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 1.9 2004/01/30 06:20:08 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/time.h> 43 #include <sys/timex.h> 44 #include <sys/timepps.h> 45 #include <sys/sysctl.h> 46 #include <sys/thread2.h> 47 48 /* 49 * Single-precision macros for 64-bit machines 50 */ 51 typedef long long l_fp; 52 #define L_ADD(v, u) ((v) += (u)) 53 #define L_SUB(v, u) ((v) -= (u)) 54 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 55 #define L_NEG(v) ((v) = -(v)) 56 #define L_RSHIFT(v, n) \ 57 do { \ 58 if ((v) < 0) \ 59 (v) = -(-(v) >> (n)); \ 60 else \ 61 (v) = (v) >> (n); \ 62 } while (0) 63 #define L_MPY(v, a) ((v) *= (a)) 64 #define L_CLR(v) ((v) = 0) 65 #define L_ISNEG(v) ((v) < 0) 66 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 67 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 68 69 /* 70 * Generic NTP kernel interface 71 * 72 * These routines constitute the Network Time Protocol (NTP) interfaces 73 * for user and daemon application programs. The ntp_gettime() routine 74 * provides the time, maximum error (synch distance) and estimated error 75 * (dispersion) to client user application programs. The ntp_adjtime() 76 * routine is used by the NTP daemon to adjust the system clock to an 77 * externally derived time. The time offset and related variables set by 78 * this routine are used by other routines in this module to adjust the 79 * phase and frequency of the clock discipline loop which controls the 80 * system clock. 81 * 82 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 83 * defined), the time at each tick interrupt is derived directly from 84 * the kernel time variable. When the kernel time is reckoned in 85 * microseconds, (NTP_NANO undefined), the time is derived from the 86 * kernel time variable together with a variable representing the 87 * leftover nanoseconds at the last tick interrupt. In either case, the 88 * current nanosecond time is reckoned from these values plus an 89 * interpolated value derived by the clock routines in another 90 * architecture-specific module. The interpolation can use either a 91 * dedicated counter or a processor cycle counter (PCC) implemented in 92 * some architectures. 93 * 94 * Note that all routines must run at priority splclock or higher. 95 */ 96 /* 97 * Phase/frequency-lock loop (PLL/FLL) definitions 98 * 99 * The nanosecond clock discipline uses two variable types, time 100 * variables and frequency variables. Both types are represented as 64- 101 * bit fixed-point quantities with the decimal point between two 32-bit 102 * halves. On a 32-bit machine, each half is represented as a single 103 * word and mathematical operations are done using multiple-precision 104 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 105 * used. 106 * 107 * A time variable is a signed 64-bit fixed-point number in ns and 108 * fraction. It represents the remaining time offset to be amortized 109 * over succeeding tick interrupts. The maximum time offset is about 110 * 0.5 s and the resolution is about 2.3e-10 ns. 111 * 112 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 113 * 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 1 114 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 * |s s s| ns | 116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 * | fraction | 118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 119 * 120 * A frequency variable is a signed 64-bit fixed-point number in ns/s 121 * and fraction. It represents the ns and fraction to be added to the 122 * kernel time variable at each second. The maximum frequency offset is 123 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 124 * 125 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 126 * 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 1 127 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 128 * |s s s s s s s s s s s s s| ns/s | 129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 * | fraction | 131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 */ 133 /* 134 * The following variables establish the state of the PLL/FLL and the 135 * residual time and frequency offset of the local clock. 