kernel/time/ntp.c

   1 /*
   2  * linux/kernel/time/ntp.c
   3  *
   4  * NTP state machine interfaces and logic.
   5  *
   6  * This code was mainly moved from kernel/timer.c and kernel/time.c
   7  * Please see those files for relevant copyright info and historical
   8  * changelogs.
   9  */
  10
  11 #include <linux/mm.h>
  12 #include <linux/time.h>
  13 #include <linux/timer.h>
  14 #include <linux/timex.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/hrtimer.h>
  17 #include <linux/capability.h>
  18 #include <asm/div64.h>
  19 #include <asm/timex.h>
  20
  21 /*
  22  * Timekeeping variables
  23  */
  24 unsigned long tick_usec = TICK_USEC;            /* USER_HZ period (usec) */
  25 unsigned long tick_nsec;                        /* ACTHZ period (nsec) */
  26 static u64 tick_length, tick_length_base;
  27
  28 #define MAX_TICKADJ             500             /* microsecs */
  29 #define MAX_TICKADJ_SCALED      (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
  30                                   TICK_LENGTH_SHIFT) / NTP_INTERVAL_FREQ)
  31
  32 /*
  33  * phase-lock loop variables
  34  */
  35 /* TIME_ERROR prevents overwriting the CMOS clock */
  36 static int time_state = TIME_OK;        /* clock synchronization status */
  37 int time_status = STA_UNSYNC;           /* clock status bits            */
  38 static s64 time_offset;         /* time adjustment (ns)         */
  39 static long time_constant = 2;          /* pll time constant            */
  40 long time_maxerror = NTP_PHASE_LIMIT;   /* maximum error (us)           */
  41 long time_esterror = NTP_PHASE_LIMIT;   /* estimated error (us)         */
  42 long time_freq;                         /* frequency offset (scaled ppm)*/
  43 static long time_reftime;               /* time at last adjustment (s)  */
  44 long time_adjust;
  45 <<<<<<< HEAD:kernel/time/ntp.c
  46 =======
  47 static long ntp_tick_adj;
  48 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c
  49
  50 static void ntp_update_frequency(void)
  51 {
  52         u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
  53                                 << TICK_LENGTH_SHIFT;
  54 <<<<<<< HEAD:kernel/time/ntp.c
  55         second_length += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
  56 =======
  57         second_length += (s64)ntp_tick_adj << TICK_LENGTH_SHIFT;
  58 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c
  59         second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
  60
  61         tick_length_base = second_length;
  62
  63         do_div(second_length, HZ);
  64         tick_nsec = second_length >> TICK_LENGTH_SHIFT;
  65
  66         do_div(tick_length_base, NTP_INTERVAL_FREQ);
  67 }
  68
  69 /**
  70  * ntp_clear - Clears the NTP state variables
  71  *
  72  * Must be called while holding a write on the xtime_lock
  73  */
  74 void ntp_clear(void)
  75 {
  76         time_adjust = 0;                /* stop active adjtime() */
  77         time_status |= STA_UNSYNC;
  78         time_maxerror = NTP_PHASE_LIMIT;
  79         time_esterror = NTP_PHASE_LIMIT;
  80
  81         ntp_update_frequency();
  82
  83         tick_length = tick_length_base;
  84         time_offset = 0;
  85 }
  86
  87 /*
  88  * this routine handles the overflow of the microsecond field
  89  *
  90  * The tricky bits of code to handle the accurate clock support
  91  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
  92  * They were originally developed for SUN and DEC kernels.
  93  * All the kudos should go to Dave for this stuff.
  94  */
  95 void second_overflow(void)
  96 {
  97         long time_adj;
  98
  99         /* Bump the maxerror field */
 100         time_maxerror += MAXFREQ >> SHIFT_USEC;
 101         if (time_maxerror > NTP_PHASE_LIMIT) {
 102                 time_maxerror = NTP_PHASE_LIMIT;
 103                 time_status |= STA_UNSYNC;
 104         }
 105
 106         /*
 107          * Leap second processing. If in leap-insert state at the end of the
 108          * day, the system clock is set back one second; if in leap-delete
 109          * state, the system clock is set ahead one second. The microtime()
 110          * routine or external clock driver will insure that reported time is
 111          * always monotonic. The ugly divides should be replaced.
