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 * $FreeBSD$ 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/lock.h> 42 #include <sys/mutex.h> 43 #include <sys/time.h> 44 #include <sys/timex.h> 45 #include <sys/timetc.h> 46 #include <sys/timepps.h> 47 #include <sys/sysctl.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 #ifndef _SYS_SYSPROTO_H_ 270 struct ntp_adjtime_args { 271 struct timex *tp; 272 }; 273 #endif 274 275 /* 276 * MPSAFE 277 */ 278 int 279 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 280 { 281 struct timex ntv; /* temporary structure */ 282 long freq; /* frequency ns/s) */ 283 int modes; /* mode bits from structure */ 284 int s; /* caller priority */ 285 int error; 286 287 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 288 if (error) 289 return(error); 290 291 /* 292 * Update selected clock variables - only the superuser can 293 * change anything. Note that there is no error checking here on 294 * the assumption the superuser should know what it is doing. 295 * Note that either the time constant or TAI offset are loaded 296 * from the ntv.constant member, depending on the mode bits. If 297 * the STA_PLL bit in the status word is cleared, the state and 298 * status words are reset to the initial values at boot. 299 */ 300 mtx_lock(&Giant); 301 modes = ntv.modes; 302 if (modes) 303 error = suser_td(td); 304 if (error) 305 goto done2; 306 s = splclock(); 307 if (modes & MOD_MAXERROR) 308 time_maxerror = ntv.maxerror; 309 if (modes & MOD_ESTERROR) 310 time_esterror = ntv.esterror; 311 if (modes & MOD_STATUS) { 312 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 313 time_state = TIME_OK; 314 time_status = STA_UNSYNC; 315 #ifdef PPS_SYNC 316 pps_shift = PPS_FAVG; 317 #endif /* PPS_SYNC */ 318 } 319 time_status &= STA_RONLY; 320 time_status |= ntv.status & ~STA_RONLY; 321 } 322 if (modes & MOD_TIMECONST) { 323 if (ntv.constant < 0) 324 time_constant = 0; 325 else if (ntv.constant > MAXTC) 326 time_constant = MAXTC; 327 else 328 time_constant = ntv.constant; 329 } 330 if (modes & MOD_TAI) { 331 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 332 time_tai = ntv.constant; 333 } 334 #ifdef PPS_SYNC 335 if (modes & MOD_PPSMAX) { 336 if (ntv.shift < PPS_FAVG) 337 pps_shiftmax = PPS_FAVG; 338 else if (ntv.shift > PPS_FAVGMAX) 339 pps_shiftmax = PPS_FAVGMAX; 340 else 341 pps_shiftmax = ntv.shift; 342 } 343 #endif /* PPS_SYNC */ 344 if (modes & MOD_NANO) 345 time_status |= STA_NANO; 346 if (modes & MOD_MICRO) 347 time_status &= ~STA_NANO; 348 if (modes & MOD_CLKB) 349 time_status |= STA_CLK; 350 if (modes & MOD_CLKA) 351 time_status &= ~STA_CLK; 352 if (modes & MOD_OFFSET) { 353 if (time_status & STA_NANO) 354 hardupdate(ntv.offset); 355 else 356 hardupdate(ntv.offset * 1000); 357 } 358 if (modes & MOD_FREQUENCY) { 359 freq = (ntv.freq * 1000LL) >> 16; 360 if (freq > MAXFREQ) 361 L_LINT(time_freq, MAXFREQ); 362 else if (freq < -MAXFREQ) 363 L_LINT(time_freq, -MAXFREQ); 364 else 365 L_LINT(time_freq, freq); 366 #ifdef PPS_SYNC 367 pps_freq = time_freq; 368 #endif /* PPS_SYNC */ 369 } 370 371 /* 372 * Retrieve all clock variables. Note that the TAI offset is 373 * returned only by ntp_gettime(); 374 */ 375 if (time_status & STA_NANO) 376 ntv.offset = time_monitor; 377 else 378 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 379 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 380 ntv.maxerror = time_maxerror; 381 ntv.esterror = time_esterror; 382 ntv.status = time_status; 383 ntv.constant = time_constant; 384 if (time_status & STA_NANO) 385 ntv.precision = time_precision; 386 else 387 ntv.precision = time_precision / 1000; 388 ntv.tolerance = MAXFREQ * SCALE_PPM; 389 #ifdef PPS_SYNC 390 ntv.shift = pps_shift; 391 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 392 if (time_status & STA_NANO) 393 ntv.jitter = pps_jitter; 394 else 395 ntv.jitter = pps_jitter / 1000; 396 ntv.stabil = pps_stabil; 397 ntv.calcnt = pps_calcnt; 398 ntv.errcnt = pps_errcnt; 399 ntv.jitcnt = pps_jitcnt; 400 ntv.stbcnt = pps_stbcnt; 401 #endif /* PPS_SYNC */ 402 splx(s); 403 404 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 405 if (error) 406 goto done2; 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 td->td_retval[0] = TIME_ERROR; 420 } else { 421 td->td_retval[0] = time_state; 422 } 423 done2: 424 mtx_unlock(&Giant); 425 return (error); 426 } 427 428 /* 429 * second_overflow() - called after ntp_tick_adjust() 430 * 431 * This routine is ordinarily called immediately following the above 432 * routine ntp_tick_adjust(). While these two routines are normally 433 * combined, they are separated here only for the purposes of 434 * simulation. 