1 /*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-2001 * 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: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $ 32 * $DragonFly: src/sys/kern/kern_ntptime.c,v 1.7 2003/07/30 00:19:14 dillon Exp $ 33 */ 34 35 #include "opt_ntp.h" 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/sysproto.h> 40 #include <sys/kernel.h> 41 #include <sys/proc.h> 42 #include <sys/time.h> 43 #include <sys/timex.h> 44 #include <sys/timepps.h> 45 #include <sys/sysctl.h> 46 47 /* 48 * Single-precision macros for 64-bit machines 49 */ 50 typedef 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) */ 138 139 static int time_state = TIME_OK; /* clock state */ 140 static int time_status = STA_UNSYNC; /* clock status bits */ 141 static long time_tai; /* TAI offset (s) */ 142 static long time_monitor; /* last time offset scaled (ns) */ 143 static long time_constant; /* poll interval (shift) (s) */ 144 static long time_precision = 1; /* clock precision (ns) */ 145 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 146 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 147 static long time_reftime; /* time at last adjustment (s) */ 148 static long time_tick; /* nanoseconds per tick (ns) */ 149 static l_fp time_offset; /* time offset (ns) */ 150 static l_fp time_freq; /* frequency offset (ns/s) */ 151 static l_fp time_adj; /* tick adjust (ns/s) */ 152 153 #ifdef PPS_SYNC 154 /* 155 * The following variables are used when a pulse-per-second (PPS) signal 156 * is available and connected via a modem control lead. They establish 157 * the engineering parameters of the clock discipline loop when 158 * controlled by the PPS signal. 159 */ 160 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 161 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 162 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 163 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 164 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 165 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 166 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 167 168 static struct timespec pps_tf[3]; /* phase median filter */ 169 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 170 static long pps_fcount; /* frequency accumulator */ 171 static long pps_jitter; /* nominal jitter (ns) */ 172 static long pps_stabil; /* nominal stability (scaled ns/s) */ 173 static long pps_lastsec; /* time at last calibration (s) */ 174 static int pps_valid; /* signal watchdog counter */ 175 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 176 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 177 static int pps_intcnt; /* wander counter */ 178 179 /* 180 * PPS signal quality monitors 181 */ 182 static long pps_calcnt; /* calibration intervals */ 183 static long pps_jitcnt; /* jitter limit exceeded */ 184 static long pps_stbcnt; /* stability limit exceeded */ 185 static long pps_errcnt; /* calibration errors */ 186 #endif /* PPS_SYNC */ 187 /* 188 * End of phase/frequency-lock loop (PLL/FLL) definitions 189 */ 190 191 static void ntp_init(void); 192 static void hardupdate(long offset); 193 194 /* 195 * ntp_gettime() - NTP user application interface 196 * 197 * See the timex.h header file for synopsis and API description. Note 198 * that the TAI offset is returned in the ntvtimeval.tai structure 199 * member. 200 */ 201 static int 202 ntp_sysctl(SYSCTL_HANDLER_ARGS) 203 { 204 struct ntptimeval ntv; /* temporary structure */ 205 struct timespec atv; /* nanosecond time */ 206 207 nanotime(&atv); 208 ntv.time.tv_sec = atv.tv_sec; 209 ntv.time.tv_nsec = atv.tv_nsec; 210 ntv.maxerror = time_maxerror; 211 ntv.esterror = time_esterror; 212 ntv.tai = time_tai; 213 ntv.time_state = time_state; 214 215 /* 216 * Status word error decode. If any of these conditions occur, 217 * an error is returned, instead of the status word. Most 218 * applications will care only about the fact the system clock 219 * may not be trusted, not about the details. 