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 1.5 2003/07/24 01:41:25 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 curproc->p_retval[0] = TIME_ERROR; 409 else 410 curproc->p_retval[0] = time_state; 411 return (error); 412 } 413 414 /* 415 * second_overflow() - called after ntp_tick_adjust() 416 * 417 * This routine is ordinarily called immediately following the above 418 * routine ntp_tick_adjust(). While these two routines are normally 419 * combined, they are separated here only for the purposes of 420 * simulation. 421 */ 422 void 423 ntp_update_second(struct timecounter *tcp) 424 { 425 u_int32_t *newsec; 426 l_fp ftemp; /* 32/64-bit temporary */ 427 428 newsec = &tcp->tc_offset_sec; 429 /* 430 * On rollover of the second both the nanosecond and microsecond 431 * clocks are updated and the state machine cranked as 432 * necessary. The phase adjustment to be used for the next 433 * second is calculated and the maximum error is increased by 434 * the tolerance. 435 */ 436 time_maxerror += MAXFREQ / 1000; 437 438 /* 439 * Leap second processing. If in leap-insert state at 440 * the end of the day, the system clock is set back one 441 * second; if in leap-delete state, the system clock is 442 * set ahead one second. The nano_time() routine or 443 * external clock driver will insure that reported time 444 * is always monotonic. 445 */ 446 switch (time_state) { 447 448 /* 449 * No warning. 450 */ 451 case TIME_OK: 452 if (time_status & STA_INS) 453 time_state = TIME_INS; 454 else if (time_status & STA_DEL) 455 time_state = TIME_DEL; 456 break; 457 458 /* 459 * Insert second 23:59:60 following second 460 * 23:59:59. 461 */ 462 case TIME_INS: 463 if (!(time_status & STA_INS)) 464 time_state = TIME_OK; 465 else if ((*newsec) % 86400 == 0) { 466 (*newsec)--; 467 time_state = TIME_OOP; 468 } 469 break; 470 471 /* 472 * Delete second 23:59:59. 473 */ 474 case TIME_DEL: 475 if (!(time_status & STA_DEL)) 476 time_state = TIME_OK; 477 else if (((*newsec) + 1) % 86400 == 0) { 478 (*newsec)++; 479 time_tai--; 480 time_state = TIME_WAIT; 481 } 482 break; 483 484 /* 485 * Insert second in progress. 486 */ 487 case TIME_OOP: 488 time_tai++; 489 time_state = TIME_WAIT; 490 break; 491 492 /* 493 * Wait for status bits to clear. 494 */ 495 case TIME_WAIT: 496 if (!(time_status & (STA_INS | STA_DEL))) 497 time_state = TIME_OK; 498 } 499 500 /* 501 * Compute the total time adjustment for the next second 502 * in ns. The offset is reduced by a factor depending on 503 * whether the PPS signal is operating. Note that the 504 * value is in effect scaled by the clock frequency, 505 * since the adjustment is added at each tick interrupt. 506 */ 507 ftemp = time_offset; 508 #ifdef PPS_SYNC 509 /* XXX even if PPS signal dies we should finish adjustment ? */ 510 if (time_status & STA_PPSTIME && time_status & 511 STA_PPSSIGNAL) 512 L_RSHIFT(ftemp, pps_shift); 513 else 514 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 515 #else 516 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 517 #endif /* PPS_SYNC */ 518 time_adj = ftemp; 519 L_SUB(time_offset, ftemp); 520 L_ADD(time_adj, time_freq); 521 tcp->tc_adjustment = time_adj; 522 #ifdef PPS_SYNC 523 if (pps_valid > 0) 524 pps_valid--; 525 else 526 time_status &= ~STA_PPSSIGNAL; 527 #endif /* PPS_SYNC */ 528 } 529 530 /* 531 * ntp_init() - initialize variables and structures 532 * 533 * This routine must be called after the kernel variables hz and tick 534 * are set or changed and before the next tick interrupt. In this 535 * particular implementation, these values are assumed set elsewhere in 536 * the kernel. The design allows the clock frequency and tick interval 537 * to be changed while the system is running. So, this routine should 538 * probably be integrated with the code that does that. 539 */ 540 static void 541 ntp_init() 542 { 543 544 /* 545 * The following variable must be initialized any time the 546 * kernel variable hz is changed. 547 */ 548 time_tick = NANOSECOND / hz; 549 550 /* 551 * The following variables are initialized only at startup. Only 552 * those structures not cleared by the compiler need to be 553 * initialized, and these only in the simulator. In the actual 554 * kernel, any nonzero values here will quickly evaporate. 555 */ 556 L_CLR(time_offset); 557 L_CLR(time_freq); 558 #ifdef PPS_SYNC 559 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 560 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 561 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 562 pps_fcount = 0; 563 L_CLR(pps_freq); 564 #endif /* PPS_SYNC */ 565 } 566 567 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 568 569 /* 570 * hardupdate() - local clock update 571 * 572 * This routine is called by ntp_adjtime() to update the local clock 573 * phase and frequency. The implementation is of an adaptive-parameter, 574 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 575 * time and frequency offset estimates for each call. If the kernel PPS 576 * discipline code is configured (PPS_SYNC), the PPS signal itself 577 * determines the new time offset, instead of the calling argument. 