435 */ 436 void 437 ntp_update_second(struct timecounter *tcp) 438 { 439 u_int32_t *newsec; 440 l_fp ftemp; /* 32/64-bit temporary */ 441 442 newsec = &tcp->tc_offset.sec; 443 /* 444 * On rollover of the second both the nanosecond and microsecond 445 * clocks are updated and the state machine cranked as 446 * necessary. The phase adjustment to be used for the next 447 * second is calculated and the maximum error is increased by 448 * the tolerance. 449 */ 450 time_maxerror += MAXFREQ / 1000; 451 452 /* 453 * Leap second processing. If in leap-insert state at 454 * the end of the day, the system clock is set back one 455 * second; if in leap-delete state, the system clock is 456 * set ahead one second. The nano_time() routine or 457 * external clock driver will insure that reported time 458 * is always monotonic. 459 */ 460 switch (time_state) { 461 462 /* 463 * No warning. 464 */ 465 case TIME_OK: 466 if (time_status & STA_INS) 467 time_state = TIME_INS; 468 else if (time_status & STA_DEL) 469 time_state = TIME_DEL; 470 break; 471 472 /* 473 * Insert second 23:59:60 following second 474 * 23:59:59. 475 */ 476 case TIME_INS: 477 if (!(time_status & STA_INS)) 478 time_state = TIME_OK; 479 else if ((*newsec) % 86400 == 0) { 480 (*newsec)--; 481 time_state = TIME_OOP; 482 } 483 break; 484 485 /* 486 * Delete second 23:59:59. 487 */ 488 case TIME_DEL: 489 if (!(time_status & STA_DEL)) 490 time_state = TIME_OK; 491 else if (((*newsec) + 1) % 86400 == 0) { 492 (*newsec)++; 493 time_tai--; 494 time_state = TIME_WAIT; 495 } 496 break; 497 498 /* 499 * Insert second in progress. 500 */ 501 case TIME_OOP: 502 time_tai++; 503 time_state = TIME_WAIT; 504 break; 505 506 /* 507 * Wait for status bits to clear. 508 */ 509 case TIME_WAIT: 510 if (!(time_status & (STA_INS | STA_DEL))) 511 time_state = TIME_OK; 512 } 513 514 /* 515 * Compute the total time adjustment for the next second 516 * in ns. The offset is reduced by a factor depending on 517 * whether the PPS signal is operating. Note that the 518 * value is in effect scaled by the clock frequency, 519 * since the adjustment is added at each tick interrupt. 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 & 525 STA_PPSSIGNAL) 526 L_RSHIFT(ftemp, pps_shift); 527 else 528 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 529 #else 530 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 531 #endif /* PPS_SYNC */ 532 time_adj = ftemp; 533 L_SUB(time_offset, ftemp); 534 L_ADD(time_adj, time_freq); 535 tcp->tc_adjustment = time_adj; 536 #ifdef PPS_SYNC 537 if (pps_valid > 0) 538 pps_valid--; 539 else 540 time_status &= ~STA_PPSSIGNAL; 541 #endif /* PPS_SYNC */ 542 } 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() 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_SUB_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(offset) 606 long offset; /* clock offset (ns) */ 607 { 608 long mtemp; 609 l_fp ftemp; 610 611 /* 612 * Select how the phase is to be controlled and from which 613 * source. If the PPS signal is present and enabled to 614 * discipline the time, the PPS offset is used; otherwise, the 615 * argument offset is used. 616 */ 617 if (!(time_status & STA_PLL)) 618 return; 619 if (!