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/timex.h> 14 #include <linux/jiffies.h> 15 #include <linux/hrtimer.h> 16 #include <linux/capability.h> 17 #include <linux/math64.h> 18 #include <linux/clocksource.h> 19 #include <linux/workqueue.h> 20 #include <asm/timex.h> 21 22 /* 23 * Timekeeping variables 24 */ 25 unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */ 26 unsigned long tick_nsec; /* ACTHZ period (nsec) */ 27 u64 tick_length; 28 static u64 tick_length_base; 29 30 static struct hrtimer leap_timer; 31 32 #define MAX_TICKADJ 500 /* microsecs */ 33 #define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \ 34 NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 35 36 /* 37 * phase-lock loop variables 38 */ 39 /* TIME_ERROR prevents overwriting the CMOS clock */ 40 static int time_state = TIME_OK; /* clock synchronization status */ 41 int time_status = STA_UNSYNC; /* clock status bits */ 42 static long time_tai; /* TAI offset (s) */ 43 static s64 time_offset; /* time adjustment (ns) */ 44 static long time_constant = 2; /* pll time constant */ 45 long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ 46 long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ 47 static s64 time_freq; /* frequency offset (scaled ns/s)*/ 48 static long time_reftime; /* time at last adjustment (s) */ 49 long time_adjust; 50 static long ntp_tick_adj; 51 52 static void ntp_update_frequency(void) 53 { 54 u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 55 << NTP_SCALE_SHIFT; 56 second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT; 57 second_length += time_freq; 58 59 tick_length_base = second_length; 60 61 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 62 tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ); 63 } 64 65 static void ntp_update_offset(long offset) 66 { 67 long mtemp; 68 s64 freq_adj; 69 70 if (!(time_status & STA_PLL)) 71 return; 72 73 if (!(time_status & STA_NANO)) 74 offset *= NSEC_PER_USEC; 75 76 /* 77 * Scale the phase adjustment and 78 * clamp to the operating range. 79 */ 80 offset = min(offset, MAXPHASE); 81 offset = max(offset, -MAXPHASE); 82 83 /* 84 * Select how the frequency is to be controlled 85 * and in which mode (PLL or FLL). 86 */ 87 if (time_status & STA_FREQHOLD || time_reftime == 0) 88 time_reftime = xtime.tv_sec; 89 mtemp = xtime.tv_sec - time_reftime; 90 time_reftime = xtime.tv_sec; 91 92 freq_adj = (s64)offset * mtemp; 93 freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant); 94 time_status &= ~STA_MODE; 95 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 96 freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL), 97 mtemp); 98 time_status |= STA_MODE; 99 } 100 freq_adj += time_freq; 101 freq_adj = min(freq_adj, MAXFREQ_SCALED); 102 time_freq = max(freq_adj, -MAXFREQ_SCALED); 103 104 time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 105 } 106 107 /** 108 * ntp_clear - Clears the NTP state variables 109 * 110 * Must be called while holding a write on the xtime_lock 111 */ 112 void ntp_clear(void) 113 { 114 time_adjust = 0; /* stop active adjtime() */ 115 time_status |= STA_UNSYNC; 116 time_maxerror = NTP_PHASE_LIMIT; 117 time_esterror = NTP_PHASE_LIMIT; 118 119 ntp_update_frequency(); 120 121 tick_length = tick_length_base; 122 time_offset = 0; 123 } 124 125 /* 126 * Leap second processing. If in leap-insert state at the end of the 127 * day, the system clock is set back one second; if in leap-delete 128 * state, the system clock is set ahead one second. 129 */ 130 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer) 131 { 132 enum hrtimer_restart res = HRTIMER_NORESTART; 133 134 write_seqlock_irq(&xtime_lock); 135 136 switch (time_state) { 137 case TIME_OK: 138 break; 139 case TIME_INS: 140 xtime.tv_sec--; 141 wall_to_monotonic.tv_sec++; 142 time_state = TIME_OOP; 143 printk(KERN_NOTICE "Clock: " 144 "inserting leap second 23:59:60 UTC\n"); 145 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC); 146 res = HRTIMER_RESTART; 147 break; 148 case TIME_DEL: 149 xtime.tv_sec++; 150 time_tai--; 151 wall_to_monotonic.tv_sec--; 152 time_state = TIME_WAIT; 153 printk(KERN_NOTICE "Clock: " 154 "deleting leap second 23:59:59 UTC\n"); 155 break; 156 case TIME_OOP: 157 time_tai++; 158 time_state = TIME_WAIT; 159 /* fall through */ 160 case TIME_WAIT: 161 if (!