1 /*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-2001 * 4 * * 5 * Permission to use, copy, modify, and distribute this software and * 6 * its documentation for any purpose and without fee is hereby * 7 * granted, provided that the above copyright notice appears in all * 8 * copies and that both the copyright notice and this permission * 9 * notice appear in supporting documentation, and that the name * 10 * University of Delaware not be used in advertising or publicity * 11 * pertaining to distribution of the software without specific, * 12 * written prior permission. The University of Delaware makes no * 13 * representations about the suitability this software for any * 14 * purpose. It is provided "as is" without express or implied * 15 * warranty. * 16 * * 17 **********************************************************************/ 18 19 /* 20 * Adapted from the original sources for FreeBSD and timecounters by: 21 * Poul-Henning Kamp <phk@FreeBSD.org>. 22 * 23 * The 32bit version of the "LP" macros seems a bit past its "sell by" 24 * date so I have retained only the 64bit version and included it directly 25 * in this file. 26 * 27 * Only minor changes done to interface with the timecounters over in 28 * sys/kern/kern_clock.c. Some of the comments below may be (even more) 29 * confusing and/or plain wrong in that context. 30 * 31 * $FreeBSD: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $ 32 * $DragonFly: src/sys/kern/kern_ntptime.c,v 1.13 2007/04/30 07:18:53 dillon Exp $ 33 */ 34 35 #include "opt_ntp.h" 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/sysproto.h> 40 #include <sys/kernel.h> 41 #include <sys/proc.h> 42 #include <sys/priv.h> 43 #include <sys/time.h> 44 #include <sys/timex.h> 45 #include <sys/timepps.h> 46 #include <sys/sysctl.h> 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 long 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 #ifdef PPS_SYNC 156 /* 157 * The following variables are used when a pulse-per-second (PPS) signal 158 * is available and connected via a modem control lead. They establish 159 * the engineering parameters of the clock discipline loop when 160 * controlled by the PPS signal. 161 */ 162 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 163 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 164 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 165 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 166 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 167 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 168 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 169 170 static struct timespec pps_tf[3]; /* phase median filter */ 171 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 172 static long pps_fcount; /* frequency accumulator */ 173 static long pps_jitter; /* nominal jitter (ns) */ 174 static long pps_stabil; /* nominal stability (scaled ns/s) */ 175 static long pps_lastsec; /* time at last calibration (s) */ 176 static int pps_valid; /* signal watchdog counter */ 177 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 178 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 179 static int pps_intcnt; /* wander counter */ 180 181 /* 182 * PPS signal quality monitors 183 */ 184 static long pps_calcnt; /* calibration intervals */ 185 static long pps_jitcnt; /* jitter limit exceeded */ 186 static long pps_stbcnt; /* stability limit exceeded */ 187 static long pps_errcnt; /* calibration errors */ 188 #endif /* PPS_SYNC */ 189 /* 190 * End of phase/frequency-lock loop (PLL/FLL) definitions 191 */ 192 193 static void ntp_init(void); 194 static void hardupdate(long offset); 195 196 /* 197 * ntp_gettime() - NTP user application interface 198 * 199 * See the timex.h header file for synopsis and API description. Note 200 * that the TAI offset is returned in the ntvtimeval.tai structure 201 * member. 202 */ 203 static int 204 ntp_sysctl(SYSCTL_HANDLER_ARGS) 205 { 206 struct ntptimeval ntv; /* temporary structure */ 207 struct timespec atv; /* nanosecond time */ 208 209 nanotime(&atv); 210 ntv.time.tv_sec = atv.tv_sec; 211 ntv.time.tv_nsec = atv.tv_nsec; 212 ntv.maxerror = time_maxerror; 213 ntv.esterror = time_esterror; 214 ntv.tai = time_tai; 215 ntv.time_state = time_state; 216 217 /* 218 * Status word error decode. If any of these conditions occur, 219 * an error is returned, instead of the status word. Most 220 * applications will care only about the fact the system clock 221 * may not be trusted, not about the details. 