Commit | Line | Data |
---|---|---|
8524070b | 1 | /* |
2 | * linux/kernel/time/timekeeping.c | |
3 | * | |
4 | * Kernel timekeeping code and accessor functions | |
5 | * | |
6 | * This code was moved from linux/kernel/timer.c. | |
7 | * Please see that file for copyright and history logs. | |
8 | * | |
9 | */ | |
10 | ||
11 | #include <linux/module.h> | |
12 | #include <linux/interrupt.h> | |
13 | #include <linux/percpu.h> | |
14 | #include <linux/init.h> | |
15 | #include <linux/mm.h> | |
16 | #include <linux/sysdev.h> | |
17 | #include <linux/clocksource.h> | |
18 | #include <linux/jiffies.h> | |
19 | #include <linux/time.h> | |
20 | #include <linux/tick.h> | |
21 | ||
22 | ||
23 | /* | |
24 | * This read-write spinlock protects us from races in SMP while | |
25 | * playing with xtime and avenrun. | |
26 | */ | |
ba2a631b | 27 | __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); |
8524070b | 28 | |
29 | ||
30 | /* | |
31 | * The current time | |
32 | * wall_to_monotonic is what we need to add to xtime (or xtime corrected | |
33 | * for sub jiffie times) to get to monotonic time. Monotonic is pegged | |
34 | * at zero at system boot time, so wall_to_monotonic will be negative, | |
35 | * however, we will ALWAYS keep the tv_nsec part positive so we can use | |
36 | * the usual normalization. | |
7c3f1a57 TJ |
37 | * |
38 | * wall_to_monotonic is moved after resume from suspend for the monotonic | |
39 | * time not to jump. We need to add total_sleep_time to wall_to_monotonic | |
40 | * to get the real boot based time offset. | |
41 | * | |
42 | * - wall_to_monotonic is no longer the boot time, getboottime must be | |
43 | * used instead. | |
8524070b | 44 | */ |
45 | struct timespec xtime __attribute__ ((aligned (16))); | |
46 | struct timespec wall_to_monotonic __attribute__ ((aligned (16))); | |
7c3f1a57 | 47 | static unsigned long total_sleep_time; /* seconds */ |
8524070b | 48 | |
17c38b74 | 49 | static struct timespec xtime_cache __attribute__ ((aligned (16))); |
1001d0a9 | 50 | void update_xtime_cache(u64 nsec) |
17c38b74 | 51 | { |
52 | xtime_cache = xtime; | |
53 | timespec_add_ns(&xtime_cache, nsec); | |
54 | } | |
17c38b74 | 55 | |
7dffa3c6 | 56 | struct clocksource *clock; |
8524070b | 57 | |
58 | ||
59 | #ifdef CONFIG_GENERIC_TIME | |
60 | /** | |
61 | * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook | |
62 | * | |
63 | * private function, must hold xtime_lock lock when being | |
64 | * called. Returns the number of nanoseconds since the | |
65 | * last call to update_wall_time() (adjusted by NTP scaling) | |
66 | */ | |
67 | static inline s64 __get_nsec_offset(void) | |
68 | { | |
69 | cycle_t cycle_now, cycle_delta; | |
70 | s64 ns_offset; | |
71 | ||
72 | /* read clocksource: */ | |
73 | cycle_now = clocksource_read(clock); | |
74 | ||
75 | /* calculate the delta since the last update_wall_time: */ | |
76 | cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; | |
77 | ||
78 | /* convert to nanoseconds: */ | |
79 | ns_offset = cyc2ns(clock, cycle_delta); | |
80 | ||
81 | return ns_offset; | |
82 | } | |
83 | ||
84 | /** | |
efd9ac86 | 85 | * getnstimeofday - Returns the time of day in a timespec |
8524070b | 86 | * @ts: pointer to the timespec to be set |
87 | * | |
efd9ac86 | 88 | * Returns the time of day in a timespec. |
8524070b | 89 | */ |
efd9ac86 | 90 | void getnstimeofday(struct timespec *ts) |
8524070b | 91 | { |
92 | unsigned long seq; | |
93 | s64 nsecs; | |
94 | ||
95 | do { | |
96 | seq = read_seqbegin(&xtime_lock); | |
97 | ||
98 | *ts = xtime; | |
99 | nsecs = __get_nsec_offset(); | |
100 | ||
101 | } while (read_seqretry(&xtime_lock, seq)); | |
102 | ||
103 | timespec_add_ns(ts, nsecs); | |
104 | } | |
105 | ||
8524070b | 106 | EXPORT_SYMBOL(getnstimeofday); |
107 | ||
108 | /** | |
109 | * do_gettimeofday - Returns the time of day in a timeval | |
