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 */ 33 34 #include "opt_ntp.h" 35 36 #include <sys/param.h> 37 #include <sys/systm.h> 38 #include <sys/sysproto.h> 39 #include <sys/kernel.h> 40 #include <sys/proc.h> 41 #include <sys/time.h> 42 #include <sys/timex.h> 43 #include <sys/timepps.h> 44 #include <sys/sysctl.h> 45 46 /* 47 * Single-precision macros for 64-bit machines 48 */ 49 typedef long long l_fp; 50 #define L_ADD(v, u) ((v) += (u)) 51 #define L_SUB(v, u) ((v) -= (u)) 52 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 53 #define L_NEG(v) ((v) = -(v)) 54 #define L_RSHIFT(v, n) \ 55 do { \ 56 if ((v) < 0) \ 57 (v) = -(-(v) >> (n)); \ 58 else \ 59 (v) = (v) >> (n); \ 60 } while (0) 61 #define L_MPY(v, a) ((v) *= (a)) 62 #define L_CLR(v) ((v) = 0) 63 #define L_ISNEG(v) ((v) < 0) 64 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 65 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 66 67 /* 68 * Generic NTP kernel interface 69 * 70 * These routines constitute the Network Time Protocol (NTP) interfaces 71 * for user and daemon application programs. The ntp_gettime() routine 72 * provides the time, maximum error (synch distance) and estimated error 73 * (dispersion) to client user application programs. The ntp_adjtime() 74 * routine is used by the NTP daemon to adjust the system clock to an 75 * externally derived time. The time offset and related variables set by 76 * this routine are used by other routines in this module to adjust the 77 * phase and frequency of the clock discipline loop which controls the 78 * system clock. 79 * 80 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 81 * defined), the time at each tick interrupt is derived directly from 82 * the kernel time variable. When the kernel time is reckoned in 83 * microseconds, (NTP_NANO undefined), the time is derived from the 84 * kernel time variable together with a variable representing the 85 * leftover nanoseconds at the last tick interrupt. In either case, the 86 * current nanosecond time is reckoned from these values plus an 87 * interpolated value derived by the clock routines in another 88 * architecture-specific module. The interpolation can use either a 89 * dedicated counter or a processor cycle counter (PCC) implemented in 90 * some architectures. 91 * 92 * Note that all routines must run at priority splclock or higher. 93 */ 94 /* 95 * Phase/frequency-lock loop (PLL/FLL) definitions 96 * 97 * The nanosecond clock discipline uses two variable types, time 98 * variables and frequency variables. Both types are represented as 64- 99 * bit fixed-point quantities with the decimal point between two 32-bit 100 * halves. On a 32-bit machine, each half is represented as a single 101 * word and mathematical operations are done using multiple-precision 102 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 103 * used. 104 * 105 * A time variable is a signed 64-bit fixed-point number in ns and 106 * fraction. It represents the remaining time offset to be amortized 107 * over succeeding tick interrupts. The maximum time offset is about 108 * 0.5 s and the resolution is about 2.3e-10 ns. 109 * 110 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 111 * 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 1 112 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 113 * |s s s| ns | 114 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 * | fraction | 116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 * 118 * A frequency variable is a signed 64-bit fixed-point number in ns/s 119 * and fraction. It represents the ns and fraction to be added to the 120 * kernel time variable at each second. The maximum frequency offset is 121 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 122 * 123 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 124 * 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 1 125 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 * |s s s s s s s s s s s s s| ns/s | 127 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 128 * | fraction | 129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 */ 131 /* 132 * The following variables establish the state of the PLL/FLL and the 133 * residual time and frequency offset of the local clock. 