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/priv.h> 42 #include <sys/time.h> 43 #include <sys/timex.h> 44 #include <sys/timepps.h> 45 #include <sys/sysctl.h> 46 47 #include <sys/thread2.h> 48 #include <sys/mplock2.h> 49 50 /* 51 * Single-precision macros for 64-bit machines 52 */ 53 typedef long long l_fp; 54 #define L_ADD(v, u) ((v) += (u)) 55 #define L_SUB(v, u) ((v) -= (u)) 56 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 57 #define L_NEG(v) ((v) = -(v)) 58 #define L_RSHIFT(v, n) \ 59 do { \ 60 if ((v) < 0) \ 61 (v) = -(-(v) >> (n)); \ 62 else \ 63 (v) = (v) >> (n); \ 64 } while (0) 65 #define L_MPY(v, a) ((v) *= (a)) 66 #define L_CLR(v) ((v) = 0) 67 #define L_ISNEG(v) ((v) < 0) 68 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 69 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 70 71 /* 72 * Generic NTP kernel interface 73 * 74 * These routines constitute the Network Time Protocol (NTP) interfaces 75 * for user and daemon application programs. The ntp_gettime() routine 76 * provides the time, maximum error (synch distance) and estimated error 77 * (dispersion) to client user application programs. The ntp_adjtime() 78 * routine is used by the NTP daemon to adjust the system clock to an 79 * externally derived time. The time offset and related variables set by 80 * this routine are used by other routines in this module to adjust the 81 * phase and frequency of the clock discipline loop which controls the 82 * system clock. 83 * 84 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 85 * defined), the time at each tick interrupt is derived directly from 86 * the kernel time variable. When the kernel time is reckoned in 87 * microseconds, (NTP_NANO undefined), the time is derived from the 88 * kernel time variable together with a variable representing the 89 * leftover nanoseconds at the last tick interrupt. In either case, the 90 * current nanosecond time is reckoned from these values plus an 91 * interpolated value derived by the clock routines in another 92 * architecture-specific module. The interpolation can use either a 93 * dedicated counter or a processor cycle counter (PCC) implemented in 94 * some architectures. 95 * 96 * Note that all routines must run at priority splclock or higher. 97 */ 98 /* 99 * Phase/frequency-lock loop (PLL/FLL) definitions 100 * 101 * The nanosecond clock discipline uses two variable types, time 102 * variables and frequency variables. Both types are represented as 64- 103 * bit fixed-point quantities with the decimal point between two 32-bit 104 * halves. On a 32-bit machine, each half is represented as a single 105 * word and mathematical operations are done using multiple-precision 106 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 107 * used. 108 * 109 * A time variable is a signed 64-bit fixed-point number in ns and 110 * fraction. It represents the remaining time offset to be amortized 111 * over succeeding tick interrupts. The maximum time offset is about 112 * 0.5 s and the resolution is about 2.3e-10 ns. 113 * 114 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 115 * 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 1 116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 * |s s s| ns | 118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 119 * | fraction | 120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 121 * 122 * A frequency variable is a signed 64-bit fixed-point number in ns/s 123 * and fraction. It represents the ns and fraction to be added to the 124 * kernel time variable at each second. The maximum frequency offset is 125 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 126 * 127 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 128 * 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 1 129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 * |s s s s s s s s s s s s s| ns/s | 131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 * | fraction | 133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 */ 135 /* 136 * The following variables establish the state of the PLL/FLL and the 137 * residual time and frequency offset of the local clock. 