blob: c09628d6b848c41cae67e060909e9ee8ac8fc6f6 [file] [log] [blame]
john stultz4c7ee8d2006-09-30 23:28:22 -07001/*
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
15#include <asm/div64.h>
16#include <asm/timex.h>
17
Roman Zippelb0ee7552006-09-30 23:28:22 -070018/*
19 * Timekeeping variables
20 */
21unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
22unsigned long tick_nsec; /* ACTHZ period (nsec) */
23static u64 tick_length, tick_length_base;
24
john stultz4c7ee8d2006-09-30 23:28:22 -070025/* Don't completely fail for HZ > 500. */
26int tickadj = 500/HZ ? : 1; /* microsecs */
27
28/*
29 * phase-lock loop variables
30 */
31/* TIME_ERROR prevents overwriting the CMOS clock */
32int time_state = TIME_OK; /* clock synchronization status */
33int time_status = STA_UNSYNC; /* clock status bits */
34long time_offset; /* time adjustment (us) */
35long time_constant = 2; /* pll time constant */
36long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */
37long time_precision = 1; /* clock precision (us) */
38long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
39long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
40long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC;
41 /* frequency offset (scaled ppm)*/
john stultz4c7ee8d2006-09-30 23:28:22 -070042long time_reftime; /* time at last adjustment (s) */
43long time_adjust;
44long time_next_adjust;
45
Roman Zippelb0ee7552006-09-30 23:28:22 -070046/**
47 * ntp_clear - Clears the NTP state variables
48 *
49 * Must be called while holding a write on the xtime_lock
50 */
51void ntp_clear(void)
52{
53 time_adjust = 0; /* stop active adjtime() */
54 time_status |= STA_UNSYNC;
55 time_maxerror = NTP_PHASE_LIMIT;
56 time_esterror = NTP_PHASE_LIMIT;
57
58 ntp_update_frequency();
59
60 tick_length = tick_length_base;
61}
62
63#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE)
64#define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE)
65
66void ntp_update_frequency(void)
67{
68 tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT;
69 tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT;
70
71 do_div(tick_length_base, HZ);
72
73 tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT;
74}
75
john stultz4c7ee8d2006-09-30 23:28:22 -070076/*
77 * this routine handles the overflow of the microsecond field
78 *
79 * The tricky bits of code to handle the accurate clock support
80 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
81 * They were originally developed for SUN and DEC kernels.
82 * All the kudos should go to Dave for this stuff.
83 */
84void second_overflow(void)
85{
Roman Zippelab8783b2006-09-30 23:28:23 -070086 long ltemp, time_adj;
john stultz4c7ee8d2006-09-30 23:28:22 -070087
88 /* Bump the maxerror field */
89 time_maxerror += time_tolerance >> SHIFT_USEC;
90 if (time_maxerror > NTP_PHASE_LIMIT) {
91 time_maxerror = NTP_PHASE_LIMIT;
92 time_status |= STA_UNSYNC;
93 }
94
95 /*
96 * Leap second processing. If in leap-insert state at the end of the
97 * day, the system clock is set back one second; if in leap-delete
98 * state, the system clock is set ahead one second. The microtime()
99 * routine or external clock driver will insure that reported time is
100 * always monotonic. The ugly divides should be replaced.
101 */
102 switch (time_state) {
103 case TIME_OK:
104 if (time_status & STA_INS)
105 time_state = TIME_INS;
106 else if (time_status & STA_DEL)
107 time_state = TIME_DEL;
108 break;
109 case TIME_INS:
110 if (xtime.tv_sec % 86400 == 0) {
111 xtime.tv_sec--;
112 wall_to_monotonic.tv_sec++;
113 /*
114 * The timer interpolator will make time change
115 * gradually instead of an immediate jump by one second
116 */
117 time_interpolator_update(-NSEC_PER_SEC);
118 time_state = TIME_OOP;
119 clock_was_set();
120 printk(KERN_NOTICE "Clock: inserting leap second "
121 "23:59:60 UTC\n");
122 }
123 break;
124 case TIME_DEL:
125 if ((xtime.tv_sec + 1) % 86400 == 0) {
126 xtime.tv_sec++;
127 wall_to_monotonic.tv_sec--;
128 /*
129 * Use of time interpolator for a gradual change of
130 * time
131 */
132 time_interpolator_update(NSEC_PER_SEC);
133 time_state = TIME_WAIT;
134 clock_was_set();
135 printk(KERN_NOTICE "Clock: deleting leap second "
136 "23:59:59 UTC\n");
137 }
138 break;
139 case TIME_OOP:
140 time_state = TIME_WAIT;
141 break;
142 case TIME_WAIT:
143 if (!(time_status & (STA_INS | STA_DEL)))
144 time_state = TIME_OK;
145 }
146
147 /*
148 * Compute the phase adjustment for the next second. In PLL mode, the
149 * offset is reduced by a fixed factor times the time constant. In FLL
150 * mode the offset is used directly. In either mode, the maximum phase
151 * adjustment for each second is clamped so as to spread the adjustment
152 * over not more than the number of seconds between updates.
