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/sysmsg.h> 39 #include <sys/kernel.h> 40 #include <sys/proc.h> 41 #include <sys/caps.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 sysmsg *sysmsg, const struct ntp_adjtime_args *uap) 283 { 284 struct timex ntv; /* temporary structure */ 285 long freq; /* frequency ns/s) */ 286 int modes; /* mode bits from structure */ 287 int error; 288 289 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 290 if (error) 291 return(error); 292 293 /* 294 * Update selected clock variables - only the superuser can 295 * change anything. Note that there is no error checking here on 296 * the assumption the superuser should know what it is doing. 297 * Note that either the time constant or TAI offset are loaded 298 * from the ntv.constant member, depending on the mode bits. If 299 * the STA_PLL bit in the status word is cleared, the state and 300 * status words are reset to the initial values at boot. 301 */ 302 modes = ntv.modes; 303 if (modes) 304 error = caps_priv_check_self(SYSCAP_NOSETTIME); 305 if (error) 306 return (error); 307 308 lockmgr(&ntp_lock, LK_EXCLUSIVE); 309 crit_enter(); 310 if (modes & MOD_MAXERROR) 311 time_maxerror = ntv.maxerror; 312 if (modes & MOD_ESTERROR) 313 time_esterror = ntv.esterror; 314 if (modes & MOD_STATUS) { 315 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 316 time_state = TIME_OK; 317 time_status = STA_UNSYNC; 318 #ifdef PPS_SYNC 319 pps_shift = PPS_FAVG; 320 #endif /* PPS_SYNC */ 321 } 322 time_status &= STA_RONLY; 323 time_status |= ntv.status & ~STA_RONLY; 324 } 325 if (modes & MOD_TIMECONST) { 326 if (ntv.constant < 0) 327 time_constant = 0; 328 else if (ntv.constant > MAXTC) 329 time_constant = MAXTC; 330 else 331 time_constant = ntv.constant; 332 } 333 if (modes & MOD_TAI) { 334 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 335 time_tai = ntv.constant; 336 } 337 #ifdef PPS_SYNC 338 if (modes & MOD_PPSMAX) { 339 if (ntv.shift < PPS_FAVG) 340 pps_shiftmax = PPS_FAVG; 341 else if (ntv.shift > PPS_FAVGMAX) 342 pps_shiftmax = PPS_FAVGMAX; 343 else 344 pps_shiftmax = ntv.shift; 345 } 346 #endif /* PPS_SYNC */ 347 if (modes & MOD_NANO) 348 time_status |= STA_NANO; 349 if (modes & MOD_MICRO) 350 time_status &= ~STA_NANO; 351 if (modes & MOD_CLKB) 352 time_status |= STA_CLK; 353 if (modes & MOD_CLKA) 354 time_status &= ~STA_CLK; 355 if (modes & MOD_OFFSET) { 356 if (time_status & STA_NANO) 357 hardupdate(ntv.offset); 358 else 359 hardupdate(ntv.offset * 1000); 360 } 361 /* 362 * Note: the userland specified frequency is in seconds per second 363 * times 65536e+6. Multiply by a thousand and divide by 65336 to 364 * get nanoseconds. 365 */ 366 if (modes & MOD_FREQUENCY) { 367 freq = (ntv.freq * 1000LL) >> 16; 368 if (freq > MAXFREQ) 369 L_LINT(time_freq, MAXFREQ); 370 else if (freq < -MAXFREQ) 371 L_LINT(time_freq, -MAXFREQ); 372 else 373 L_LINT(time_freq, freq); 374 #ifdef PPS_SYNC 375 pps_freq = time_freq; 376 #endif /* PPS_SYNC */ 377 } 378 379 /* 380 * Retrieve all clock variables. Note that the TAI offset is 381 * returned only by ntp_gettime(); 382 */ 383 if (time_status & STA_NANO) 384 ntv.offset = time_monitor; 385 else 386 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 387 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 388 ntv.maxerror = time_maxerror; 389 ntv.esterror = time_esterror; 390 ntv.status = time_status; 391 ntv.constant = time_constant; 392 if (time_status & STA_NANO) 393 ntv.precision = time_precision; 394 else 395 ntv.precision = time_precision / 1000; 396 ntv.tolerance = MAXFREQ * SCALE_PPM; 397 #ifdef PPS_SYNC 398 ntv.shift = pps_shift; 399 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 400 if (time_status & STA_NANO) 401 ntv.jitter = pps_jitter; 402 else 403 ntv.jitter = pps_jitter / 1000; 404 ntv.stabil = pps_stabil; 405 ntv.calcnt = pps_calcnt; 406 ntv.errcnt = pps_errcnt; 407 ntv.jitcnt = pps_jitcnt; 408 ntv.stbcnt = pps_stbcnt; 409 #endif /* PPS_SYNC */ 410 crit_exit(); 411 lockmgr(&ntp_lock, LK_RELEASE); 412 413 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 414 if (error) 415 return (error); 416 417 /* 418 * Status word error decode. See comments in 419 * ntp_gettime() routine. 