138 */ 139 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 140 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 141 142 static int time_state = TIME_OK; /* clock state */ 143 static int time_status = STA_UNSYNC; /* clock status bits */ 144 static long time_tai; /* TAI offset (s) */ 145 static long time_monitor; /* last time offset scaled (ns) */ 146 static long time_constant; /* poll interval (shift) (s) */ 147 static long time_precision = 1; /* clock precision (ns) */ 148 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 149 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 150 static time_t time_reftime; /* time at last adjustment (s) */ 151 static long time_tick; /* nanoseconds per tick (ns) */ 152 static l_fp time_offset; /* time offset (ns) */ 153 static l_fp time_freq; /* frequency offset (ns/s) */ 154 static l_fp time_adj; /* tick adjust (ns/s) */ 155 156 #ifdef PPS_SYNC 157 /* 158 * The following variables are used when a pulse-per-second (PPS) signal 159 * is available and connected via a modem control lead. They establish 160 * the engineering parameters of the clock discipline loop when 161 * controlled by the PPS signal. 162 */ 163 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 164 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 165 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 166 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 167 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 168 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 169 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 170 171 static struct timespec pps_tf[3]; /* phase median filter */ 172 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 173 static long pps_fcount; /* frequency accumulator */ 174 static long pps_jitter; /* nominal jitter (ns) */ 175 static long pps_stabil; /* nominal stability (scaled ns/s) */ 176 static long pps_lastsec; /* time at last calibration (s) */ 177 static int pps_valid; /* signal watchdog counter */ 178 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 179 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 180 static int pps_intcnt; /* wander counter */ 181 182 /* 183 * PPS signal quality monitors 184 */ 185 static long pps_calcnt; /* calibration intervals */ 186 static long pps_jitcnt; /* jitter limit exceeded */ 187 static long pps_stbcnt; /* stability limit exceeded */ 188 static long pps_errcnt; /* calibration errors */ 189 #endif /* PPS_SYNC */ 190 /* 191 * End of phase/frequency-lock loop (PLL/FLL) definitions 192 */ 193 194 static void ntp_init(void); 195 static void hardupdate(long offset); 196 197 /* 198 * ntp_gettime() - NTP user application interface 199 * 200 * See the timex.h header file for synopsis and API description. Note 201 * that the TAI offset is returned in the ntvtimeval.tai structure 202 * member. 203 */ 204 static int 205 ntp_sysctl(SYSCTL_HANDLER_ARGS) 206 { 207 struct ntptimeval ntv; /* temporary structure */ 208 struct timespec atv; /* nanosecond time */ 209 210 nanotime(&atv); 211 ntv.time.tv_sec = atv.tv_sec; 212 ntv.time.tv_nsec = atv.tv_nsec; 213 ntv.maxerror = time_maxerror; 214 ntv.esterror = time_esterror; 215 ntv.tai = time_tai; 216 ntv.time_state = time_state; 217 218 /* 219 * Status word error decode. If any of these conditions occur, 220 * an error is returned, instead of the status word. Most 221 * applications will care only about the fact the system clock 222 * may not be trusted, not about the details. 223 * 224 * Hardware or software error 225 */ 226 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 227 228 /* 229 * PPS signal lost when either time or frequency synchronization 230 * requested 231 */ 232 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 233 !