sys/kern/kern_ntptime.c

   1 /***********************************************************************
   2  *                                                                     *
   3  * Copyright (c) David L. Mills 1993-2001                              *
   4  *                                                                     *
   5  * Permission to use, copy, modify, and distribute this software and   *
   6  * its documentation for any purpose and without fee is hereby         *
   7  * granted, provided that the above copyright notice appears in all    *
   8  * copies and that both the copyright notice and this permission       *
   9  * notice appear in supporting documentation, and that the name        *
  10  * University of Delaware not be used in advertising or publicity      *
  11  * pertaining to distribution of the software without specific,        *
  12  * written prior permission. The University of Delaware makes no       *
  13  * representations about the suitability this software for any         *
  14  * purpose. It is provided "as is" without express or implied          *
  15  * warranty.                                                           *
  16  *                                                                     *
  17  **********************************************************************/
  18
  19 /*
  20  * Adapted from the original sources for FreeBSD and timecounters by:
  21  * Poul-Henning Kamp <phk@FreeBSD.org>.
  22  *
  23  * The 32bit version of the "LP" macros seems a bit past its "sell by"
  24  * date so I have retained only the 64bit version and included it directly
  25  * in this file.
  26  *
  27  * Only minor changes done to interface with the timecounters over in
  28  * sys/kern/kern_clock.c.   Some of the comments below may be (even more)
  29  * confusing and/or plain wrong in that context.
  30  *
  31  * $FreeBSD: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $
  32  */
  33
  34 #include "opt_ntp.h"
  35
  36 #include <sys/param.h>
  37 #include <sys/systm.h>
  38 #include <sys/sysproto.h>
  39 #include <sys/kernel.h>
  40 #include <sys/proc.h>
  41 #include <sys/priv.h>
  42 #include <sys/time.h>
  43 #include <sys/timex.h>
  44 #include <sys/timepps.h>
  45 #include <sys/sysctl.h>
  46
  47 #include <sys/thread2.h>
  48
  49 /*
  50  * Single-precision macros for 64-bit machines
  51  */
  52 typedef long long l_fp;
  53 #define L_ADD(v, u)     ((v) += (u))
  54 #define L_SUB(v, u)     ((v) -= (u))
  55 #define L_ADDHI(v, a)   ((v) += (long long)(a) << 32)
  56 #define L_NEG(v)        ((v) = -(v))
  57 #define L_RSHIFT(v, n) \
  58         do { \
  59                 if ((v) < 0) \
  60                         (v) = -(-(v) >> (n)); \
  61                 else \
  62                         (v) = (v) >> (n); \
  63         } while (0)
  64 #define L_MPY(v, a)     ((v) *= (a))
  65 #define L_CLR(v)        ((v) = 0)
  66 #define L_ISNEG(v)      ((v) < 0)
  67 #define L_LINT(v, a)    ((v) = (long long)(a) << 32)
  68 #define L_GINT(v)       ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
  69
  70 /*
  71  * Generic NTP kernel interface
  72  *
  73  * These routines constitute the Network Time Protocol (NTP) interfaces
  74  * for user and daemon application programs. The ntp_gettime() routine
  75  * provides the time, maximum error (synch distance) and estimated error
  76  * (dispersion) to client user application programs. The ntp_adjtime()
  77  * routine is used by the NTP daemon to adjust the system clock to an
  78  * externally derived time. The time offset and related variables set by
  79  * this routine are used by other routines in this module to adjust the
  80  * phase and frequency of the clock discipline loop which controls the
  81  * system clock.
  82  *
  83  * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
  84  * defined), the time at each tick interrupt is derived directly from
  85  * the kernel time variable. When the kernel time is reckoned in
  86  * microseconds, (NTP_NANO undefined), the time is derived from the
  87  * kernel time variable together with a variable representing the
  88  * leftover nanoseconds at the last tick interrupt. In either case, the
  89  * current nanosecond time is reckoned from these values plus an
  90  * interpolated value derived by the clock routines in another
  91  * architecture-specific module. The interpolation can use either a
  92  * dedicated counter or a processor cycle counter (PCC) implemented in
  93  * some architectures.
  94  *
  95  * Note that all routines must run at priority splclock or higher.
