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