110 | * @tv: pointer to the timeval to be set | |
111 | * | |
efd9ac86 | 112 | * NOTE: Users should be converted to using getnstimeofday() |
8524070b | 113 | */ |
114 | void do_gettimeofday(struct timeval *tv) | |
115 | { | |
116 | struct timespec now; | |
117 | ||
efd9ac86 | 118 | getnstimeofday(&now); |
8524070b | 119 | tv->tv_sec = now.tv_sec; |
120 | tv->tv_usec = now.tv_nsec/1000; | |
121 | } | |
122 | ||
123 | EXPORT_SYMBOL(do_gettimeofday); | |
124 | /** | |
125 | * do_settimeofday - Sets the time of day | |
126 | * @tv: pointer to the timespec variable containing the new time | |
127 | * | |
128 | * Sets the time of day to the new time and update NTP and notify hrtimers | |
129 | */ | |
130 | int do_settimeofday(struct timespec *tv) | |
131 | { | |
132 | unsigned long flags; | |
133 | time_t wtm_sec, sec = tv->tv_sec; | |
134 | long wtm_nsec, nsec = tv->tv_nsec; | |
135 | ||
136 | if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) | |
137 | return -EINVAL; | |
138 | ||
139 | write_seqlock_irqsave(&xtime_lock, flags); | |
140 | ||
141 | nsec -= __get_nsec_offset(); | |
142 | ||
143 | wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); | |
144 | wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); | |
145 | ||
146 | set_normalized_timespec(&xtime, sec, nsec); | |
147 | set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); | |
1001d0a9 | 148 | update_xtime_cache(0); |
8524070b | 149 | |
150 | clock->error = 0; | |
151 | ntp_clear(); | |
152 | ||
153 | update_vsyscall(&xtime, clock); | |
154 | ||
155 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
156 | ||
157 | /* signal hrtimers about time change */ | |
158 | clock_was_set(); | |
159 | ||
160 | return 0; | |
161 | } | |
162 | ||
163 | EXPORT_SYMBOL(do_settimeofday); | |
164 | ||
165 | /** | |
166 | * change_clocksource - Swaps clocksources if a new one is available | |
167 | * | |
168 | * Accumulates current time interval and initializes new clocksource | |
169 | */ | |
170 | static void change_clocksource(void) | |
171 | { | |
172 | struct clocksource *new; | |
173 | cycle_t now; | |
174 | u64 nsec; | |
175 | ||
176 | new = clocksource_get_next(); | |
177 | ||
178 | if (clock == new) | |
179 | return; | |
180 | ||
d8bb6f4c | 181 | new->cycle_last = 0; |
8524070b | 182 | now = clocksource_read(new); |
183 | nsec = __get_nsec_offset(); | |
184 | timespec_add_ns(&xtime, nsec); | |
185 | ||
186 | clock = new; | |
187 | clock->cycle_last = now; | |
188 | ||
189 | clock->error = 0; | |
190 | clock->xtime_nsec = 0; | |
10a398d0 | 191 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); |
8524070b | 192 | |
193 | tick_clock_notify(); | |
194 | ||
92896bd9 LT |
195 | /* |
196 | * We're holding xtime lock and waking up klogd would deadlock | |
197 | * us on enqueue. So no printing! | |
8524070b | 198 | printk(KERN_INFO "Time: %s clocksource has been installed.\n", |
199 | clock->name); | |
92896bd9 | 200 | */ |
8524070b | 201 | } |
202 | #else | |
203 | static inline void change_clocksource(void) { } | |
6a669ee8 | 204 | static inline s64 __get_nsec_offset(void) { return 0; } |
8524070b | 205 | #endif |
206 | ||
207 | /** | |
cf4fc6cb | 208 | * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres |
8524070b | 209 | */ |
cf4fc6cb | 210 | int timekeeping_valid_for_hres(void) |
8524070b | 211 | { |
212 | unsigned long seq; | |
213 | int ret; | |
214 | ||
215 | do { | |
216 | seq = read_seqbegin(&xtime_lock); | |
217 | ||
218 | ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; | |
219 | ||
220 | } while (read_seqretry(&xtime_lock, seq)); | |
221 | ||
222 | return ret; | |
223 | } | |
224 | ||
225 | /** | |
226 | * read_persistent_clock - Return time in seconds from the persistent clock. | |
227 | * | |
228 | * Weak dummy function for arches that do not yet support it. | |