578 * Presumably, calls to ntp_adjtime() occur only when the caller 579 * believes the local clock is valid within some bound (+-128 ms with 580 * NTP). If the caller's time is far different than the PPS time, an 581 * argument will ensue, and it's not clear who will lose. 582 * 583 * For uncompensated quartz crystal oscillators and nominal update 584 * intervals less than 256 s, operation should be in phase-lock mode, 585 * where the loop is disciplined to phase. For update intervals greater 586 * than 1024 s, operation should be in frequency-lock mode, where the 587 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 588 * is selected by the STA_MODE status bit. 589 */ 590 static void 591 hardupdate(offset) 592 long offset; /* clock offset (ns) */ 593 { 594 long mtemp; 595 l_fp ftemp; 596 597 /* 598 * Select how the phase is to be controlled and from which 599 * source. If the PPS signal is present and enabled to 600 * discipline the time, the PPS offset is used; otherwise, the 601 * argument offset is used. 602 */ 603 if (!(time_status & STA_PLL)) 604 return; 605 if (!(time_status & STA_PPSTIME && time_status & 606 STA_PPSSIGNAL)) { 607 if (offset > MAXPHASE) 608 time_monitor = MAXPHASE; 609 else if (offset < -MAXPHASE) 610 time_monitor = -MAXPHASE; 611 else 612 time_monitor = offset; 613 L_LINT(time_offset, time_monitor); 614 } 615 616 /* 617 * Select how the frequency is to be controlled and in which 618 * mode (PLL or FLL). If the PPS signal is present and enabled 619 * to discipline the frequency, the PPS frequency is used; 620 * otherwise, the argument offset is used to compute it. 621 */ 622 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 623 time_reftime = time_second; 624 return; 625 } 626 if (time_status & STA_FREQHOLD || time_reftime == 0) 627 time_reftime = time_second; 628 mtemp = time_second - time_reftime; 629 L_LINT(ftemp, time_monitor); 630 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 631 L_MPY(ftemp, mtemp); 632 L_ADD(time_freq, ftemp); 633 time_status &= ~STA_MODE; 634 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 635 MAXSEC)) { 636 L_LINT(ftemp, (time_monitor << 4) / mtemp); 637 L_RSHIFT(ftemp, SHIFT_FLL + 4); 638 L_ADD(time_freq, ftemp); 639 time_status |= STA_MODE; 640 } 641 time_reftime = time_second; 642 if (L_GINT(time_freq) > MAXFREQ) 643 L_LINT(time_freq, MAXFREQ); 644 else if (L_GINT(time_freq) < -MAXFREQ) 645 L_LINT(time_freq, -MAXFREQ); 646 } 647 648 #ifdef PPS_SYNC 649 /* 650 * hardpps() - discipline CPU clock oscillator to external PPS signal 651 * 652 * This routine is called at each PPS interrupt in order to discipline 653 * the CPU clock oscillator to the PPS signal. There are two independent 654 * first-order feedback loops, one for the phase, the other for the 655 * frequency. The phase loop measures and grooms the PPS phase offset 656 * and leaves it in a handy spot for the seconds overflow routine. The 657 * frequency loop averages successive PPS phase differences and 658 * calculates the PPS frequency offset, which is also processed by the 659 * seconds overflow routine. The code requires the caller to capture the 660 * time and architecture-dependent hardware counter values in 661 * nanoseconds at the on-time PPS signal transition. 662 * 663 * Note that, on some Unix systems this routine runs at an interrupt 664 * priority level higher than the timer interrupt routine hardclock(). 665 * Therefore, the variables used are distinct from the hardclock() 666 * variables, except for the actual time and frequency variables, which 667 * are determined by this routine and updated atomically. 668 */ 669 void 670 hardpps(tsp, nsec) 671 struct timespec *tsp; /* time at PPS */ 672 long nsec; /* hardware counter at PPS */ 673 { 674 long u_sec, u_nsec, v_nsec; /* temps */ 675 l_fp ftemp; 676 677 /* 678 * The signal is first processed by a range gate and frequency 679 * discriminator. The range gate rejects noise spikes outside 680 * the range +-500 us. The frequency discriminator rejects input 681 * signals with apparent frequency outside the range 1 +-500 682 * PPM. If two hits occur in the same second, we ignore the 683 * later hit; if not and a hit occurs outside the range gate, 684 * keep the later hit for later comparison, but do not process 685 * it. 686 */ 687 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 688 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 689 pps_valid = PPS_VALID; 690 u_sec = tsp->tv_sec; 691 u_nsec = tsp->tv_nsec; 692 if (u_nsec >= (NANOSECOND >> 1)) { 693 u_nsec -= NANOSECOND; 694 u_sec++; 695 } 696 v_nsec = u_nsec - pps_tf[0].tv_nsec; 697 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 698 MAXFREQ) 699 return; 700 pps_tf[2] = pps_tf[1]; 701 pps_tf[1] = pps_tf[0]; 702 pps_tf[0].tv_sec = u_sec; 703 pps_tf[0].tv_nsec = u_nsec; 704 705 /* 706 * Compute the difference between the current and previous 707 * counter values. If the difference exceeds 0.5 s, assume it 708 * has wrapped around, so correct 1.0 s. If the result exceeds 709 * the tick interval, the sample point has crossed a tick 710 * boundary during the last second, so correct the tick. Very 711 * intricate. 