  96  */
  97 /*
  98  * Phase/frequency-lock loop (PLL/FLL) definitions
  99  *
 100  * The nanosecond clock discipline uses two variable types, time
 101  * variables and frequency variables. Both types are represented as 64-
 102  * bit fixed-point quantities with the decimal point between two 32-bit
 103  * halves. On a 32-bit machine, each half is represented as a single
 104  * word and mathematical operations are done using multiple-precision
 105  * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
 106  * used.
 107  *
 108  * A time variable is a signed 64-bit fixed-point number in ns and
 109  * fraction. It represents the remaining time offset to be amortized
 110  * over succeeding tick interrupts. The maximum time offset is about
 111  * 0.5 s and the resolution is about 2.3e-10 ns.
 112  *
 113  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
 114  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 115  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 116  * |s s s|                       ns                                |
 117  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 118  * |                        fraction                               |
 119  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 120  *
 121  * A frequency variable is a signed 64-bit fixed-point number in ns/s
 122  * and fraction. It represents the ns and fraction to be added to the
 123  * kernel time variable at each second. The maximum frequency offset is
 124  * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
 125  *
 126  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
 127  *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 128  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 129  * |s s s s s s s s s s s s s|            ns/s                     |
 130  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 131  * |                        fraction                               |
 132  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 133  */
 134 /*
 135  * The following variables establish the state of the PLL/FLL and the
 136  * residual time and frequency offset of the local clock.
 137  */
 138 #define SHIFT_PLL       4               /* PLL loop gain (shift) */
 139 #define SHIFT_FLL       2               /* FLL loop gain (shift) */
 140
 141 static int time_state = TIME_OK;        /* clock state */
 142 static int time_status = STA_UNSYNC;    /* clock status bits */
 143 static long time_tai;                   /* TAI offset (s) */
 144 static long time_monitor;               /* last time offset scaled (ns) */
 145 static long time_constant;              /* poll interval (shift) (s) */
 146 static long time_precision = 1;         /* clock precision (ns) */
 147 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
 148 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
 149 static time_t time_reftime;             /* time at last adjustment (s) */
 150 static long time_tick;                  /* nanoseconds per tick (ns) */
 151 static l_fp time_offset;                /* time offset (ns) */
 152 static l_fp time_freq;                  /* frequency offset (ns/s) */
 153 static l_fp time_adj;                   /* tick adjust (ns/s) */
 154
 155 static struct lock ntp_lock = LOCK_INITIALIZER("ntplk", 0, 0);
 156
 157 #ifdef PPS_SYNC
 158 /*
 159  * The following variables are used when a pulse-per-second (PPS) signal
 160  * is available and connected via a modem control lead. They establish
 161  * the engineering parameters of the clock discipline loop when
 162  * controlled by the PPS signal.
 163  */
 164 #define PPS_FAVG        2               /* min freq avg interval (s) (shift) */
 165 #define PPS_FAVGDEF     8               /* default freq avg int (s) (shift) */
 166 #define PPS_FAVGMAX     15              /* max freq avg interval (s) (shift) */
 167 #define PPS_PAVG        4               /* phase avg interval (s) (shift) */
 168 #define PPS_VALID       120             /* PPS signal watchdog max (s) */
 169 #define PPS_MAXWANDER   100000          /* max PPS wander (ns/s) */
 170 #define PPS_POPCORN     2               /* popcorn spike threshold (shift) */
 171
 172 static struct timespec pps_tf[3];       /* phase median filter */
 173 static l_fp pps_freq;                   /* scaled frequency offset (ns/s) */
 174 static long pps_fcount;                 /* frequency accumulator */
 175 static long pps_jitter;                 /* nominal jitter (ns) */
 176 static long pps_stabil;                 /* nominal stability (scaled ns/s) */
 177 static long pps_lastsec;                /* time at last calibration (s) */
 178 static int pps_valid;                   /* signal watchdog counter */
 179 static int pps_shift = PPS_FAVG;        /* interval duration (s) (shift) */
 180 static int pps_shiftmax = PPS_FAVGDEF;  /* max interval duration (s) (shift) */
 181 static int pps_intcnt;                  /* wander counter */
 182
 183 /*
 184  * PPS signal quality monitors
 185  */
 186 static long pps_calcnt;                 /* calibration intervals */
 187 static long pps_jitcnt;                 /* jitter limit exceeded */
 188 static long pps_stbcnt;                 /* stability limit exceeded */
 189 static long pps_errcnt;                 /* calibration errors */
 190 #endif /* PPS_SYNC */
 191 /*
 192  * End of phase/frequency-lock loop (PLL/FLL) definitions
 193  */
 194
 195 static void ntp_init(void);
 196 static void hardupdate(long offset);
 197
 198 /*
 199  * ntp_gettime() - NTP user application interface
 200  *
 201  * See the timex.h header file for synopsis and API description. Note
 202  * that the TAI offset is returned in the ntvtimeval.tai structure
 203  * member.