229 | * Returns seconds from epoch using the battery backed persistent clock. | |
230 | * Returns zero if unsupported. | |
231 | * | |
232 | * XXX - Do be sure to remove it once all arches implement it. | |
233 | */ | |
234 | unsigned long __attribute__((weak)) read_persistent_clock(void) | |
235 | { | |
236 | return 0; | |
237 | } | |
238 | ||
239 | /* | |
240 | * timekeeping_init - Initializes the clocksource and common timekeeping values | |
241 | */ | |
242 | void __init timekeeping_init(void) | |
243 | { | |
244 | unsigned long flags; | |
245 | unsigned long sec = read_persistent_clock(); | |
246 | ||
247 | write_seqlock_irqsave(&xtime_lock, flags); | |
248 | ||
7dffa3c6 | 249 | ntp_init(); |
8524070b | 250 | |
251 | clock = clocksource_get_next(); | |
10a398d0 | 252 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); |
8524070b | 253 | clock->cycle_last = clocksource_read(clock); |
254 | ||
255 | xtime.tv_sec = sec; | |
256 | xtime.tv_nsec = 0; | |
257 | set_normalized_timespec(&wall_to_monotonic, | |
258 | -xtime.tv_sec, -xtime.tv_nsec); | |
1001d0a9 | 259 | update_xtime_cache(0); |
7c3f1a57 | 260 | total_sleep_time = 0; |
8524070b | 261 | write_sequnlock_irqrestore(&xtime_lock, flags); |
262 | } | |
263 | ||
264 | /* flag for if timekeeping is suspended */ | |
265 | static int timekeeping_suspended; | |
266 | /* time in seconds when suspend began */ | |
267 | static unsigned long timekeeping_suspend_time; | |
6a669ee8 TG |
268 | /* xtime offset when we went into suspend */ |
269 | static s64 timekeeping_suspend_nsecs; | |
8524070b | 270 | |
271 | /** | |
272 | * timekeeping_resume - Resumes the generic timekeeping subsystem. | |
273 | * @dev: unused | |
274 | * | |
275 | * This is for the generic clocksource timekeeping. | |
276 | * xtime/wall_to_monotonic/jiffies/etc are | |
277 | * still managed by arch specific suspend/resume code. | |
278 | */ | |
279 | static int timekeeping_resume(struct sys_device *dev) | |
280 | { | |
281 | unsigned long flags; | |
282 | unsigned long now = read_persistent_clock(); | |
283 | ||
d10ff3fb TG |
284 | clocksource_resume(); |
285 | ||
8524070b | 286 | write_seqlock_irqsave(&xtime_lock, flags); |
287 | ||
288 | if (now && (now > timekeeping_suspend_time)) { | |
289 | unsigned long sleep_length = now - timekeeping_suspend_time; | |
290 | ||
291 | xtime.tv_sec += sleep_length; | |
292 | wall_to_monotonic.tv_sec -= sleep_length; | |
7c3f1a57 | 293 | total_sleep_time += sleep_length; |
8524070b | 294 | } |
6a669ee8 TG |
295 | /* Make sure that we have the correct xtime reference */ |
296 | timespec_add_ns(&xtime, timekeeping_suspend_nsecs); | |
1001d0a9 | 297 | update_xtime_cache(0); |
8524070b | 298 | /* re-base the last cycle value */ |
d8bb6f4c | 299 | clock->cycle_last = 0; |
8524070b | 300 | clock->cycle_last = clocksource_read(clock); |
301 | clock->error = 0; | |
302 | timekeeping_suspended = 0; | |
303 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
304 | ||
305 | touch_softlockup_watchdog(); | |
306 | ||
307 | clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); | |
308 | ||
309 | /* Resume hrtimers */ | |
310 | hres_timers_resume(); | |
311 | ||
312 | return 0; | |
313 | } | |
314 | ||
315 | static int timekeeping_suspend(struct sys_device *dev, pm_message_t state) | |
316 | { | |
317 | unsigned long flags; | |
318 | ||
3be90950 TG |
319 | timekeeping_suspend_time = read_persistent_clock(); |
320 | ||
8524070b | 321 | write_seqlock_irqsave(&xtime_lock, flags); |
6a669ee8 TG |
322 | /* Get the current xtime offset */ |
323 | timekeeping_suspend_nsecs = __get_nsec_offset(); | |
8524070b | 324 | timekeeping_suspended = 1; |
8524070b | 325 | write_sequnlock_irqrestore(&xtime_lock, flags); |
326 | ||
327 | clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); | |
328 | ||
329 | return 0; | |
330 | } | |