420 */ 421 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 422 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 423 !(time_status & STA_PPSSIGNAL)) || 424 (time_status & STA_PPSTIME && 425 time_status & STA_PPSJITTER) || 426 (time_status & STA_PPSFREQ && 427 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 428 sysmsg->sysmsg_result = TIME_ERROR; 429 } else { 430 sysmsg->sysmsg_result = time_state; 431 } 432 return (0); 433 } 434 435 /* 436 * second_overflow() - called after ntp_tick_adjust() 437 * 438 * This routine is ordinarily called from hardclock() whenever the seconds 439 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 440 * to the total adjustment to make over the next second in (ns << 32). 441 * 442 * This routine is only called by cpu #0. 443 */ 444 int 445 ntp_update_second(time_t newsec, int64_t *nsec_adj) 446 { 447 l_fp ftemp; /* 32/64-bit temporary */ 448 int adjsec = 0; 449 450 /* 451 * On rollover of the second both the nanosecond and microsecond 452 * clocks are updated and the state machine cranked as 453 * necessary. The phase adjustment to be used for the next 454 * second is calculated and the maximum error is increased by 455 * the tolerance. 456 */ 457 time_maxerror += MAXFREQ / 1000; 458 459 /* 460 * Leap second processing. If in leap-insert state at 461 * the end of the day, the system clock is set back one 462 * second; if in leap-delete state, the system clock is 463 * set ahead one second. The nano_time() routine or 464 * external clock driver will insure that reported time 465 * is always monotonic. 466 */ 467 switch (time_state) { 468 469 /* 470 * No warning. 471 */ 472 case TIME_OK: 473 if (time_status & STA_INS) 474 time_state = TIME_INS; 475 else if (time_status & STA_DEL) 476 time_state = TIME_DEL; 477 break; 478 479 /* 480 * Insert second 23:59:60 following second 481 * 23:59:59. 482 */ 483 case TIME_INS: 484 if (!(time_status & STA_INS)) 485 time_state = TIME_OK; 486 else if ((newsec) % 86400 == 0) { 487 --adjsec; 488 time_state = TIME_OOP; 489 } 490 break; 491 492 /* 493 * Delete second 23:59:59. 494 */ 495 case TIME_DEL: 496 if (!(time_status & STA_DEL)) 497 time_state = TIME_OK; 498 else if (((newsec) + 1) % 86400 == 0) { 499 ++adjsec; 500 time_tai--; 501 time_state = TIME_WAIT; 502 } 503 break; 504 505 /* 506 * Insert second in progress. 507 */ 508 case TIME_OOP: 509 time_tai++; 510 time_state = TIME_WAIT; 511 break; 512 513 /* 514 * Wait for status bits to clear. 515 */ 516 case TIME_WAIT: 517 if (!(time_status & (STA_INS | STA_DEL))) 518 time_state = TIME_OK; 519 } 520 521 /* 522 * time_offset represents the total time adjustment we wish to 523 * make (over no particular period of time). time_freq represents 524 * the frequency compensation we wish to apply. 525 * 526 * time_adj represents the total adjustment we wish to make over 527 * one full second. hardclock usually applies this adjustment in 528 * time_adj / hz jumps, hz times a second. 529 */ 530 ftemp = time_offset; 531 #ifdef PPS_SYNC 532 /* XXX even if PPS signal dies we should finish adjustment ? */ 533 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL)) 534 L_RSHIFT(ftemp, pps_shift); 535 else 536 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 537 #else 538 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 539 #endif /* PPS_SYNC */ 540 time_adj = ftemp; /* adjustment for part of the offset */ 541 L_SUB(time_offset, ftemp); 542 L_ADD(time_adj, time_freq); /* add frequency correction */ 543 *nsec_adj = time_adj; 544 #ifdef PPS_SYNC 545 if (pps_valid > 0) 546 pps_valid--; 547 else 548 time_status &= ~STA_PPSSIGNAL; 549 #endif /* PPS_SYNC */ 550 return(adjsec); 551 } 552 553 /* 554 * ntp_init() - initialize variables and structures 555 * 556 * This routine must be called after the kernel variables hz and tick 557 * are set or changed and before the next tick interrupt. In this 558 * particular implementation, these values are assumed set elsewhere in 559 * the kernel. The design allows the clock frequency and tick interval 560 * to be changed while the system is running. So, this routine should 561 * probably be integrated with the code that does that. 562 */ 563 static void 564 ntp_init(void) 565 { 566 567 /* 568 * The following variable must be initialized any time the 569 * kernel variable hz is changed. 570 */ 571 time_tick = NANOSECOND / hz; 572 573 /* 574 * The following variables are initialized only at startup. Only 575 * those structures not cleared by the compiler need to be 576 * initialized, and these only in the simulator. In the actual 577 * kernel, any nonzero values here will quickly evaporate. 578 */ 579 L_CLR(time_offset); 580 L_CLR(time_freq); 581 #ifdef PPS_SYNC 582 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 583 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 584 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 585 pps_fcount = 0; 586 L_CLR(pps_freq); 587 #endif /* PPS_SYNC */ 588 } 589 590 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL); 591 592 /* 593 * hardupdate() - local clock update 594 * 595 * This routine is called by ntp_adjtime() to update the local clock 596 * phase and frequency. The implementation is of an adaptive-parameter, 597 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 598 * time and frequency offset estimates for each call. If the kernel PPS 599 * discipline code is configured (PPS_SYNC), the PPS signal itself 600 * determines the new time offset, instead of the calling argument. 601 * Presumably, calls to ntp_adjtime() occur only when the caller 602 * believes the local clock is valid within some bound (+-128 ms with 603 * NTP). If the caller's time is far different than the PPS time, an 604 * argument will ensue, and it's not clear who will lose. 605 * 606 * For uncompensated quartz crystal oscillators and nominal update 607 * intervals less than 256 s, operation should be in phase-lock mode, 608 * where the loop is disciplined to phase. For update intervals greater 609 * than 1024 s, operation should be in frequency-lock mode, where the 610 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 611 * is selected by the STA_MODE status bit. 612 */ 613 static void 614 hardupdate(long offset) 615 { 616 long mtemp; 617 l_fp ftemp; 618 619 /* 620 * Select how the phase is to be controlled and from which 621 * source. If the PPS signal is present and enabled to 622 * discipline the time, the PPS offset is used; otherwise, the 623 * argument offset is used. 624 */ 625 if (!(time_status & STA_PLL)) 626 return; 627 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 628 if (offset > MAXPHASE) 629 time_monitor = MAXPHASE; 630 else if (offset < -MAXPHASE) 631 time_monitor = -MAXPHASE; 632 else 633 time_monitor = offset; 634 L_LINT(time_offset, time_monitor); 635 } 636 637 /* 638 * Select how the frequency is to be controlled and in which 639 * mode (PLL or FLL). If the PPS signal is present and enabled 640 * to discipline the frequency, the PPS frequency is used; 641 * otherwise, the argument offset is used to compute it. 642 */ 643 if ((time_status & STA_PPSFREQ) && time_status & STA_PPSSIGNAL) { 644 time_reftime = time_uptime; 645 return; 646 } 647 if ((time_status & STA_FREQHOLD) || time_reftime == 0) 648 time_reftime = time_uptime; 649 mtemp = time_uptime - time_reftime; 650 L_LINT(ftemp, time_monitor); 651 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 652 L_MPY(ftemp, mtemp); 653 L_ADD(time_freq, ftemp); 654 time_status &= ~STA_MODE; 655 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 