 204  */
 205 static int
 206 ntp_sysctl(SYSCTL_HANDLER_ARGS)
 207 {
 208         struct ntptimeval ntv;  /* temporary structure */
 209         struct timespec atv;    /* nanosecond time */
 210         int error;
 211
 212         lockmgr(&ntp_lock, LK_EXCLUSIVE);
 213
 214         nanotime(&atv);
 215         ntv.time.tv_sec = atv.tv_sec;
 216         ntv.time.tv_nsec = atv.tv_nsec;
 217         ntv.maxerror = time_maxerror;
 218         ntv.esterror = time_esterror;
 219         ntv.tai = time_tai;
 220         ntv.time_state = time_state;
 221
 222         /*
 223          * Status word error decode. If any of these conditions occur,
 224          * an error is returned, instead of the status word. Most
 225          * applications will care only about the fact the system clock
 226          * may not be trusted, not about the details.
 227          *
 228          * Hardware or software error
 229          */
 230         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
 231
 232         /*
 233          * PPS signal lost when either time or frequency synchronization
 234          * requested
 235          */
 236             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
 237             !(time_status & STA_PPSSIGNAL)) ||
 238
 239         /*
 240          * PPS jitter exceeded when time synchronization requested
 241          */
 242             (time_status & STA_PPSTIME &&
 243             time_status & STA_PPSJITTER) ||
 244
 245         /*
 246          * PPS wander exceeded or calibration error when frequency
 247          * synchronization requested
 248          */
 249             (time_status & STA_PPSFREQ &&
 250             time_status & (STA_PPSWANDER | STA_PPSERROR))) {
 251                 ntv.time_state = TIME_ERROR;
 252         }
 253
 254         error = sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req);
 255         lockmgr(&ntp_lock, LK_RELEASE);
 256
 257         return error;
 258 }
 259
 260 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
 261 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
 262         0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
 263
 264 #ifdef PPS_SYNC
 265 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
 266 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
 267 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
 268
 269 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
 270 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
 271 #endif
 272 /*
 273  * ntp_adjtime() - NTP daemon application interface
 274  *
 275  * See the timex.h header file for synopsis and API description. Note
 276  * that the timex.constant structure member has a dual purpose to set
 277  * the time constant and to set the TAI offset.
 278  *
 279  * MPALMOSTSAFE
 280  */
 281 int
 282 sys_ntp_adjtime(struct ntp_adjtime_args *uap)
 283 {
 284         struct thread *td = curthread;
 285         struct timex ntv;       /* temporary structure */
 286         long freq;              /* frequency ns/s) */
 287         int modes;              /* mode bits from structure */
 288         int error;
 289
 290         error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
 291         if (error)
 292                 return(error);
 293
 294         /*
 295          * Update selected clock variables - only the superuser can
 296          * change anything. Note that there is no error checking here on
 297          * the assumption the superuser should know what it is doing.
 298          * Note that either the time constant or TAI offset are loaded
 299          * from the ntv.constant member, depending on the mode bits. If
 300          * the STA_PLL bit in the status word is cleared, the state and
 301          * status words are reset to the initial values at boot.
