT; 477 } 478 break; 479 480 /* 481 * Insert second in progress. 482 */ 483 case TIME_OOP: 484 time_tai++; 485 time_state = TIME_WAIT; 486 break; 487 488 /* 489 * Wait for status bits to clear. 490 */ 491 case TIME_WAIT: 492 if (!(time_status & (STA_INS | STA_DEL))) 493 time_state = TIME_OK; 494 } 495 496 /* 497 * Compute the total time adjustment for the next second 498 * in ns. The offset is reduced by a factor depending on 499 * whether the PPS signal is operating. Note that the 500 * value is in effect scaled by the clock frequency, 501 * since the adjustment is added at each tick interrupt. 502 */ 503 ftemp = time_offset; 504#ifdef PPS_SYNC 505 /* XXX even if PPS signal dies we should finish adjustment ? */ 506 if (time_status & STA_PPSTIME && time_status & 507 STA_PPSSIGNAL) 508 L_RSHIFT(ftemp, pps_shift); 509 else 510 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 511#else 512 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 513#endif /* PPS_SYNC */ 514 time_adj = ftemp; 515 L_SUB(time_offset, ftemp); 516 L_ADD(time_adj, time_freq); 517 tcp->tc_adjustment = time_adj; 518#ifdef PPS_SYNC 519 if (pps_valid > 0) 520 pps_valid--; 521 else 522 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 523 STA_PPSWANDER | STA_PPSERROR); 524#endif /* PPS_SYNC */ 525} 526 527/* 528 * ntp_init() - initialize variables and structures 529 * 530 * This routine must be called after the kernel variables hz and tick 531 * are set or changed and before the next tick interrupt. In this 532 * particular implementation, these values are assumed set elsewhere in 533 * the kernel. The design allows the clock frequency and tick interval 534 * to be changed while the system is running. So, this routine should 535 * probably be integrated with the code that does that. 536 */ 537static void 538ntp_init() 539{ 540 541 /* 542 * The following variable must be initialized any time the 543 * kernel variable hz is changed. 544 */ 545 time_tick = NANOSECOND / hz; 546 547 /* 548 * The following variables are initialized only at startup. Only 549 * those structures not cleared by the compiler need to be 550 * initialized, and these only in the simulator. In the actual 551 * kernel, any nonzero values here will quickly evaporate. 552 */ 553 L_CLR(time_offset); 554 L_CLR(time_freq); 555#ifdef PPS_SYNC 556 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 557 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 558 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 559 pps_fcount = 0; 560 L_CLR(pps_freq); 561#endif /* PPS_SYNC */ 562} 563 564SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 565 566/* 567 * hardupdate() - local clock update 568 * 569 * This routine is called by ntp_adjtime() to update the local clock 570 * phase and frequency. The implementation is of an adaptive-parameter, 571 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 572 * time and frequency offset estimates for each call. If the kernel PPS 573 * discipline code is configured (PPS_SYNC), the PPS signal itself 574 * determines the new time offset, instead of the calling argument. 575 * Presumably, calls to ntp_adjtime() occur only when the caller 576 * believes the local clock is valid within some bound (+-128 ms with 577 * NTP). If the caller's time is far different than the PPS time, an 578 * argument will ensue, and it's not clear who will lose. 579 * 580 * For uncompensated quartz crystal oscillators and nominal update 581 * intervals less than 256 s, operation should be in phase-lock mode, 582 * where the loop is disciplined to phase. For update intervals greater 583 * than 1024 s, operation should be in frequency-lock mode, where the 584 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 585 * is selected by the STA_MODE status bit. 586 */ 587static void 588hardupdate(offset) 589 long offset; /* clock offset (ns) */ 590{ 591 long mtemp; 592 l_fp ftemp; 593 594 /* 595 * Select how the phase is to be controlled and from which 596 * source. If the PPS signal is present and enabled to 597 * discipline the time, the PPS offset is used; otherwise, the 598 * argument offset is used. 599 */ 600 if (!(time_status & STA_PLL)) 601 return; 602 if (!