656 L_LINT(ftemp, (time_monitor << 4) / mtemp); 657 L_RSHIFT(ftemp, SHIFT_FLL + 4); 658 L_ADD(time_freq, ftemp); 659 time_status |= STA_MODE; 660 } 661 time_reftime = time_uptime; 662 if (L_GINT(time_freq) > MAXFREQ) 663 L_LINT(time_freq, MAXFREQ); 664 else if (L_GINT(time_freq) < -MAXFREQ) 665 L_LINT(time_freq, -MAXFREQ); 666 } 667 668 #ifdef PPS_SYNC 669 /* 670 * hardpps() - discipline CPU clock oscillator to external PPS signal 671 * 672 * This routine is called at each PPS interrupt in order to discipline 673 * the CPU clock oscillator to the PPS signal. There are two independent 674 * first-order feedback loops, one for the phase, the other for the 675 * frequency. The phase loop measures and grooms the PPS phase offset 676 * and leaves it in a handy spot for the seconds overflow routine. The 677 * frequency loop averages successive PPS phase differences and 678 * calculates the PPS frequency offset, which is also processed by the 679 * seconds overflow routine. The code requires the caller to capture the 680 * time and architecture-dependent hardware counter values in 681 * nanoseconds at the on-time PPS signal transition. 682 * 683 * Note that, on some Unix systems this routine runs at an interrupt 684 * priority level higher than the timer interrupt routine hardclock(). 685 * Therefore, the variables used are distinct from the hardclock() 686 * variables, except for the actual time and frequency variables, which 687 * are determined by this routine and updated atomically. 688 */ 689 void 690 hardpps(struct timespec *tsp, long nsec) 691 { 692 long u_sec, u_nsec, v_nsec; /* temps */ 693 l_fp ftemp; 694 695 /* 696 * The signal is first processed by a range gate and frequency 697 * discriminator. The range gate rejects noise spikes outside 698 * the range +-500 us. The frequency discriminator rejects input 699 * signals with apparent frequency outside the range 1 +-500 700 * PPM. If two hits occur in the same second, we ignore the 701 * later hit; if not and a hit occurs outside the range gate, 702 * keep the later hit for later comparison, but do not process 703 * it. 704 */ 705 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 706 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 707 pps_valid = PPS_VALID; 708 u_sec = tsp->tv_sec; 709 u_nsec = tsp->tv_nsec; 710 if (u_nsec >= (NANOSECOND >> 1)) { 711 u_nsec -= NANOSECOND; 712 u_sec++; 713 } 714 v_nsec = u_nsec - pps_tf[0].tv_nsec; 715 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 716 MAXFREQ) 717 return; 718 pps_tf[2] = pps_tf[1]; 719 pps_tf[1] = pps_tf[0]; 720 pps_tf[0].tv_sec = u_sec; 721 pps_tf[0].tv_nsec = u_nsec; 722 723 /* 724 * Compute the difference between the current and previous 725 * counter values. If the difference exceeds 0.5 s, assume it 726 * has wrapped around, so correct 1.0 s. If the result exceeds 727 * the tick interval, the sample point has crossed a tick 728 * boundary during the last second, so correct the tick. Very 729 * intricate. 730 */ 731 u_nsec = nsec; 732 if (u_nsec > (NANOSECOND >> 1)) 733 u_nsec -= NANOSECOND; 734 else if (u_nsec < -(NANOSECOND >> 1)) 735 u_nsec += NANOSECOND; 736 pps_fcount += u_nsec; 737 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 738 return; 739 time_status &= ~STA_PPSJITTER; 740 741 /* 742 * A three-stage median filter is used to help denoise the PPS 743 * time. The median sample becomes the time offset estimate; the 744 * difference between the other two samples becomes the time 745 * dispersion (jitter) estimate. 