1 /*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-1999 * 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/time.h> 42 #include <sys/timex.h> 43 #include <sys/timetc.h> 44 #include <sys/timepps.h> 45 #include <sys/sysctl.h> 46 47 /* 48 * Single-precision macros for 64-bit machines 49 */ 50 typedef long long l_fp; 51 #define L_ADD(v, u) ((v) += (u)) 52 #define L_SUB(v, u) ((v) -= (u)) 53 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 54 #define L_NEG(v) ((v) = -(v)) 55 #define L_RSHIFT(v, n) \ 56 do { \ 57 if ((v) < 0) \ 58 (v) = -(-(v) >> (n)); \ 59 else \ 60 (v) = (v) >> (n); \ 61 } while (0) 62 #define L_MPY(v, a) ((v) *= (a)) 63 #define L_CLR(v) ((v) = 0) 64 #define L_ISNEG(v) ((v) < 0) 65 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 66 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 67 68 /* 69 * Generic NTP kernel interface 70 * 71 * These routines constitute the Network Time Protocol (NTP) interfaces 72 * for user and daemon application programs. The ntp_gettime() routine 73 * provides the time, maximum error (synch distance) and estimated error 74 * (dispersion) to client user application programs. The ntp_adjtime() 75 * routine is used by the NTP daemon to adjust the system clock to an 76 * externally derived time. The time offset and related variables set by 77 * this routine are used by other routines in this module to adjust the 78 * phase and frequency of the clock discipline loop which controls the 79 * system clock. 80 * 81 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 82 * defined), the time at each tick interrupt is derived directly from 83 * the kernel time variable. When the kernel time is reckoned in 84 * microseconds, (NTP_NANO undefined), the time is derived from the 85 * kernel time variable together with a variable representing the 86 * leftover nanoseconds at the last tick interrupt. In either case, the 87 * current nanosecond time is reckoned from these values plus an 88 * interpolated value derived by the clock routines in another 89 * architecture-specific module. The interpolation can use either a 90 * dedicated counter or a processor cycle counter (PCC) implemented in 91 * some architectures. 92 * 93 * Note that all routines must run at priority splclock or higher. 94 */ 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_constant; /* poll interval (shift) (s) */ 143 static long time_precision = 1; /* clock precision (ns) */ 144 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 145 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 146 static long time_reftime; /* time at last adjustment (s) */ 147 static long time_tick; /* nanoseconds per tick (ns) */ 148 static l_fp time_offset; /* time offset (ns) */ 149 static l_fp time_freq; /* frequency offset (ns/s) */ 150 static l_fp time_adj; /* resulting adjustment */ 151 152 #ifdef PPS_SYNC 153 /* 154 * The following variables are used when a pulse-per-second (PPS) signal 155 * is available and connected via a modem control lead. They establish 156 * the engineering parameters of the clock discipline loop when 157 * controlled by the PPS signal. 158 */ 159 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 160 #define PPS_FAVGDEF 7 /* default freq avg int (s) (shift) */ 161 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 162 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 163 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 164 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 165 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 166 167 static struct timespec pps_tf[3]; /* phase median filter */ 168 static l_fp pps_offset; /* time offset (ns) */ 169 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 170 static long pps_fcount; /* frequency accumulator */ 171 static long pps_jitter; /* nominal jitter (ns) */ 172 static long pps_stabil; /* nominal stability (scaled ns/s) */ 173 static long pps_lastsec; /* time at last calibration (s) */ 174 static int pps_valid; /* signal watchdog counter */ 175 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 176 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 177 static int pps_intcnt; /* wander counter */ 178 static int pps_letgo; /* PLL frequency hold-off */ 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. 