(time_status & STA_PPSSIGNAL)) || 234 235 /* 236 * PPS jitter exceeded when time synchronization requested 237 */ 238 (time_status & STA_PPSTIME && 239 time_status & STA_PPSJITTER) || 240 241 /* 242 * PPS wander exceeded or calibration error when frequency 243 * synchronization requested 244 */ 245 (time_status & STA_PPSFREQ && 246 time_status & (STA_PPSWANDER | STA_PPSERROR))) 247 ntv.time_state = TIME_ERROR; 248 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 249 } 250 251 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 252 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 253 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 254 255 #ifdef PPS_SYNC 256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 259 260 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 262 #endif 263 /* 264 * ntp_adjtime() - NTP daemon application interface 265 * 266 * See the timex.h header file for synopsis and API description. Note 267 * that the timex.constant structure member has a dual purpose to set 268 * the time constant and to set the TAI offset. 269 * 270 * MPALMOSTSAFE 271 */ 272 int 273 sys_ntp_adjtime(struct ntp_adjtime_args *uap) 274 { 275 struct thread *td = curthread; 276 struct timex ntv; /* temporary structure */ 277 long freq; /* frequency ns/s) */ 278 int modes; /* mode bits from structure */ 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 = priv_check(td, PRIV_NTP_ADJTIME); 297 if (error) 298 return (error); 299 300 get_mplock(); 301 crit_enter(); 302 if (modes & MOD_MAXERROR) 303 time_maxerror = ntv.maxerror; 304 if (modes & MOD_ESTERROR) 305 time_esterror = ntv.esterror; 306 if (modes & MOD_STATUS) { 307 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 308 time_state = TIME_OK; 309 time_status = STA_UNSYNC; 310 #ifdef PPS_SYNC 311 pps_shift = PPS_FAVG; 312 #endif /* PPS_SYNC */ 313 } 314 time_status &= STA_RONLY; 315 time_status |= ntv.status & ~STA_RONLY; 316 } 317 if (modes & MOD_TIMECONST) { 318 if (ntv.constant < 0) 319 time_constant = 0; 320 else if (ntv.constant > MAXTC) 321 time_constant = MAXTC; 322 else 323 time_constant = ntv.constant; 324 } 325 if (modes & MOD_TAI) { 326 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 327 time_tai = ntv.constant; 328 } 329 #ifdef PPS_SYNC 330 if (modes & MOD_PPSMAX) { 331 if (ntv.shift < PPS_FAVG) 332 pps_shiftmax = PPS_FAVG; 333 else if (ntv.shift > PPS_FAVGMAX) 334 pps_shiftmax = PPS_FAVGMAX; 335 else 336 pps_shiftmax = ntv.shift; 337 } 338 #endif /* PPS_SYNC */ 339 if (modes & MOD_NANO) 340 time_status |= STA_NANO; 341 if (modes & MOD_MICRO) 342 time_status &= ~STA_NANO; 343 if (modes & MOD_CLKB) 344 time_status |= STA_CLK; 345 if (modes & MOD_CLKA) 346 time_status &= ~STA_CLK; 347 if (modes & MOD_OFFSET) { 348 if (time_status & STA_NANO) 349 hardupdate(ntv.offset); 350 else 351 hardupdate(ntv.offset * 1000); 352 } 353 /* 354 * Note: the userland specified frequency is in seconds per second 355 * times 65536e+6. Multiply by a thousand and divide by 65336 to 356 * get nanoseconds. 357 */ 358 if (modes & MOD_FREQUENCY) { 359 freq = (ntv.freq * 1000LL) >> 16; 360 if (freq > MAXFREQ) 361 L_LINT(time_freq, MAXFREQ); 362 else if (freq < -MAXFREQ) 363 L_LINT(time_freq, -MAXFREQ); 364 else 365 L_LINT(time_freq, freq); 366 #ifdef PPS_SYNC 367 pps_freq = time_freq; 368 #endif /* PPS_SYNC */ 369 } 370 371 /* 372 * Retrieve all clock variables. Note that the TAI offset is 373 * returned only by ntp_gettime(); 374 */ 375 if (time_status & STA_NANO) 376 ntv.offset = time_monitor; 377 else 378 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 379 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 380 ntv.maxerror = time_maxerror; 381 ntv.esterror = time_esterror; 382 ntv.status = time_status; 383 ntv.constant = time_constant; 384 if (time_status & STA_NANO) 385 ntv.precision = time_precision; 386 else 387 ntv.precision = time_precision / 1000; 388 ntv.tolerance = MAXFREQ * SCALE_PPM; 389 #ifdef PPS_SYNC 390 ntv.shift = pps_shift; 391 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 392 if (time_status & STA_NANO) 393 ntv.jitter = pps_jitter; 394 else 395 ntv.jitter = pps_jitter / 1000; 396 ntv.stabil = pps_stabil; 397 ntv.calcnt = pps_calcnt; 398 ntv.errcnt = pps_errcnt; 399 ntv.jitcnt = pps_jitcnt; 400 ntv.stbcnt = pps_stbcnt; 401 #endif /* PPS_SYNC */ 402 crit_exit(); 403 rel_mplock(); 404 405 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 406 if (error) 407 return (error); 408 409 /* 410 * Status word error decode. See comments in 411 * ntp_gettime() routine. 