136 */ 137 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 138 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 139 140 static int time_state = TIME_OK; /* clock state */ 141 static int time_status = STA_UNSYNC; /* clock status bits */ 142 static long time_tai; /* TAI offset (s) */ 143 static long time_monitor; /* last time offset scaled (ns) */ 144 static long time_constant; /* poll interval (shift) (s) */ 145 static long time_precision = 1; /* clock precision (ns) */ 146 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 147 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 148 static long time_reftime; /* time at last adjustment (s) */ 149 static long time_tick; /* nanoseconds per tick (ns) */ 150 static l_fp time_offset; /* time offset (ns) */ 151 static l_fp time_freq; /* frequency offset (ns/s) */ 152 static l_fp time_adj; /* tick adjust (ns/s) */ 153 154 #ifdef PPS_SYNC 155 /* 156 * The following variables are used when a pulse-per-second (PPS) signal 157 * is available and connected via a modem control lead. They establish 158 * the engineering parameters of the clock discipline loop when 159 * controlled by the PPS signal. 160 */ 161 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 162 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 163 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 164 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 165 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 166 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 167 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 168 169 static struct timespec pps_tf[3]; /* phase median filter */ 170 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 171 static long pps_fcount; /* frequency accumulator */ 172 static long pps_jitter; /* nominal jitter (ns) */ 173 static long pps_stabil; /* nominal stability (scaled ns/s) */ 174 static long pps_lastsec; /* time at last calibration (s) */ 175 static int pps_valid; /* signal watchdog counter */ 176 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 177 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 178 static int pps_intcnt; /* wander counter */ 179 180 /* 181 * PPS signal quality monitors 182 */ 183 static long pps_calcnt; /* calibration intervals */ 184 static long pps_jitcnt; /* jitter limit exceeded */ 185 static long pps_stbcnt; /* stability limit exceeded */ 186 static long pps_errcnt; /* calibration errors */ 187 #endif /* PPS_SYNC */ 188 /* 189 * End of phase/frequency-lock loop (PLL/FLL) definitions 190 */ 191 192 static void ntp_init(void); 193 static void hardupdate(long offset); 194 195 /* 196 * ntp_gettime() - NTP user application interface 197 * 198 * See the timex.h header file for synopsis and API description. Note 199 * that the TAI offset is returned in the ntvtimeval.tai structure 200 * member. 201 */ 202 static int 203 ntp_sysctl(SYSCTL_HANDLER_ARGS) 204 { 205 struct ntptimeval ntv; /* temporary structure */ 206 struct timespec atv; /* nanosecond time */ 207 208 nanotime(&atv); 209 ntv.time.tv_sec = atv.tv_sec; 210 ntv.time.tv_nsec = atv.tv_nsec; 211 ntv.maxerror = time_maxerror; 212 ntv.esterror = time_esterror; 213 ntv.tai = time_tai; 214 ntv.time_state = time_state; 215 216 /* 217 * Status word error decode. If any of these conditions occur, 218 * an error is returned, instead of the status word. Most 219 * applications will care only about the fact the system clock 220 * may not be trusted, not about the details. 221 * 222 * Hardware or software error 223 */ 224 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 225 226 /* 227 * PPS signal lost when either time or frequency synchronization 228 * requested 229 */ 230 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 231 !