746 */ 747 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 748 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 749 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 750 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 751 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 752 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 753 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 754 } else { 755 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 756 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 757 } 758 } else { 759 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 760 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 761 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 762 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 763 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 764 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 765 } else { 766 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 767 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 768 } 769 } 770 771 /* 772 * Nominal jitter is due to PPS signal noise and interrupt 773 * latency. If it exceeds the popcorn threshold, the sample is 774 * discarded. otherwise, if so enabled, the time offset is 775 * updated. We can tolerate a modest loss of data here without 776 * much degrading time accuracy. 777 */ 778 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 779 time_status |= STA_PPSJITTER; 780 pps_jitcnt++; 781 } else if (time_status & STA_PPSTIME) { 782 time_monitor = -v_nsec; 783 L_LINT(time_offset, time_monitor); 784 } 785 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 786 u_sec = pps_tf[0].tv_sec - pps_lastsec; 787 if (u_sec < (1 << pps_shift)) 788 return; 789 790 /* 791 * At the end of the calibration interval the difference between 792 * the first and last counter values becomes the scaled 793 * frequency. It will later be divided by the length of the 794 * interval to determine the frequency update. If the frequency 795 * exceeds a sanity threshold, or if the actual calibration 796 * interval is not equal to the expected length, the data are 797 * discarded. We can tolerate a modest loss of data here without 798 * much degrading frequency accuracy. 799 */ 800 pps_calcnt++; 801 v_nsec = -pps_fcount; 802 pps_lastsec = pps_tf[0].tv_sec; 803 pps_fcount = 0; 804 u_nsec = MAXFREQ << pps_shift; 805 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 806 pps_shift)) { 807 time_status |= STA_PPSERROR; 808 pps_errcnt++; 809 return; 810 } 811 812 /* 813 * Here the raw frequency offset and wander (stability) is 814 * calculated. If the wander is less than the wander threshold 815 * for four consecutive averaging intervals, the interval is 816 * doubled; if it is greater than the threshold for four 817 * consecutive intervals, the interval is halved. The scaled 818 * frequency offset is converted to frequency offset. The 819 * stability metric is calculated as the average of recent 820 * frequency changes, but is used only for performance 821 * monitoring. 822 */ 823 L_LINT(ftemp, v_nsec); 824 L_RSHIFT(ftemp, pps_shift); 825 L_SUB(ftemp, pps_freq); 826 u_nsec = L_GINT(ftemp); 827 if (u_nsec > PPS_MAXWANDER) { 828 L_LINT(ftemp, PPS_MAXWANDER); 829 pps_intcnt--; 830 time_status |= STA_PPSWANDER; 831 pps_stbcnt++; 832 } else if (u_nsec < -PPS_MAXWANDER) { 833 L_LINT(ftemp, -PPS_MAXWANDER); 834 pps_intcnt--; 835 time_status |= STA_PPSWANDER; 836 pps_stbcnt++; 837 } else { 838 pps_intcnt++; 839 } 840 if (pps_intcnt >= 4) { 841 pps_intcnt = 4; 842 if (pps_shift < pps_shiftmax) { 843 pps_shift++; 844 pps_intcnt = 0; 845 } 846 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 847 pps_intcnt = -4; 848 if (pps_shift > PPS_FAVG) { 849 pps_shift--; 850 pps_intcnt = 0; 851 } 852 } 853 if (u_nsec < 0) 854 u_nsec = -u_nsec; 855 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 856 857 /* 858 * The PPS frequency is recalculated and clamped to the maximum 859 * MAXFREQ. If enabled, the system clock frequency is updated as 860 * well. 861 */ 862 L_ADD(pps_freq, ftemp); 863 u_nsec = L_GINT(pps_freq); 864 if (u_nsec > MAXFREQ) 865 L_LINT(pps_freq, MAXFREQ); 866 else if (u_nsec < -MAXFREQ) 867 L_LINT(pps_freq, -MAXFREQ); 868 if (time_status & STA_PPSFREQ) 869 time_freq = pps_freq; 870 } 871 #endif /* PPS_SYNC */ 872