412 */ 413 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 414 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 415 !(time_status & STA_PPSSIGNAL)) || 416 (time_status & STA_PPSTIME && 417 time_status & STA_PPSJITTER) || 418 (time_status & STA_PPSFREQ && 419 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 420 uap->sysmsg_result = TIME_ERROR; 421 } else { 422 uap->sysmsg_result = time_state; 423 } 424 return (error); 425 } 426 427 /* 428 * second_overflow() - called after ntp_tick_adjust() 429 * 430 * This routine is ordinarily called from hardclock() whenever the seconds 431 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 432 * to the total adjustment to make over the next second in (ns << 32). 433 * 434 * This routine is only called by cpu #0. 435 */ 436 int 437 ntp_update_second(time_t newsec, int64_t *nsec_adj) 438 { 439 l_fp ftemp; /* 32/64-bit temporary */ 440 int adjsec = 0; 441 442 /* 443 * On rollover of the second both the nanosecond and microsecond 444 * clocks are updated and the state machine cranked as 445 * necessary. The phase adjustment to be used for the next 446 * second is calculated and the maximum error is increased by 447 * the tolerance. 448 */ 449 time_maxerror += MAXFREQ / 1000; 450 451 /* 452 * Leap second processing. If in leap-insert state at 453 * the end of the day, the system clock is set back one 454 * second; if in leap-delete state, the system clock is 455 * set ahead one second. The nano_time() routine or 456 * external clock driver will insure that reported time 457 * is always monotonic. 458 */ 459 switch (time_state) { 460 461 /* 462 * No warning. 463 */ 464 case TIME_OK: 465 if (time_status & STA_INS) 466 time_state = TIME_INS; 467 else if (time_status & STA_DEL) 468 time_state = TIME_DEL; 469 break; 470 471 /* 472 * Insert second 23:59:60 following second 473 * 23:59:59. 474 */ 475 case TIME_INS: 476 if (!(time_status & STA_INS)) 477 time_state = TIME_OK; 478 else if ((newsec) % 86400 == 0) { 479 --adjsec; 480 time_state = TIME_OOP; 481 } 482 break; 483 484 /* 485 * Delete second 23:59:59. 486 */ 487 case TIME_DEL: 488 if (!(time_status & STA_DEL)) 489 time_state = TIME_OK; 490 else if (((newsec) + 1) % 86400 == 0) { 491 ++adjsec; 492 time_tai--; 493 time_state = TIME_WAIT; 494 } 495 break; 496 497 /* 498 * Insert second in progress. 499 */ 500 case TIME_OOP: 501 time_tai++; 502 time_state = TIME_WAIT; 503 break; 504 505 /* 506 * Wait for status bits to clear. 507 */ 508 case TIME_WAIT: 509 if (!(time_status & (STA_INS | STA_DEL))) 510 time_state = TIME_OK; 511 } 512 513 /* 514 * time_offset represents the total time adjustment we wish to 515 * make (over no particular period of time). time_freq represents 516 * the frequency compensation we wish to apply. 517 * 518 * time_adj represents the total adjustment we wish to make over 519 * one full second. hardclock usually applies this adjustment in 520 * time_adj / hz jumps, hz times a second. 