222 * 223 * Hardware or software error 224 */ 225 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 226 227 /* 228 * PPS signal lost when either time or frequency synchronization 229 * requested 230 */ 231 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 232 !(time_status & STA_PPSSIGNAL)) || 233 234 /* 235 * PPS jitter exceeded when time synchronization requested 236 */ 237 (time_status & STA_PPSTIME && 238 time_status & STA_PPSJITTER) || 239 240 /* 241 * PPS wander exceeded or calibration error when frequency 242 * synchronization requested 243 */ 244 (time_status & STA_PPSFREQ && 245 time_status & (STA_PPSWANDER | STA_PPSERROR))) 246 ntv.time_state = TIME_ERROR; 247 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 248 } 249 250 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 251 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 252 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 253 254 #ifdef PPS_SYNC 255 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 258 259 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 260 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 261 #endif 262 /* 263 * ntp_adjtime() - NTP daemon application interface 264 * 265 * See the timex.h header file for synopsis and API description. Note 266 * that the timex.constant structure member has a dual purpose to set 267 * the time constant and to set the TAI offset. 268 * 269 * MPALMOSTSAFE 270 */ 271 int 272 sys_ntp_adjtime(struct ntp_adjtime_args *uap) 273 { 274 struct thread *td = curthread; 275 struct timex ntv; /* temporary structure */ 276 long freq; /* frequency ns/s) */ 277 int modes; /* mode bits from structure */ 278 int error; 279 280 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 281 if (error) 282 return(error); 283 284 /* 285 * Update selected clock variables - only the superuser can 286 * change anything. Note that there is no error checking here on 287 * the assumption the superuser should know what it is doing. 288 * Note that either the time constant or TAI offset are loaded 289 * from the ntv.constant member, depending on the mode bits. If 290 * the STA_PLL bit in the status word is cleared, the state and 291 * status words are reset to the initial values at boot. 292 */ 293 modes = ntv.modes; 294 if (modes) 295 error = priv_check(td, PRIV_NTP_ADJTIME); 296 if (error) 297 return (error); 298 299 get_mplock(); 300 crit_enter(); 301 if (modes & MOD_MAXERROR) 302 time_maxerror = ntv.maxerror; 303 if (modes & MOD_ESTERROR) 304 time_esterror = ntv.esterror; 305 if (modes & MOD_STATUS) { 306 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 307 time_state = TIME_OK; 308 time_status = STA_UNSYNC; 309 #ifdef PPS_SYNC 310 pps_shift = PPS_FAVG; 311 #endif /* PPS_SYNC */ 312 } 313 time_status &= STA_RONLY; 314 time_status |= ntv.status & ~STA_RONLY; 315 } 316 if (modes & MOD_TIMECONST) { 317 if (ntv.constant < 0) 318 time_constant = 0; 319 else if (ntv.constant > MAXTC) 320 time_constant = MAXTC; 321 else 322 time_constant = ntv.constant; 323 } 324 if (modes & MOD_TAI) { 325 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 326 time_tai = ntv.constant; 327 } 328 #ifdef PPS_SYNC 329 if (modes & MOD_PPSMAX) { 330 if (ntv.shift < PPS_FAVG) 331 pps_shiftmax = PPS_FAVG; 332 else if (ntv.shift > PPS_FAVGMAX) 333 pps_shiftmax = PPS_FAVGMAX; 334 else 335 pps_shiftmax = ntv.shift; 336 } 337 #endif /* PPS_SYNC */ 338 if (modes & MOD_NANO) 339 time_status |= STA_NANO; 340 if (modes & MOD_MICRO) 341 time_status &= ~STA_NANO; 342 if (modes & MOD_CLKB) 343 time_status |= STA_CLK; 344 if (modes & MOD_CLKA) 345 time_status &= ~STA_CLK; 346 if (modes & MOD_OFFSET) { 347 if (time_status & STA_NANO) 348 hardupdate(ntv.offset); 349 else 350 hardupdate(ntv.offset * 1000); 351 } 352 /* 353 * Note: the userland specified frequency is in seconds per second 354 * times 65536e+6. Multiply by a thousand and divide by 65336 to 355 * get nanoseconds. 