134 */ 135 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 136 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 137 138 static int time_state = TIME_OK; /* clock state */ 139 static int time_status = STA_UNSYNC; /* clock status bits */ 140 static long time_tai; /* TAI offset (s) */ 141 static long time_monitor; /* last time offset scaled (ns) */ 142 static long time_constant; /* poll interval (shift) (s) */ 143 static long time_precision = 1; /* clock precision (ns) */ 144 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 145 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 146 static long time_reftime; /* time at last adjustment (s) */ 147 static long time_tick; /* nanoseconds per tick (ns) */ 148 static l_fp time_offset; /* time offset (ns) */ 149 static l_fp time_freq; /* frequency offset (ns/s) */ 150 static l_fp time_adj; /* tick adjust (ns/s) */ 151 152 #ifdef PPS_SYNC 153 /* 154 * The following variables are used when a pulse-per-second (PPS) signal 155 * is available and connected via a modem control lead. They establish 156 * the engineering parameters of the clock discipline loop when 157 * controlled by the PPS signal. 158 */ 159 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 160 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 161 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 162 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 163 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 164 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 165 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 166 167 static struct timespec pps_tf[3]; /* phase median filter */ 168 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 169 static long pps_fcount; /* frequency accumulator */ 170 static long pps_jitter; /* nominal jitter (ns) */ 171 static long pps_stabil; /* nominal stability (scaled ns/s) */ 172 static long pps_lastsec; /* time at last calibration (s) */ 173 static int pps_valid; /* signal watchdog counter */ 174 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 175 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 176 static int pps_intcnt; /* wander counter */ 177 178 /* 179 * PPS signal quality monitors 180 */ 181 static long pps_calcnt; /* calibration intervals */ 182 static long pps_jitcnt; /* jitter limit exceeded */ 183 static long pps_stbcnt; /* stability limit exceeded */ 184 static long pps_errcnt; /* calibration errors */ 185 #endif /* PPS_SYNC */ 186 /* 187 * End of phase/frequency-lock loop (PLL/FLL) definitions 188 */ 189 190 static void ntp_init(void); 191 static void hardupdate(long offset); 192 193 /* 194 * ntp_gettime() - NTP user application interface 195 * 196 * See the timex.h header file for synopsis and API description. Note 197 * that the TAI offset is returned in the ntvtimeval.tai structure 198 * member. 199 */ 200 static int 201 ntp_sysctl(SYSCTL_HANDLER_ARGS) 202 { 203 struct ntptimeval ntv; /* temporary structure */ 204 struct timespec atv; /* nanosecond time */ 205 206 nanotime(&atv); 207 ntv.time.tv_sec = atv.tv_sec; 208 ntv.time.tv_nsec = atv.tv_nsec; 209 ntv.maxerror = time_maxerror; 210 ntv.esterror = time_esterror; 211 ntv.tai = time_tai; 212 ntv.time_state = time_state; 213 214 /* 215 * Status word error decode. If any of these conditions occur, 216 * an error is returned, instead of the status word. Most 217 * applications will care only about the fact the system clock 218 * may not be trusted, not about the details. 219 * 220 * Hardware or software error 221 */ 222 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 223 224 /* 225 * PPS signal lost when either time or frequency synchronization 226 * requested 227 */ 228 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 229 !