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 49 /* 50 * Single-precision macros for 64-bit machines 51 */ 52 typedef long long l_fp; 53 #define L_ADD(v, u) ((v) += (u)) 54 #define L_SUB(v, u) ((v) -= (u)) 55 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 56 #define L_NEG(v) ((v) = -(v)) 57 #define L_RSHIFT(v, n) \ 58 do { \ 59 if ((v) < 0) \ 60 (v) = -(-(v) >> (n)); \ 61 else \ 62 (v) = (v) >> (n); \ 63 } while (0) 64 #define L_MPY(v, a) ((v) *= (a)) 65 #define L_CLR(v) ((v) = 0) 66 #define L_ISNEG(v) ((v) < 0) 67 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 68 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 69 70 /* 71 * Generic NTP kernel interface 72 * 73 * These routines constitute the Network Time Protocol (NTP) interfaces 74 * for user and daemon application programs. The ntp_gettime() routine 75 * provides the time, maximum error (synch distance) and estimated error 76 * (dispersion) to client user application programs. The ntp_adjtime() 77 * routine is used by the NTP daemon to adjust the system clock to an 78 * externally derived time. The time offset and related variables set by 79 * this routine are used by other routines in this module to adjust the 80 * phase and frequency of the clock discipline loop which controls the 81 * system clock. 82 * 83 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 84 * defined), the time at each tick interrupt is derived directly from 85 * the kernel time variable. When the kernel time is reckoned in 86 * microseconds, (NTP_NANO undefined), the time is derived from the 87 * kernel time variable together with a variable representing the 88 * leftover nanoseconds at the last tick interrupt. In either case, the 89 * current nanosecond time is reckoned from these values plus an 90 * interpolated value derived by the clock routines in another 91 * architecture-specific module. The interpolation can use either a 92 * dedicated counter or a processor cycle counter (PCC) implemented in 93 * some architectures. 94 * 95 * Note that all routines must run at priority splclock or higher. 96 */ 97 /* 98 * Phase/frequency-lock loop (PLL/FLL) definitions 99 * 100 * The nanosecond clock discipline uses two variable types, time 101 * variables and frequency variables. Both types are represented as 64- 102 * bit fixed-point quantities with the decimal point between two 32-bit 103 * halves. On a 32-bit machine, each half is represented as a single 104 * word and mathematical operations are done using multiple-precision 105 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 106 * used. 107 * 108 * A time variable is a signed 64-bit fixed-point number in ns and 109 * fraction. It represents the remaining time offset to be amortized 110 * over succeeding tick interrupts. The maximum time offset is about 111 * 0.5 s and the resolution is about 2.3e-10 ns. 112 * 113 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 114 * 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 1 115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 116 * |s s s| ns | 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * | fraction | 119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 * 121 * A frequency variable is a signed 64-bit fixed-point number in ns/s 122 * and fraction. It represents the ns and fraction to be added to the 123 * kernel time variable at each second. The maximum frequency offset is 124 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 125 * 126 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 127 * 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 1 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * |s s s s s s s s s s s s s| ns/s | 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 * | fraction | 132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 */ 134 /* 135 * The following variables establish the state of the PLL/FLL and the 136 * residual time and frequency offset of the local clock. 