199 */ 200 static int 201 ntp_sysctl(SYSCTL_HANDLER_ARGS) 202 { 203 struct ntptimeval ntv; /* temporary structure */ 204 struct timespec atv; /* nanosecond time */ 205 206 nanotime(&atv); 207 ntv.time.tv_sec = atv.tv_sec; 208 ntv.time.tv_nsec = atv.tv_nsec; 209 ntv.maxerror = time_maxerror; 210 ntv.esterror = time_esterror; 211 ntv.time_state = time_state; 212 213 /* 214 * Status word error decode. If any of these conditions occur, 215 * an error is returned, instead of the status word. Most 216 * applications will care only about the fact the system clock 217 * may not be trusted, not about the details. 218 * 219 * Hardware or software error 220 */ 221 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 222 223 /* 224 * PPS signal lost when either time or frequency synchronization 225 * requested 226 */ 227 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 228 !(time_status & STA_PPSSIGNAL)) || 229 230 /* 231 * PPS jitter exceeded when time synchronization requested 232 */ 233 (time_status & STA_PPSTIME && 234 time_status & STA_PPSJITTER) || 235 236 /* 237 * PPS wander exceeded or calibration error when frequency 238 * synchronization requested 239 */ 240 (time_status & STA_PPSFREQ && 241 time_status & (STA_PPSWANDER | STA_PPSERROR))) 242 ntv.time_state = TIME_ERROR; 243 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 244 } 245 246 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 247 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 248 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 249 250 #ifdef PPS_SYNC 251 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 252 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 253 254 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 255 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 256 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_offset, CTLFLAG_RD, &pps_offset, sizeof(pps_offset), "I", ""); 257 #endif 258 /* 259 * ntp_adjtime() - NTP daemon application interface 260 * 261 * See the timex.h header file for synopsis and API description. 262 */ 263 #ifndef _SYS_SYSPROTO_H_ 264 struct ntp_adjtime_args { 265 struct timex *tp; 266 }; 267 #endif 268 269 int 270 ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 271 { 272 struct timex ntv; /* temporary structure */ 273 long freq; /* frequency ns/s) */ 274 int modes; /* mode bits from structure */ 275 int s; /* caller priority */ 276 int error; 277 278 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 279 if (error) 280 return(error); 281 282 /* 283 * Update selected clock variables - only the superuser can 284 * change anything. Note that there is no error checking here on 285 * the assumption the superuser should know what it is doing. 286 */ 287 modes = ntv.modes; 288 if (modes) 289 error = suser(p); 290 if (error) 291 return (error); 292 s = splclock(); 293 if (modes & MOD_FREQUENCY) { 294 freq = (ntv.freq * 1000LL) >> 16; 295 if (freq > MAXFREQ) 296 L_LINT(time_freq, MAXFREQ); 297 else if (freq < -MAXFREQ) 298 L_LINT(time_freq, -MAXFREQ); 299 else 300 L_LINT(time_freq, freq); 301 302 #ifdef PPS_SYNC 303 pps_freq = time_freq; 304 #endif /* PPS_SYNC */ 305 } 306 if (modes & MOD_MAXERROR) 307 time_maxerror = ntv.maxerror; 308 if (modes & MOD_ESTERROR) 309 time_esterror = ntv.esterror; 310 if (modes & MOD_STATUS) { 311 time_status &= STA_RONLY; 312 time_status |= ntv.status & ~STA_RONLY; 313 } 314 if (modes & MOD_TIMECONST) { 315 if (ntv.constant < 0) 316 time_constant = 0; 317 else if (ntv.constant > MAXTC) 318 time_constant = MAXTC; 319 else 320 time_constant = ntv.constant; 321 } 322 #ifdef PPS_SYNC 323 if (modes & MOD_PPSMAX) { 324 if (ntv.shift < PPS_FAVG) 325 pps_shiftmax = PPS_FAVG; 326 else if (ntv.shift > PPS_FAVGMAX) 327 pps_shiftmax = PPS_FAVGMAX; 328 else 329 pps_shiftmax = ntv.shift; 330 } 331 #endif /* PPS_SYNC */ 332 if (modes & MOD_NANO) 333 time_status |= STA_NANO; 334 if (modes & MOD_MICRO) 335 time_status &= ~STA_NANO; 336 if (modes & MOD_CLKB) 337 time_status |= STA_CLK; 338 if (modes & MOD_CLKA) 339 time_status &= ~STA_CLK; 340 if (modes & MOD_OFFSET) { 341 if (time_status & STA_NANO) 342 hardupdate(ntv.offset); 343 else 344 