(time_status & STA_PPSSIGNAL)) || 230 231 /* 232 * PPS jitter exceeded when time synchronization requested 233 */ 234 (time_status & STA_PPSTIME && 235 time_status & STA_PPSJITTER) || 236 237 /* 238 * PPS wander exceeded or calibration error when frequency 239 * synchronization requested 240 */ 241 (time_status & STA_PPSFREQ && 242 time_status & (STA_PPSWANDER | STA_PPSERROR))) 243 ntv.time_state = TIME_ERROR; 244 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 245 } 246 247 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 248 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 249 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 250 251 #ifdef PPS_SYNC 252 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 253 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 254 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 255 256 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 257 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 258 #endif 259 /* 260 * ntp_adjtime() - NTP daemon application interface 261 * 262 * See the timex.h header file for synopsis and API description. Note 263 * that the timex.constant structure member has a dual purpose to set 264 * the time constant and to set the TAI offset. 265 */ 266 #ifndef _SYS_SYSPROTO_H_ 267 struct ntp_adjtime_args { 268 struct timex *tp; 269 }; 270 #endif 271 272 int 273 ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 274 { 275 struct timex ntv; /* temporary structure */ 276 long freq; /* frequency ns/s) */ 277 int modes; /* mode bits from structure */ 278 int s; /* caller priority */ 279 int error; 280 281 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 282 if (error) 283 return(error); 284 285 /* 286 * Update selected clock variables - only the superuser can 287 * change anything. Note that there is no error checking here on 288 * the assumption the superuser should know what it is doing. 289 * Note that either the time constant or TAI offset are loaded 290 * from the ntv.constant member, depending on the mode bits. If 291 * the STA_PLL bit in the status word is cleared, the state and 292 * status words are reset to the initial values at boot. 293 */ 294 modes = ntv.modes; 295 if (modes) 296 error = suser(p); 297 if (error) 298 return (error); 299 s = splclock(); 300 if (modes & MOD_MAXERROR) 301 time_maxerror = ntv.maxerror; 302 if (modes & MOD_ESTERROR) 303 time_esterror = ntv.esterror; 304 if (modes & MOD_STATUS) { 305 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 306 time_state = TIME_OK; 307 time_status = STA_UNSYNC; 308 #ifdef PPS_SYNC 309 pps_shift = PPS_FAVG; 310 #endif /* PPS_SYNC */ 311 } 312 time_status &= STA_RONLY; 313 time_status |= ntv.status & ~STA_RONLY; 314 } 315 if (modes & MOD_TIMECONST) { 316 if (ntv.constant < 0) 317 time_constant = 0; 318 else if (ntv.constant > MAXTC) 319 time_constant = MAXTC; 320 else 321 time_constant = ntv.constant; 322 } 323 if (modes & MOD_TAI) { 324 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 325 time_tai = ntv.constant; 326 } 327 #ifdef PPS_SYNC 328 if (modes & MOD_PPSMAX) { 329 if (ntv.shift < PPS_FAVG) 330 pps_shiftmax = PPS_FAVG; 331 else if (ntv.shift > PPS_FAVGMAX) 332 pps_shiftmax = PPS_FAVGMAX; 333 else 334 pps_shiftmax = ntv.shift; 335 } 336 #endif /* PPS_SYNC */ 337 if (modes & MOD_NANO) 338 time_status |= STA_NANO; 339 if (modes & MOD_MICRO) 340 time_status &= ~STA_NANO; 341 if (modes & MOD_CLKB) 342 time_status |= STA_CLK; 343 if (modes & MOD_CLKA) 344 time_status &= ~STA_CLK; 345 if (modes & MOD_OFFSET) { 346 if (time_status & STA_NANO) 347 hardupdate(ntv.offset); 348 else 349 hardupdate(ntv.offset * 1000); 350 } 351 if (modes & MOD_FREQUENCY) { 352 freq = (ntv.freq * 1000LL) >> 16; 353 if (freq > MAXFREQ) 354 L_LINT(time_freq, MAXFREQ); 355 else if (freq < -MAXFREQ) 356 L_LINT(time_freq, -MAXFREQ); 357 else 358 L_LINT(time_freq, freq); 359 #ifdef PPS_SYNC 360 pps_freq = time_freq; 361 #endif /* PPS_SYNC */ 362 } 363 364 /* 365 * Retrieve all clock variables. Note that the TAI offset is 366 * returned only by ntp_gettime(); 367 */ 368 if (time_status & STA_NANO) 369 ntv.offset = time_monitor; 370 else 371 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 