137 */ 138 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 139 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 140 141 static int time_state = TIME_OK; /* clock state */ 142 static int time_status = STA_UNSYNC; /* clock status bits */ 143 static long time_tai; /* TAI offset (s) */ 144 static long time_monitor; /* last time offset scaled (ns) */ 145 static long time_constant; /* poll interval (shift) (s) */ 146 static long time_precision = 1; /* clock precision (ns) */ 147 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 148 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 149 static time_t time_reftime; /* time at last adjustment (s) */ 150 static long time_tick; /* nanoseconds per tick (ns) */ 151 static l_fp time_offset; /* time offset (ns) */ 152 static l_fp time_freq; /* frequency offset (ns/s) */ 153 static l_fp time_adj; /* tick adjust (ns/s) */ 154 155 static struct lock ntp_lock = LOCK_INITIALIZER("ntplk", 0, 0); 156 157 #ifdef PPS_SYNC 158 /* 159 * The following variables are used when a pulse-per-second (PPS) signal 160 * is available and connected via a modem control lead. They establish 161 * the engineering parameters of the clock discipline loop when 162 * controlled by the PPS signal. 163 */ 164 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 165 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 166 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 167 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 168 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 169 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 170 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 171 172 static struct timespec pps_tf[3]; /* phase median filter */ 173 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 174 static long pps_fcount; /* frequency accumulator */ 175 static long pps_jitter; /* nominal jitter (ns) */ 176 static long pps_stabil; /* nominal stability (scaled ns/s) */ 177 static long pps_lastsec; /* time at last calibration (s) */ 178 static int pps_valid; /* signal watchdog counter */ 179 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 180 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 181 static int pps_intcnt; /* wander counter */ 182 183 /* 184 * PPS signal quality monitors 185 */ 186 static long pps_calcnt; /* calibration intervals */ 187 static long pps_jitcnt; /* jitter limit exceeded */ 188 static long pps_stbcnt; /* stability limit exceeded */ 189 static long pps_errcnt; /* calibration errors */ 190 #endif /* PPS_SYNC */ 191 /* 192 * End of phase/frequency-lock loop (PLL/FLL) definitions 193 */ 194 195 static void ntp_init(void); 196 static void hardupdate(long offset); 197 198 /* 199 * ntp_gettime() - NTP user application interface 200 * 201 * See the timex.h header file for synopsis and API description. Note 202 * that the TAI offset is returned in the ntvtimeval.tai structure 203 * member. 204 */ 205 static int 206 ntp_sysctl(SYSCTL_HANDLER_ARGS) 207 { 208 struct ntptimeval ntv; /* temporary structure */ 209 struct timespec atv; /* nanosecond time */ 210 int error; 211 212 lockmgr(&ntp_lock, LK_EXCLUSIVE); 213 214 nanotime(&atv); 215 ntv.time.tv_sec = atv.tv_sec; 216 ntv.time.tv_nsec = atv.tv_nsec; 217 ntv.maxerror = time_maxerror; 218 ntv.esterror = time_esterror; 219 ntv.tai = time_tai; 220 ntv.time_state = time_state; 221 222 /* 223 * Status word error decode. If any of these conditions occur, 224 * an error is returned, instead of the status word. Most 225 * applications will care only about the fact the system clock 226 * may not be trusted, not about the details. 227 * 228 * Hardware or software error 229 */ 230 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 231 232 /* 233 * PPS signal lost when either time or frequency synchronization 234 * requested 235 */ 236 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 237 !