220 * 221 * Hardware or software error 222 */ 223 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 224 225 /* 226 * PPS signal lost when either time or frequency synchronization 227 * requested 228 */ 229 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 230 !(time_status & STA_PPSSIGNAL)) || 231 232 /* 233 * PPS jitter exceeded when time synchronization requested 234 */ 235 (time_status & STA_PPSTIME && 236 time_status & STA_PPSJITTER) || 237 238 /* 239 * PPS wander exceeded or calibration error when frequency 240 * synchronization requested 241 */ 242 (time_status & STA_PPSFREQ && 243 time_status & (STA_PPSWANDER | STA_PPSERROR))) 244 ntv.time_state = TIME_ERROR; 245 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 246 } 247 248 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 249 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 250 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 251 252 #ifdef PPS_SYNC 253 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 254 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 255 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 256 257 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 258 SYSCTL_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 int 268 ntp_adjtime(struct ntp_adjtime_args *uap) 269 { 270 struct thread *td = curthread; 271 struct timex ntv; /* temporary structure */ 272 long freq; /* frequency ns/s) */ 273 int modes; /* mode bits from structure */ 274 int s; /* caller priority */ 275 int error; 276 277 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 278 if (error) 279 return(error); 280 281 /* 282 * Update selected clock variables - only the superuser can 283 * change anything. Note that there is no error checking here on 284 * the assumption the superuser should know what it is doing. 285 * Note that either the time constant or TAI offset are loaded 286 * from the ntv.constant member, depending on the mode bits. If 287 * the STA_PLL bit in the status word is cleared, the state and 288 * status words are reset to the initial values at boot. 289 */ 290 modes = ntv.modes; 291 if (modes) 292 error = suser(td); 293 if (error) 294 return (error); 295 s = splclock(); 296 if (modes & MOD_MAXERROR) 297 time_maxerror = ntv.maxerror; 298 if (modes & MOD_ESTERROR) 299 time_esterror = ntv.esterror; 300 if (modes & MOD_STATUS) { 301 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 302 time_state = TIME_OK; 303 time_status = STA_UNSYNC; 304 #ifdef PPS_SYNC 305 pps_shift = PPS_FAVG; 306 #endif /* PPS_SYNC */ 307 } 308 time_status &= STA_RONLY; 309 time_status |= ntv.status & ~STA_RONLY; 310 } 311 if (modes & MOD_TIMECONST) { 312 if (ntv.constant < 0) 313 time_constant = 0; 314 else if (ntv.constant > MAXTC) 315 time_constant = MAXTC; 316 else 317 time_constant = ntv.constant; 318 } 319 if (modes & MOD_TAI) { 320 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 321 time_tai = ntv.constant; 322 } 323 #ifdef PPS_SYNC 324 if (modes & MOD_PPSMAX) { 325 if (ntv.shift < PPS_FAVG) 326 pps_shiftmax = PPS_FAVG; 327 else if (ntv.shift > PPS_FAVGMAX) 328 pps_shiftmax = PPS_FAVGMAX; 329 else 330 pps_shiftmax = ntv.shift; 331 } 332 #endif /* PPS_SYNC */ 333 if (modes & MOD_NANO) 334 time_status |= STA_NANO; 335 if (modes & MOD_MICRO) 336 time_status &= ~STA_NANO; 337 if (modes & MOD_CLKB) 338 time_status |= STA_CLK; 339 if (modes & MOD_CLKA) 340 time_status &= ~STA_CLK; 341 if (modes & MOD_OFFSET) { 342 if (time_status & STA_NANO) 343 hardupdate(ntv.offset); 344 else 345 hardupdate(ntv.offset * 1000); 346 } 347 if (modes & MOD_FREQUENCY) { 348 freq = (ntv.freq * 1000LL) >> 16; 349 if (freq > MAXFREQ) 350 L_LINT(time_freq, MAXFREQ); 351 else if (freq < -MAXFREQ) 352 L_LINT(time_freq, -MAXFREQ); 353 else 354 L_LINT(time_freq, freq); 355 #ifdef PPS_SYNC 356 pps_freq = time_freq; 357 #endif /* PPS_SYNC */ 358 } 359 360 /* 361 * Retrieve all clock variables. Note that the TAI offset is 362 * returned only by ntp_gettime(); 363 */ 364 if (time_status & STA_NANO) 365 ntv.offset = time_monitor; 366 else 367 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 368 