372 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 373 ntv.maxerror = time_maxerror; 374 ntv.esterror = time_esterror; 375 ntv.status = time_status; 376 ntv.constant = time_constant; 377 if (time_status & STA_NANO) 378 ntv.precision = time_precision; 379 else 380 ntv.precision = time_precision / 1000; 381 ntv.tolerance = MAXFREQ * SCALE_PPM; 382 #ifdef PPS_SYNC 383 ntv.shift = pps_shift; 384 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 385 if (time_status & STA_NANO) 386 ntv.jitter = pps_jitter; 387 else 388 ntv.jitter = pps_jitter / 1000; 389 ntv.stabil = pps_stabil; 390 ntv.calcnt = pps_calcnt; 391 ntv.errcnt = pps_errcnt; 392 ntv.jitcnt = pps_jitcnt; 393 ntv.stbcnt = pps_stbcnt; 394 #endif /* PPS_SYNC */ 395 splx(s); 396 397 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 398 if (error) 399 return (error); 400 401 /* 402 * Status word error decode. See comments in 403 * ntp_gettime() routine. 404 */ 405 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 406 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 407 !(time_status & STA_PPSSIGNAL)) || 408 (time_status & STA_PPSTIME && 409 time_status & STA_PPSJITTER) || 410 (time_status & STA_PPSFREQ && 411 time_status & (STA_PPSWANDER | STA_PPSERROR))) 412 p->p_retval[0] = TIME_ERROR; 413 else 414 p->p_retval[0] = time_state; 415 return (error); 416 } 417 418 /* 419 * second_overflow() - called after ntp_tick_adjust() 420 * 421 * This routine is ordinarily called immediately following the above 422 * routine ntp_tick_adjust(). While these two routines are normally 423 * combined, they are separated here only for the purposes of 424 * simulation. 425 */ 426 void 427 ntp_update_second(struct timecounter *tcp) 428 { 429 u_int32_t *newsec; 430 l_fp ftemp; /* 32/64-bit temporary */ 431 432 newsec = &tcp->tc_offset_sec; 433 /* 434 * On rollover of the second both the nanosecond and microsecond 435 * clocks are updated and the state machine cranked as 436 * necessary. The phase adjustment to be used for the next 437 * second is calculated and the maximum error is increased by 438 * the tolerance. 439 */ 440 time_maxerror += MAXFREQ / 1000; 441 442 /* 443 * Leap second processing. If in leap-insert state at 444 * the end of the day, the system clock is set back one 445 * second; if in leap-delete state, the system clock is 446 * set ahead one second. The nano_time() routine or 447 * external clock driver will insure that reported time 448 * is always monotonic. 449 */ 450 switch (time_state) { 451 452 /* 453 * No warning. 454 */ 455 case TIME_OK: 456 if (time_status & STA_INS) 457 time_state = TIME_INS; 458 else if (time_status & STA_DEL) 459 time_state = TIME_DEL; 460 break; 461 462 /* 463 * Insert second 23:59:60 following second 464 * 23:59:59. 465 */ 466 case TIME_INS: 467 if (!(time_status & STA_INS)) 468 time_state = TIME_OK; 469 else if ((*newsec) % 86400 == 0) { 470 (*newsec)--; 471 time_state = TIME_OOP; 472 } 473 break; 474 475 /* 476 * Delete second 23:59:59. 477 */ 478 case TIME_DEL: 479 if (!(time_status & STA_DEL)) 480 time_state = TIME_OK; 481 else if (((*newsec) + 1) % 86400 == 0) { 482 (*newsec)++; 483 time_tai--; 484 time_state = TIME_WAIT; 485 } 486 break; 487 488 /* 489 * Insert second in progress. 490 */ 491 case TIME_OOP: 492 time_tai++; 493 time_state = TIME_WAIT; 494 break; 495 496 /* 497 * Wait for status bits to clear. 498 */ 499 case TIME_WAIT: 500 if (!(time_status & (STA_INS | STA_DEL))) 501 time_state = TIME_OK; 502 } 503 504 /* 505 * Compute the total time adjustment for the next second 506 * in ns. The offset is reduced by a factor depending on 507 * whether the PPS signal is operating. Note that the 508 * value is in effect scaled by the clock frequency, 509 * since the adjustment is added at each tick interrupt. 