(time_status & STA_PPSSIGNAL)) || 232 233 /* 234 * PPS jitter exceeded when time synchronization requested 235 */ 236 (time_status & STA_PPSTIME && 237 time_status & STA_PPSJITTER) || 238 239 /* 240 * PPS wander exceeded or calibration error when frequency 241 * synchronization requested 242 */ 243 (time_status & STA_PPSFREQ && 244 time_status & (STA_PPSWANDER | STA_PPSERROR))) 245 ntv.time_state = TIME_ERROR; 246 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 247 } 248 249 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 250 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 251 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 252 253 #ifdef PPS_SYNC 254 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 255 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 257 258 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 259 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 260 #endif 261 /* 262 * ntp_adjtime() - NTP daemon application interface 263 * 264 * See the timex.h header file for synopsis and API description. Note 265 * that the timex.constant structure member has a dual purpose to set 266 * the time constant and to set the TAI offset. 267 */ 268 int 269 ntp_adjtime(struct ntp_adjtime_args *uap) 270 { 271 struct thread *td = curthread; 272 struct timex ntv; /* temporary structure */ 273 long freq; /* frequency ns/s) */ 274 int modes; /* mode bits from structure */ 275 int error; 276 277 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 278 if (error) 279 return(error); 280 281 /* 282 * Update selected clock variables - only the superuser can 283 * change anything. Note that there is no error checking here on 284 * the assumption the superuser should know what it is doing. 285 * Note that either the time constant or TAI offset are loaded 286 * from the ntv.constant member, depending on the mode bits. If 287 * the STA_PLL bit in the status word is cleared, the state and 288 * status words are reset to the initial values at boot. 289 */ 290 modes = ntv.modes; 291 if (modes) 292 error = suser(td); 293 if (error) 294 return (error); 295 crit_enter(); 296 if (modes & MOD_MAXERROR) 297 time_maxerror = ntv.maxerror; 298 if (modes & MOD_ESTERROR) 299 time_esterror = ntv.esterror; 300 if (modes & MOD_STATUS) { 301 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 302 time_state = TIME_OK; 303 time_status = STA_UNSYNC; 304 #ifdef PPS_SYNC 305 pps_shift = PPS_FAVG; 306 #endif /* PPS_SYNC */ 307 } 308 time_status &= STA_RONLY; 309 time_status |= ntv.status & ~STA_RONLY; 310 } 311 if (modes & MOD_TIMECONST) { 312 if (ntv.constant < 0) 313 time_constant = 0; 314 else if (ntv.constant > MAXTC) 315 time_constant = MAXTC; 316 else 317 time_constant = ntv.constant; 318 } 319 if (modes & MOD_TAI) { 320 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 321 time_tai = ntv.constant; 322 } 323 #ifdef PPS_SYNC 324 if (modes & MOD_PPSMAX) { 325 if (ntv.shift < PPS_FAVG) 326 pps_shiftmax = PPS_FAVG; 327 else if (ntv.shift > PPS_FAVGMAX) 328 pps_shiftmax = PPS_FAVGMAX; 329 else 330 pps_shiftmax = ntv.shift; 331 } 332 #endif /* PPS_SYNC */ 333 if (modes & MOD_NANO) 334 time_status |= STA_NANO; 335 if (modes & MOD_MICRO) 336 time_status &= ~STA_NANO; 337 if (modes & MOD_CLKB) 338 time_status |= STA_CLK; 339 if (modes & MOD_CLKA) 340 time_status &= ~STA_CLK; 341 if (modes & MOD_OFFSET) { 342 if (time_status & STA_NANO) 343 hardupdate(ntv.offset); 344 else 345 hardupdate(ntv.offset * 1000); 346 } 347 /* 348 * Note: the userland specified frequency is in seconds per second 349 * times 65536e+6. Multiply by a thousand and divide by 65336 to 350 * get nanoseconds. 351 */ 352 if (modes & MOD_FREQUENCY) { 353 freq = (ntv.freq * 1000LL) >> 16; 354 if (freq > MAXFREQ) 355 L_LINT(time_freq, MAXFREQ); 356 else if (freq < -MAXFREQ) 357 L_LINT(time_freq, -MAXFREQ); 358 else 359 L_LINT(time_freq, freq); 360 #ifdef PPS_SYNC 361 pps_freq = time_freq; 362 #endif /* PPS_SYNC */ 363 } 364 365 /* 366 * Retrieve all clock variables. Note that the TAI offset is 367 * returned only by ntp_gettime(); 368 */ 369 if (time_status & STA_NANO) 370 ntv.offset = time_monitor; 371 else 372 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 373 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 374 ntv.maxerror = time_maxerror; 375 ntv.esterror = time_esterror; 376 ntv.status = time_status; 377 ntv.constant = time_constant; 378 if (time_status & STA_NANO) 379 ntv.precision = time_precision; 380 else 381 ntv.precision = time_precision / 1000; 382 ntv.tolerance = MAXFREQ * SCALE_PPM; 383 #ifdef PPS_SYNC 384 ntv.shift = pps_shift; 385 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 386 if (time_status & STA_NANO) 387 ntv.jitter = pps_jitter; 388 else 389 ntv.jitter = pps_jitter / 1000; 390 ntv.stabil = pps_stabil; 391 ntv.calcnt = pps_calcnt; 392 ntv.errcnt = pps_errcnt; 393 ntv.jitcnt = pps_jitcnt; 394 ntv.stbcnt = pps_stbcnt; 395 #endif /* PPS_SYNC */ 396 crit_exit(); 397 398 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 399 if (error) 400 return (error); 401 402 /* 403 * Status word error decode. See comments in 404 * ntp_gettime() routine. 405 */ 406 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 407 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 408 !(time_status & STA_PPSSIGNAL)) || 409 (time_status & STA_PPSTIME && 410 time_status & STA_PPSJITTER) || 411 (time_status & STA_PPSFREQ && 412 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 413 uap->sysmsg_result = TIME_ERROR; 414 } else { 415 uap->sysmsg_result = time_state; 416 } 417 return (error); 418 } 419 420 /* 421 * second_overflow() - called after ntp_tick_adjust() 422 * 423 * This routine is ordinarily called from hardclock() whenever the seconds 424 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 425 * to the total adjustment to make over the next second in (ns << 32). 426 */ 427 int 428 ntp_update_second(time_t newsec, int64_t *nsec_adj) 429 { 430 l_fp ftemp; /* 32/64-bit temporary */ 431 int adjsec = 0; 432 433 /* 434 * On rollover of the second both the nanosecond and microsecond 435 * clocks are updated and the state machine cranked as 436 * necessary. The phase adjustment to be used for the next 437 * second is calculated and the maximum error is increased by 438 * the tolerance. 439 */ 440 time_maxerror += MAXFREQ / 1000; 441 442 /* 443 * Leap second processing. If in leap-insert state at 444 * the end of the day, the system clock is set back one 445 * second; if in leap-delete state, the system clock is 446 * set ahead one second. The nano_time() routine or 447 * external clock driver will insure that reported time 448 * is always monotonic. 449 */ 450 switch (time_state) { 451 452 /* 453 * No warning. 454 */ 455 case TIME_OK: 456 if (time_status & STA_INS) 457 time_state = TIME_INS; 458 else if (time_status & STA_DEL) 459 time_state = TIME_DEL; 460 break; 461 462 /* 463 * Insert second 23:59:60 following second 464 * 23:59:59. 465 */ 466 case TIME_INS: 467 if (!(time_status & STA_INS)) 468 time_state = TIME_OK; 469 else if ((newsec) % 86400 == 0) { 470 --adjsec; 471 time_state = TIME_OOP; 472 } 473 break; 474 475 /* 476 * Delete second 23:59:59. 477 */ 478 case TIME_DEL: 479 if (!(time_status & STA_DEL)) 480 time_state = TIME_OK; 481 else if (((newsec) + 1) % 86400 == 0) { 482 ++adjsec; 483 time_tai--; 484 time_state = TIME_WAIT; 485 } 486 break; 487 488 /* 489 * Insert second in progress. 490 */ 491 case TIME_OOP: 492 time_tai++; 493 time_state = TIME_WAIT; 494 break; 495 496 /* 497 * Wait for status bits to clear. 498 */ 499 case TIME_WAIT: 500 if (!(time_status & (STA_INS | STA_DEL))) 501 time_state = TIME_OK; 502 } 503 504 /* 505 * time_offset represents the total time adjustment we wish to 506 * make (over no particular period of time). time_freq represents 507 * the frequency compensation we wish to apply. 508 * 509 * time_adj represents the total adjustment we wish to make over 510 * one full second. hardclock usually applies this adjustment in 511 * time_adj / hz jumps, hz times a second. 