521 */ 522 ftemp = time_offset; 523 #ifdef PPS_SYNC 524 /* XXX even if PPS signal dies we should finish adjustment ? */ 525 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL)) 526 L_RSHIFT(ftemp, pps_shift); 527 else 528 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 529 #else 530 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 531 #endif /* PPS_SYNC */ 532 time_adj = ftemp; /* adjustment for part of the offset */ 533 L_SUB(time_offset, ftemp); 534 L_ADD(time_adj, time_freq); /* add frequency correction */ 535 *nsec_adj = time_adj; 536 #ifdef PPS_SYNC 537 if (pps_valid > 0) 538 pps_valid--; 539 else 540 time_status &= ~STA_PPSSIGNAL; 541 #endif /* PPS_SYNC */ 542 return(adjsec); 543 } 544 545 /* 546 * ntp_init() - initialize variables and structures 547 * 548 * This routine must be called after the kernel variables hz and tick 549 * are set or changed and before the next tick interrupt. In this 550 * particular implementation, these values are assumed set elsewhere in 551 * the kernel. The design allows the clock frequency and tick interval 552 * to be changed while the system is running. So, this routine should 553 * probably be integrated with the code that does that. 554 */ 555 static void 556 ntp_init(void) 557 { 558 559 /* 560 * The following variable must be initialized any time the 561 * kernel variable hz is changed. 562 */ 563 time_tick = NANOSECOND / hz; 564 565 /* 566 * The following variables are initialized only at startup. Only 567 * those structures not cleared by the compiler need to be 568 * initialized, and these only in the simulator. In the actual 569 * kernel, any nonzero values here will quickly evaporate. 570 */ 571 L_CLR(time_offset); 572 L_CLR(time_freq); 573 #ifdef PPS_SYNC 574 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 575 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 576 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 577 pps_fcount = 0; 578 L_CLR(pps_freq); 579 #endif /* PPS_SYNC */ 580 } 581 582 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 583 584 /* 585 * hardupdate() - local clock update 586 * 587 * This routine is called by ntp_adjtime() to update the local clock 588 * phase and frequency. The implementation is of an adaptive-parameter, 589 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 590 * time and frequency offset estimates for each call. If the kernel PPS 591 * discipline code is configured (PPS_SYNC), the PPS signal itself 592 * determines the new time offset, instead of the calling argument. 593 * Presumably, calls to ntp_adjtime() occur only when the caller 594 * believes the local clock is valid within some bound (+-128 ms with 595 * NTP). If the caller's time is far different than the PPS time, an 596 * argument will ensue, and it's not clear who will lose. 597 * 598 * For uncompensated quartz crystal oscillators and nominal update 599 * intervals less than 256 s, operation should be in phase-lock mode, 600 * where the loop is disciplined to phase. For update intervals greater 601 * than 1024 s, operation should be in frequency-lock mode, where the 602 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 603 * is selected by the STA_MODE status bit. 604 */ 605 static void 606 hardupdate(long offset) 607 { 608 long mtemp; 609 l_fp ftemp; 610 611 /* 612 * Select how the phase is to be controlled and from which 613 * source. If the PPS signal is present and enabled to 614 * discipline the time, the PPS offset is used; otherwise, the 615 * argument offset is used. 616 */ 617 if (!(time_status & STA_PLL)) 618 return; 619 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 620 if (offset > MAXPHASE) 621 time_monitor = MAXPHASE; 622 else if (offset < -MAXPHASE) 623 time_monitor = -MAXPHASE; 624 else 625 time_monitor = offset; 626 L_LINT(time_offset, time_monitor); 627 } 628 629 /* 630 * Select how the frequency is to be controlled and in which 631 * mode (PLL or FLL). If the PPS signal is present and enabled 632 * to discipline the frequency, the PPS frequency is used; 633 * otherwise, the argument offset is used to compute it. 634 */ 635 if ((time_status & STA_PPSFREQ) && time_status & STA_PPSSIGNAL) { 636 time_reftime = time_uptime; 637 return; 638 } 639 if ((time_status & STA_FREQHOLD) || time_reftime == 0) 640 time_reftime = time_uptime; 641 mtemp = time_uptime - time_reftime; 642 L_LINT(ftemp, time_monitor); 643 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 644 L_MPY(ftemp, mtemp); 645 