510 */ 511 ftemp = time_offset; 512 #ifdef PPS_SYNC 513 /* XXX even if PPS signal dies we should finish adjustment ? */ 514 if (time_status & STA_PPSTIME && time_status & 515 STA_PPSSIGNAL) 516 L_RSHIFT(ftemp, pps_shift); 517 else 518 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 519 #else 520 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 521 #endif /* PPS_SYNC */ 522 time_adj = ftemp; 523 L_SUB(time_offset, ftemp); 524 L_ADD(time_adj, time_freq); 525 tcp->tc_adjustment = time_adj; 526 #ifdef PPS_SYNC 527 if (pps_valid > 0) 528 pps_valid--; 529 else 530 time_status &= ~STA_PPSSIGNAL; 531 #endif /* PPS_SYNC */ 532 } 533 534 /* 535 * ntp_init() - initialize variables and structures 536 * 537 * This routine must be called after the kernel variables hz and tick 538 * are set or changed and before the next tick interrupt. In this 539 * particular implementation, these values are assumed set elsewhere in 540 * the kernel. The design allows the clock frequency and tick interval 541 * to be changed while the system is running. So, this routine should 542 * probably be integrated with the code that does that. 543 */ 544 static void 545 ntp_init() 546 { 547 548 /* 549 * The following variable must be initialized any time the 550 * kernel variable hz is changed. 551 */ 552 time_tick = NANOSECOND / hz; 553 554 /* 555 * The following variables are initialized only at startup. Only 556 * those structures not cleared by the compiler need to be 557 * initialized, and these only in the simulator. In the actual 558 * kernel, any nonzero values here will quickly evaporate. 559 */ 560 L_CLR(time_offset); 561 L_CLR(time_freq); 562 #ifdef PPS_SYNC 563 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 564 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 565 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 566 pps_fcount = 0; 567 L_CLR(pps_freq); 568 #endif /* PPS_SYNC */ 569 } 570 571 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 572 573 /* 574 * hardupdate() - local clock update 575 * 576 * This routine is called by ntp_adjtime() to update the local clock 577 * phase and frequency. The implementation is of an adaptive-parameter, 578 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 579 * time and frequency offset estimates for each call. If the kernel PPS 580 * discipline code is configured (PPS_SYNC), the PPS signal itself 581 * determines the new time offset, instead of the calling argument. 582 * Presumably, calls to ntp_adjtime() occur only when the caller 583 * believes the local clock is valid within some bound (+-128 ms with 584 * NTP). If the caller's time is far different than the PPS time, an 585 * argument will ensue, and it's not clear who will lose. 586 * 587 * For uncompensated quartz crystal oscillators and nominal update 588 * intervals less than 256 s, operation should be in phase-lock mode, 589 * where the loop is disciplined to phase. For update intervals greater 590 * than 1024 s, operation should be in frequency-lock mode, where the 591 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 592 * is selected by the STA_MODE status bit. 593 */ 594 static void 595 hardupdate(offset) 596 long offset; /* clock offset (ns) */ 597 { 598 long mtemp; 599 l_fp ftemp; 600 601 /* 602 * Select how the phase is to be controlled and from which 603 * source. If the PPS signal is present and enabled to 604 * discipline the time, the PPS offset is used; otherwise, the 605 * argument offset is used. 606 */ 607 if (!(time_status & STA_PLL)) 608 return; 609 if (!(time_status & STA_PPSTIME && time_status & 610 STA_PPSSIGNAL)) { 611 if (offset > MAXPHASE) 612 time_monitor = MAXPHASE; 613 else if (offset < -MAXPHASE) 614 time_monitor = -MAXPHASE; 615 else 616 time_monitor = offset; 617 L_LINT(time_offset, time_monitor); 618 } 619 620 /* 621 * Select how the frequency is to be controlled and in which 622 * mode (PLL or FLL). If the PPS signal is present and enabled 623 * to discipline the frequency, the PPS frequency is used; 624 * otherwise, the argument offset is used to compute it. 625 */ 626 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 627 time_reftime = time_second; 628 return; 629 } 630 if (time_status & STA_FREQHOLD || time_reftime == 0) 631 time_reftime = time_second; 632 mtemp = time_second - time_reftime; 633 L_LINT(ftemp, time_monitor); 