512 */ 513 ftemp = time_offset; 514 #ifdef PPS_SYNC 515 /* XXX even if PPS signal dies we should finish adjustment ? */ 516 if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL)) 517 L_RSHIFT(ftemp, pps_shift); 518 else 519 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 520 #else 521 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 522 #endif /* PPS_SYNC */ 523 time_adj = ftemp; /* adjustment for part of the offset */ 524 L_SUB(time_offset, ftemp); 525 L_ADD(time_adj, time_freq); /* add frequency correction */ 526 *nsec_adj = time_adj; 527 #ifdef PPS_SYNC 528 if (pps_valid > 0) 529 pps_valid--; 530 else 531 time_status &= ~STA_PPSSIGNAL; 532 #endif /* PPS_SYNC */ 533 return(adjsec); 534 } 535 536 /* 537 * ntp_init() - initialize variables and structures 538 * 539 * This routine must be called after the kernel variables hz and tick 540 * are set or changed and before the next tick interrupt. In this 541 * particular implementation, these values are assumed set elsewhere in 542 * the kernel. The design allows the clock frequency and tick interval 543 * to be changed while the system is running. So, this routine should 544 * probably be integrated with the code that does that. 545 */ 546 static void 547 ntp_init() 548 { 549 550 /* 551 * The following variable must be initialized any time the 552 * kernel variable hz is changed. 553 */ 554 time_tick = NANOSECOND / hz; 555 556 /* 557 * The following variables are initialized only at startup. Only 558 * those structures not cleared by the compiler need to be 559 * initialized, and these only in the simulator. In the actual 560 * kernel, any nonzero values here will quickly evaporate. 561 */ 562 L_CLR(time_offset); 563 L_CLR(time_freq); 564 #ifdef PPS_SYNC 565 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 566 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 567 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 568 pps_fcount = 0; 569 L_CLR(pps_freq); 570 #endif /* PPS_SYNC */ 571 } 572 573 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 574 575 /* 576 * hardupdate() - local clock update 577 * 578 * This routine is called by ntp_adjtime() to update the local clock 579 * phase and frequency. The implementation is of an adaptive-parameter, 580 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 581 * time and frequency offset estimates for each call. If the kernel PPS 582 * discipline code is configured (PPS_SYNC), the PPS signal itself 583 * determines the new time offset, instead of the calling argument. 584 * Presumably, calls to ntp_adjtime() occur only when the caller 585 * believes the local clock is valid within some bound (+-128 ms with 586 * NTP). If the caller's time is far different than the PPS time, an 587 * argument will ensue, and it's not clear who will lose. 588 * 589 * For uncompensated quartz crystal oscillators and nominal update 590 * intervals less than 256 s, operation should be in phase-lock mode, 591 * where the loop is disciplined to phase. For update intervals greater 592 * than 1024 s, operation should be in frequency-lock mode, where the 593 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 594 * is selected by the STA_MODE status bit. 595 */ 596 static void 597 hardupdate(offset) 598 long offset; /* clock offset (ns) */ 599 { 600 long mtemp; 601 l_fp ftemp; 602 globaldata_t gd; 603 604 gd = mycpu; 605 606 /* 607 * Select how the phase is to be controlled and from which 608 * source. If the PPS signal is present and enabled to 609 * discipline the time, the PPS offset is used; otherwise, the 610 * argument offset is used. 611 */ 612 if (!(time_status & STA_PLL)) 613 return; 614 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 615 if (offset > MAXPHASE) 616 time_monitor = MAXPHASE; 617 else if (offset < -MAXPHASE) 618 time_monitor = -MAXPHASE; 619 else 620 time_monitor = offset; 621 L_LINT(time_offset, time_monitor); 622 } 623 624 /* 625 * Select how the frequency is to be controlled and in which 626 * mode (PLL or FLL). If the PPS signal is present and enabled 627 * to discipline the frequency, the PPS frequency is used; 628 * otherwise, the argument offset is used to compute it. 629 * 630 * gd_time_seconds is basically an uncompensated uptime. We use 631 * this for consistency. 