 302          */
 303         modes = ntv.modes;
 304         if (modes)
 305                 error = priv_check(td, PRIV_NTP_ADJTIME);
 306         if (error)
 307                 return (error);
 308
 309         lockmgr(&ntp_lock, LK_EXCLUSIVE);
 310         crit_enter();
 311         if (modes & MOD_MAXERROR)
 312                 time_maxerror = ntv.maxerror;
 313         if (modes & MOD_ESTERROR)
 314                 time_esterror = ntv.esterror;
 315         if (modes & MOD_STATUS) {
 316                 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
 317                         time_state = TIME_OK;
 318                         time_status = STA_UNSYNC;
 319 #ifdef PPS_SYNC
 320                         pps_shift = PPS_FAVG;
 321 #endif /* PPS_SYNC */
 322                 }
 323                 time_status &= STA_RONLY;
 324                 time_status |= ntv.status & ~STA_RONLY;
 325         }
 326         if (modes & MOD_TIMECONST) {
 327                 if (ntv.constant < 0)
 328                         time_constant = 0;
 329                 else if (ntv.constant > MAXTC)
 330                         time_constant = MAXTC;
 331                 else
 332                         time_constant = ntv.constant;
 333         }
 334         if (modes & MOD_TAI) {
 335                 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
 336                         time_tai = ntv.constant;
 337         }
 338 #ifdef PPS_SYNC
 339         if (modes & MOD_PPSMAX) {
 340                 if (ntv.shift < PPS_FAVG)
 341                         pps_shiftmax = PPS_FAVG;
 342                 else if (ntv.shift > PPS_FAVGMAX)
 343                         pps_shiftmax = PPS_FAVGMAX;
 344                 else
 345                         pps_shiftmax = ntv.shift;
 346         }
 347 #endif /* PPS_SYNC */
 348         if (modes & MOD_NANO)
 349                 time_status |= STA_NANO;
 350         if (modes & MOD_MICRO)
 351                 time_status &= ~STA_NANO;
 352         if (modes & MOD_CLKB)
 353                 time_status |= STA_CLK;
 354         if (modes & MOD_CLKA)
 355                 time_status &= ~STA_CLK;
 356         if (modes & MOD_OFFSET) {
 357                 if (time_status & STA_NANO)
 358                         hardupdate(ntv.offset);
 359                 else
 360                         hardupdate(ntv.offset * 1000);
 361         }
 362         /*
 363          * Note: the userland specified frequency is in seconds per second
 364          * times 65536e+6.  Multiply by a thousand and divide by 65336 to
 365          * get nanoseconds.
 366          */
 367         if (modes & MOD_FREQUENCY) {
 368                 freq = (ntv.freq * 1000LL) >> 16;
 369                 if (freq > MAXFREQ)
 370                         L_LINT(time_freq, MAXFREQ);
 371                 else if (freq < -MAXFREQ)
 372                         L_LINT(time_freq, -MAXFREQ);
 373                 else
 374                         L_LINT(time_freq, freq);
 375 #ifdef PPS_SYNC
 376                 pps_freq = time_freq;
 377 #endif /* PPS_SYNC */
 378         }
 379
 380         /*
 381          * Retrieve all clock variables. Note that the TAI offset is
 382          * returned only by ntp_gettime();
 383          */
 384         if (time_status & STA_NANO)
 385                 ntv.offset = time_monitor;
 386         else
 387                 ntv.offset = time_monitor / 1000; /* XXX rounding ? */
 388         ntv.freq = L_GINT((time_freq / 1000LL) << 16);
 389         ntv.maxerror = time_maxerror;
 390         ntv.esterror = time_esterror;
 391         ntv.status = time_status;
 392         ntv.constant = time_constant;
 393         if (time_status & STA_NANO)
 394                 ntv.precision = time_precision;
 395         else
 396                 ntv.precision = time_precision / 1000;
 397         ntv.tolerance = MAXFREQ * SCALE_PPM;
 398 #ifdef PPS_SYNC
 399         ntv.shift = pps_shift;
 400         ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
 401         if (time_status & STA_NANO)
 402                 ntv.jitter = pps_jitter;
 403         else
 404                 ntv.jitter = pps_jitter / 1000;
 405         ntv.stabil = pps_stabil;
 406         ntv.calcnt = pps_calcnt;
 407         ntv.errcnt = pps_errcnt;
 408         ntv.jitcnt = pps_jitcnt;
 409         ntv.stbcnt = pps_stbcnt;
 410 #endif /* PPS_SYNC */
 411         crit_exit();
 412         lockmgr(&ntp_lock, LK_RELEASE);
 413
 414         error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
 415         if (error)
 416                 return (error);
 417
 418         /*
 419          * Status word error decode. See comments in
 420          * ntp_gettime() routine.