356 */ 357 if (modes & MOD_FREQUENCY) { 358 freq = (ntv.freq * 1000LL) >> 16; 359 if (freq > MAXFREQ) 360 L_LINT(time_freq, MAXFREQ); 361 else if (freq < -MAXFREQ) 362 L_LINT(time_freq, -MAXFREQ); 363 else 364 L_LINT(time_freq, freq); 365 #ifdef PPS_SYNC 366 pps_freq = time_freq; 367 #endif /* PPS_SYNC */ 368 } 369 370 /* 371 * Retrieve all clock variables. Note that the TAI offset is 372 * returned only by ntp_gettime(); 373 */ 374 if (time_status & STA_NANO) 375 ntv.offset = time_monitor; 376 else 377 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 378 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 379 ntv.maxerror = time_maxerror; 380 ntv.esterror = time_esterror; 381 ntv.status = time_status; 382 ntv.constant = time_constant; 383 if (time_status & STA_NANO) 384 ntv.precision = time_precision; 385 else 386 ntv.precision = time_precision / 1000; 387 ntv.tolerance = MAXFREQ * SCALE_PPM; 388 #ifdef PPS_SYNC 389 ntv.shift = pps_shift; 390 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 391 if (time_status & STA_NANO) 392 ntv.jitter = pps_jitter; 393 else 394 ntv.jitter = pps_jitter / 1000; 395 ntv.stabil = pps_stabil; 396 ntv.calcnt = pps_calcnt; 397 ntv.errcnt = pps_errcnt; 398 ntv.jitcnt = pps_jitcnt; 399 ntv.stbcnt = pps_stbcnt; 400 #endif /* PPS_SYNC */ 401 crit_exit(); 402 rel_mplock(); 403 404 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 405 if (error) 406 return (error); 407 408 /* 409 * Status word error decode. See comments in 410 * ntp_gettime() routine. 411 */ 412 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 413 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 414 !(time_status & STA_PPSSIGNAL)) || 415 (time_status & STA_PPSTIME && 416 time_status & STA_PPSJITTER) || 417 (time_status & STA_PPSFREQ && 418 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 419 uap->sysmsg_result = TIME_ERROR; 420 } else { 421 uap->sysmsg_result = time_state; 422 } 423 return (error); 424 } 425 426 /* 427 * second_overflow() - called after ntp_tick_adjust() 428 * 429 * This routine is ordinarily called from hardclock() whenever the seconds 430 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 431 * to the total adjustment to make over the next second in (ns << 32). 432 * 433 * This routine is only called by cpu #0. 434 */ 435 int 436 ntp_update_second(time_t newsec, int64_t *nsec_adj) 437 { 438 l_fp ftemp; /* 32/64-bit temporary */ 439 int adjsec = 0; 440 441 /* 442 * On rollover of the second both the nanosecond and microsecond 443 * clocks are updated and the state machine cranked as 444 * necessary. The phase adjustment to be used for the next 445 * second is calculated and the maximum error is increased by 446 * the tolerance. 447 */ 448 time_maxerror += MAXFREQ / 1000; 449 450 /* 451 * Leap second processing. If in leap-insert state at 452 * the end of the day, the system clock is set back one 453 * second; if in leap-delete state, the system clock is 454 * set ahead one second. The nano_time() routine or 455 * external clock driver will insure that reported time 456 * is always monotonic. 457 */ 458 switch (time_state) { 459 460 /* 461 * No warning. 462 */ 463 case TIME_OK: 464 if (time_status & STA_INS) 465 time_state = TIME_INS; 466 else if (time_status & STA_DEL) 467 time_state = TIME_DEL; 468 break; 469 470 /* 471 * Insert second 23:59:60 following second 472 * 23:59:59. 473 */ 474 case TIME_INS: 475 if (!(time_status & STA_INS)) 476 time_state = TIME_OK; 477 else if ((newsec) % 86400 == 0) { 478 --adjsec; 479 time_state = TIME_OOP; 480 } 481 break; 482 483 /* 484 * Delete second 23:59:59. 485 */ 486 case TIME_DEL: 487 if (!(time_status & STA_DEL)) 488 time_state = TIME_OK; 489 else if (((newsec) + 1) % 86400 == 0) { 490 ++adjsec; 491 time_tai--; 492 time_state = TIME_WAIT; 493 } 494 break; 495 496 /* 497 * Insert second in progress. 498 */ 499 case TIME_OOP: 500 time_tai++; 501 time_state = TIME_WAIT; 502 break; 503 504 /* 505 * Wait for status bits to clear. 506 */ 507 case TIME_WAIT: 508 if (!(time_status & (STA_INS | STA_DEL))) 509 time_state = TIME_OK; 510 } 511 512 /* 513 * time_offset represents the total time adjustment we wish to 514 * make (over no particular period of time). time_freq represents 515 * the frequency compensation we wish to apply. 