hardupdate(ntv.offset * 1000); 345 } 346 347 /* 348 * Retrieve all clock variables 349 */ 350 if (time_status & STA_NANO) 351 ntv.offset = L_GINT(time_offset); 352 else 353 ntv.offset = L_GINT(time_offset) / 1000; 354 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 355 ntv.maxerror = time_maxerror; 356 ntv.esterror = time_esterror; 357 ntv.status = time_status; 358 ntv.constant = time_constant; 359 if (time_status & STA_NANO) 360 ntv.precision = time_precision; 361 else 362 ntv.precision = time_precision / 1000; 363 ntv.tolerance = MAXFREQ * SCALE_PPM; 364 #ifdef PPS_SYNC 365 ntv.shift = pps_shift; 366 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 367 if (time_status & STA_NANO) 368 ntv.jitter = pps_jitter; 369 else 370 ntv.jitter = pps_jitter / 1000; 371 ntv.stabil = pps_stabil; 372 ntv.calcnt = pps_calcnt; 373 ntv.errcnt = pps_errcnt; 374 ntv.jitcnt = pps_jitcnt; 375 ntv.stbcnt = pps_stbcnt; 376 #endif /* PPS_SYNC */ 377 splx(s); 378 379 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 380 if (error) 381 return (error); 382 383 /* 384 * Status word error decode. See comments in 385 * ntp_gettime() routine. 386 */ 387 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 388 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 389 !(time_status & STA_PPSSIGNAL)) || 390 (time_status & STA_PPSTIME && 391 time_status & STA_PPSJITTER) || 392 (time_status & STA_PPSFREQ && 393 time_status & (STA_PPSWANDER | STA_PPSERROR))) 394 p->p_retval[0] = TIME_ERROR; 395 else 396 p->p_retval[0] = time_state; 397 return (error); 398 } 399 400 /* 401 * second_overflow() - called after ntp_tick_adjust() 402 * 403 * This routine is ordinarily called immediately following the above 404 * routine ntp_tick_adjust(). While these two routines are normally 405 * combined, they are separated here only for the purposes of 406 * simulation. 407 */ 408 void 409 ntp_update_second(struct timecounter *tcp) 410 { 411 u_int32_t *newsec; 412 413 newsec = &tcp->tc_offset_sec; 414 /* 415 * On rollover of the second both the nanosecond and microsecond 416 * clocks are updated and the state machine cranked as 417 * necessary. The phase adjustment to be used for the next 418 * second is calculated and the maximum error is increased by 419 * the tolerance. 420 */ 421 time_maxerror += MAXFREQ / 1000; 422 423 /* 424 * Leap second processing. If in leap-insert state at 425 * the end of the day, the system clock is set back one 426 * second; if in leap-delete state, the system clock is 427 * set ahead one second. The nano_time() routine or 428 * external clock driver will insure that reported time 429 * is always monotonic. 430 */ 431 switch (time_state) { 432 433 /* 434 * No warning. 435 */ 436 case TIME_OK: 437 if (time_status & STA_INS) 438 time_state = TIME_INS; 439 else if (time_status & STA_DEL) 440 time_state = TIME_DEL; 441 break; 442 443 /* 444 * Insert second 23:59:60 following second 445 * 23:59:59. 446 */ 447 case TIME_INS: 448 if (!(time_status & STA_INS)) 449 time_state = TIME_OK; 450 else if ((*newsec) % 86400 == 0) { 451 (*newsec)--; 452 time_state = TIME_OOP; 453 } 454 break; 455 456 /* 457 * Delete second 23:59:59. 458 */ 459 case TIME_DEL: 460 if (!(time_status & STA_DEL)) 461 time_state = TIME_OK; 462 else if (((*newsec) + 1) % 86400 == 0) { 463 (*newsec)++; 464 time_state = TIME_WAIT; 465 } 466 break; 467 468 /* 469 * Insert second in progress. 470 */ 471 case TIME_OOP: 472 time_state = TIME_WAIT; 473 break; 474 475 /* 476 * Wait for status bits to clear. 477 */ 478 case TIME_WAIT: 479 if (!(time_status & (STA_INS | STA_DEL))) 480 time_state = TIME_OK; 481 } 482 483 /* 484 * Compute the total time adjustment for the next second 485 * in ns. The offset is reduced by a factor depending on 486 * whether the PPS signal is operating. Note that the 487 * value is in effect scaled by the clock frequency, 488 * since the adjustment is added at each tick interrupt. 