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 369 ntv.maxerror = time_maxerror; 370 ntv.esterror = time_esterror; 371 ntv.status = time_status; 372 ntv.constant = time_constant; 373 if (time_status & STA_NANO) 374 ntv.precision = time_precision; 375 else 376 ntv.precision = time_precision / 1000; 377 ntv.tolerance = MAXFREQ * SCALE_PPM; 378 #ifdef PPS_SYNC 379 ntv.shift = pps_shift; 380 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 381 if (time_status & STA_NANO) 382 ntv.jitter = pps_jitter; 383 else 384 ntv.jitter = pps_jitter / 1000; 385 ntv.stabil = pps_stabil; 386 ntv.calcnt = pps_calcnt; 387 ntv.errcnt = pps_errcnt; 388 ntv.jitcnt = pps_jitcnt; 389 ntv.stbcnt = pps_stbcnt; 390 #endif /* PPS_SYNC */ 391 splx(s); 392 393 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 394 if (error) 395 return (error); 396 397 /* 398 * Status word error decode. See comments in 399 * ntp_gettime() routine. 400 */ 401 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 402 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 403 !(time_status & STA_PPSSIGNAL)) || 404 (time_status & STA_PPSTIME && 405 time_status & STA_PPSJITTER) || 406 (time_status & STA_PPSFREQ && 407 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 408 uap->sysmsg_result = TIME_ERROR; 409 } else { 410 uap->sysmsg_result = time_state; 411 } 412 return (error); 413 } 414 415 /* 416 * second_overflow() - called after ntp_tick_adjust() 417 * 418 * This routine is ordinarily called immediately following the above 419 * routine ntp_tick_adjust(). While these two routines are normally 420 * combined, they are separated here only for the purposes of 421 * simulation. 422 */ 423 void 424 ntp_update_second(struct timecounter *tcp) 425 { 426 u_int32_t *newsec; 427 l_fp ftemp; /* 32/64-bit temporary */ 428 429 newsec = &tcp->tc_offset_sec; 430 /* 431 * On rollover of the second both the nanosecond and microsecond 432 * clocks are updated and the state machine cranked as 433 * necessary. The phase adjustment to be used for the next 434 * second is calculated and the maximum error is increased by 435 * the tolerance. 436 */ 437 time_maxerror += MAXFREQ / 1000; 438 439 /* 440 * Leap second processing. If in leap-insert state at 441 * the end of the day, the system clock is set back one 442 * second; if in leap-delete state, the system clock is 443 * set ahead one second. The nano_time() routine or 444 * external clock driver will insure that reported time 445 * is always monotonic. 446 */ 447 switch (time_state) { 448 449 /* 450 * No warning. 451 */ 452 case TIME_OK: 453 if (time_status & STA_INS) 454 time_state = TIME_INS; 455 else if (time_status & STA_DEL) 456 time_state = TIME_DEL; 457 break; 458 459 /* 460 * Insert second 23:59:60 following second 461 * 23:59:59. 462 */ 463 case TIME_INS: 464 if (!(time_status & STA_INS)) 465 time_state = TIME_OK; 466 else if ((*newsec) % 86400 == 0) { 467 (*newsec)--; 468 time_state = TIME_OOP; 469 } 470 break; 471 472 /* 473 * Delete second 23:59:59. 474 */ 475 case TIME_DEL: 476 if (!(time_status & STA_DEL)) 477 time_state = TIME_OK; 478 else if (((*newsec) + 1) % 86400 == 0) { 479 (*newsec)++; 480 time_tai--; 481 time_state = TIME_WAIT; 482 } 483 break; 484 485 /* 486 * Insert second in progress. 487 */ 488 case TIME_OOP: 489 time_tai++; 490 time_state = TIME_WAIT; 491 break; 492 493 /* 494 * Wait for status bits to clear. 495 */ 496 case TIME_WAIT: 497 if (!(time_status & (STA_INS | STA_DEL))) 498 time_state = TIME_OK; 499 } 500 501 /* 502 * Compute the total time adjustment for the next second 503 * in ns. The offset is reduced by a factor depending on 504 * whether the PPS signal is operating. Note that the 505 * value is in effect scaled by the clock frequency, 506 * since the adjustment is added at each tick interrupt. 