516 * 517 * time_adj represents the total adjustment we wish to make over 518 * one full second. hardclock usually applies this adjustment in 519 * time_adj / hz jumps, hz times a second. 520 */ 521 ftemp = time_offset; 522 #ifdef PPS_SYNC 523 /* XXX even if PPS signal dies we should finish adjustment ? */ 524 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL)) 525 L_RSHIFT(ftemp, pps_shift); 526 else 527 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 528 #else 529 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 530 #endif /* PPS_SYNC */ 531 time_adj = ftemp; /* adjustment for part of the offset */ 532 L_SUB(time_offset, ftemp); 533 L_ADD(time_adj, time_freq); /* add frequency correction */ 534 *nsec_adj = time_adj; 535 #ifdef PPS_SYNC 536 if (pps_valid > 0) 537 pps_valid--; 538 else 539 time_status &= ~STA_PPSSIGNAL; 540 #endif /* PPS_SYNC */ 541 return(adjsec); 542 } 543 544 /* 545 * ntp_init() - initialize variables and structures 546 * 547 * This routine must be called after the kernel variables hz and tick 548 * are set or changed and before the next tick interrupt. In this 549 * particular implementation, these values are assumed set elsewhere in 550 * the kernel. The design allows the clock frequency and tick interval 551 * to be changed while the system is running. So, this routine should 552 * probably be integrated with the code that does that. 553 */ 554 static void 555 ntp_init(void) 556 { 557 558 /* 559 * The following variable must be initialized any time the 560 * kernel variable hz is changed. 561 */ 562 time_tick = NANOSECOND / hz; 563 564 /* 565 * The following variables are initialized only at startup. Only 566 * those structures not cleared by the compiler need to be 567 * initialized, and these only in the simulator. In the actual 568 * kernel, any nonzero values here will quickly evaporate. 569 */ 570 L_CLR(time_offset); 571 L_CLR(time_freq); 572 #ifdef PPS_SYNC 573 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 574 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 575 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 576 pps_fcount = 0; 577 L_CLR(pps_freq); 578 #endif /* PPS_SYNC */ 579 } 580 581 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 582 583 /* 584 * hardupdate() - local clock update 585 * 586 * This routine is called by ntp_adjtime() to update the local clock 587 * phase and frequency. The implementation is of an adaptive-parameter, 588 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 589 * time and frequency offset estimates for each call. If the kernel PPS 590 * discipline code is configured (PPS_SYNC), the PPS signal itself 591 * determines the new time offset, instead of the calling argument. 592 * Presumably, calls to ntp_adjtime() occur only when the caller 593 * believes the local clock is valid within some bound (+-128 ms with 594 * NTP). If the caller's time is far different than the PPS time, an 595 * argument will ensue, and it's not clear who will lose. 596 * 597 * For uncompensated quartz crystal oscillators and nominal update 598 * intervals less than 256 s, operation should be in phase-lock mode, 599 * where the loop is disciplined to phase. For update intervals greater 600 * than 1024 s, operation should be in frequency-lock mode, where the 601 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 602 * is selected by the STA_MODE status bit. 603 */ 604 static void 605 hardupdate(long offset) 606 { 607 long mtemp; 608 l_fp ftemp; 609 globaldata_t gd; 610 611 gd = mycpu; 612 613 /* 614 * Select how the phase is to be controlled and from which 615 * source. If the PPS signal is present and enabled to 616 * discipline the time, the PPS offset is used; otherwise, the 617 * argument offset is used. 618 */ 619 if (!(time_status & STA_PLL)) 620 return; 621 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 622 if (offset > MAXPHASE) 623 time_monitor = MAXPHASE; 624 else if (offset < -MAXPHASE) 625 time_monitor = -MAXPHASE; 626 else 627 time_monitor = offset; 628 L_LINT(time_offset, time_monitor); 629 } 630 631 /* 632 * Select how the frequency is to be controlled and in which 633 * mode (PLL or FLL). If the PPS signal is present and enabled 634 * to discipline the frequency, the PPS frequency is used; 635 * otherwise, the argument offset is used to compute it. 636 * 637 * gd_time_seconds is basically an uncompensated uptime. We use 638 * this for consistency. 