634 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 635 L_MPY(ftemp, mtemp); 636 L_ADD(time_freq, ftemp); 637 time_status &= ~STA_MODE; 638 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 639 MAXSEC)) { 640 L_LINT(ftemp, (time_monitor << 4) / mtemp); 641 L_RSHIFT(ftemp, SHIFT_FLL + 4); 642 L_ADD(time_freq, ftemp); 643 time_status |= STA_MODE; 644 } 645 time_reftime = time_second; 646 if (L_GINT(time_freq) > MAXFREQ) 647 L_LINT(time_freq, MAXFREQ); 648 else if (L_GINT(time_freq) < -MAXFREQ) 649 L_LINT(time_freq, -MAXFREQ); 650 } 651 652 #ifdef PPS_SYNC 653 /* 654 * hardpps() - discipline CPU clock oscillator to external PPS signal 655 * 656 * This routine is called at each PPS interrupt in order to discipline 657 * the CPU clock oscillator to the PPS signal. There are two independent 658 * first-order feedback loops, one for the phase, the other for the 659 * frequency. The phase loop measures and grooms the PPS phase offset 660 * and leaves it in a handy spot for the seconds overflow routine. The 661 * frequency loop averages successive PPS phase differences and 662 * calculates the PPS frequency offset, which is also processed by the 663 * seconds overflow routine. The code requires the caller to capture the 664 * time and architecture-dependent hardware counter values in 665 * nanoseconds at the on-time PPS signal transition. 666 * 667 * Note that, on some Unix systems this routine runs at an interrupt 668 * priority level higher than the timer interrupt routine hardclock(). 669 * Therefore, the variables used are distinct from the hardclock() 670 * variables, except for the actual time and frequency variables, which 671 * are determined by this routine and updated atomically. 672 */ 673 void 674 hardpps(tsp, nsec) 675 struct timespec *tsp; /* time at PPS */ 676 long nsec; /* hardware counter at PPS */ 677 { 678 long u_sec, u_nsec, v_nsec; /* temps */ 679 l_fp ftemp; 680 681 /* 682 * The signal is first processed by a range gate and frequency 683 * discriminator. The range gate rejects noise spikes outside 684 * the range +-500 us. The frequency discriminator rejects input 685 * signals with apparent frequency outside the range 1 +-500 686 * PPM. If two hits occur in the same second, we ignore the 687 * later hit; if not and a hit occurs outside the range gate, 688 * keep the later hit for later comparison, but do not process 689 * it. 690 */ 691 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 692 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 693 pps_valid = PPS_VALID; 694 u_sec = tsp->tv_sec; 695 u_nsec = tsp->tv_nsec; 696 if (u_nsec >= (NANOSECOND >> 1)) { 697 u_nsec -= NANOSECOND; 698 u_sec++; 699 } 700 v_nsec = u_nsec - pps_tf[0].tv_nsec; 701 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 702 MAXFREQ) 703 return; 704 pps_tf[2] = pps_tf[1]; 705 pps_tf[1] = pps_tf[0]; 706 pps_tf[0].tv_sec = u_sec; 707 pps_tf[0].tv_nsec = u_nsec; 708 709 /* 710 * Compute the difference between the current and previous 711 * counter values. If the difference exceeds 0.5 s, assume it 712 * has wrapped around, so correct 1.0 s. If the result exceeds 713 * the tick interval, the sample point has crossed a tick 714 * boundary during the last second, so correct the tick. Very 715 * intricate. 716 */ 717 u_nsec = nsec; 718 if (u_nsec > (NANOSECOND >> 1)) 719 u_nsec -= NANOSECOND; 720 else if (u_nsec < -(NANOSECOND >> 1)) 721 u_nsec += NANOSECOND; 722 pps_fcount += u_nsec; 723 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 724 return; 725 time_status &= ~STA_PPSJITTER; 726 727 /* 728 * A three-stage median filter is used to help denoise the PPS 729 * time. The median sample becomes the time offset estimate; the 730 * difference between the other two samples becomes the time 731 * dispersion (jitter) estimate. 