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