639 */ 640 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 641 time_reftime = time_second; 642 return; 643 } 644 if (time_status & STA_FREQHOLD || time_reftime == 0) 645 time_reftime = time_second; 646 mtemp = time_second - time_reftime; 647 L_LINT(ftemp, time_monitor); 648 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 649 L_MPY(ftemp, mtemp); 650 L_ADD(time_freq, ftemp); 651 time_status &= ~STA_MODE; 652 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 653 L_LINT(ftemp, (time_monitor << 4) / mtemp); 654 L_RSHIFT(ftemp, SHIFT_FLL + 4); 655 L_ADD(time_freq, ftemp); 656 time_status |= STA_MODE; 657 } 658 time_reftime = time_second; 659 if (L_GINT(time_freq) > MAXFREQ) 660 L_LINT(time_freq, MAXFREQ); 661 else if (L_GINT(time_freq) < -MAXFREQ) 662 L_LINT(time_freq, -MAXFREQ); 663 } 664 665 #ifdef PPS_SYNC 666 /* 667 * hardpps() - discipline CPU clock oscillator to external PPS signal 668 * 669 * This routine is called at each PPS interrupt in order to discipline 670 * the CPU clock oscillator to the PPS signal. There are two independent 671 * first-order feedback loops, one for the phase, the other for the 672 * frequency. The phase loop measures and grooms the PPS phase offset 673 * and leaves it in a handy spot for the seconds overflow routine. The 674 * frequency loop averages successive PPS phase differences and 675 * calculates the PPS frequency offset, which is also processed by the 676 * seconds overflow routine. The code requires the caller to capture the 677 * time and architecture-dependent hardware counter values in 678 * nanoseconds at the on-time PPS signal transition. 679 * 680 * Note that, on some Unix systems this routine runs at an interrupt 681 * priority level higher than the timer interrupt routine hardclock(). 682 * Therefore, the variables used are distinct from the hardclock() 683 * variables, except for the actual time and frequency variables, which 684 * are determined by this routine and updated atomically. 685 */ 686 void 687 hardpps(struct timespec *tsp, long nsec) 688 { 689 long u_sec, u_nsec, v_nsec; /* temps */ 690 l_fp ftemp; 691 692 /* 693 * The signal is first processed by a range gate and frequency 694 * discriminator. The range gate rejects noise spikes outside 695 * the range +-500 us. The frequency discriminator rejects input 696 * signals with apparent frequency outside the range 1 +-500 697 * PPM. If two hits occur in the same second, we ignore the 698 * later hit; if not and a hit occurs outside the range gate, 699 * keep the later hit for later comparison, but do not process 700 * it. 701 */ 702 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 703 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 704 pps_valid = PPS_VALID; 705 u_sec = tsp->tv_sec; 706 u_nsec = tsp->tv_nsec; 707 if (u_nsec >= (NANOSECOND >> 1)) { 708 u_nsec -= NANOSECOND; 709 u_sec++; 710 } 711 v_nsec = u_nsec - pps_tf[0].tv_nsec; 712 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 713 MAXFREQ) 714 return; 715 pps_tf[2] = pps_tf[1]; 716 pps_tf[1] = pps_tf[0]; 717 pps_tf[0].tv_sec = u_sec; 718 pps_tf[0].tv_nsec = u_nsec; 719 720 /* 721 * Compute the difference between the current and previous 722 * counter values. If the difference exceeds 0.5 s, assume it 723 * has wrapped around, so correct 1.0 s. If the result exceeds 724 * the tick interval, the sample point has crossed a tick 725 * boundary during the last second, so correct the tick. Very 726 * intricate. 727 */ 728 u_nsec = nsec; 729 if (u_nsec > (NANOSECOND >> 1)) 730 u_nsec -= NANOSECOND; 731 else if (u_nsec < -(NANOSECOND >> 1)) 732 u_nsec += NANOSECOND; 733 pps_fcount += u_nsec; 734 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 735 return; 736 time_status &= ~STA_PPSJITTER; 737 738 /* 739 * A three-stage median filter is used to help denoise the PPS 740 * time. The median sample becomes the time offset estimate; the 741 * difference between the other two samples becomes the time 742 * dispersion (jitter) estimate. 