153 */
154 ltemp = time_offset;
155 if (!(time_status & STA_FLL))
156 ltemp = shift_right(ltemp, SHIFT_KG + time_constant);
157 ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE);
158 ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE);
159 time_offset -= ltemp;
160 time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE);
161
162 /*
163 * Compute the frequency estimate and additional phase adjustment due
164 * to frequency error for the next second.
165 */
166 ltemp = time_freq;
167 time_adj += shift_right(ltemp,(SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE));
168
169#if HZ == 100
170 /*
171 * Compensate for (HZ==100) != (1 << SHIFT_HZ). Add 25% and 3.125% to
172 * get 128.125; => only 0.125% error (p. 14)
173 */
174 time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5);
175#endif
176#if HZ == 250
177 /*
178 * Compensate for (HZ==250) != (1 << SHIFT_HZ). Add 1.5625% and
179 * 0.78125% to get 255.85938; => only 0.05% error (p. 14)
180 */
181 time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
182#endif
183#if HZ == 1000
184 /*
185 * Compensate for (HZ==1000) != (1 << SHIFT_HZ). Add 1.5625% and
186 * 0.78125% to get 1023.4375; => only 0.05% error (p. 14)
187 */
188 time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7);
189#endif
Roman Zippelb0ee7552006-09-30 23:28:22 -0700190 tick_length = tick_length_base;
Roman Zippelab8783b2006-09-30 23:28:23 -0700191 tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10));
john stultz4c7ee8d2006-09-30 23:28:22 -0700192}
193
194/*
195 * Returns how many microseconds we need to add to xtime this tick
196 * in doing an adjustment requested with adjtime.
197 */
198static long adjtime_adjustment(void)
199{
200 long time_adjust_step;
201
202 time_adjust_step = time_adjust;
203 if (time_adjust_step) {
204 /*
205 * We are doing an adjtime thing. Prepare time_adjust_step to
206 * be within bounds. Note that a positive time_adjust means we
207 * want the clock to run faster.
208 *
209 * Limit the amount of the step to be in the range
210 * -tickadj .. +tickadj
211 */
212 time_adjust_step = min(time_adjust_step, (long)tickadj);
213 time_adjust_step = max(time_adjust_step, (long)-tickadj);
214 }
215 return time_adjust_step;
216}
217
218/* in the NTP reference this is called "hardclock()" */
219void update_ntp_one_tick(void)
220{
221 long time_adjust_step;
222
223 time_adjust_step = adjtime_adjustment();
224 if (time_adjust_step)
225 /* Reduce by this step the amount of time left */
226 time_adjust -= time_adjust_step;
227
228 /* Changes by adjtime() do not take effect till next tick. */
229 if (time_next_adjust != 0) {
230 time_adjust = time_next_adjust;
231 time_next_adjust = 0;
232 }
233}
234
235/*
236 * Return how long ticks are at the moment, that is, how much time
237 * update_wall_time_one_tick will add to xtime next time we call it
238 * (assuming no calls to do_adjtimex in the meantime).
239 * The return value is in fixed-point nanoseconds shifted by the
240 * specified number of bits to the right of the binary point.
241 * This function has no side-effects.
242 */
243u64 current_tick_length(void)
244{
john stultz4c7ee8d2006-09-30 23:28:22 -0700245 u64 ret;
246
247 /* calculate the finest interval NTP will allow.
john stultz4c7ee8d2006-09-30 23:28:22 -0700248 */
Roman Zippelb0ee7552006-09-30 23:28:22 -0700249 ret = tick_length;
250 ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
john stultz4c7ee8d2006-09-30 23:28:22 -0700251
252 return ret;
253}
254
255
256void __attribute__ ((weak)) notify_arch_cmos_timer(void)
257{
258 return;
259}
260
261/* adjtimex mainly allows reading (and writing, if superuser) of
262 * kernel time-keeping variables. used by xntpd.