712 */ 713 u_nsec = nsec; 714 if (u_nsec > (NANOSECOND >> 1)) 715 u_nsec -= NANOSECOND; 716 else if (u_nsec < -(NANOSECOND >> 1)) 717 u_nsec += NANOSECOND; 718 pps_fcount += u_nsec; 719 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 720 return; 721 time_status &= ~STA_PPSJITTER; 722 723 /* 724 * A three-stage median filter is used to help denoise the PPS 725 * time. The median sample becomes the time offset estimate; the 726 * difference between the other two samples becomes the time 727 * dispersion (jitter) estimate. 728 */ 729 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 730 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 731 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 732 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 733 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 734 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 735 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 736 } else { 737 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 738 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 739 } 740 } else { 741 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 742 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 743 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 744 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 745 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 746 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 747 } else { 748 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 749 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 750 } 751 } 752 753 /* 754 * Nominal jitter is due to PPS signal noise and interrupt 755 * latency. If it exceeds the popcorn threshold, the sample is 756 * discarded. otherwise, if so enabled, the time offset is 757 * updated. We can tolerate a modest loss of data here without 758 * much degrading time accuracy. 759 */ 760 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 761 time_status |= STA_PPSJITTER; 762 pps_jitcnt++; 763 } else if (time_status & STA_PPSTIME) { 764 time_monitor = -v_nsec; 765 L_LINT(time_offset, time_monitor); 766 } 767 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 768 u_sec = pps_tf[0].tv_sec - pps_lastsec; 769 if (u_sec < (1 << pps_shift)) 770 return; 771 772 /* 773 * At the end of the calibration interval the difference between 774 * the first and last counter values becomes the scaled 775 * frequency. It will later be divided by the length of the 776 * interval to determine the frequency update. If the frequency 777 * exceeds a sanity threshold, or if the actual calibration 778 * interval is not equal to the expected length, the data are 779 * discarded. We can tolerate a modest loss of data here without 780 * much degrading frequency accuracy. 781 */ 782 pps_calcnt++; 783 v_nsec = -pps_fcount; 784 pps_lastsec = pps_tf[0].tv_sec; 785 pps_fcount = 0; 786 u_nsec = MAXFREQ << pps_shift; 787 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 788 pps_shift)) { 789 time_status |= STA_PPSERROR; 790 pps_errcnt++; 791 return; 792 } 793 794 /* 795 * Here the raw frequency offset and wander (stability) is 796 * calculated. If the wander is less than the wander threshold 797 * for four consecutive averaging intervals, the interval is 798 * doubled; if it is greater than the threshold for four 799 * consecutive intervals, the interval is halved. The scaled 800 * frequency offset is converted to frequency offset. The 801 * stability metric is calculated as the average of recent 802 * frequency changes, but is used only for performance 803 * monitoring. 804 */ 805 L_LINT(ftemp, v_nsec); 806 L_RSHIFT(ftemp, pps_shift); 807 L_SUB(ftemp, pps_freq); 808 u_nsec = L_GINT(ftemp); 809 if (u_nsec > PPS_MAXWANDER) { 810 L_LINT(ftemp, PPS_MAXWANDER); 811 pps_intcnt--; 812 time_status |= STA_PPSWANDER; 813 pps_stbcnt++; 814 } else if (u_nsec < -PPS_MAXWANDER) { 815 L_LINT(ftemp, -PPS_MAXWANDER); 816 pps_intcnt--; 817 time_status |= STA_PPSWANDER; 818 pps_stbcnt++; 819 } else { 820 pps_intcnt++; 821 } 822 if (pps_intcnt >= 4) { 823 pps_intcnt = 4; 824 if (pps_shift < pps_shiftmax) { 825 pps_shift++; 826 pps_intcnt = 0; 827 } 828 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 829 pps_intcnt = -4; 830 if (pps_shift > PPS_FAVG) { 831 pps_shift--; 832 pps_intcnt = 0; 833 } 834 } 835 if (u_nsec < 0) 836 u_nsec = -u_nsec; 837 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 838 839 /* 840 * The PPS frequency is recalculated and clamped to the maximum 841 * MAXFREQ. If enabled, the system clock frequency is updated as 842 * well. 843 */ 844 L_ADD(pps_freq, ftemp); 845 u_nsec = L_GINT(pps_freq); 846 if (u_nsec > MAXFREQ) 847 L_LINT(pps_freq, MAXFREQ); 848 else if (u_nsec < -MAXFREQ) 849 L_LINT(pps_freq, -MAXFREQ); 850 if (time_status & STA_PPSFREQ) 851 time_freq = pps_freq; 852 } 853 #endif /* PPS_SYNC */ 854