(time_status & (STA_INS | STA_DEL))) 162 time_state = TIME_OK; 163 break; 164 } 165 update_vsyscall(&xtime, clock); 166 167 write_sequnlock_irq(&xtime_lock); 168 169 return res; 170 } 171 172 /* 173 * this routine handles the overflow of the microsecond field 174 * 175 * The tricky bits of code to handle the accurate clock support 176 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 177 * They were originally developed for SUN and DEC kernels. 178 * All the kudos should go to Dave for this stuff. 179 */ 180 void second_overflow(void) 181 { 182 s64 time_adj; 183 184 /* Bump the maxerror field */ 185 time_maxerror += MAXFREQ / NSEC_PER_USEC; 186 if (time_maxerror > NTP_PHASE_LIMIT) { 187 time_maxerror = NTP_PHASE_LIMIT; 188 time_status |= STA_UNSYNC; 189 } 190 191 /* 192 * Compute the phase adjustment for the next second. The offset is 193 * reduced by a fixed factor times the time constant. 194 */ 195 tick_length = tick_length_base; 196 time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); 197 time_offset -= time_adj; 198 tick_length += time_adj; 199 200 if (unlikely(time_adjust)) { 201 if (time_adjust > MAX_TICKADJ) { 202 time_adjust -= MAX_TICKADJ; 203 tick_length += MAX_TICKADJ_SCALED; 204 } else if (time_adjust < -MAX_TICKADJ) { 205 time_adjust += MAX_TICKADJ; 206 tick_length -= MAX_TICKADJ_SCALED; 207 } else { 208 tick_length += (s64)(time_adjust * NSEC_PER_USEC / 209 NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT; 210 time_adjust = 0; 211 } 212 } 213 } 214 215 #ifdef CONFIG_GENERIC_CMOS_UPDATE 216 217 /* Disable the cmos update - used by virtualization and embedded */ 218 int no_sync_cmos_clock __read_mostly; 219 220 static void sync_cmos_clock(struct work_struct *work); 221 222 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 223 224 static void sync_cmos_clock(struct work_struct *work) 225 { 226 struct timespec now, next; 227 int fail = 1; 228 229 /* 230 * If we have an externally synchronized Linux clock, then update 231 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 232 * called as close as possible to 500 ms before the new second starts. 233 * This code is run on a timer. If the clock is set, that timer 234 * may not expire at the correct time. Thus, we adjust... 235 */ 236 if (!ntp_synced()) 237 /* 238 * Not synced, exit, do not restart a timer (if one is 239 * running, let it run out). 240 */ 241 return; 242 243 getnstimeofday(&now); 244 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) 245 fail = update_persistent_clock(now); 246 247 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 248 if (next.tv_nsec <= 0) 249 next.tv_nsec += NSEC_PER_SEC; 250 251 if (!fail) 252 next.tv_sec = 659; 253 else 254 next.tv_sec = 0; 255 256 if (next.tv_nsec >= NSEC_PER_SEC) { 257 next.tv_sec++; 258 next.tv_nsec -= NSEC_PER_SEC; 259 } 260 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next)); 261 } 262 263 static void notify_cmos_timer(void) 264 { 265 if (!no_sync_cmos_clock) 266 schedule_delayed_work(&sync_cmos_work, 0); 267 } 268 269 #else 270 static inline void notify_cmos_timer(void) { } 271 #endif 272 273 /* adjtimex mainly allows reading (and writing, if superuser) of 274 * kernel time-keeping variables. used by xntpd. 275 */ 276 int do_adjtimex(struct timex *txc) 277 { 278 struct timespec ts; 279 int result; 280 281 /* Validate the data before disabling interrupts */ 282 if (txc->modes & ADJ_ADJTIME) { 283 /* singleshot must not be used with any other mode bits */ 284 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 285 return -EINVAL; 286 if (!