507 */ 508 ftemp = time_offset; 509 #ifdef PPS_SYNC 510 /* XXX even if PPS signal dies we should finish adjustment ? */ 511 if (time_status & STA_PPSTIME && time_status & 512 STA_PPSSIGNAL) 513 L_RSHIFT(ftemp, pps_shift); 514 else 515 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 516 #else 517 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 518 #endif /* PPS_SYNC */ 519 time_adj = ftemp; 520 L_SUB(time_offset, ftemp); 521 L_ADD(time_adj, time_freq); 522 tcp->tc_adjustment = time_adj; 523 #ifdef PPS_SYNC 524 if (pps_valid > 0) 525 pps_valid--; 526 else 527 time_status &= ~STA_PPSSIGNAL; 528 #endif /* PPS_SYNC */ 529 } 530 531 /* 532 * ntp_init() - initialize variables and structures 533 * 534 * This routine must be called after the kernel variables hz and tick 535 * are set or changed and before the next tick interrupt. In this 536 * particular implementation, these values are assumed set elsewhere in 537 * the kernel. The design allows the clock frequency and tick interval 538 * to be changed while the system is running. So, this routine should 539 * probably be integrated with the code that does that. 540 */ 541 static void 542 ntp_init() 543 { 544 545 /* 546 * The following variable must be initialized any time the 547 * kernel variable hz is changed. 548 */ 549 time_tick = NANOSECOND / hz; 550 551 /* 552 * The following variables are initialized only at startup. Only 553 * those structures not cleared by the compiler need to be 554 * initialized, and these only in the simulator. In the actual 555 * kernel, any nonzero values here will quickly evaporate. 556 */ 557 L_CLR(time_offset); 558 L_CLR(time_freq); 559 #ifdef PPS_SYNC 560 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 561 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 562 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 563 pps_fcount = 0; 564 L_CLR(pps_freq); 565 #endif /* PPS_SYNC */ 566 } 567 568 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 569 570 /* 571 * hardupdate() - local clock update 572 * 573 * This routine is called by ntp_adjtime() to update the local clock 574 * phase and frequency. The implementation is of an adaptive-parameter, 575 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 576 * time and frequency offset estimates for each call. If the kernel PPS 577 * discipline code is configured (PPS_SYNC), the PPS signal itself 578 * determines the new time offset, instead of the calling argument. 579 * Presumably, calls to ntp_adjtime() occur only when the caller 580 * believes the local clock is valid within some bound (+-128 ms with 581 * NTP). If the caller's time is far different than the PPS time, an 582 * argument will ensue, and it's not clear who will lose. 583 * 584 * For uncompensated quartz crystal oscillators and nominal update 585 * intervals less than 256 s, operation should be in phase-lock mode, 586 * where the loop is disciplined to phase. For update intervals greater 587 * than 1024 s, operation should be in frequency-lock mode, where the 588 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 589 * is selected by the STA_MODE status bit. 590 */ 591 static void 592 hardupdate(offset) 593 long offset; /* clock offset (ns) */ 594 { 595 long mtemp; 596 l_fp ftemp; 597 598 /* 599 * Select how the phase is to be controlled and from which 600 * source. If the PPS signal is present and enabled to 601 * discipline the time, the PPS offset is used; otherwise, the 602 * argument offset is used. 603 */ 604 if (!(time_status & STA_PLL)) 605 return; 606 if (!(time_status & STA_PPSTIME && time_status & 607 STA_PPSSIGNAL)) { 608 if (offset > MAXPHASE) 609 time_monitor = MAXPHASE; 610 else if (offset < -MAXPHASE) 611 time_monitor = -MAXPHASE; 612 else 613 time_monitor = offset; 614 L_LINT(time_offset, time_monitor); 615 } 616 617 /* 618 * Select how the frequency is to be controlled and in which 619 * mode (PLL or FLL). If the PPS signal is present and enabled 620 * to discipline the frequency, the PPS frequency is used; 621 * otherwise, the argument offset is used to compute it. 622 */ 623 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 624 time_reftime = time_second; 625 return; 626 } 627 if (time_status & STA_FREQHOLD || time_reftime == 0) 628 time_reftime = time_second; 629 mtemp = time_second - time_reftime; 630 