 112          */
 113         switch (time_state) {
 114         case TIME_OK:
 115                 if (time_status & STA_INS)
 116                         time_state = TIME_INS;
 117                 else if (time_status & STA_DEL)
 118                         time_state = TIME_DEL;
 119                 break;
 120         case TIME_INS:
 121                 if (xtime.tv_sec % 86400 == 0) {
 122                         xtime.tv_sec--;
 123                         wall_to_monotonic.tv_sec++;
 124                         time_state = TIME_OOP;
 125                         printk(KERN_NOTICE "Clock: inserting leap second "
 126                                         "23:59:60 UTC\n");
 127                 }
 128                 break;
 129         case TIME_DEL:
 130                 if ((xtime.tv_sec + 1) % 86400 == 0) {
 131                         xtime.tv_sec++;
 132                         wall_to_monotonic.tv_sec--;
 133                         time_state = TIME_WAIT;
 134                         printk(KERN_NOTICE "Clock: deleting leap second "
 135                                         "23:59:59 UTC\n");
 136                 }
 137                 break;
 138         case TIME_OOP:
 139                 time_state = TIME_WAIT;
 140                 break;
 141         case TIME_WAIT:
 142                 if (!(time_status & (STA_INS | STA_DEL)))
 143                 time_state = TIME_OK;
 144         }
 145
 146         /*
 147          * Compute the phase adjustment for the next second. The offset is
 148          * reduced by a fixed factor times the time constant.
 149          */
 150         tick_length = tick_length_base;
 151         time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
 152         time_offset -= time_adj;
 153         tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
 154
 155         if (unlikely(time_adjust)) {
 156                 if (time_adjust > MAX_TICKADJ) {
 157                         time_adjust -= MAX_TICKADJ;
 158                         tick_length += MAX_TICKADJ_SCALED;
 159                 } else if (time_adjust < -MAX_TICKADJ) {
 160                         time_adjust += MAX_TICKADJ;
 161                         tick_length -= MAX_TICKADJ_SCALED;
 162                 } else {
 163                         tick_length += (s64)(time_adjust * NSEC_PER_USEC /
 164                                         NTP_INTERVAL_FREQ) << TICK_LENGTH_SHIFT;
 165                         time_adjust = 0;
 166                 }
 167         }
 168 }
 169
 170 /*
 171  * Return how long ticks are at the moment, that is, how much time
 172  * update_wall_time_one_tick will add to xtime next time we call it
 173  * (assuming no calls to do_adjtimex in the meantime).
 174  * The return value is in fixed-point nanoseconds shifted by the
 175  * specified number of bits to the right of the binary point.
 176  * This function has no side-effects.
 177  */
 178 u64 current_tick_length(void)
 179 {
 180         return tick_length;
 181 }
 182
 183 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 184
 185 /* Disable the cmos update - used by virtualization and embedded */
 186 int no_sync_cmos_clock  __read_mostly;
 187
 188 static void sync_cmos_clock(unsigned long dummy);
 189
 190 static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);
 191
 192 static void sync_cmos_clock(unsigned long dummy)
 193 {
 194         struct timespec now, next;
 195         int fail = 1;
 196
 197         /*
 198          * If we have an externally synchronized Linux clock, then update
 199          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 200          * called as close as possible to 500 ms before the new second starts.
 201          * This code is run on a timer.  If the clock is set, that timer
 202          * may not expire at the correct time.  Thus, we adjust...
 203          */
 204         if (!ntp_synced())
 205                 /*
 206                  * Not synced, exit, do not restart a timer (if one is
 207                  * running, let it run out).