489 */ 490 #ifdef PPS_SYNC 491 /* XXX even if signal dies we should finish adjustment ? */ 492 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) { 493 time_adj = pps_offset; 494 L_RSHIFT(time_adj, pps_shift); 495 L_SUB(pps_offset, time_adj); 496 } else { 497 time_adj = time_offset; 498 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 499 L_SUB(time_offset, time_adj); 500 } 501 #else 502 time_adj = time_offset; 503 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 504 L_SUB(time_offset, time_adj); 505 #endif /* PPS_SYNC */ 506 L_ADD(time_adj, time_freq); 507 tcp->tc_adjustment = time_adj; 508 #ifdef PPS_SYNC 509 if (pps_valid > 0) 510 pps_valid--; 511 else 512 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 513 STA_PPSWANDER | STA_PPSERROR); 514 #endif /* PPS_SYNC */ 515 } 516 517 /* 518 * ntp_init() - initialize variables and structures 519 * 520 * This routine must be called after the kernel variables hz and tick 521 * are set or changed and before the next tick interrupt. In this 522 * particular implementation, these values are assumed set elsewhere in 523 * the kernel. The design allows the clock frequency and tick interval 524 * to be changed while the system is running. So, this routine should 525 * probably be integrated with the code that does that. 526 */ 527 static void 528 ntp_init() 529 { 530 531 /* 532 * The following variable must be initialized any time the 533 * kernel variable hz is changed. 534 */ 535 time_tick = NANOSECOND / hz; 536 537 /* 538 * The following variables are initialized only at startup. Only 539 * those structures not cleared by the compiler need to be 540 * initialized, and these only in the simulator. In the actual 541 * kernel, any nonzero values here will quickly evaporate. 542 */ 543 L_CLR(time_offset); 544 L_CLR(time_freq); 545 #ifdef PPS_SYNC 546 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 547 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 548 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 549 pps_fcount = 0; 550 L_CLR(pps_freq); 551 #endif /* PPS_SYNC */ 552 } 553 554 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 555 556 /* 557 * hardupdate() - local clock update 558 * 559 * This routine is called by ntp_adjtime() to update the local clock 560 * phase and frequency. The implementation is of an adaptive-parameter, 561 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 562 * time and frequency offset estimates for each call. If the kernel PPS 563 * discipline code is configured (PPS_SYNC), the PPS signal itself 564 * determines the new time offset, instead of the calling argument. 565 * Presumably, calls to ntp_adjtime() occur only when the caller 566 * believes the local clock is valid within some bound (+-128 ms with 567 * NTP). If the caller's time is far different than the PPS time, an 568 * argument will ensue, and it's not clear who will lose. 569 * 570 * For uncompensated quartz crystal oscillators and nominal update 571 * intervals less than 256 s, operation should be in phase-lock mode, 572 * where the loop is disciplined to phase. For update intervals greater 573 * than 1024 s, operation should be in frequency-lock mode, where the 574 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 575 * is selected by the STA_MODE status bit. 576 */ 577 static void 578 hardupdate(offset) 579 long offset; /* clock offset (ns) */ 580 { 581 long ltemp, mtemp; 582 l_fp ftemp; 583 584 /* 585 * Select how the phase is to be controlled and from which 586 * source. If the PPS signal is present and enabled to 587 * discipline the time, the PPS offset is used; otherwise, the 588 * argument offset is used. 589 */ 590 if (!(time_status & STA_PLL)) 591 return; 592 ltemp = offset; 593 if (ltemp > MAXPHASE) 594 ltemp = MAXPHASE; 595 else if (ltemp < -MAXPHASE) 596 ltemp = -MAXPHASE; 597 if (!(time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)) 598 L_LINT(time_offset, ltemp); 599 600 /* 601 * Select how the frequency is to be controlled and in which 602 * mode (PLL or FLL). If the PPS signal is present and enabled 603 * to discipline the frequency, the PPS frequency is used; 604 * otherwise, the argument offset is used to compute it. 605 */ 606 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 607 time_reftime = time_second; 608 return; 609 } 610 if (time_status & STA_FREQHOLD || time_reftime == 0) 611 time_reftime = time_second; 612 mtemp = time_second - time_reftime; 613 L_LINT(ftemp, ltemp); 614 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 615 