L_LINT(ftemp, time_monitor); 631 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 632 L_MPY(ftemp, mtemp); 633 L_ADD(time_freq, ftemp); 634 time_status &= ~STA_MODE; 635 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 636 MAXSEC)) { 637 L_LINT(ftemp, (time_monitor << 4) / mtemp); 638 L_RSHIFT(ftemp, SHIFT_FLL + 4); 639 L_ADD(time_freq, ftemp); 640 time_status |= STA_MODE; 641 } 642 time_reftime = time_second; 643 if (L_GINT(time_freq) > MAXFREQ) 644 L_LINT(time_freq, MAXFREQ); 645 else if (L_GINT(time_freq) < -MAXFREQ) 646 L_LINT(time_freq, -MAXFREQ); 647 } 648 649 #ifdef PPS_SYNC 650 /* 651 * hardpps() - discipline CPU clock oscillator to external PPS signal 652 * 653 * This routine is called at each PPS interrupt in order to discipline 654 * the CPU clock oscillator to the PPS signal. There are two independent 655 * first-order feedback loops, one for the phase, the other for the 656 * frequency. The phase loop measures and grooms the PPS phase offset 657 * and leaves it in a handy spot for the seconds overflow routine. The 658 * frequency loop averages successive PPS phase differences and 659 * calculates the PPS frequency offset, which is also processed by the 660 * seconds overflow routine. The code requires the caller to capture the 661 * time and architecture-dependent hardware counter values in 662 * nanoseconds at the on-time PPS signal transition. 663 * 664 * Note that, on some Unix systems this routine runs at an interrupt 665 * priority level higher than the timer interrupt routine hardclock(). 666 * Therefore, the variables used are distinct from the hardclock() 667 * variables, except for the actual time and frequency variables, which 668 * are determined by this routine and updated atomically. 669 */ 670 void 671 hardpps(tsp, nsec) 672 struct timespec *tsp; /* time at PPS */ 673 long nsec; /* hardware counter at PPS */ 674 { 675 long u_sec, u_nsec, v_nsec; /* temps */ 676 l_fp ftemp; 677 678 /* 679 * The signal is first processed by a range gate and frequency 680 * discriminator. The range gate rejects noise spikes outside 681 * the range +-500 us. The frequency discriminator rejects input 682 * signals with apparent frequency outside the range 1 +-500 683 * PPM. If two hits occur in the same second, we ignore the 684 * later hit; if not and a hit occurs outside the range gate, 685 * keep the later hit for later comparison, but do not process 686 * it. 687 */ 688 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 689 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 690 pps_valid = PPS_VALID; 691 u_sec = tsp->tv_sec; 692 u_nsec = tsp->tv_nsec; 693 if (u_nsec >= (NANOSECOND >> 1)) { 694 u_nsec -= NANOSECOND; 695 u_sec++; 696 } 697 v_nsec = u_nsec - pps_tf[0].tv_nsec; 698 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 699 MAXFREQ) 700 return; 701 pps_tf[2] = pps_tf[1]; 702 pps_tf[1] = pps_tf[0]; 703 pps_tf[0].tv_sec = u_sec; 704 pps_tf[0].tv_nsec = u_nsec; 705 706 /* 707 * Compute the difference between the current and previous 708 * counter values. If the difference exceeds 0.5 s, assume it 709 * has wrapped around, so correct 1.0 s. If the result exceeds 710 * the tick interval, the sample point has crossed a tick 711 * boundary during the last second, so correct the tick. Very 712 * intricate. 713 */ 714 u_nsec = nsec; 715 if (u_nsec > (NANOSECOND >> 1)) 716 u_nsec -= NANOSECOND; 717 else if (u_nsec < -(NANOSECOND >> 1)) 718 u_nsec += NANOSECOND; 719 pps_fcount += u_nsec; 720 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 721 return; 722 time_status &= ~STA_PPSJITTER; 723 724 /* 725 * A three-stage median filter is used to help denoise the PPS 726 * time. The median sample becomes the time offset estimate; the 727 * difference between the other two samples becomes the time 728 * dispersion (jitter) estimate. 