 421          */
 422         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
 423             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
 424             !(time_status & STA_PPSSIGNAL)) ||
 425             (time_status & STA_PPSTIME &&
 426             time_status & STA_PPSJITTER) ||
 427             (time_status & STA_PPSFREQ &&
 428             time_status & (STA_PPSWANDER | STA_PPSERROR))) {
 429                 uap->sysmsg_result = TIME_ERROR;
 430         } else {
 431                 uap->sysmsg_result = time_state;
 432         }
 433         return (error);
 434 }
 435
 436 /*
 437  * second_overflow() - called after ntp_tick_adjust()
 438  *
 439  * This routine is ordinarily called from hardclock() whenever the seconds
 440  * hand rolls over.  It returns leap seconds to add or drop, and sets nsec_adj
 441  * to the total adjustment to make over the next second in (ns << 32).
 442  *
 443  * This routine is only called by cpu #0.
 444  */
 445 int
 446 ntp_update_second(time_t newsec, int64_t *nsec_adj)
 447 {
 448         l_fp ftemp;             /* 32/64-bit temporary */
 449         int  adjsec = 0;
 450
 451         /*
 452          * On rollover of the second both the nanosecond and microsecond
 453          * clocks are updated and the state machine cranked as
 454          * necessary. The phase adjustment to be used for the next
 455          * second is calculated and the maximum error is increased by
 456          * the tolerance.
 457          */
 458         time_maxerror += MAXFREQ / 1000;
 459
 460         /*
 461          * Leap second processing. If in leap-insert state at
 462          * the end of the day, the system clock is set back one
 463          * second; if in leap-delete state, the system clock is
 464          * set ahead one second. The nano_time() routine or
 465          * external clock driver will insure that reported time
 466          * is always monotonic.
 467          */
 468         switch (time_state) {
 469
 470                 /*
 471                  * No warning.
 472                  */
 473                 case TIME_OK:
 474                 if (time_status & STA_INS)
 475                         time_state = TIME_INS;
 476                 else if (time_status & STA_DEL)
 477                         time_state = TIME_DEL;
 478                 break;
 479
 480                 /*
 481                  * Insert second 23:59:60 following second
 482                  * 23:59:59.
 483                  */
 484                 case TIME_INS:
 485                 if (!(time_status & STA_INS))
 486                         time_state = TIME_OK;
 487                 else if ((newsec) % 86400 == 0) {
 488                         --adjsec;
 489                         time_state = TIME_OOP;
 490                 }
 491                 break;
 492
 493                 /*
 494                  * Delete second 23:59:59.
 495                  */
 496                 case TIME_DEL:
 497                 if (!(time_status & STA_DEL))
 498                         time_state = TIME_OK;
 499                 else if (((newsec) + 1) % 86400 == 0) {
 500                         ++adjsec;
 501                         time_tai--;
 502                         time_state = TIME_WAIT;
 503                 }
 504                 break;
 505
 506                 /*
 507                  * Insert second in progress.
 508                  */
 509                 case TIME_OOP:
 510                         time_tai++;
 511                         time_state = TIME_WAIT;
 512                 break;
 513
 514                 /*
 515                  * Wait for status bits to clear.
 516                  */
 517                 case TIME_WAIT:
 518                 if (!(time_status & (STA_INS | STA_DEL)))
 519                         time_state = TIME_OK;
 520         }
 521
 522         /*
 523          * time_offset represents the total time adjustment we wish to
 524          * make (over no particular period of time).  time_freq represents
 525          * the frequency compensation we wish to apply.
 526          *
 527          * time_adj represents the total adjustment we wish to make over
 528          * one full second.  hardclock usually applies this adjustment in
 529          * time_adj / hz jumps, hz times a second.
 530          */
 531         ftemp = time_offset;
 532 #ifdef PPS_SYNC
 533         /* XXX even if PPS signal dies we should finish adjustment ? */
 534         if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))
 535                 L_RSHIFT(ftemp, pps_shift);
 536         else
 537                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
 538 #else
 539                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
 540 #endif /* PPS_SYNC */
 541         time_adj = ftemp;               /* adjustment for part of the offset */
 542         L_SUB(time_offset, ftemp);
 543         L_ADD(time_adj, time_freq);     /* add frequency correction */
 544         *nsec_adj = time_adj;
 545 #ifdef PPS_SYNC
 546         if (pps_valid > 0)
 547                 pps_valid--;
 548         else
 549                 time_status &= ~STA_PPSSIGNAL;
 550 #endif /* PPS_SYNC */
 551         return(adjsec);
 552 }
 553
 554 /*
 555  * ntp_init() - initialize variables and structures
 556  *
 557  * This routine must be called after the kernel variables hz and tick
 558  * are set or changed and before the next tick interrupt. In this
 559  * particular implementation, these values are assumed set elsewhere in
 560  * the kernel. The design allows the clock frequency and tick interval
 561  * to be changed while the system is running. So, this routine should
 562  * probably be integrated with the code that does that.