632 */ 633 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 634 time_reftime = time_second; 635 return; 636 } 637 if (time_status & STA_FREQHOLD || time_reftime == 0) 638 time_reftime = time_second; 639 mtemp = time_second - time_reftime; 640 L_LINT(ftemp, time_monitor); 641 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 642 L_MPY(ftemp, mtemp); 643 L_ADD(time_freq, ftemp); 644 time_status &= ~STA_MODE; 645 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 646 L_LINT(ftemp, (time_monitor << 4) / mtemp); 647 L_RSHIFT(ftemp, SHIFT_FLL + 4); 648 L_ADD(time_freq, ftemp); 649 time_status |= STA_MODE; 650 } 651 time_reftime = time_second; 652 if (L_GINT(time_freq) > MAXFREQ) 653 L_LINT(time_freq, MAXFREQ); 654 else if (L_GINT(time_freq) < -MAXFREQ) 655 L_LINT(time_freq, -MAXFREQ); 656 } 657 658 #ifdef PPS_SYNC 659 /* 660 * hardpps() - discipline CPU clock oscillator to external PPS signal 661 * 662 * This routine is called at each PPS interrupt in order to discipline 663 * the CPU clock oscillator to the PPS signal. There are two independent 664 * first-order feedback loops, one for the phase, the other for the 665 * frequency. The phase loop measures and grooms the PPS phase offset 666 * and leaves it in a handy spot for the seconds overflow routine. The 667 * frequency loop averages successive PPS phase differences and 668 * calculates the PPS frequency offset, which is also processed by the 669 * seconds overflow routine. The code requires the caller to capture the 670 * time and architecture-dependent hardware counter values in 671 * nanoseconds at the on-time PPS signal transition. 672 * 673 * Note that, on some Unix systems this routine runs at an interrupt 674 * priority level higher than the timer interrupt routine hardclock(). 675 * Therefore, the variables used are distinct from the hardclock() 676 * variables, except for the actual time and frequency variables, which 677 * are determined by this routine and updated atomically. 678 */ 679 void 680 hardpps(tsp, nsec) 681 struct timespec *tsp; /* time at PPS */ 682 long nsec; /* hardware counter at PPS */ 683 { 684 long u_sec, u_nsec, v_nsec; /* temps */ 685 l_fp ftemp; 686 687 /* 688 * The signal is first processed by a range gate and frequency 689 * discriminator. The range gate rejects noise spikes outside 690 * the range +-500 us. The frequency discriminator rejects input 691 * signals with apparent frequency outside the range 1 +-500 692 * PPM. If two hits occur in the same second, we ignore the 693 * later hit; if not and a hit occurs outside the range gate, 694 * keep the later hit for later comparison, but do not process 695 * it. 696 */ 697 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 698 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 699 pps_valid = PPS_VALID; 700 u_sec = tsp->tv_sec; 701 u_nsec = tsp->tv_nsec; 702 if (u_nsec >= (NANOSECOND >> 1)) { 703 u_nsec -= NANOSECOND; 704 u_sec++; 705 } 706 v_nsec = u_nsec - pps_tf[0].tv_nsec; 707 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 708 MAXFREQ) 709 return; 710 pps_tf[2] = pps_tf[1]; 711 pps_tf[1] = pps_tf[0]; 712 pps_tf[0].tv_sec = u_sec; 713 pps_tf[0].tv_nsec = u_nsec; 714 715 /* 716 * Compute the difference between the current and previous 717 * counter values. If the difference exceeds 0.5 s, assume it 718 * has wrapped around, so correct 1.0 s. If the result exceeds 719 * the tick interval, the sample point has crossed a tick 720 * boundary during the last second, so correct the tick. Very 721 * intricate. 722 */ 723 u_nsec = nsec; 724 if (u_nsec > (NANOSECOND >> 1)) 725 u_nsec -= NANOSECOND; 726 else if (u_nsec < -(NANOSECOND >> 1)) 727 u_nsec += NANOSECOND; 728 pps_fcount += u_nsec; 729 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 730 return; 731 time_status &= ~STA_PPSJITTER; 732 733 /* 734 * A three-stage median filter is used to help denoise the PPS 735 * time. The median sample becomes the time offset estimate; the 736 * difference between the other two samples becomes the time 737 * dispersion (jitter) estimate. 