(time_status & STA_PPSSIGNAL)) || 238 239 /* 240 * PPS jitter exceeded when time synchronization requested 241 */ 242 (time_status & STA_PPSTIME && 243 time_status & STA_PPSJITTER) || 244 245 /* 246 * PPS wander exceeded or calibration error when frequency 247 * synchronization requested 248 */ 249 (time_status & STA_PPSFREQ && 250 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 251 ntv.time_state = TIME_ERROR; 252 } 253 254 error = sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req); 255 lockmgr(&ntp_lock, LK_RELEASE); 256 257 return error; 258 } 259 260 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 261 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 262 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 263 264 #ifdef PPS_SYNC 265 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 266 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 267 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 268 269 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 270 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 271 #endif 272 /* 273 * ntp_adjtime() - NTP daemon application interface 274 * 275 * See the timex.h header file for synopsis and API description. Note 276 * that the timex.constant structure member has a dual purpose to set 277 * the time constant and to set the TAI offset. 278 * 279 * MPALMOSTSAFE 280 */ 281 int 282 sys_ntp_adjtime(struct ntp_adjtime_args *uap) 283 { 284 struct thread *td = curthread; 285 struct timex ntv; /* temporary structure */ 286 long freq; /* frequency ns/s) */ 287 int modes; /* mode bits from structure */ 288 int error; 289 290 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 291 if (error) 292 return(error); 293 294 /* 295 * Update selected clock variables - only the superuser can 296 * change anything. Note that there is no error checking here on 297 * the assumption the superuser should know what it is doing. 298 * Note that either the time constant or TAI offset are loaded 299 * from the ntv.constant member, depending on the mode bits. If 300 * the STA_PLL bit in the status word is cleared, the state and 301 * status words are reset to the initial values at boot. 302 */ 303 modes = ntv.modes; 304 if (modes) 305 error = priv_check(td, PRIV_NTP_ADJTIME); 306 if (error) 307 return (error); 308 309 lockmgr(&ntp_lock, LK_EXCLUSIVE); 310 crit_enter(); 311 if (modes & MOD_MAXERROR) 312 time_maxerror = ntv.maxerror; 313 if (modes & MOD_ESTERROR) 314 time_esterror = ntv.esterror; 315 if (modes & MOD_STATUS) { 316 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 317 time_state = TIME_OK; 318 time_status = STA_UNSYNC; 319 #ifdef PPS_SYNC 320 pps_shift = PPS_FAVG; 321 #endif /* PPS_SYNC */ 322 } 323 time_status &= STA_RONLY; 324 time_status |= ntv.status & ~STA_RONLY; 325 } 326 if (modes & MOD_TIMECONST) { 327 if (ntv.constant < 0) 328 time_constant = 0; 329 else if (ntv.constant > MAXTC) 330 time_constant = MAXTC; 331 else 332 time_constant = ntv.constant; 333 } 334 if (modes & MOD_TAI) { 335 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 336 time_tai = ntv.constant; 337 } 338 #ifdef PPS_SYNC 339 if (modes & MOD_PPSMAX) { 340 if (ntv.shift < PPS_FAVG) 341 pps_shiftmax = PPS_FAVG; 342 else if (ntv.shift > PPS_FAVGMAX) 343 pps_shiftmax = PPS_FAVGMAX; 344 else 345 pps_shiftmax = ntv.shift; 346 } 347 #endif /* PPS_SYNC */ 348 if (modes & MOD_NANO) 349 time_status |= STA_NANO; 350 if (modes & MOD_MICRO) 351 time_status &= ~STA_NANO; 352 if (modes & MOD_CLKB) 353 time_status |= STA_CLK; 354 if (modes & MOD_CLKA) 355 time_status &= ~STA_CLK; 356 if (modes & MOD_OFFSET) { 357 if (time_status & STA_NANO) 358 hardupdate(ntv.offset); 359 else 360 hardupdate(ntv.offset * 1000); 361 } 362 /* 363 * Note: the userland specified frequency is in seconds per second 364 * times 65536e+6. Multiply by a thousand and divide by 65336 to 365 * get nanoseconds. 