729 */ 730 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 731 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 732 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 733 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 734 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 735 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 736 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 737 } else { 738 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 739 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 740 } 741 } else { 742 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 743 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 744 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 745 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 746 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 747 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 748 } else { 749 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 750 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 751 } 752 } 753 754 /* 755 * Nominal jitter is due to PPS signal noise and interrupt 756 * latency. If it exceeds the popcorn threshold, the sample is 757 * discarded. otherwise, if so enabled, the time offset is 758 * updated. We can tolerate a modest loss of data here without 759 * much degrading time accuracy. 760 */ 761 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 762 time_status |= STA_PPSJITTER; 763 pps_jitcnt++; 764 } else if (time_status & STA_PPSTIME) { 765 time_monitor = -v_nsec; 766 L_LINT(time_offset, time_monitor); 767 } 768 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 769 u_sec = pps_tf[0].tv_sec - pps_lastsec; 770 if (u_sec < (1 << pps_shift)) 771 return; 772 773 /* 774 * At the end of the calibration interval the difference between 775 * the first and last counter values becomes the scaled 776 * frequency. It will later be divided by the length of the 777 * interval to determine the frequency update. If the frequency 778 * exceeds a sanity threshold, or if the actual calibration 779 * interval is not equal to the expected length, the data are 780 * discarded. We can tolerate a modest loss of data here without 781 * much degrading frequency accuracy. 782 */ 783 pps_calcnt++; 784 v_nsec = -pps_fcount; 785 pps_lastsec = pps_tf[0].tv_sec; 786 pps_fcount = 0; 787 u_nsec = MAXFREQ << pps_shift; 788 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 789 pps_shift)) { 790 time_status |= STA_PPSERROR; 791 pps_errcnt++; 792 return; 793 } 794 795 /* 796 * Here the raw frequency offset and wander (stability) is 797 * calculated. If the wander is less than the wander threshold 798 * for four consecutive averaging intervals, the interval is 799 * doubled; if it is greater than the threshold for four 800 * consecutive intervals, the interval is halved. The scaled 801 * frequency offset is converted to frequency offset. The 802 * stability metric is calculated as the average of recent 803 * frequency changes, but is used only for performance 804 * monitoring. 805 */ 806 L_LINT(ftemp, v_nsec); 807 L_RSHIFT(ftemp, pps_shift); 808 L_SUB(ftemp, pps_freq); 809 u_nsec = L_GINT(ftemp); 810 if (u_nsec > PPS_MAXWANDER) { 811 L_LINT(ftemp, PPS_MAXWANDER); 812 pps_intcnt--; 813 time_status |= STA_PPSWANDER; 814 pps_stbcnt++; 815 } else if (u_nsec < -PPS_MAXWANDER) { 816 L_LINT(ftemp, -PPS_MAXWANDER); 817 pps_intcnt--; 818 time_status |= STA_PPSWANDER; 819 pps_stbcnt++; 820 } else { 821 pps_intcnt++; 822 } 823 if (pps_intcnt >= 4) { 824 pps_intcnt = 4; 825 if (pps_shift < pps_shiftmax) { 826 pps_shift++; 827 pps_intcnt = 0; 828 } 829 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 830 pps_intcnt = -4; 831 if (pps_shift > PPS_FAVG) { 832 pps_shift--; 833 pps_intcnt = 0; 834 } 835 } 836 if (u_nsec < 0) 837 u_nsec = -u_nsec; 838 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 839 840 /* 841 * The PPS frequency is recalculated and clamped to the maximum 842 * MAXFREQ. If enabled, the system clock frequency is updated as 843 * well. 844 */ 845 L_ADD(pps_freq, ftemp); 846 u_nsec = L_GINT(pps_freq); 847 if (u_nsec > MAXFREQ) 848 L_LINT(pps_freq, MAXFREQ); 849 else if (u_nsec < -MAXFREQ) 850 L_LINT(pps_freq, -MAXFREQ); 851 if (time_status & STA_PPSFREQ) 852 time_freq = pps_freq; 853 } 854 #endif /* PPS_SYNC */ 855