Commit | Line | Data |
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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))); |
50 | static inline void update_xtime_cache(u64 nsec) | |
51 | { | |
52 | xtime_cache = xtime; | |
53 | timespec_add_ns(&xtime_cache, nsec); | |
54 | } | |
17c38b74 | 55 | |
8524070b | 56 | static struct clocksource *clock; /* pointer to current clocksource */ |
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 | /** | |
85 | * __get_realtime_clock_ts - Returns the time of day in a timespec | |
86 | * @ts: pointer to the timespec to be set | |
87 | * | |
88 | * Returns the time of day in a timespec. Used by | |
89 | * do_gettimeofday() and get_realtime_clock_ts(). | |
90 | */ | |
91 | static inline void __get_realtime_clock_ts(struct timespec *ts) | |
92 | { | |
93 | unsigned long seq; | |
94 | s64 nsecs; | |
95 | ||
96 | do { | |
97 | seq = read_seqbegin(&xtime_lock); | |
98 | ||
99 | *ts = xtime; | |
100 | nsecs = __get_nsec_offset(); | |
101 | ||
102 | } while (read_seqretry(&xtime_lock, seq)); | |
103 | ||
104 | timespec_add_ns(ts, nsecs); | |
105 | } | |
106 | ||
107 | /** | |
108 | * getnstimeofday - Returns the time of day in a timespec | |
109 | * @ts: pointer to the timespec to be set | |
110 | * | |
111 | * Returns the time of day in a timespec. | |
112 | */ | |
113 | void getnstimeofday(struct timespec *ts) | |
114 | { | |
115 | __get_realtime_clock_ts(ts); | |
116 | } | |
117 | ||
118 | EXPORT_SYMBOL(getnstimeofday); | |
119 | ||
120 | /** | |
121 | * do_gettimeofday - Returns the time of day in a timeval | |
122 | * @tv: pointer to the timeval to be set | |
123 | * | |
124 | * NOTE: Users should be converted to using get_realtime_clock_ts() | |
125 | */ | |
126 | void do_gettimeofday(struct timeval *tv) | |
127 | { | |
128 | struct timespec now; | |
129 | ||
130 | __get_realtime_clock_ts(&now); | |
131 | tv->tv_sec = now.tv_sec; | |
132 | tv->tv_usec = now.tv_nsec/1000; | |
133 | } | |
134 | ||
135 | EXPORT_SYMBOL(do_gettimeofday); | |
136 | /** | |
137 | * do_settimeofday - Sets the time of day | |
138 | * @tv: pointer to the timespec variable containing the new time | |
139 | * | |
140 | * Sets the time of day to the new time and update NTP and notify hrtimers | |
141 | */ | |
142 | int do_settimeofday(struct timespec *tv) | |
143 | { | |
144 | unsigned long flags; | |
145 | time_t wtm_sec, sec = tv->tv_sec; | |
146 | long wtm_nsec, nsec = tv->tv_nsec; | |
147 | ||
148 | if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) | |
149 | return -EINVAL; | |
150 | ||
151 | write_seqlock_irqsave(&xtime_lock, flags); | |
152 | ||
153 | nsec -= __get_nsec_offset(); | |
154 | ||
155 | wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); | |
156 | wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); | |
157 | ||
158 | set_normalized_timespec(&xtime, sec, nsec); | |
159 | set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); | |
160 | ||
161 | clock->error = 0; | |
162 | ntp_clear(); | |
163 | ||
164 | update_vsyscall(&xtime, clock); | |
165 | ||
166 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
167 | ||
168 | /* signal hrtimers about time change */ | |
169 | clock_was_set(); | |
170 | ||
171 | return 0; | |
172 | } | |
173 | ||
174 | EXPORT_SYMBOL(do_settimeofday); | |
175 | ||
176 | /** | |
177 | * change_clocksource - Swaps clocksources if a new one is available | |
178 | * | |
179 | * Accumulates current time interval and initializes new clocksource | |
180 | */ | |
181 | static void change_clocksource(void) | |
182 | { | |
183 | struct clocksource *new; | |
184 | cycle_t now; | |
185 | u64 nsec; | |
186 | ||
187 | new = clocksource_get_next(); | |
188 | ||
189 | if (clock == new) | |
190 | return; | |
191 | ||