 563  */
 564 static void
 565 ntp_init(void)
 566 {
 567
 568         /*
 569          * The following variable must be initialized any time the
 570          * kernel variable hz is changed.
 571          */
 572         time_tick = NANOSECOND / hz;
 573
 574         /*
 575          * The following variables are initialized only at startup. Only
 576          * those structures not cleared by the compiler need to be
 577          * initialized, and these only in the simulator. In the actual
 578          * kernel, any nonzero values here will quickly evaporate.
 579          */
 580         L_CLR(time_offset);
 581         L_CLR(time_freq);
 582 #ifdef PPS_SYNC
 583         pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
 584         pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
 585         pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
 586         pps_fcount = 0;
 587         L_CLR(pps_freq);
 588 #endif /* PPS_SYNC */
 589 }
 590
 591 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL);
 592
 593 /*
 594  * hardupdate() - local clock update
 595  *
 596  * This routine is called by ntp_adjtime() to update the local clock
 597  * phase and frequency. The implementation is of an adaptive-parameter,
 598  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
 599  * time and frequency offset estimates for each call. If the kernel PPS
 600  * discipline code is configured (PPS_SYNC), the PPS signal itself
 601  * determines the new time offset, instead of the calling argument.
 602  * Presumably, calls to ntp_adjtime() occur only when the caller
 603  * believes the local clock is valid within some bound (+-128 ms with
 604  * NTP). If the caller's time is far different than the PPS time, an
 605  * argument will ensue, and it's not clear who will lose.
 606  *
 607  * For uncompensated quartz crystal oscillators and nominal update
 608  * intervals less than 256 s, operation should be in phase-lock mode,
 609  * where the loop is disciplined to phase. For update intervals greater
 610  * than 1024 s, operation should be in frequency-lock mode, where the
 611  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
 612  * is selected by the STA_MODE status bit.
 613  */
 614 static void
 615 hardupdate(long offset)
 616 {
 617         long mtemp;
 618         l_fp ftemp;
 619
 620         /*
 621          * Select how the phase is to be controlled and from which
 622          * source. If the PPS signal is present and enabled to
 623          * discipline the time, the PPS offset is used; otherwise, the
 624          * argument offset is used.
 625          */
 626         if (!(time_status & STA_PLL))
 627                 return;
 628         if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) {
 629                 if (offset > MAXPHASE)
 630                         time_monitor = MAXPHASE;
 631                 else if (offset < -MAXPHASE)
 632                         time_monitor = -MAXPHASE;
 633                 else
 634                         time_monitor = offset;
 635                 L_LINT(time_offset, time_monitor);
 636         }
 637
 638         /*
 639          * Select how the frequency is to be controlled and in which
 640          * mode (PLL or FLL). If the PPS signal is present and enabled
 641          * to discipline the frequency, the PPS frequency is used;
 642          * otherwise, the argument offset is used to compute it.
 643          */
 644         if ((time_status & STA_PPSFREQ) && time_status & STA_PPSSIGNAL) {
 645                 time_reftime = time_uptime;
 646                 return;
 647         }
 648         if ((time_status & STA_FREQHOLD) || time_reftime == 0)
 649                 time_reftime = time_uptime;
 650         mtemp = time_uptime - time_reftime;
 651         L_LINT(ftemp, time_monitor);
 652         L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
 653         L_MPY(ftemp, mtemp);
 654         L_ADD(time_freq, ftemp);
 655         time_status &= ~STA_MODE;
 656         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
 657                 L_LINT(ftemp, (time_monitor << 4) / mtemp);
 658                 L_RSHIFT(ftemp, SHIFT_FLL + 4);
 659                 L_ADD(time_freq, ftemp);
 660                 time_status |= STA_MODE;
 661         }
 662         time_reftime = time_uptime;
 663         if (L_GINT(time_freq) > MAXFREQ)
 664                 L_LINT(time_freq, MAXFREQ);
 665         else if (L_GINT(time_freq) < -MAXFREQ)
 666                 L_LINT(time_freq, -MAXFREQ);
 667 }
 668
 669 #ifdef PPS_SYNC
 670 /*
 671  * hardpps() - discipline CPU clock oscillator to external PPS signal
 672  *
 673  * This routine is called at each PPS interrupt in order to discipline
 674  * the CPU clock oscillator to the PPS signal. There are two independent
 675  * first-order feedback loops, one for the phase, the other for the
 676  * frequency. The phase loop measures and grooms the PPS phase offset
 677  * and leaves it in a handy spot for the seconds overflow routine. The
 678  * frequency loop averages successive PPS phase differences and
 679  * calculates the PPS frequency offset, which is also processed by the
 680  * seconds overflow routine. The code requires the caller to capture the
 681  * time and architecture-dependent hardware counter values in
 682  * nanoseconds at the on-time PPS signal transition.