(time_status & STA_PPSTIME && time_status & 620 STA_PPSSIGNAL)) { 621 if (offset > MAXPHASE) 622 time_monitor = MAXPHASE; 623 else if (offset < -MAXPHASE) 624 time_monitor = -MAXPHASE; 625 else 626 time_monitor = offset; 627 L_LINT(time_offset, time_monitor); 628 } 629 630 /* 631 * Select how the frequency is to be controlled and in which 632 * mode (PLL or FLL). If the PPS signal is present and enabled 633 * to discipline the frequency, the PPS frequency is used; 634 * otherwise, the argument offset is used to compute it. 635 */ 636 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 637 time_reftime = time_second; 638 return; 639 } 640 if (time_status & STA_FREQHOLD || time_reftime == 0) 641 time_reftime = time_second; 642 mtemp = time_second - time_reftime; 643 L_LINT(ftemp, time_monitor); 644 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 645 L_MPY(ftemp, mtemp); 646 L_ADD(time_freq, ftemp); 647 time_status &= ~STA_MODE; 648 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 649 MAXSEC)) { 650 L_LINT(ftemp, (time_monitor << 4) / mtemp); 651 L_RSHIFT(ftemp, SHIFT_FLL + 4); 652 L_ADD(time_freq, ftemp); 653 time_status |= STA_MODE; 654 } 655 time_reftime = time_second; 656 if (L_GINT(time_freq) > MAXFREQ) 657 L_LINT(time_freq, MAXFREQ); 658 else if (L_GINT(time_freq) < -MAXFREQ) 659 L_LINT(time_freq, -MAXFREQ); 660 } 661 662 #ifdef PPS_SYNC 663 /* 664 * hardpps() - discipline CPU clock oscillator to external PPS signal 665 * 666 * This routine is called at each PPS interrupt in order to discipline 667 * the CPU clock oscillator to the PPS signal. There are two independent 668 * first-order feedback loops, one for the phase, the other for the 669 * frequency. The phase loop measures and grooms the PPS phase offset 670 * and leaves it in a handy spot for the seconds overflow routine. The 671 * frequency loop averages successive PPS phase differences and 672 * calculates the PPS frequency offset, which is also processed by the 673 * seconds overflow routine. The code requires the caller to capture the 674 * time and architecture-dependent hardware counter values in 675 * nanoseconds at the on-time PPS signal transition. 676 * 677 * Note that, on some Unix systems this routine runs at an interrupt 678 * priority level higher than the timer interrupt routine hardclock(). 679 * Therefore, the variables used are distinct from the hardclock() 680 * variables, except for the actual time and frequency variables, which 681 * are determined by this routine and updated atomically. 682 */ 683 void 684 hardpps(tsp, nsec) 685 struct timespec *tsp; /* time at PPS */ 686 long nsec; /* hardware counter at PPS */ 687 { 688 long u_sec, u_nsec, v_nsec; /* temps */ 689 l_fp ftemp; 690 691 /* 692 * The signal is first processed by a range gate and frequency 693 * discriminator. The range gate rejects noise spikes outside 694 * the range +-500 us. The frequency discriminator rejects input 695 * signals with apparent frequency outside the range 1 +-500 696 * PPM. If two hits occur in the same second, we ignore the 697 * later hit; if not and a hit occurs outside the range gate, 698 * keep the later hit for later comparison, but do not process 699 * it. 700 */ 701 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 702 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 703 pps_valid = PPS_VALID; 704 u_sec = tsp->tv_sec; 705 u_nsec = tsp->tv_nsec; 706 if (u_nsec >= (NANOSECOND >> 1)) { 707 u_nsec -= NANOSECOND; 708 u_sec++; 709 } 710 v_nsec = u_nsec - pps_tf[0].tv_nsec; 711 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 712 MAXFREQ) 713 return; 714 pps_tf[2] = pps_tf[1]; 715 pps_tf[1] = pps_tf[0]; 716 pps_tf[0].tv_sec = u_sec; 717 pps_tf[0].tv_nsec = u_nsec; 718 719 /* 720 * Compute the difference between the current and previous 721 * counter values. If the difference exceeds 0.5 s, assume it 722 * has wrapped around, so correct 1.0 s. If the result exceeds 723 * the tick interval, the sample point has crossed a tick 724 * boundary during the last second, so correct the tick. Very 725 * intricate. 726 */ 727 u_nsec = nsec; 728 if (u_nsec > (NANOSECOND >> 1)) 729 u_nsec -= NANOSECOND; 730 else if (u_nsec < -(NANOSECOND >> 1)) 731 u_nsec += NANOSECOND; 732 pps_fcount += u_nsec; 733 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 734 return; 735 time_status &= ~STA_PPSJITTER; 736 737 /* 738 * A three-stage median filter is used to help denoise the PPS 739 * time. The median sample becomes the time offset estimate; the 740 * difference between the other two samples becomes the time 741 * dispersion (jitter) estimate. 