(time_status & STA_PPSTIME && time_status & 603 STA_PPSSIGNAL)) { 604 if (offset > MAXPHASE) 605 time_monitor = MAXPHASE; 606 else if (offset < -MAXPHASE) 607 time_monitor = -MAXPHASE; 608 else 609 time_monitor = offset; 610 L_LINT(time_offset, time_monitor); 611 } 612 613 /* 614 * Select how the frequency is to be controlled and in which 615 * mode (PLL or FLL). If the PPS signal is present and enabled 616 * to discipline the frequency, the PPS frequency is used; 617 * otherwise, the argument offset is used to compute it. 618 */ 619 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 620 time_reftime = time_second; 621 return; 622 } 623 if (time_status & STA_FREQHOLD || time_reftime == 0) 624 time_reftime = time_second; 625 mtemp = time_second - time_reftime; 626 L_LINT(ftemp, time_monitor); 627 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 628 L_MPY(ftemp, mtemp); 629 L_ADD(time_freq, ftemp); 630 time_status &= ~STA_MODE; 631 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 632 MAXSEC)) { 633 L_LINT(ftemp, (time_monitor << 4) / mtemp); 634 L_RSHIFT(ftemp, SHIFT_FLL + 4); 635 L_ADD(time_freq, ftemp); 636 time_status |= STA_MODE; 637 } 638 time_reftime = time_second; 639 if (L_GINT(time_freq) > MAXFREQ) 640 L_LINT(time_freq, MAXFREQ); 641 else if (L_GINT(time_freq) < -MAXFREQ) 642 L_LINT(time_freq, -MAXFREQ); 643} 644 645#ifdef PPS_SYNC 646/* 647 * hardpps() - discipline CPU clock oscillator to external PPS signal 648 * 649 * This routine is called at each PPS interrupt in order to discipline 650 * the CPU clock oscillator to the PPS signal. There are two independent 651 * first-order feedback loops, one for the phase, the other for the 652 * frequency. The phase loop measures and grooms the PPS phase offset 653 * and leaves it in a handy spot for the seconds overflow routine. The 654 * frequency loop averages successive PPS phase differences and 655 * calculates the PPS frequency offset, which is also processed by the 656 * seconds overflow routine. The code requires the caller to capture the 657 * time and architecture-dependent hardware counter values in 658 * nanoseconds at the on-time PPS signal transition. 659 * 660 * Note that, on some Unix systems this routine runs at an interrupt 661 * priority level higher than the timer interrupt routine hardclock(). 662 * Therefore, the variables used are distinct from the hardclock() 663 * variables, except for the actual time and frequency variables, which 664 * are determined by this routine and updated atomically. 665 */ 666void 667hardpps(tsp, nsec) 668 struct timespec *tsp; /* time at PPS */ 669 long nsec; /* hardware counter at PPS */ 670{ 671 long u_sec, u_nsec, v_nsec; /* temps */ 672 l_fp ftemp; 673 674 /* 675 * The signal is first processed by a range gate and frequency 676 * discriminator. The range gate rejects noise spikes outside 677 * the range +-500 us. The frequency discriminator rejects input 678 * signals with apparent frequency outside the range 1 +-500 679 * PPM. If two hits occur in the same second, we ignore the 680 * later hit; if not and a hit occurs outside the range gate, 681 * keep the later hit for later comparison, but do not process 682 * it. 683 */ 684 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 685 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 686 pps_valid = PPS_VALID; 687 u_sec = tsp->tv_sec; 688 u_nsec = tsp->tv_nsec; 689 if (u_nsec >= (NANOSECOND >> 1)) { 690 u_nsec -= NANOSECOND; 691 u_sec++; 692 } 693 v_nsec = u_nsec - pps_tf[0].tv_nsec; 694 /* XXX: This test seems incomplete ? */ 695 if (u_sec == pps_tf[0].tv_sec && v_nsec < -MAXFREQ) { 696 return; 697 } 698 pps_tf[2] = pps_tf[1]; 699 pps_tf[1] = pps_tf[0]; 700 pps_tf[0].tv_sec = u_sec; 701 pps_tf[0].tv_nsec = u_nsec; 702 703 /* 704 * Compute the difference between the current and previous 705 * counter values. If the difference exceeds 0.5 s, assume it 706 * has wrapped around, so correct 1.0 s. If the result exceeds 707 * the tick interval, the sample point has crossed a tick 708 * boundary during the last second, so correct the tick. Very 709 * intricate. 710 */ 711 u_nsec = nsec; 712 if (u_nsec > (NANOSECOND >> 1)) 713 u_nsec -= NANOSECOND; 714 else if (u_nsec < -(NANOSECOND >> 1)) 715 u_nsec += NANOSECOND; 716 pps_fcount += u_nsec; 717 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) { 718 return; 719 } 720 time_status &= ~STA_PPSJITTER; 721 722 /* 723 * A three-stage median filter is used to help denoise the PPS 724 * time. The median sample becomes the time offset estimate; the 725 * difference between the other two samples becomes the time 726 * dispersion (jitter) estimate. 