192 | now = clocksource_read(new); | |
193 | nsec = __get_nsec_offset(); | |
194 | timespec_add_ns(&xtime, nsec); | |
195 | ||
196 | clock = new; | |
197 | clock->cycle_last = now; | |
198 | ||
199 | clock->error = 0; | |
200 | clock->xtime_nsec = 0; | |
201 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); | |
202 | ||
203 | tick_clock_notify(); | |
204 | ||
205 | printk(KERN_INFO "Time: %s clocksource has been installed.\n", | |
206 | clock->name); | |
207 | } | |
208 | #else | |
209 | static inline void change_clocksource(void) { } | |
6a669ee8 | 210 | static inline s64 __get_nsec_offset(void) { return 0; } |
8524070b | 211 | #endif |
212 | ||
213 | /** | |
214 | * timekeeping_is_continuous - check to see if timekeeping is free running | |
215 | */ | |
216 | int timekeeping_is_continuous(void) | |
217 | { | |
218 | unsigned long seq; | |
219 | int ret; | |
220 | ||
221 | do { | |
222 | seq = read_seqbegin(&xtime_lock); | |
223 | ||
224 | ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; | |
225 | ||
226 | } while (read_seqretry(&xtime_lock, seq)); | |
227 | ||
228 | return ret; | |
229 | } | |
230 | ||
231 | /** | |
232 | * read_persistent_clock - Return time in seconds from the persistent clock. | |
233 | * | |
234 | * Weak dummy function for arches that do not yet support it. | |
235 | * Returns seconds from epoch using the battery backed persistent clock. | |
236 | * Returns zero if unsupported. | |
237 | * | |
238 | * XXX - Do be sure to remove it once all arches implement it. | |
239 | */ | |
240 | unsigned long __attribute__((weak)) read_persistent_clock(void) | |
241 | { | |
242 | return 0; | |
243 | } | |
244 | ||
245 | /* | |
246 | * timekeeping_init - Initializes the clocksource and common timekeeping values | |
247 | */ | |
248 | void __init timekeeping_init(void) | |
249 | { | |
250 | unsigned long flags; | |
251 | unsigned long sec = read_persistent_clock(); | |
252 | ||
253 | write_seqlock_irqsave(&xtime_lock, flags); | |
254 | ||
255 | ntp_clear(); | |
256 | ||
257 | clock = clocksource_get_next(); | |
258 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); | |
259 | clock->cycle_last = clocksource_read(clock); | |
260 | ||
261 | xtime.tv_sec = sec; | |
262 | xtime.tv_nsec = 0; | |
263 | set_normalized_timespec(&wall_to_monotonic, | |
264 | -xtime.tv_sec, -xtime.tv_nsec); | |
7c3f1a57 | 265 | total_sleep_time = 0; |
8524070b | 266 | |
267 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
268 | } | |
269 | ||
270 | /* flag for if timekeeping is suspended */ | |
271 | static int timekeeping_suspended; | |
272 | /* time in seconds when suspend began */ | |
273 | static unsigned long timekeeping_suspend_time; | |
6a669ee8 TG |
274 | /* xtime offset when we went into suspend */ |
275 | static s64 timekeeping_suspend_nsecs; | |
8524070b | 276 | |
277 | /** | |
278 | * timekeeping_resume - Resumes the generic timekeeping subsystem. | |
279 | * @dev: unused | |
280 | * | |
281 | * This is for the generic clocksource timekeeping. | |
282 | * xtime/wall_to_monotonic/jiffies/etc are | |
283 | * still managed by arch specific suspend/resume code. | |
284 | */ | |
285 | static int timekeeping_resume(struct sys_device *dev) | |
286 | { | |
287 | unsigned long flags; | |
288 | unsigned long now = read_persistent_clock(); | |
289 | ||
d10ff3fb TG |
290 | clocksource_resume(); |
291 | ||
8524070b | 292 | write_seqlock_irqsave(&xtime_lock, flags); |
293 | ||
294 | if (now && (now > timekeeping_suspend_time)) { | |
295 | unsigned long sleep_length = now - timekeeping_suspend_time; | |
296 | ||
297 | xtime.tv_sec += sleep_length; | |
298 | wall_to_monotonic.tv_sec -= sleep_length; | |
7c3f1a57 | 299 | total_sleep_time += sleep_length; |
8524070b | 300 | } |
6a669ee8 TG |