331 | ||
332 | /* sysfs resume/suspend bits for timekeeping */ | |
333 | static struct sysdev_class timekeeping_sysclass = { | |
af5ca3f4 | 334 | .name = "timekeeping", |
8524070b | 335 | .resume = timekeeping_resume, |
336 | .suspend = timekeeping_suspend, | |
8524070b | 337 | }; |
338 | ||
339 | static struct sys_device device_timer = { | |
340 | .id = 0, | |
341 | .cls = &timekeeping_sysclass, | |
342 | }; | |
343 | ||
344 | static int __init timekeeping_init_device(void) | |
345 | { | |
346 | int error = sysdev_class_register(&timekeeping_sysclass); | |
347 | if (!error) | |
348 | error = sysdev_register(&device_timer); | |
349 | return error; | |
350 | } | |
351 | ||
352 | device_initcall(timekeeping_init_device); | |
353 | ||
354 | /* | |
355 | * If the error is already larger, we look ahead even further | |
356 | * to compensate for late or lost adjustments. | |
357 | */ | |
358 | static __always_inline int clocksource_bigadjust(s64 error, s64 *interval, | |
359 | s64 *offset) | |
360 | { | |
361 | s64 tick_error, i; | |
362 | u32 look_ahead, adj; | |
363 | s32 error2, mult; | |
364 | ||
365 | /* | |
366 | * Use the current error value to determine how much to look ahead. | |
367 | * The larger the error the slower we adjust for it to avoid problems | |
368 | * with losing too many ticks, otherwise we would overadjust and | |
369 | * produce an even larger error. The smaller the adjustment the | |
370 | * faster we try to adjust for it, as lost ticks can do less harm | |
3eb05676 | 371 | * here. This is tuned so that an error of about 1 msec is adjusted |
8524070b | 372 | * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). |
373 | */ | |
7fc5c784 | 374 | error2 = clock->error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ); |
8524070b | 375 | error2 = abs(error2); |
376 | for (look_ahead = 0; error2 > 0; look_ahead++) | |
377 | error2 >>= 2; | |
378 | ||
379 | /* | |
380 | * Now calculate the error in (1 << look_ahead) ticks, but first | |
381 | * remove the single look ahead already included in the error. | |
382 | */ | |
8383c423 | 383 | tick_error = tick_length >> (NTP_SCALE_SHIFT - clock->shift + 1); |
8524070b | 384 | tick_error -= clock->xtime_interval >> 1; |
385 | error = ((error - tick_error) >> look_ahead) + tick_error; | |
386 | ||
387 | /* Finally calculate the adjustment shift value. */ | |
388 | i = *interval; | |
389 | mult = 1; | |
390 | if (error < 0) { | |
391 | error = -error; | |
392 | *interval = -*interval; | |
393 | *offset = -*offset; | |
394 | mult = -1; | |
395 | } | |
396 | for (adj = 0; error > i; adj++) | |
397 | error >>= 1; | |
398 | ||
399 | *interval <<= adj; | |
400 | *offset <<= adj; | |
401 | return mult << adj; | |
402 | } | |
403 | ||
404 | /* | |
405 | * Adjust the multiplier to reduce the error value, | |
406 | * this is optimized for the most common adjustments of -1,0,1, | |
407 | * for other values we can do a bit more work. | |
408 | */ | |
71120f18 | 409 | static void clocksource_adjust(s64 offset) |
8524070b | 410 | { |
411 | s64 error, interval = clock->cycle_interval; | |
412 | int adj; | |
413 | ||
7fc5c784 | 414 | error = clock->error >> (NTP_SCALE_SHIFT - clock->shift - 1); |
8524070b | 415 | if (error > interval) { |
416 | error >>= 2; | |
417 | if (likely(error <= interval)) | |
418 | adj = 1; | |
419 | else | |
420 | adj = clocksource_bigadjust(error, &interval, &offset); | |
421 | } else if (error < -interval) { | |
422 | error >>= 2; | |
423 | if (likely(error >= -interval)) { | |
424 | adj = -1; | |
425 | interval = -interval; | |
426 | offset = -offset; | |
427 | } else | |
428 | adj = clocksource_bigadjust(error, &interval, &offset); | |
429 | } else | |
430 | return; | |
431 | ||
432 | clock->mult += adj; | |
433 | clock->xtime_interval += interval; | |
434 | clock->xtime_nsec -= offset; | |