 683  *
 684  * Note that, on some Unix systems this routine runs at an interrupt
 685  * priority level higher than the timer interrupt routine hardclock().
 686  * Therefore, the variables used are distinct from the hardclock()
 687  * variables, except for the actual time and frequency variables, which
 688  * are determined by this routine and updated atomically.
 689  */
 690 void
 691 hardpps(struct timespec *tsp, long nsec)
 692 {
 693         long u_sec, u_nsec, v_nsec; /* temps */
 694         l_fp ftemp;
 695
 696         /*
 697          * The signal is first processed by a range gate and frequency
 698          * discriminator. The range gate rejects noise spikes outside
 699          * the range +-500 us. The frequency discriminator rejects input
 700          * signals with apparent frequency outside the range 1 +-500
 701          * PPM. If two hits occur in the same second, we ignore the
 702          * later hit; if not and a hit occurs outside the range gate,
 703          * keep the later hit for later comparison, but do not process
 704          * it.
 705          */
 706         time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
 707         time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
 708         pps_valid = PPS_VALID;
 709         u_sec = tsp->tv_sec;
 710         u_nsec = tsp->tv_nsec;
 711         if (u_nsec >= (NANOSECOND >> 1)) {
 712                 u_nsec -= NANOSECOND;
 713                 u_sec++;
 714         }
 715         v_nsec = u_nsec - pps_tf[0].tv_nsec;
 716         if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
 717             MAXFREQ)
 718                 return;
 719         pps_tf[2] = pps_tf[1];
 720         pps_tf[1] = pps_tf[0];
 721         pps_tf[0].tv_sec = u_sec;
 722         pps_tf[0].tv_nsec = u_nsec;
 723
 724         /*
 725          * Compute the difference between the current and previous
 726          * counter values. If the difference exceeds 0.5 s, assume it
 727          * has wrapped around, so correct 1.0 s. If the result exceeds
 728          * the tick interval, the sample point has crossed a tick
 729          * boundary during the last second, so correct the tick. Very
 730          * intricate.
 731          */
 732         u_nsec = nsec;
 733         if (u_nsec > (NANOSECOND >> 1))
 734                 u_nsec -= NANOSECOND;
 735         else if (u_nsec < -(NANOSECOND >> 1))
 736                 u_nsec += NANOSECOND;
 737         pps_fcount += u_nsec;
 738         if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
 739                 return;
 740         time_status &= ~STA_PPSJITTER;
 741
 742         /*
 743          * A three-stage median filter is used to help denoise the PPS
 744          * time. The median sample becomes the time offset estimate; the
 745          * difference between the other two samples becomes the time
 746          * dispersion (jitter) estimate.
 747          */
 748         if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
 749                 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
 750                         v_nsec = pps_tf[1].tv_nsec;     /* 0 1 2 */
 751                         u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
 752                 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
 753                         v_nsec = pps_tf[0].tv_nsec;     /* 2 0 1 */
 754                         u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
 755                 } else {
 756                         v_nsec = pps_tf[2].tv_nsec;     /* 0 2 1 */
 757                         u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
 758                 }
 759         } else {
 760                 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
 761                         v_nsec = pps_tf[1].tv_nsec;     /* 2 1 0 */
 762                         u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
 763                 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
 764                         v_nsec = pps_tf[0].tv_nsec;     /* 1 0 2 */
 765                         u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
 766                 } else {
 767                         v_nsec = pps_tf[2].tv_nsec;     /* 1 2 0 */
 768                         u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
 769                 }
 770         }
 771
 772         /*
 773          * Nominal jitter is due to PPS signal noise and interrupt
 774          * latency. If it exceeds the popcorn threshold, the sample is
 775          * discarded. otherwise, if so enabled, the time offset is
 776          * updated. We can tolerate a modest loss of data here without
 777          * much degrading time accuracy.