366 */ 367 if (modes & MOD_FREQUENCY) { 368 freq = (ntv.freq * 1000LL) >> 16; 369 if (freq > MAXFREQ) 370 L_LINT(time_freq, MAXFREQ); 371 else if (freq < -MAXFREQ) 372 L_LINT(time_freq, -MAXFREQ); 373 else 374 L_LINT(time_freq, freq); 375 #ifdef PPS_SYNC 376 pps_freq = time_freq; 377 #endif /* PPS_SYNC */ 378 } 379 380 /* 381 * Retrieve all clock variables. Note that the TAI offset is 382 * returned only by ntp_gettime(); 383 */ 384 if (time_status & STA_NANO) 385 ntv.offset = time_monitor; 386 else 387 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 388 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 389 ntv.maxerror = time_maxerror; 390 ntv.esterror = time_esterror; 391 ntv.status = time_status; 392 ntv.constant = time_constant; 393 if (time_status & STA_NANO) 394 ntv.precision = time_precision; 395 else 396 ntv.precision = time_precision / 1000; 397 ntv.tolerance = MAXFREQ * SCALE_PPM; 398 #ifdef PPS_SYNC 399 ntv.shift = pps_shift; 400 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 401 if (time_status & STA_NANO) 402 ntv.jitter = pps_jitter; 403 else 404 ntv.jitter = pps_jitter / 1000; 405 ntv.stabil = pps_stabil; 406 ntv.calcnt = pps_calcnt; 407 ntv.errcnt = pps_errcnt; 408 ntv.jitcnt = pps_jitcnt; 409 ntv.stbcnt = pps_stbcnt; 410 #endif /* PPS_SYNC */ 411 crit_exit(); 412 lockmgr(&ntp_lock, LK_RELEASE); 413 414 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 415 if (error) 416 return (error); 417 418 /* 419 * Status word error decode. See comments in 420 * ntp_gettime() routine. 421 */ 422 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 423 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 424 !(time_status & STA_PPSSIGNAL)) || 425 (time_status & STA_PPSTIME && 426 time_status & STA_PPSJITTER) || 427 (time_status & STA_PPSFREQ && 428 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 429 uap->sysmsg_result = TIME_ERROR; 430 } else { 431 uap->sysmsg_result = time_state; 432 } 433 return (error); 434 } 435 436 /* 437 * second_overflow() - called after ntp_tick_adjust() 438 * 439 * This routine is ordinarily called from hardclock() whenever the seconds 440 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 441 * to the total adjustment to make over the next second in (ns << 32). 442 * 443 * This routine is only called by cpu #0. 444 */ 445 int 446 ntp_update_second(time_t newsec, int64_t *nsec_adj) 447 { 448 l_fp ftemp; /* 32/64-bit temporary */ 449 int adjsec = 0; 450 451 /* 452 * On rollover of the second both the nanosecond and microsecond 453 * clocks are updated and the state machine cranked as 454 * necessary. The phase adjustment to be used for the next 455 * second is calculated and the maximum error is increased by 456 * the tolerance. 457 */ 458 time_maxerror += MAXFREQ / 1000; 459 460 /* 461 * Leap second processing. If in leap-insert state at 462 * the end of the day, the system clock is set back one 463 * second; if in leap-delete state, the system clock is 464 * set ahead one second. The nano_time() routine or 465 * external clock driver will insure that reported time 466 * is always monotonic. 467 */ 468 switch (time_state) { 469 470 /* 471 * No warning. 472 */ 473 case TIME_OK: 474 if (time_status & STA_INS) 475 time_state = TIME_INS; 476 else if (time_status & STA_DEL) 477 time_state = TIME_DEL; 478 break; 479 480 /* 481 * Insert second 23:59:60 following second 482 * 23:59:59. 483 */ 484 case TIME_INS: 485 if (!(time_status & STA_INS)) 486 time_state = TIME_OK; 487 else if ((newsec) % 86400 == 0) { 488 --adjsec; 489 time_state = TIME_OOP; 490 } 491 break; 492 493 /* 494 * Delete second 23:59:59. 495 */ 496 case TIME_DEL: 497 if (!(time_status & STA_DEL)) 498 time_state = TIME_OK; 499 else if (((newsec) + 1) % 86400 == 0) { 500 ++adjsec; 501 time_tai--; 502 time_state = TIME_WAIT; 503 } 504 break; 505 506 /* 507 * Insert second in progress. 508 */ 509 case TIME_OOP: 510 time_tai++; 511 time_state = TIME_WAIT; 512 break; 513 514 /* 515 * Wait for status bits to clear. 516 */ 517 case TIME_WAIT: 518 if (!(time_status & (STA_INS | STA_DEL))) 519 time_state = TIME_OK; 520 } 521 522 /* 523 * time_offset represents the total time adjustment we wish to 524 * make (over no particular period of time). time_freq represents 525 * the frequency compensation we wish to apply. 526 * 527 * time_adj represents the total adjustment we wish to make over 528 * one full second. hardclock usually applies this adjustment in 529 * time_adj / hz jumps, hz times a second. 