727 */ 728 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 729 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 730 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 731 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 732 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 733 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 734 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 735 } else { 736 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 737 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 738 } 739 } else { 740 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 741 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 742 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 743 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 744 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 745 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 746 } else { 747 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 748 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 749 } 750 } 751 752 /* 753 * Nominal jitter is due to PPS signal noise and interrupt 754 * latency. If it exceeds the popcorn threshold, the sample is 755 * discarded. otherwise, if so enabled, the time offset is 756 * updated. We can tolerate a modest loss of data here without 757 * much degrading time accuracy. 758 */ 759 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 760 time_status |= STA_PPSJITTER; 761 pps_jitcnt++; 762 } else if (time_status & STA_PPSTIME) { 763 time_monitor = -v_nsec; 764 L_LINT(time_offset, time_monitor); 765 } 766 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 767 u_sec = pps_tf[0].tv_sec - pps_lastsec; 768 if (u_sec < (1 << pps_shift)) 769 return; 770 771 /* 772 * At the end of the calibration interval the difference between 773 * the first and last counter values becomes the scaled 774 * frequency. It will later be divided by the length of the 775 * interval to determine the frequency update. If the frequency 776 * exceeds a sanity threshold, or if the actual calibration 777 * interval is not equal to the expected length, the data are 778 * discarded. We can tolerate a modest loss of data here without 779 * much degrading frequency accuracy. 780 */ 781 pps_calcnt++; 782 v_nsec = -pps_fcount; 783 pps_lastsec = pps_tf[0].tv_sec; 784 pps_fcount = 0; 785 u_nsec = MAXFREQ << pps_shift; 786 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 787 pps_shift)) { 788 time_status |= STA_PPSERROR; 789 pps_errcnt++; 790 return; 791 } 792 793 /* 794 * Here the raw frequency offset and wander (stability) is 795 * calculated. If the wander is less than the wander threshold 796 * for four consecutive averaging intervals, the interval is 797 * doubled; if it is greater than the threshold for four 798 * consecutive intervals, the interval is halved. The scaled 799 * frequency offset is converted to frequency offset. The 800 * stability metric is calculated as the average of recent 801 * frequency changes, but is used only for performance 802 * monitoring. 803 */ 804 L_LINT(ftemp, v_nsec); 805 L_RSHIFT(ftemp, pps_shift); 806 L_SUB(ftemp, pps_freq); 807 u_nsec = L_GINT(ftemp); 808 if (u_nsec > PPS_MAXWANDER) { 809 L_LINT(ftemp, PPS_MAXWANDER); 810 pps_intcnt--; 811 time_status |= STA_PPSWANDER; 812 pps_stbcnt++; 813 } else if (u_nsec < -PPS_MAXWANDER) { 814 L_LINT(ftemp, -PPS_MAXWANDER); 815 pps_intcnt--; 816 time_status |= STA_PPSWANDER; 817 pps_stbcnt++; 818 } else { 819 pps_intcnt++; 820 } 821 if (pps_intcnt >= 4) { 822 pps_intcnt = 4; 823 if (pps_shift < pps_shiftmax) { 824 pps_shift++; 825 pps_intcnt = 0; 826 } 827 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 828 pps_intcnt = -4; 829 if (pps_shift > PPS_FAVG) { 830 pps_shift--; 831 pps_intcnt = 0; 832 } 833 } 834 if (u_nsec < 0) 835 u_nsec = -u_nsec; 836 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 837 838 /* 839 * The PPS frequency is recalculated and clamped to the maximum 840 * MAXFREQ. If enabled, the system clock frequency is updated as 841 * well. 842 */ 843 L_ADD(pps_freq, ftemp); 844 u_nsec = L_GINT(pps_freq); 845 if (u_nsec > MAXFREQ) 846 L_LINT(pps_freq, MAXFREQ); 847 else if (u_nsec < -MAXFREQ) 848 L_LINT(pps_freq, -MAXFREQ); 849 if (time_status & STA_PPSFREQ) 850 time_freq = pps_freq; 851} 852#endif /* PPS_SYNC */ 853