L_MPY(ftemp, mtemp); 616 L_ADD(time_freq, ftemp); 617 time_status &= ~STA_MODE; 618 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 619 L_LINT(ftemp, (ltemp << 4) / mtemp); 620 L_RSHIFT(ftemp, SHIFT_FLL + 4); 621 L_ADD(time_freq, ftemp); 622 time_status |= STA_MODE; 623 } 624 time_reftime = time_second; 625 if (L_GINT(time_freq) > MAXFREQ) 626 L_LINT(time_freq, MAXFREQ); 627 else if (L_GINT(time_freq) < -MAXFREQ) 628 L_LINT(time_freq, -MAXFREQ); 629 } 630 631 #ifdef PPS_SYNC 632 /* 633 * hardpps() - discipline CPU clock oscillator to external PPS signal 634 * 635 * This routine is called at each PPS interrupt in order to discipline 636 * the CPU clock oscillator to the PPS signal. It measures the PPS phase 637 * and leaves it in a handy spot for the hardclock() routine. It 638 * integrates successive PPS phase differences and calculates the 639 * frequency offset. This is used in hardclock() to discipline the CPU 640 * clock oscillator so that the intrinsic frequency error is cancelled 641 * out. The code requires the caller to capture the time and 642 * architecture-dependent hardware counter values in nanoseconds at the 643 * on-time PPS signal transition. 644 * 645 * Note that, on some Unix systems this routine runs at an interrupt 646 * priority level higher than the timer interrupt routine hardclock(). 647 * Therefore, the variables used are distinct from the hardclock() 648 * variables, except for the actual time and frequency variables, which 649 * are determined by this routine and updated atomically. 650 */ 651 void 652 hardpps(tsp, nsec) 653 struct timespec *tsp; /* time at PPS */ 654 long nsec; /* hardware counter at PPS */ 655 { 656 long u_sec, u_nsec, v_nsec, w_nsec; /* temps */ 657 l_fp ftemp; 658 659 /* 660 * The signal is first processed by a frequency discriminator 661 * which rejects noise and input signals with frequencies 662 * outside the range 1 +-MAXFREQ PPS. If two hits occur in the 663 * same second, we ignore the later hit; if not and a hit occurs 664 * outside the range gate, keep the later hit but do not 665 * process it. 666 */ 667 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 668 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 669 pps_valid = PPS_VALID; 670 u_sec = tsp->tv_sec; 671 u_nsec = tsp->tv_nsec; 672 if (u_nsec >= (NANOSECOND >> 1)) { 673 u_nsec -= NANOSECOND; 674 u_sec++; 675 } 676 v_nsec = u_nsec - pps_tf[0].tv_nsec; 677 if (u_sec == pps_tf[0].tv_sec && v_nsec < -MAXFREQ) { 678 return; 679 } 680 pps_tf[2] = pps_tf[1]; 681 pps_tf[1] = pps_tf[0]; 682 pps_tf[0].tv_sec = u_sec; 683 pps_tf[0].tv_nsec = u_nsec; 684 685 /* 686 * Compute the difference between the current and previous 687 * counter values. If the difference exceeds 0.5 s, assume it 688 * has wrapped around, so correct 1.0 s. If the result exceeds 689 * the tick interval, the sample point has crossed a tick 690 * boundary during the last second, so correct the tick. Very 691 * intricate. 692 */ 693 u_nsec = nsec; 694 if (u_nsec > (NANOSECOND >> 1)) 695 u_nsec -= NANOSECOND; 696 else if (u_nsec < -(NANOSECOND >> 1)) 697 u_nsec += NANOSECOND; 698 pps_fcount += u_nsec; 699 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) { 700 return; 701 } 702 time_status &= ~STA_PPSJITTER; 703 704 /* 705 * A three-stage median filter is used to help denoise the PPS 706 * time. The median sample becomes the time offset estimate; the 707 * difference between the other two samples becomes the time 708 * dispersion (jitter) estimate. 709 */ 710 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 711 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 712 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 713 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 714 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 715 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 716 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 717 } else { 718 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 719 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 720 } 721 } else { 722 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 723 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 724 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 725 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 726 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 727 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 728 } else { 729 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 730 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 731 } 732 } 733 734 /* 735 * Nominal jitter is due to PPS signal noise and interrupt 736 * latency. If it exceeds the popcorn threshold, 737 * the sample is discarded. otherwise, if so enabled, the time 738 * offset is updated. We can tolerate a modest loss of data here 739 * without degrading time accuracy. 