 208                  */
 209                 return;
 210
 211         getnstimeofday(&now);
 212         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
 213                 fail = update_persistent_clock(now);
 214
 215         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec;
 216         if (next.tv_nsec <= 0)
 217                 next.tv_nsec += NSEC_PER_SEC;
 218
 219         if (!fail)
 220                 next.tv_sec = 659;
 221         else
 222                 next.tv_sec = 0;
 223
 224         if (next.tv_nsec >= NSEC_PER_SEC) {
 225                 next.tv_sec++;
 226                 next.tv_nsec -= NSEC_PER_SEC;
 227         }
 228         mod_timer(&sync_cmos_timer, jiffies + timespec_to_jiffies(&next));
 229 }
 230
 231 static void notify_cmos_timer(void)
 232 {
 233         if (!no_sync_cmos_clock)
 234                 mod_timer(&sync_cmos_timer, jiffies + 1);
 235 }
 236
 237 #else
 238 static inline void notify_cmos_timer(void) { }
 239 #endif
 240
 241 /* adjtimex mainly allows reading (and writing, if superuser) of
 242  * kernel time-keeping variables. used by xntpd.
 243  */
 244 int do_adjtimex(struct timex *txc)
 245 {
 246         long mtemp, save_adjust, rem;
 247         s64 freq_adj, temp64;
 248         int result;
 249
 250         /* In order to modify anything, you gotta be super-user! */
 251         if (txc->modes && !capable(CAP_SYS_TIME))
 252                 return -EPERM;
 253
 254         /* Now we validate the data before disabling interrupts */
 255
 256         if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) {
 257           /* singleshot must not be used with any other mode bits */
 258                 if (txc->modes != ADJ_OFFSET_SINGLESHOT &&
 259                                         txc->modes != ADJ_OFFSET_SS_READ)
 260                         return -EINVAL;
 261         }
 262
 263         if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
 264           /* adjustment Offset limited to +- .512 seconds */
 265                 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
 266                         return -EINVAL;
 267
 268         /* if the quartz is off by more than 10% something is VERY wrong ! */
 269         if (txc->modes & ADJ_TICK)
 270                 if (txc->tick <  900000/USER_HZ ||
 271                     txc->tick > 1100000/USER_HZ)
 272                         return -EINVAL;
 273
 274         write_seqlock_irq(&xtime_lock);
 275         result = time_state;    /* mostly `TIME_OK' */
 276
 277         /* Save for later - semantics of adjtime is to return old value */
 278         save_adjust = time_adjust;
 279
 280 #if 0   /* STA_CLOCKERR is never set yet */
 281         time_status &= ~STA_CLOCKERR;           /* reset STA_CLOCKERR */
 282 #endif
 283         /* If there are input parameters, then process them */
 284         if (txc->modes)
 285         {
 286             if (txc->modes & ADJ_STATUS)        /* only set allowed bits */
 287                 time_status =  (txc->status & ~STA_RONLY) |
 288                               (time_status & STA_RONLY);
 289
 290             if (txc->modes & ADJ_FREQUENCY) {   /* p. 22 */
 291                 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
 292                     result = -EINVAL;
 293                     goto leave;
 294                 }
 295                 time_freq = ((s64)txc->freq * NSEC_PER_USEC)
 296                                 >> (SHIFT_USEC - SHIFT_NSEC);
 297             }
 298
 299             if (txc->modes & ADJ_MAXERROR) {
 300                 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
 301                     result = -EINVAL;
 302                     goto leave;
 303                 }
 304                 time_maxerror = txc->maxerror;
 305             }
 306
 307             if (txc->modes & ADJ_ESTERROR) {
 308                 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
 309                     result = -EINVAL;
 310                     goto leave;
 311                 }
 312                 time_esterror = txc->esterror;
 313             }
 314
 315             if (txc->modes & ADJ_TIMECONST) {   /* p. 24 */
 316                 if (txc->constant < 0) {        /* NTP v4 uses values > 6 */
 317                     result = -EINVAL;
 318                     goto leave;
 319                 }
 320                 time_constant = min(txc->constant + 4, (long)MAXTC);
 321             }
 322
 323             if (txc->modes & ADJ_OFFSET) {      /* values checked earlier */
 324                 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
 325                     /* adjtime() is independent from ntp_adjtime() */
 326                     time_adjust = txc->offset;
 327                 }
 328                 else if (time_status & STA_PLL) {
 329                     time_offset = txc->offset * NSEC_PER_USEC;
 330
 331                     /*
 332                      * Scale the phase adjustment and
 333                      * clamp to the operating range.