435 | clock->error -= (interval - offset) << | |
7fc5c784 | 436 | (NTP_SCALE_SHIFT - clock->shift); |
8524070b | 437 | } |
438 | ||
439 | /** | |
440 | * update_wall_time - Uses the current clocksource to increment the wall time | |
441 | * | |
442 | * Called from the timer interrupt, must hold a write on xtime_lock. | |
443 | */ | |
444 | void update_wall_time(void) | |
445 | { | |
446 | cycle_t offset; | |
447 | ||
448 | /* Make sure we're fully resumed: */ | |
449 | if (unlikely(timekeeping_suspended)) | |
450 | return; | |
451 | ||
452 | #ifdef CONFIG_GENERIC_TIME | |
453 | offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask; | |
454 | #else | |
455 | offset = clock->cycle_interval; | |
456 | #endif | |
457 | clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift; | |
458 | ||
459 | /* normally this loop will run just once, however in the | |
460 | * case of lost or late ticks, it will accumulate correctly. | |
461 | */ | |
462 | while (offset >= clock->cycle_interval) { | |
463 | /* accumulate one interval */ | |
464 | clock->xtime_nsec += clock->xtime_interval; | |
465 | clock->cycle_last += clock->cycle_interval; | |
466 | offset -= clock->cycle_interval; | |
467 | ||
468 | if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) { | |
469 | clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift; | |
470 | xtime.tv_sec++; | |
471 | second_overflow(); | |
472 | } | |
473 | ||
8524070b | 474 | /* accumulate error between NTP and clock interval */ |
8383c423 | 475 | clock->error += tick_length; |
7fc5c784 | 476 | clock->error -= clock->xtime_interval << (NTP_SCALE_SHIFT - clock->shift); |
8524070b | 477 | } |
478 | ||
479 | /* correct the clock when NTP error is too big */ | |
71120f18 | 480 | clocksource_adjust(offset); |
8524070b | 481 | |
482 | /* store full nanoseconds into xtime */ | |
483 | xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift; | |
484 | clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift; | |
485 | ||
17c38b74 | 486 | update_xtime_cache(cyc2ns(clock, offset)); |
487 | ||
8524070b | 488 | /* check to see if there is a new clocksource to use */ |
489 | change_clocksource(); | |
490 | update_vsyscall(&xtime, clock); | |
491 | } | |
7c3f1a57 TJ |
492 | |
493 | /** | |
494 | * getboottime - Return the real time of system boot. | |
495 | * @ts: pointer to the timespec to be set | |
496 | * | |
497 | * Returns the time of day in a timespec. | |
498 | * | |
499 | * This is based on the wall_to_monotonic offset and the total suspend | |
500 | * time. Calls to settimeofday will affect the value returned (which | |
501 | * basically means that however wrong your real time clock is at boot time, | |
502 | * you get the right time here). | |
503 | */ | |
504 | void getboottime(struct timespec *ts) | |
505 | { | |
506 | set_normalized_timespec(ts, | |
507 | - (wall_to_monotonic.tv_sec + total_sleep_time), | |
508 | - wall_to_monotonic.tv_nsec); | |
509 | } | |
510 | ||
511 | /** | |
512 | * monotonic_to_bootbased - Convert the monotonic time to boot based. | |
513 | * @ts: pointer to the timespec to be converted | |
514 | */ | |
515 | void monotonic_to_bootbased(struct timespec *ts) | |
516 | { | |
517 | ts->tv_sec += total_sleep_time; | |
518 | } | |
2c6b47de | 519 | |
17c38b74 | 520 | unsigned long get_seconds(void) |
521 | { | |
522 | return xtime_cache.tv_sec; | |
523 | } | |
524 | EXPORT_SYMBOL(get_seconds); | |
525 | ||
526 | ||
2c6b47de | 527 | struct timespec current_kernel_time(void) |
528 | { | |
529 | struct timespec now; | |
530 | unsigned long seq; | |
531 | ||
532 | do { | |
533 | seq = read_seqbegin(&xtime_lock); | |
534 | ||
17c38b74 | 535 | now = xtime_cache; |
2c6b47de | 536 | } while (read_seqretry(&xtime_lock, seq)); |
537 | ||
538 | return now; | |
539 | } | |
2c6b47de | 540 | EXPORT_SYMBOL(current_kernel_time); |