740 */ 741 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 742 time_status |= STA_PPSJITTER; 743 pps_jitcnt++; 744 } else if (time_status & STA_PPSTIME) { 745 L_LINT(time_offset, -v_nsec); 746 L_LINT(pps_offset, -v_nsec); 747 748 if (pps_letgo >= 2) { 749 L_LINT(ftemp, -v_nsec); 750 L_RSHIFT(ftemp, (pps_shift * 2)); 751 L_ADD(ftemp, time_freq); 752 w_nsec = L_GINT(ftemp); 753 if (w_nsec > MAXFREQ) 754 L_LINT(ftemp, MAXFREQ); 755 else if (w_nsec < -MAXFREQ) 756 L_LINT(ftemp, -MAXFREQ); 757 time_freq = ftemp; 758 } 759 760 } 761 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 762 u_sec = pps_tf[0].tv_sec - pps_lastsec; 763 if (u_sec < (1 << pps_shift)) 764 return; 765 766 /* 767 * At the end of the calibration interval the difference between 768 * the first and last counter values becomes the scaled 769 * frequency. It will later be divided by the length of the 770 * interval to determine the frequency update. If the frequency 771 * exceeds a sanity threshold, or if the actual calibration 772 * interval is not equal to the expected length, the data are 773 * discarded. We can tolerate a modest loss of data here without 774 * degrading frequency ccuracy. 775 */ 776 pps_calcnt++; 777 v_nsec = -pps_fcount; 778 pps_lastsec = pps_tf[0].tv_sec; 779 pps_fcount = 0; 780 u_nsec = MAXFREQ << pps_shift; 781 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 782 pps_shift)) { 783 time_status |= STA_PPSERROR; 784 pps_errcnt++; 785 return; 786 } 787 788 /* 789 * Here the raw frequency offset and wander (stability) is 790 * calculated. If the wander is less than the wander threshold 791 * for four consecutive averaging intervals, the interval is 792 * doubled; if it is greater than the threshold for four 793 * consecutive intervals, the interval is halved. The scaled 794 * frequency offset is converted to frequency offset. The 795 * stability metric is calculated as the average of recent 796 * frequency changes, but is used only for performance 797 * monitoring. 798 */ 799 L_LINT(ftemp, v_nsec); 800 L_RSHIFT(ftemp, pps_shift); 801 L_SUB(ftemp, pps_freq); 802 u_nsec = L_GINT(ftemp); 803 if (u_nsec > PPS_MAXWANDER) { 804 L_LINT(ftemp, PPS_MAXWANDER); 805 pps_intcnt--; 806 time_status |= STA_PPSWANDER; 807 pps_stbcnt++; 808 } else if (u_nsec < -PPS_MAXWANDER) { 809 L_LINT(ftemp, -PPS_MAXWANDER); 810 pps_intcnt--; 811 time_status |= STA_PPSWANDER; 812 pps_stbcnt++; 813 } else { 814 pps_intcnt++; 815 } 816 if (!(time_status & STA_PPSFREQ)) { 817 pps_intcnt = 0; 818 pps_shift = PPS_FAVG; 819 } else if (pps_shift > pps_shiftmax) { 820 /* If we lowered pps_shiftmax */ 821 pps_shift = pps_shiftmax; 822 pps_intcnt = 0; 823 } else if (pps_intcnt >= 4) { 824 pps_intcnt = 4; 825 if (pps_shift < pps_shiftmax) { 826 pps_shift++; 827 pps_intcnt = 0; 828 } 829 } else if (pps_intcnt <= -4) { 830 pps_intcnt = -4; 831 if (pps_shift > PPS_FAVG) { 832 pps_shift--; 833 pps_intcnt = 0; 834 } 835 } 836 if (u_nsec < 0) 837 u_nsec = -u_nsec; 838 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 839 840 /* 841 * The PPS frequency is recalculated and clamped to the maximum 842 * MAXFREQ. If enabled, the system clock frequency is updated as 843 * well. 844 */ 845 L_ADD(pps_freq, ftemp); 846 u_nsec = L_GINT(pps_freq); 847 if (u_nsec > MAXFREQ) 848 L_LINT(pps_freq, MAXFREQ); 849 else if (u_nsec < -MAXFREQ) 850 L_LINT(pps_freq, -MAXFREQ); 851 if ((time_status & (STA_PPSFREQ | STA_PPSTIME)) == STA_PPSFREQ) { 852 pps_letgo = 0; 853 time_freq = pps_freq; 854 } else if (time_status & STA_PPSTIME) { 855 if (pps_letgo < 2) 856 pps_letgo++; 857 } 858 } 859 #endif /* PPS_SYNC */ 860