L_ADD(time_freq, ftemp); 646 time_status &= ~STA_MODE; 647 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 648 L_LINT(ftemp, (time_monitor << 4) / mtemp); 649 L_RSHIFT(ftemp, SHIFT_FLL + 4); 650 L_ADD(time_freq, ftemp); 651 time_status |= STA_MODE; 652 } 653 time_reftime = time_uptime; 654 if (L_GINT(time_freq) > MAXFREQ) 655 L_LINT(time_freq, MAXFREQ); 656 else if (L_GINT(time_freq) < -MAXFREQ) 657 L_LINT(time_freq, -MAXFREQ); 658 } 659 660 #ifdef PPS_SYNC 661 /* 662 * hardpps() - discipline CPU clock oscillator to external PPS signal 663 * 664 * This routine is called at each PPS interrupt in order to discipline 665 * the CPU clock oscillator to the PPS signal. There are two independent 666 * first-order feedback loops, one for the phase, the other for the 667 * frequency. The phase loop measures and grooms the PPS phase offset 668 * and leaves it in a handy spot for the seconds overflow routine. The 669 * frequency loop averages successive PPS phase differences and 670 * calculates the PPS frequency offset, which is also processed by the 671 * seconds overflow routine. The code requires the caller to capture the 672 * time and architecture-dependent hardware counter values in 673 * nanoseconds at the on-time PPS signal transition. 674 * 675 * Note that, on some Unix systems this routine runs at an interrupt 676 * priority level higher than the timer interrupt routine hardclock(). 677 * Therefore, the variables used are distinct from the hardclock() 678 * variables, except for the actual time and frequency variables, which 679 * are determined by this routine and updated atomically. 680 */ 681 void 682 hardpps(struct timespec *tsp, long nsec) 683 { 684 long u_sec, u_nsec, v_nsec; /* temps */ 685 l_fp ftemp; 686 687 /* 688 * The signal is first processed by a range gate and frequency 689 * discriminator. The range gate rejects noise spikes outside 690 * the range +-500 us. The frequency discriminator rejects input 691 * signals with apparent frequency outside the range 1 +-500 692 * PPM. If two hits occur in the same second, we ignore the 693 * later hit; if not and a hit occurs outside the range gate, 694 * keep the later hit for later comparison, but do not process 695 * it. 696 */ 697 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 698 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 699 pps_valid = PPS_VALID; 700 u_sec = tsp->tv_sec; 701 u_nsec = tsp->tv_nsec; 702 if (u_nsec >= (NANOSECOND >> 1)) { 703 u_nsec -= NANOSECOND; 704 u_sec++; 705 } 706 v_nsec = u_nsec - pps_tf[0].tv_nsec; 707 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 708 MAXFREQ) 709 return; 710 pps_tf[2] = pps_tf[1]; 711 pps_tf[1] = pps_tf[0]; 712 pps_tf[0].tv_sec = u_sec; 713 pps_tf[0].tv_nsec = u_nsec; 714 715 /* 716 * Compute the difference between the current and previous 717 * counter values. If the difference exceeds 0.5 s, assume it 718 * has wrapped around, so correct 1.0 s. If the result exceeds 719 * the tick interval, the sample point has crossed a tick 720 * boundary during the last second, so correct the tick. Very 721 * intricate. 722 */ 723 u_nsec = nsec; 724 if (u_nsec > (NANOSECOND >> 1)) 725 u_nsec -= NANOSECOND; 726 else if (u_nsec < -(NANOSECOND >> 1)) 727 u_nsec += NANOSECOND; 728 pps_fcount += u_nsec; 729 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 730 return; 731 time_status &= ~STA_PPSJITTER; 732 733 /* 734 * A three-stage median filter is used to help denoise the PPS 735 * time. The median sample becomes the time offset estimate; the 736 * difference between the other two samples becomes the time 737 * dispersion (jitter) estimate. 