 334                      */
 335                     time_offset = min(time_offset, (s64)MAXPHASE * NSEC_PER_USEC);
 336                     time_offset = max(time_offset, (s64)-MAXPHASE * NSEC_PER_USEC);
 337
 338                     /*
 339                      * Select whether the frequency is to be controlled
 340                      * and in which mode (PLL or FLL). Clamp to the operating
 341                      * range. Ugly multiply/divide should be replaced someday.
 342                      */
 343
 344                     if (time_status & STA_FREQHOLD || time_reftime == 0)
 345                         time_reftime = xtime.tv_sec;
 346                     mtemp = xtime.tv_sec - time_reftime;
 347                     time_reftime = xtime.tv_sec;
 348
 349                     freq_adj = time_offset * mtemp;
 350                     freq_adj = shift_right(freq_adj, time_constant * 2 +
 351                                            (SHIFT_PLL + 2) * 2 - SHIFT_NSEC);
 352                     if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
 353 <<<<<<< HEAD:kernel/time/ntp.c
 354 =======
 355                         u64 utemp64;
 356 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c
 357                         temp64 = time_offset << (SHIFT_NSEC - SHIFT_FLL);
 358                         if (time_offset < 0) {
 359 <<<<<<< HEAD:kernel/time/ntp.c
 360                             temp64 = -temp64;
 361                             do_div(temp64, mtemp);
 362                             freq_adj -= temp64;
 363 =======
 364                             utemp64 = -temp64;
 365                             do_div(utemp64, mtemp);
 366                             freq_adj -= utemp64;
 367 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c
 368                         } else {
 369 <<<<<<< HEAD:kernel/time/ntp.c
 370                             do_div(temp64, mtemp);
 371                             freq_adj += temp64;
 372 =======
 373                             utemp64 = temp64;
 374                             do_div(utemp64, mtemp);
 375                             freq_adj += utemp64;
 376 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c
 377                         }
 378                     }
 379                     freq_adj += time_freq;
 380                     freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC);
 381                     time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC);
 382                     time_offset = div_long_long_rem_signed(time_offset,
 383                                                            NTP_INTERVAL_FREQ,
 384                                                            &rem);
 385                     time_offset <<= SHIFT_UPDATE;
 386                 } /* STA_PLL */
 387             } /* txc->modes & ADJ_OFFSET */
 388             if (txc->modes & ADJ_TICK)
 389                 tick_usec = txc->tick;
 390
 391             if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 392                     ntp_update_frequency();
 393         } /* txc->modes */
 394 leave:  if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
 395                 result = TIME_ERROR;
 396
 397         if ((txc->modes == ADJ_OFFSET_SINGLESHOT) ||
 398                         (txc->modes == ADJ_OFFSET_SS_READ))
 399                 txc->offset = save_adjust;
 400         else
 401                 txc->offset = ((long)shift_right(time_offset, SHIFT_UPDATE)) *
 402                                 NTP_INTERVAL_FREQ / 1000;
 403         txc->freq          = (time_freq / NSEC_PER_USEC) <<
 404                                 (SHIFT_USEC - SHIFT_NSEC);
 405         txc->maxerror      = time_maxerror;
 406         txc->esterror      = time_esterror;
 407         txc->status        = time_status;
 408         txc->constant      = time_constant;
 409         txc->precision     = 1;
 410         txc->tolerance     = MAXFREQ;
 411         txc->tick          = tick_usec;
 412
 413         /* PPS is not implemented, so these are zero */
 414         txc->ppsfreq       = 0;
 415         txc->jitter        = 0;
 416         txc->shift         = 0;
 417         txc->stabil        = 0;
 418         txc->jitcnt        = 0;
 419         txc->calcnt        = 0;
 420         txc->errcnt        = 0;
 421         txc->stbcnt        = 0;
 422         write_sequnlock_irq(&xtime_lock);
 423         do_gettimeofday(&txc->time);
 424         notify_cmos_timer();
 425         return(result);
 426 }
 427 <<<<<<< HEAD:kernel/time/ntp.c
 428 =======
 429
 430 static int __init ntp_tick_adj_setup(char *str)
 431 {
 432         ntp_tick_adj = simple_strtol(str, NULL, 0);
 433         return 1;
 434 }
 435
 436 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 437 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:kernel/time/ntp.c