738 */ 739 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 740 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 741 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 742 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 743 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 744 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 745 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 746 } else { 747 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 748 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 749 } 750 } else { 751 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 752 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 753 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 754 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 755 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 756 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 757 } else { 758 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 759 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 760 } 761 } 762 763 /* 764 * Nominal jitter is due to PPS signal noise and interrupt 765 * latency. If it exceeds the popcorn threshold, the sample is 766 * discarded. otherwise, if so enabled, the time offset is 767 * updated. We can tolerate a modest loss of data here without 768 * much degrading time accuracy. 769 */ 770 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 771 time_status |= STA_PPSJITTER; 772 pps_jitcnt++; 773 } else if (time_status & STA_PPSTIME) { 774 time_monitor = -v_nsec; 775 L_LINT(time_offset, time_monitor); 776 } 777 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 778 u_sec = pps_tf[0].tv_sec - pps_lastsec; 779 if (u_sec < (1 << pps_shift)) 780 return; 781 782 /* 783 * At the end of the calibration interval the difference between 784 * the first and last counter values becomes the scaled 785 * frequency. It will later be divided by the length of the 786 * interval to determine the frequency update. If the frequency 787 * exceeds a sanity threshold, or if the actual calibration 788 * interval is not equal to the expected length, the data are 789 * discarded. We can tolerate a modest loss of data here without 790 * much degrading frequency accuracy. 791 */ 792 pps_calcnt++; 793 v_nsec = -pps_fcount; 794 pps_lastsec = pps_tf[0].tv_sec; 795 pps_fcount = 0; 796 u_nsec = MAXFREQ << pps_shift; 797 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 798 pps_shift)) { 799 time_status |= STA_PPSERROR; 800 pps_errcnt++; 801 return; 802 } 803 804 /* 805 * Here the raw frequency offset and wander (stability) is 806 * calculated. If the wander is less than the wander threshold 807 * for four consecutive averaging intervals, the interval is 808 * doubled; if it is greater than the threshold for four 809 * consecutive intervals, the interval is halved. The scaled 810 * frequency offset is converted to frequency offset. The 811 * stability metric is calculated as the average of recent 812 * frequency changes, but is used only for performance 813 * monitoring. 814 */ 815 L_LINT(ftemp, v_nsec); 816 L_RSHIFT(ftemp, pps_shift); 817 L_SUB(ftemp, pps_freq); 818 u_nsec = L_GINT(ftemp); 819 if (u_nsec > PPS_MAXWANDER) { 820 L_LINT(ftemp, PPS_MAXWANDER); 821 pps_intcnt--; 822 time_status |= STA_PPSWANDER; 823 pps_stbcnt++; 824 } else if (u_nsec < -PPS_MAXWANDER) { 825 L_LINT(ftemp, -PPS_MAXWANDER); 826 pps_intcnt--; 827 time_status |= STA_PPSWANDER; 828 pps_stbcnt++; 829 } else { 830 pps_intcnt++; 831 } 832 if (pps_intcnt >= 4) { 833 pps_intcnt = 4; 834 if (pps_shift < pps_shiftmax) { 835 pps_shift++; 836 pps_intcnt = 0; 837 } 838 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 839 pps_intcnt = -4; 840 if (pps_shift > PPS_FAVG) { 841 pps_shift--; 842 pps_intcnt = 0; 843 } 844 } 845 if (u_nsec < 0) 846 u_nsec = -u_nsec; 847 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 848 849 /* 850 * The PPS frequency is recalculated and clamped to the maximum 851 * MAXFREQ. If enabled, the system clock frequency is updated as 852 * well. 853 */ 854 L_ADD(pps_freq, ftemp); 855 u_nsec = L_GINT(pps_freq); 856 if (u_nsec > MAXFREQ) 857 L_LINT(pps_freq, MAXFREQ); 858 else if (u_nsec < -MAXFREQ) 859 L_LINT(pps_freq, -MAXFREQ); 860 if (time_status & STA_PPSFREQ) 861 time_freq = pps_freq; 862 } 863 #endif /* PPS_SYNC */ 864