738 */ 739 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 740 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 741 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 742 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 743 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 744 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 745 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 746 } else { 747 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 748 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 749 } 750 } else { 751 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 752 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 753 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 754 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 755 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 756 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 757 } else { 758 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 759 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 760 } 761 } 762 763 /* 764 * Nominal jitter is due to PPS signal noise and interrupt 765 * latency. If it exceeds the popcorn threshold, the sample is 766 * discarded. otherwise, if so enabled, the time offset is 767 * updated. We can tolerate a modest loss of data here without 768 * much degrading time accuracy. 769 */ 770 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 771 time_status |= STA_PPSJITTER; 772 pps_jitcnt++; 773 } else if (time_status & STA_PPSTIME) { 774 time_monitor = -v_nsec; 775 L_LINT(time_offset, time_monitor); 776 } 777 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 778 u_sec = pps_tf[0].tv_sec - pps_lastsec; 779 if (u_sec < (1 << pps_shift)) 780 return; 781 782 /* 783 * At the end of the calibration interval the difference between 784 * the first and last counter values becomes the scaled 785 * frequency. It will later be divided by the length of the 786 * interval to determine the frequency update. If the frequency 787 * exceeds a sanity threshold, or if the actual calibration 788 * interval is not equal to the expected length, the data are 789 * discarded. We can tolerate a modest loss of data here without 790 * much degrading frequency accuracy. 791 */ 792 pps_calcnt++; 793 v_nsec = -pps_fcount; 794 pps_lastsec = pps_tf[0].tv_sec; 795 pps_fcount = 0; 796 u_nsec = MAXFREQ << pps_shift; 797 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 798 pps_shift)) { 799 time_status |= STA_PPSERROR; 800 pps_errcnt++; 801 return; 802 } 803 804 /* 805 * Here the raw frequency offset and wander (stability) is 806 * calculated. If the wander is less than the wander threshold 807 * for four consecutive averaging intervals, the interval is 808 * doubled; if it is greater than the threshold for four 809 * consecutive intervals, the interval is halved. The scaled 810 * frequency offset is converted to frequency offset. The 811 * stability metric is calculated as the average of recent 812 * frequency changes, but is used only for performance 813 * monitoring. 814 */ 815 L_LINT(ftemp, v_nsec); 816 L_RSHIFT(ftemp, pps_shift); 817 L_SUB(ftemp, pps_freq); 818 u_nsec = L_GINT(ftemp); 819 if (u_nsec > PPS_MAXWANDER) { 820 L_LINT(ftemp, PPS_MAXWANDER); 821 pps_intcnt--; 822 time_status |= STA_PPSWANDER; 823 pps_stbcnt++; 824 } else if (u_nsec < -PPS_MAXWANDER) { 825 L_LINT(ftemp, -PPS_MAXWANDER); 826 pps_intcnt--; 827 time_status |= STA_PPSWANDER; 828 pps_stbcnt++; 829 } else { 830 pps_intcnt++; 831 } 832 if (pps_intcnt >= 4) { 833 pps_intcnt = 4; 834 if (pps_shift < pps_shiftmax) { 835 pps_shift++; 836 pps_intcnt = 0; 837 } 838 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 839 pps_intcnt = -4; 840 if (pps_shift > PPS_FAVG) { 841 pps_shift--; 842 pps_intcnt = 0; 843 } 844 } 845 if (u_nsec < 0) 846 u_nsec = -u_nsec; 847 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 848 849 /* 850 * The PPS frequency is recalculated and clamped to the maximum 851 * MAXFREQ. If enabled, the system clock frequency is updated as 852 * well. 853 */ 854 L_ADD(pps_freq, ftemp); 855 u_nsec = L_GINT(pps_freq); 856 if (u_nsec > MAXFREQ) 857 L_LINT(pps_freq, MAXFREQ); 858 else if (u_nsec < -MAXFREQ) 859 L_LINT(pps_freq, -MAXFREQ); 860 if (time_status & STA_PPSFREQ) 861 time_freq = pps_freq; 862 } 863 #endif /* PPS_SYNC */ 864