530 */ 531 ftemp = time_offset; 532 #ifdef PPS_SYNC 533 /* XXX even if PPS signal dies we should finish adjustment ? */ 534 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL)) 535 L_RSHIFT(ftemp, pps_shift); 536 else 537 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 538 #else 539 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 540 #endif /* PPS_SYNC */ 541 time_adj = ftemp; /* adjustment for part of the offset */ 542 L_SUB(time_offset, ftemp); 543 L_ADD(time_adj, time_freq); /* add frequency correction */ 544 *nsec_adj = time_adj; 545 #ifdef PPS_SYNC 546 if (pps_valid > 0) 547 pps_valid--; 548 else 549 time_status &= ~STA_PPSSIGNAL; 550 #endif /* PPS_SYNC */ 551 return(adjsec); 552 } 553 554 /* 555 * ntp_init() - initialize variables and structures 556 * 557 * This routine must be called after the kernel variables hz and tick 558 * are set or changed and before the next tick interrupt. In this 559 * particular implementation, these values are assumed set elsewhere in 560 * the kernel. The design allows the clock frequency and tick interval 561 * to be changed while the system is running. So, this routine should 562 * probably be integrated with the code that does that. 563 */ 564 static void 565 ntp_init(void) 566 { 567 568 /* 569 * The following variable must be initialized any time the 570 * kernel variable hz is changed. 571 */ 572 time_tick = NANOSECOND / hz; 573 574 /* 575 * The following variables are initialized only at startup. Only 576 * those structures not cleared by the compiler need to be 577 * initialized, and these only in the simulator. In the actual 578 * kernel, any nonzero values here will quickly evaporate. 579 */ 580 L_CLR(time_offset); 581 L_CLR(time_freq); 582 #ifdef PPS_SYNC 583 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 584 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 585 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 586 pps_fcount = 0; 587 L_CLR(pps_freq); 588 #endif /* PPS_SYNC */ 589 } 590 591 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL); 592 593 /* 594 * hardupdate() - local clock update 595 * 596 * This routine is called by ntp_adjtime() to update the local clock 597 * phase and frequency. The implementation is of an adaptive-parameter, 598 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 599 * time and frequency offset estimates for each call. If the kernel PPS 600 * discipline code is configured (PPS_SYNC), the PPS signal itself 601 * determines the new time offset, instead of the calling argument. 602 * Presumably, calls to ntp_adjtime() occur only when the caller 603 * believes the local clock is valid within some bound (+-128 ms with 604 * NTP). If the caller's time is far different than the PPS time, an 605 * argument will ensue, and it's not clear who will lose. 606 * 607 * For uncompensated quartz crystal oscillators and nominal update 608 * intervals less than 256 s, operation should be in phase-lock mode, 609 * where the loop is disciplined to phase. For update intervals greater 610 * than 1024 s, operation should be in frequency-lock mode, where the 611 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 612 * is selected by the STA_MODE status bit. 613 */ 614 static void 615 hardupdate(long offset) 616 { 617 long mtemp; 618 l_fp ftemp; 619 620 /* 621 * Select how the phase is to be controlled and from which 622 * source. If the PPS signal is present and enabled to 623 * discipline the time, the PPS offset is used; otherwise, the 624 * argument offset is used. 625 */ 626 if (!(time_status & STA_PLL)) 627 return; 628 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 629 if (offset > MAXPHASE) 630 time_monitor = MAXPHASE; 631 else if (offset < -MAXPHASE) 632 time_monitor = -MAXPHASE; 633 else 634 time_monitor = offset; 635 L_LINT(time_offset, time_monitor); 636 } 637 638 /* 639 * Select how the frequency is to be controlled and in which 640 * mode (PLL or FLL). If the PPS signal is present and enabled 641 * to discipline the frequency, the PPS frequency is used; 642 * otherwise, the argument offset is used to compute it. 643 */ 644 if ((time_status & STA_PPSFREQ) && time_status & STA_PPSSIGNAL) { 645 time_reftime = time_uptime; 646 return; 647 } 648 if ((time_status & STA_FREQHOLD) || time_reftime == 0) 649 time_reftime = time_uptime; 650 mtemp = time_uptime - time_reftime; 651 L_LINT(ftemp, time_monitor); 652 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 653 L_MPY(ftemp, mtemp); 654 L_ADD(time_freq, ftemp); 655 time_status &= ~STA_MODE; 656 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 657 L_LINT(ftemp, (time_monitor << 4) / mtemp); 658 L_RSHIFT(ftemp, SHIFT_FLL + 4); 659 L_ADD(time_freq, ftemp); 660 time_status |= STA_MODE; 661 } 662 time_reftime = time_uptime; 663 if (L_GINT(time_freq) > MAXFREQ) 664 L_LINT(time_freq, MAXFREQ); 665 else if (L_GINT(time_freq) < -MAXFREQ) 666 L_LINT(time_freq, -MAXFREQ); 667 } 668 669 #ifdef PPS_SYNC 670 /* 671 * hardpps() - discipline CPU clock oscillator to external PPS signal 672 * 673 * This routine is called at each PPS interrupt in order to discipline 674 * the CPU clock oscillator to the PPS signal. There are two independent 675 * first-order feedback loops, one for the phase, the other for the 676 * frequency. The phase loop measures and grooms the PPS phase offset 677 * and leaves it in a handy spot for the seconds overflow routine. The 678 * frequency loop averages successive PPS phase differences and 679 * calculates the PPS frequency offset, which is also processed by the 680 * seconds overflow routine. The code requires the caller to capture the 681 * time and architecture-dependent hardware counter values in 682 * nanoseconds at the on-time PPS signal transition. 683 * 684 * Note that, on some Unix systems this routine runs at an interrupt 685 * priority level higher than the timer interrupt routine hardclock(). 686 * Therefore, the variables used are distinct from the hardclock() 687 * variables, except for the actual time and frequency variables, which 688 * are determined by this routine and updated atomically. 689 */ 690 void 691 hardpps(struct timespec *tsp, long nsec) 692 { 693 long u_sec, u_nsec, v_nsec; /* temps */ 694 l_fp ftemp; 695 696 /* 697 * The signal is first processed by a range gate and frequency 698 * discriminator. The range gate rejects noise spikes outside 699 * the range +-500 us. The frequency discriminator rejects input 700 * signals with apparent frequency outside the range 1 +-500 701 * PPM. If two hits occur in the same second, we ignore the 702 * later hit; if not and a hit occurs outside the range gate, 703 * keep the later hit for later comparison, but do not process 704 * it. 705 */ 706 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 707 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 708 pps_valid = PPS_VALID; 709 u_sec = tsp->tv_sec; 710 u_nsec = tsp->tv_nsec; 711 if (u_nsec >= (NANOSECOND >> 1)) { 712 u_nsec -= NANOSECOND; 713 u_sec++; 714 } 715 v_nsec = u_nsec - pps_tf[0].tv_nsec; 716 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 717 MAXFREQ) 718 return; 719 pps_tf[2] = pps_tf[1]; 720 pps_tf[1] = pps_tf[0]; 721 pps_tf[0].tv_sec = u_sec; 722 pps_tf[0].tv_nsec = u_nsec; 723 724 /* 725 * Compute the difference between the current and previous 726 * counter values. If the difference exceeds 0.5 s, assume it 727 * has wrapped around, so correct 1.0 s. If the result exceeds 728 * the tick interval, the sample point has crossed a tick 729 * boundary during the last second, so correct the tick. Very 730 * intricate. 731 */ 732 u_nsec = nsec; 733 if (u_nsec > (NANOSECOND >> 1)) 734 u_nsec -= NANOSECOND; 735 else if (u_nsec < -(NANOSECOND >> 1)) 736 u_nsec += NANOSECOND; 737 pps_fcount += u_nsec; 738 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 739 return; 740 time_status &= ~STA_PPSJITTER; 741 742 /* 743 * A three-stage median filter is used to help denoise the PPS 744 * time. The median sample becomes the time offset estimate; the 745 * difference between the other two samples becomes the time 746 * dispersion (jitter) estimate. 