 778          */
 779         if (u_nsec > (pps_jitter << PPS_POPCORN)) {
 780                 time_status |= STA_PPSJITTER;
 781                 pps_jitcnt++;
 782         } else if (time_status & STA_PPSTIME) {
 783                 time_monitor = -v_nsec;
 784                 L_LINT(time_offset, time_monitor);
 785         }
 786         pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
 787         u_sec = pps_tf[0].tv_sec - pps_lastsec;
 788         if (u_sec < (1 << pps_shift))
 789                 return;
 790
 791         /*
 792          * At the end of the calibration interval the difference between
 793          * the first and last counter values becomes the scaled
 794          * frequency. It will later be divided by the length of the
 795          * interval to determine the frequency update. If the frequency
 796          * exceeds a sanity threshold, or if the actual calibration
 797          * interval is not equal to the expected length, the data are
 798          * discarded. We can tolerate a modest loss of data here without
 799          * much degrading frequency accuracy.
 800          */
 801         pps_calcnt++;
 802         v_nsec = -pps_fcount;
 803         pps_lastsec = pps_tf[0].tv_sec;
 804         pps_fcount = 0;
 805         u_nsec = MAXFREQ << pps_shift;
 806         if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
 807             pps_shift)) {
 808                 time_status |= STA_PPSERROR;
 809                 pps_errcnt++;
 810                 return;
 811         }
 812
 813         /*
 814          * Here the raw frequency offset and wander (stability) is
 815          * calculated. If the wander is less than the wander threshold
 816          * for four consecutive averaging intervals, the interval is
 817          * doubled; if it is greater than the threshold for four
 818          * consecutive intervals, the interval is halved. The scaled
 819          * frequency offset is converted to frequency offset. The
 820          * stability metric is calculated as the average of recent
 821          * frequency changes, but is used only for performance
 822          * monitoring.
 823          */
 824         L_LINT(ftemp, v_nsec);
 825         L_RSHIFT(ftemp, pps_shift);
 826         L_SUB(ftemp, pps_freq);
 827         u_nsec = L_GINT(ftemp);
 828         if (u_nsec > PPS_MAXWANDER) {
 829                 L_LINT(ftemp, PPS_MAXWANDER);
 830                 pps_intcnt--;
 831                 time_status |= STA_PPSWANDER;
 832                 pps_stbcnt++;
 833         } else if (u_nsec < -PPS_MAXWANDER) {
 834                 L_LINT(ftemp, -PPS_MAXWANDER);
 835                 pps_intcnt--;
 836                 time_status |= STA_PPSWANDER;
 837                 pps_stbcnt++;
 838         } else {
 839                 pps_intcnt++;
 840         }
 841         if (pps_intcnt >= 4) {
 842                 pps_intcnt = 4;
 843                 if (pps_shift < pps_shiftmax) {
 844                         pps_shift++;
 845                         pps_intcnt = 0;
 846                 }
 847         } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
 848                 pps_intcnt = -4;
 849                 if (pps_shift > PPS_FAVG) {
 850                         pps_shift--;
 851                         pps_intcnt = 0;
 852                 }
 853         }
 854         if (u_nsec < 0)
 855                 u_nsec = -u_nsec;
 856         pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
 857
 858         /*
 859          * The PPS frequency is recalculated and clamped to the maximum
 860          * MAXFREQ. If enabled, the system clock frequency is updated as
 861          * well.
 862          */
 863         L_ADD(pps_freq, ftemp);
 864         u_nsec = L_GINT(pps_freq);
 865         if (u_nsec > MAXFREQ)
 866                 L_LINT(pps_freq, MAXFREQ);
 867         else if (u_nsec < -MAXFREQ)
 868                 L_LINT(pps_freq, -MAXFREQ);
 869         if (time_status & STA_PPSFREQ)
 870                 time_freq = pps_freq;
 871 }
 872 #endif /* PPS_SYNC */