732 */ 733 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 734 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 735 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 736 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 737 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 738 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 739 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 740 } else { 741 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 742 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 743 } 744 } else { 745 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 746 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 747 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 748 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 749 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 750 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 751 } else { 752 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 753 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 754 } 755 } 756 757 /* 758 * Nominal jitter is due to PPS signal noise and interrupt 759 * latency. If it exceeds the popcorn threshold, the sample is 760 * discarded. otherwise, if so enabled, the time offset is 761 * updated. We can tolerate a modest loss of data here without 762 * much degrading time accuracy. 763 */ 764 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 765 time_status |= STA_PPSJITTER; 766 pps_jitcnt++; 767 } else if (time_status & STA_PPSTIME) { 768 time_monitor = -v_nsec; 769 L_LINT(time_offset, time_monitor); 770 } 771 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 772 u_sec = pps_tf[0].tv_sec - pps_lastsec; 773 if (u_sec < (1 << pps_shift)) 774 return; 775 776 /* 777 * At the end of the calibration interval the difference between 778 * the first and last counter values becomes the scaled 779 * frequency. It will later be divided by the length of the 780 * interval to determine the frequency update. If the frequency 781 * exceeds a sanity threshold, or if the actual calibration 782 * interval is not equal to the expected length, the data are 783 * discarded. We can tolerate a modest loss of data here without 784 * much degrading frequency accuracy. 785 */ 786 pps_calcnt++; 787 v_nsec = -pps_fcount; 788 pps_lastsec = pps_tf[0].tv_sec; 789 pps_fcount = 0; 790 u_nsec = MAXFREQ << pps_shift; 791 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 792 pps_shift)) { 793 time_status |= STA_PPSERROR; 794 pps_errcnt++; 795 return; 796 } 797 798 /* 799 * Here the raw frequency offset and wander (stability) is 800 * calculated. If the wander is less than the wander threshold 801 * for four consecutive averaging intervals, the interval is 802 * doubled; if it is greater than the threshold for four 803 * consecutive intervals, the interval is halved. The scaled 804 * frequency offset is converted to frequency offset. The 805 * stability metric is calculated as the average of recent 806 * frequency changes, but is used only for performance 807 * monitoring. 808 */ 809 L_LINT(ftemp, v_nsec); 810 L_RSHIFT(ftemp, pps_shift); 811 L_SUB(ftemp, pps_freq); 812 u_nsec = L_GINT(ftemp); 813 if (u_nsec > PPS_MAXWANDER) { 814 L_LINT(ftemp, PPS_MAXWANDER); 815 pps_intcnt--; 816 time_status |= STA_PPSWANDER; 817 pps_stbcnt++; 818 } else if (u_nsec < -PPS_MAXWANDER) { 819 L_LINT(ftemp, -PPS_MAXWANDER); 820 pps_intcnt--; 821 time_status |= STA_PPSWANDER; 822 pps_stbcnt++; 823 } else { 824 pps_intcnt++; 825 } 826 if (pps_intcnt >= 4) { 827 pps_intcnt = 4; 828 if (pps_shift < pps_shiftmax) { 829 pps_shift++; 830 pps_intcnt = 0; 831 } 832 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 833 pps_intcnt = -4; 834 if (pps_shift > PPS_FAVG) { 835 pps_shift--; 836 pps_intcnt = 0; 837 } 838 } 839 if (u_nsec < 0) 840 u_nsec = -u_nsec; 841 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 842 843 /* 844 * The PPS frequency is recalculated and clamped to the maximum 845 * MAXFREQ. If enabled, the system clock frequency is updated as 846 * well. 847 */ 848 L_ADD(pps_freq, ftemp); 849 u_nsec = L_GINT(pps_freq); 850 if (u_nsec > MAXFREQ) 851 L_LINT(pps_freq, MAXFREQ); 852 else if (u_nsec < -MAXFREQ) 853 L_LINT(pps_freq, -MAXFREQ); 854 if (time_status & STA_PPSFREQ) 855 time_freq = pps_freq; 856 } 857 #endif /* PPS_SYNC */ 858