747 */ 748 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 749 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 750 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 751 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 752 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 753 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 754 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 755 } else { 756 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 757 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 758 } 759 } else { 760 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 761 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 762 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 763 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 764 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 765 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 766 } else { 767 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 768 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 769 } 770 } 771 772 /* 773 * Nominal jitter is due to PPS signal noise and interrupt 774 * latency. If it exceeds the popcorn threshold, the sample is 775 * discarded. otherwise, if so enabled, the time offset is 776 * updated. We can tolerate a modest loss of data here without 777 * much degrading time accuracy. 778 */ 779 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 780 time_status |= STA_PPSJITTER; 781 pps_jitcnt++; 782 } else if (time_status & STA_PPSTIME) { 783 time_monitor = -v_nsec; 784 L_LINT(time_offset, time_monitor); 785 } 786 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 787 u_sec = pps_tf[0].tv_sec - pps_lastsec; 788 if (u_sec < (1 << pps_shift)) 789 return; 790 791 /* 792 * At the end of the calibration interval the difference between 793 * the first and last counter values becomes the scaled 794 * frequency. It will later be divided by the length of the 795 * interval to determine the frequency update. If the frequency 796 * exceeds a sanity threshold, or if the actual calibration 797 * interval is not equal to the expected length, the data are 798 * discarded. We can tolerate a modest loss of data here without 799 * much degrading frequency accuracy. 800 */ 801 pps_calcnt++; 802 v_nsec = -pps_fcount; 803 pps_lastsec = pps_tf[0].tv_sec; 804 pps_fcount = 0; 805 u_nsec = MAXFREQ << pps_shift; 806 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 807 pps_shift)) { 808 time_status |= STA_PPSERROR; 809 pps_errcnt++; 810 return; 811 } 812 813 /* 814 * Here the raw frequency offset and wander (stability) is 815 * calculated. If the wander is less than the wander threshold 816 * for four consecutive averaging intervals, the interval is 817 * doubled; if it is greater than the threshold for four 818 * consecutive intervals, the interval is halved. The scaled 819 * frequency offset is converted to frequency offset. The 820 * stability metric is calculated as the average of recent 821 * frequency changes, but is used only for performance 822 * monitoring. 823 */ 824 L_LINT(ftemp, v_nsec); 825 L_RSHIFT(ftemp, pps_shift); 826 L_SUB(ftemp, pps_freq); 827 u_nsec = L_GINT(ftemp); 828 if (u_nsec > PPS_MAXWANDER) { 829 L_LINT(ftemp, PPS_MAXWANDER); 830 pps_intcnt--; 831 time_status |= STA_PPSWANDER; 832 pps_stbcnt++; 833 } else if (u_nsec < -PPS_MAXWANDER) { 834 L_LINT(ftemp, -PPS_MAXWANDER); 835 pps_intcnt--; 836 time_status |= STA_PPSWANDER; 837 pps_stbcnt++; 838 } else { 839 pps_intcnt++; 840 } 841 if (pps_intcnt >= 4) { 842 pps_intcnt = 4; 843 if (pps_shift < pps_shiftmax) { 844 pps_shift++; 845 pps_intcnt = 0; 846 } 847 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 848 pps_intcnt = -4; 849 if (pps_shift > PPS_FAVG) { 850 pps_shift--; 851 pps_intcnt = 0; 852 } 853 } 854 if (u_nsec < 0) 855 u_nsec = -u_nsec; 856 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 857 858 /* 859 * The PPS frequency is recalculated and clamped to the maximum 860 * MAXFREQ. If enabled, the system clock frequency is updated as 861 * well. 862 */ 863 L_ADD(pps_freq, ftemp); 864 u_nsec = L_GINT(pps_freq); 865 if (u_nsec > MAXFREQ) 866 L_LINT(pps_freq, MAXFREQ); 867 else if (u_nsec < -MAXFREQ) 868 L_LINT(pps_freq, -MAXFREQ); 869 if (time_status & STA_PPSFREQ) 870 time_freq = pps_freq; 871 } 872 #endif /* PPS_SYNC */ 873