263 */
264int do_adjtimex(struct timex *txc)
265{
266 long ltemp, mtemp, save_adjust;
267 int result;
268
269 /* In order to modify anything, you gotta be super-user! */
270 if (txc->modes && !capable(CAP_SYS_TIME))
271 return -EPERM;
272
273 /* Now we validate the data before disabling interrupts */
274
275 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
276 /* singleshot must not be used with any other mode bits */
277 if (txc->modes != ADJ_OFFSET_SINGLESHOT)
278 return -EINVAL;
279
280 if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET))
281 /* adjustment Offset limited to +- .512 seconds */
282 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE )
283 return -EINVAL;
284
285 /* if the quartz is off by more than 10% something is VERY wrong ! */
286 if (txc->modes & ADJ_TICK)
287 if (txc->tick < 900000/USER_HZ ||
288 txc->tick > 1100000/USER_HZ)
289 return -EINVAL;
290
291 write_seqlock_irq(&xtime_lock);
292 result = time_state; /* mostly `TIME_OK' */
293
294 /* Save for later - semantics of adjtime is to return old value */
295 save_adjust = time_next_adjust ? time_next_adjust : time_adjust;
296
297#if 0 /* STA_CLOCKERR is never set yet */
298 time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
299#endif
300 /* If there are input parameters, then process them */
301 if (txc->modes)
302 {
303 if (txc->modes & ADJ_STATUS) /* only set allowed bits */
304 time_status = (txc->status & ~STA_RONLY) |
305 (time_status & STA_RONLY);
306
307 if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */
308 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) {
309 result = -EINVAL;
310 goto leave;
311 }
312 time_freq = txc->freq;
313 }
314
315 if (txc->modes & ADJ_MAXERROR) {
316 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) {
317 result = -EINVAL;
318 goto leave;
319 }
320 time_maxerror = txc->maxerror;
321 }
322
323 if (txc->modes & ADJ_ESTERROR) {
324 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) {
325 result = -EINVAL;
326 goto leave;
327 }
328 time_esterror = txc->esterror;
329 }
330
331 if (txc->modes & ADJ_TIMECONST) { /* p. 24 */
332 if (txc->constant < 0) { /* NTP v4 uses values > 6 */
333 result = -EINVAL;
334 goto leave;
335 }
336 time_constant = txc->constant;
337 }
338
339 if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
340 if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
341 /* adjtime() is independent from ntp_adjtime() */
342 if ((time_next_adjust = txc->offset) == 0)
343 time_adjust = 0;
344 }
345 else if (time_status & STA_PLL) {
346 ltemp = txc->offset;
347
348 /*
349 * Scale the phase adjustment and
350 * clamp to the operating range.
351 */
352 if (ltemp > MAXPHASE)
353 time_offset = MAXPHASE << SHIFT_UPDATE;
354 else if (ltemp < -MAXPHASE)
355 time_offset = -(MAXPHASE << SHIFT_UPDATE);
356 else
357 time_offset = ltemp << SHIFT_UPDATE;
358
359 /*
360 * Select whether the frequency is to be controlled
361 * and in which mode (PLL or FLL). Clamp to the operating
362 * range. Ugly multiply/divide should be replaced someday.
363 */
364
365 if (time_status & STA_FREQHOLD || time_reftime == 0)
366 time_reftime = xtime.tv_sec;
367 mtemp = xtime.tv_sec - time_reftime;
368 time_reftime = xtime.tv_sec;
369 if (time_status & STA_FLL) {
370 if (mtemp >= MINSEC) {
371 ltemp = (time_offset / mtemp) << (SHIFT_USEC -
372 SHIFT_UPDATE);
373 time_freq += shift_right(ltemp, SHIFT_KH);
374 } else /* calibration interval too short (p. 12) */
375 result = TIME_ERROR;
376 } else { /* PLL mode */
377 if (mtemp < MAXSEC) {
378 ltemp *= mtemp;
379 time_freq += shift_right(ltemp,(time_constant +
380 time_constant +
381 SHIFT_KF - SHIFT_USEC));
382 } else /* calibration interval too long (p. 12) */
383 result = TIME_ERROR;
384 }
385 time_freq = min(time_freq, time_tolerance);
386 time_freq = max(time_freq, -time_tolerance);
387 } /* STA_PLL */
388 } /* txc->modes & ADJ_OFFSET */
Roman Zippelb0ee7552006-09-30 23:28:22 -0700389 if (txc->modes & ADJ_TICK)
john stultz4c7ee8d2006-09-30 23:28:22 -0700390 tick_usec = txc->tick;
Roman Zippelb0ee7552006-09-30 23:28:22 -0700391
392 if (txc->modes & ADJ_TICK)
393 ntp_update_frequency();
john stultz4c7ee8d2006-09-30 23:28:22 -0700394 } /* txc->modes */
395leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0)
396 result = TIME_ERROR;
397
398 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT)
399 txc->offset = save_adjust;
400 else {
401 txc->offset = shift_right(time_offset, SHIFT_UPDATE);
402 }
403 txc->freq = time_freq;
404 txc->maxerror = time_maxerror;
405 txc->esterror = time_esterror;
406 txc->status = time_status;
407 txc->constant = time_constant;
408 txc->precision = time_precision;
409 txc->tolerance = time_tolerance;
410 txc->tick = tick_usec;
411
412 /* PPS is not implemented, so these are zero */
413 txc->ppsfreq = 0;
414 txc->jitter = 0;
415 txc->shift = 0;
416 txc->stabil = 0;
417 txc->jitcnt = 0;
418 txc->calcnt = 0;
419 txc->errcnt = 0;
420 txc->stbcnt = 0;
421 write_sequnlock_irq(&xtime_lock);
422 do_gettimeofday(&txc->time);
423 notify_arch_cmos_timer();
424 return(result);
425}