742 */ 743 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 744 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 745 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 746 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 747 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 748 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 749 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 750 } else { 751 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 752 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 753 } 754 } else { 755 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 756 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 757 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 758 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 759 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 760 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 761 } else { 762 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 763 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 764 } 765 } 766 767 /* 768 * Nominal jitter is due to PPS signal noise and interrupt 769 * latency. If it exceeds the popcorn threshold, the sample is 770 * discarded. otherwise, if so enabled, the time offset is 771 * updated. We can tolerate a modest loss of data here without 772 * much degrading time accuracy. 773 */ 774 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 775 time_status |= STA_PPSJITTER; 776 pps_jitcnt++; 777 } else if (time_status & STA_PPSTIME) { 778 time_monitor = -v_nsec; 779 L_LINT(time_offset, time_monitor); 780 } 781 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 782 u_sec = pps_tf[0].tv_sec - pps_lastsec; 783 if (u_sec < (1 << pps_shift)) 784 return; 785 786 /* 787 * At the end of the calibration interval the difference between 788 * the first and last counter values becomes the scaled 789 * frequency. It will later be divided by the length of the 790 * interval to determine the frequency update. If the frequency 791 * exceeds a sanity threshold, or if the actual calibration 792 * interval is not equal to the expected length, the data are 793 * discarded. We can tolerate a modest loss of data here without 794 * much degrading frequency accuracy. 795 */ 796 pps_calcnt++; 797 v_nsec = -pps_fcount; 798 pps_lastsec = pps_tf[0].tv_sec; 799 pps_fcount = 0; 800 u_nsec = MAXFREQ << pps_shift; 801 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 802 pps_shift)) { 803 time_status |= STA_PPSERROR; 804 pps_errcnt++; 805 return; 806 } 807 808 /* 809 * Here the raw frequency offset and wander (stability) is 810 * calculated. If the wander is less than the wander threshold 811 * for four consecutive averaging intervals, the interval is 812 * doubled; if it is greater than the threshold for four 813 * consecutive intervals, the interval is halved. The scaled 814 * frequency offset is converted to frequency offset. The 815 * stability metric is calculated as the average of recent 816 * frequency changes, but is used only for performance 817 * monitoring. 818 */ 819 L_LINT(ftemp, v_nsec); 820 L_RSHIFT(ftemp, pps_shift); 821 L_SUB(ftemp, pps_freq); 822 u_nsec = L_GINT(ftemp); 823 if (u_nsec > PPS_MAXWANDER) { 824 L_LINT(ftemp, PPS_MAXWANDER); 825 pps_intcnt--; 826 time_status |= STA_PPSWANDER; 827 pps_stbcnt++; 828 } else if (u_nsec < -PPS_MAXWANDER) { 829 L_LINT(ftemp, -PPS_MAXWANDER); 830 pps_intcnt--; 831 time_status |= STA_PPSWANDER; 832 pps_stbcnt++; 833 } else { 834 pps_intcnt++; 835 } 836 if (pps_intcnt >= 4) { 837 pps_intcnt = 4; 838 if (pps_shift < pps_shiftmax) { 839 pps_shift++; 840 pps_intcnt = 0; 841 } 842 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 843 pps_intcnt = -4; 844 if (pps_shift > PPS_FAVG) { 845 pps_shift--; 846 pps_intcnt = 0; 847 } 848 } 849 if (u_nsec < 0) 850 u_nsec = -u_nsec; 851 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 852 853 /* 854 * The PPS frequency is recalculated and clamped to the maximum 855 * MAXFREQ. If enabled, the system clock frequency is updated as 856 * well. 857 */ 858 L_ADD(pps_freq, ftemp); 859 u_nsec = L_GINT(pps_freq); 860 if (u_nsec > MAXFREQ) 861 L_LINT(pps_freq, MAXFREQ); 862 else if (u_nsec < -MAXFREQ) 863 L_LINT(pps_freq, -MAXFREQ); 864 if (time_status & STA_PPSFREQ) 865 time_freq = pps_freq; 866 } 867 #endif /* PPS_SYNC */ 868