743 */ 744 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 745 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 746 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 747 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 748 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 749 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 750 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 751 } else { 752 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 753 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 754 } 755 } else { 756 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 757 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 758 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 759 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 760 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 761 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 762 } else { 763 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 764 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 765 } 766 } 767 768 /* 769 * Nominal jitter is due to PPS signal noise and interrupt 770 * latency. If it exceeds the popcorn threshold, the sample is 771 * discarded. otherwise, if so enabled, the time offset is 772 * updated. We can tolerate a modest loss of data here without 773 * much degrading time accuracy. 774 */ 775 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 776 time_status |= STA_PPSJITTER; 777 pps_jitcnt++; 778 } else if (time_status & STA_PPSTIME) { 779 time_monitor = -v_nsec; 780 L_LINT(time_offset, time_monitor); 781 } 782 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 783 u_sec = pps_tf[0].tv_sec - pps_lastsec; 784 if (u_sec < (1 << pps_shift)) 785 return; 786 787 /* 788 * At the end of the calibration interval the difference between 789 * the first and last counter values becomes the scaled 790 * frequency. It will later be divided by the length of the 791 * interval to determine the frequency update. If the frequency 792 * exceeds a sanity threshold, or if the actual calibration 793 * interval is not equal to the expected length, the data are 794 * discarded. We can tolerate a modest loss of data here without 795 * much degrading frequency accuracy. 796 */ 797 pps_calcnt++; 798 v_nsec = -pps_fcount; 799 pps_lastsec = pps_tf[0].tv_sec; 800 pps_fcount = 0; 801 u_nsec = MAXFREQ << pps_shift; 802 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 803 pps_shift)) { 804 time_status |= STA_PPSERROR; 805 pps_errcnt++; 806 return; 807 } 808 809 /* 810 * Here the raw frequency offset and wander (stability) is 811 * calculated. If the wander is less than the wander threshold 812 * for four consecutive averaging intervals, the interval is 813 * doubled; if it is greater than the threshold for four 814 * consecutive intervals, the interval is halved. The scaled 815 * frequency offset is converted to frequency offset. The 816 * stability metric is calculated as the average of recent 817 * frequency changes, but is used only for performance 818 * monitoring. 819 */ 820 L_LINT(ftemp, v_nsec); 821 L_RSHIFT(ftemp, pps_shift); 822 L_SUB(ftemp, pps_freq); 823 u_nsec = L_GINT(ftemp); 824 if (u_nsec > PPS_MAXWANDER) { 825 L_LINT(ftemp, PPS_MAXWANDER); 826 pps_intcnt--; 827 time_status |= STA_PPSWANDER; 828 pps_stbcnt++; 829 } else if (u_nsec < -PPS_MAXWANDER) { 830 L_LINT(ftemp, -PPS_MAXWANDER); 831 pps_intcnt--; 832 time_status |= STA_PPSWANDER; 833 pps_stbcnt++; 834 } else { 835 pps_intcnt++; 836 } 837 if (pps_intcnt >= 4) { 838 pps_intcnt = 4; 839 if (pps_shift < pps_shiftmax) { 840 pps_shift++; 841 pps_intcnt = 0; 842 } 843 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 844 pps_intcnt = -4; 845 if (pps_shift > PPS_FAVG) { 846 pps_shift--; 847 pps_intcnt = 0; 848 } 849 } 850 if (u_nsec < 0) 851 u_nsec = -u_nsec; 852 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 853 854 /* 855 * The PPS frequency is recalculated and clamped to the maximum 856 * MAXFREQ. If enabled, the system clock frequency is updated as 857 * well. 858 */ 859 L_ADD(pps_freq, ftemp); 860 u_nsec = L_GINT(pps_freq); 861 if (u_nsec > MAXFREQ) 862 L_LINT(pps_freq, MAXFREQ); 863 else if (u_nsec < -MAXFREQ) 864 L_LINT(pps_freq, -MAXFREQ); 865 if (time_status & STA_PPSFREQ) 866 time_freq = pps_freq; 867 } 868 #endif /* PPS_SYNC */ 869