(txc->modes & ADJ_OFFSET_READONLY) && 287 !capable(CAP_SYS_TIME)) 288 return -EPERM; 289 } else { 290 /* In order to modify anything, you gotta be super-user! */ 291 if (txc->modes && !capable(CAP_SYS_TIME)) 292 return -EPERM; 293 294 /* if the quartz is off by more than 10% something is VERY wrong! */ 295 if (txc->modes & ADJ_TICK && 296 (txc->tick < 900000/USER_HZ || 297 txc->tick > 1100000/USER_HZ)) 298 return -EINVAL; 299 300 if (txc->modes & ADJ_STATUS && time_state != TIME_OK) 301 hrtimer_cancel(&leap_timer); 302 } 303 304 getnstimeofday(&ts); 305 306 write_seqlock_irq(&xtime_lock); 307 308 /* If there are input parameters, then process them */ 309 if (txc->modes & ADJ_ADJTIME) { 310 long save_adjust = time_adjust; 311 312 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 313 /* adjtime() is independent from ntp_adjtime() */ 314 time_adjust = txc->offset; 315 ntp_update_frequency(); 316 } 317 txc->offset = save_adjust; 318 goto adj_done; 319 } 320 if (txc->modes) { 321 long sec; 322 323 if (txc->modes & ADJ_STATUS) { 324 if ((time_status & STA_PLL) && 325 !(txc->status & STA_PLL)) { 326 time_state = TIME_OK; 327 time_status = STA_UNSYNC; 328 } 329 /* only set allowed bits */ 330 time_status &= STA_RONLY; 331 time_status |= txc->status & ~STA_RONLY; 332 333 switch (time_state) { 334 case TIME_OK: 335 start_timer: 336 sec = ts.tv_sec; 337 if (time_status & STA_INS) { 338 time_state = TIME_INS; 339 sec += 86400 - sec % 86400; 340 hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS); 341 } else if (time_status & STA_DEL) { 342 time_state = TIME_DEL; 343 sec += 86400 - (sec + 1) % 86400; 344 hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS); 345 } 346 break; 347 case TIME_INS: 348 case TIME_DEL: 349 time_state = TIME_OK; 350 goto start_timer; 351 break; 352 case TIME_WAIT: 353 if (!(time_status & (STA_INS | STA_DEL))) 354 time_state = TIME_OK; 355 break; 356 case TIME_OOP: 357 hrtimer_restart(&leap_timer); 358 break; 359 } 360 } 361 362 if (txc->modes & ADJ_NANO) 363 time_status |= STA_NANO; 364 if (txc->modes & ADJ_MICRO) 365 time_status &= ~STA_NANO; 366 367 if (txc->modes & ADJ_FREQUENCY) { 368 time_freq = (s64)txc->freq * PPM_SCALE; 369 time_freq = min(time_freq, MAXFREQ_SCALED); 370 time_freq = max(time_freq, -MAXFREQ_SCALED); 371 } 372 373 if (txc->modes & ADJ_MAXERROR) 374 time_maxerror = txc->maxerror; 375 if (txc->modes & ADJ_ESTERROR) 376 time_esterror = txc->esterror; 377 378 if (txc->modes & ADJ_TIMECONST) { 379 time_constant = txc->constant; 380 if (!(time_status & STA_NANO)) 381 time_constant += 4; 382 time_constant = min(time_constant, (long)MAXTC); 383 time_constant = max(time_constant, 0l); 384 } 385 386 if (txc->modes & ADJ_TAI && txc->constant > 0) 387 time_tai = txc->constant; 388 389 if (txc->modes & ADJ_OFFSET) 390 ntp_update_offset(txc->offset); 391 if (txc->modes & ADJ_TICK) 392 tick_usec = txc->tick; 393 394 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 395 ntp_update_frequency(); 396 } 397 398 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 399 NTP_SCALE_SHIFT); 400 if (!(time_status & STA_NANO)) 401 txc->offset /= NSEC_PER_USEC; 402 403 adj_done: 404 result = time_state; /* mostly `TIME_OK' */ 405 if (time_status & (STA_UNSYNC|STA_CLOCKERR)) 406 result = TIME_ERROR; 407 408 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 409 (s64)PPM_SCALE_INV, NTP_SCALE_SHIFT); 410 txc->maxerror = time_maxerror; 411 txc->esterror = time_esterror; 412 txc->status = time_status; 413 txc->constant = time_constant; 414 txc->precision = 1; 415 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 416 txc->tick = tick_usec; 417 txc->tai = time_tai; 418 419 /* PPS is not implemented, so these are zero */ 420 txc->ppsfreq = 0; 421 txc->jitter = 0; 422 txc->shift = 0; 423 txc->stabil = 0; 424 txc->jitcnt = 0; 425 txc->calcnt = 0; 426 txc->errcnt = 0; 427 txc->stbcnt = 0; 428 write_sequnlock_irq(&xtime_lock); 429 430 txc->time.tv_sec = ts.tv_sec; 431 txc->time.tv_usec = ts.tv_nsec; 432 if (!(time_status & STA_NANO)) 433 txc->time.tv_usec /= NSEC_PER_USEC; 434 435 notify_cmos_timer(); 436 437 return result; 438 } 439 440 static int __init ntp_tick_adj_setup(char *str) 441 { 442 ntp_tick_adj = simple_strtol(str, NULL, 0); 443 return 1; 444 } 445 446 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 447 448 void __init ntp_init(void) 449 { 450 ntp_clear(); 451 hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS); 452 leap_timer.function = ntp_leap_second; 453 } 454