301 | /* Make sure that we have the correct xtime reference */ |
302 | timespec_add_ns(&xtime, timekeeping_suspend_nsecs); | |
8524070b | 303 | /* re-base the last cycle value */ |
304 | clock->cycle_last = clocksource_read(clock); | |
305 | clock->error = 0; | |
306 | timekeeping_suspended = 0; | |
307 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
308 | ||
309 | touch_softlockup_watchdog(); | |
310 | ||
311 | clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); | |
312 | ||
313 | /* Resume hrtimers */ | |
314 | hres_timers_resume(); | |
315 | ||
316 | return 0; | |
317 | } | |
318 | ||
319 | static int timekeeping_suspend(struct sys_device *dev, pm_message_t state) | |
320 | { | |
321 | unsigned long flags; | |
322 | ||
3be90950 TG |
323 | timekeeping_suspend_time = read_persistent_clock(); |
324 | ||
8524070b | 325 | write_seqlock_irqsave(&xtime_lock, flags); |
6a669ee8 TG |
326 | /* Get the current xtime offset */ |
327 | timekeeping_suspend_nsecs = __get_nsec_offset(); | |
8524070b | 328 | timekeeping_suspended = 1; |
8524070b | 329 | write_sequnlock_irqrestore(&xtime_lock, flags); |
330 | ||
331 | clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); | |
332 | ||
333 | return 0; | |
334 | } | |
335 | ||
336 | /* sysfs resume/suspend bits for timekeeping */ | |
337 | static struct sysdev_class timekeeping_sysclass = { | |
338 | .resume = timekeeping_resume, | |
339 | .suspend = timekeeping_suspend, | |
340 | set_kset_name("timekeeping"), | |
341 | }; | |
342 | ||
343 | static struct sys_device device_timer = { | |
344 | .id = 0, | |
345 | .cls = &timekeeping_sysclass, | |
346 | }; | |
347 | ||
348 | static int __init timekeeping_init_device(void) | |
349 | { | |
350 | int error = sysdev_class_register(&timekeeping_sysclass); | |
351 | if (!error) | |
352 | error = sysdev_register(&device_timer); | |
353 | return error; | |
354 | } | |
355 | ||
356 | device_initcall(timekeeping_init_device); | |
357 | ||
358 | /* | |
359 | * If the error is already larger, we look ahead even further | |
360 | * to compensate for late or lost adjustments. | |
361 | */ | |
362 | static __always_inline int clocksource_bigadjust(s64 error, s64 *interval, | |
363 | s64 *offset) | |
364 | { | |
365 | s64 tick_error, i; | |
366 | u32 look_ahead, adj; | |
367 | s32 error2, mult; | |
368 | ||
369 | /* | |
370 | * Use the current error value to determine how much to look ahead. | |
371 | * The larger the error the slower we adjust for it to avoid problems | |
372 | * with losing too many ticks, otherwise we would overadjust and | |
373 | * produce an even larger error. The smaller the adjustment the | |
374 | * faster we try to adjust for it, as lost ticks can do less harm | |
375 | * here. This is tuned so that an error of about 1 msec is adusted | |
376 | * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). | |
377 | */ | |
378 | error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ); | |
379 | error2 = abs(error2); | |
380 | for (look_ahead = 0; error2 > 0; look_ahead++) | |
381 | error2 >>= 2; | |
382 | ||
383 | /* | |
384 | * Now calculate the error in (1 << look_ahead) ticks, but first | |
385 | * remove the single look ahead already included in the error. | |
386 | */ | |
387 | tick_error = current_tick_length() >> | |
388 | (TICK_LENGTH_SHIFT - clock->shift + 1); | |
389 | tick_error -= clock->xtime_interval >> 1; | |
390 | error = ((error - tick_error) >> look_ahead) + tick_error; | |
391 | ||
392 | /* Finally calculate the adjustment shift value. */ | |
393 | i = *interval; | |
394 | mult = 1; | |
395 | if (error < 0) { | |
396 | error = -error; | |
397 | *interval = -*interval; | |
398 | *offset = -*offset; | |
399 | mult = -1; | |
400 | } | |
401 | for (adj = 0; error > i; adj++) | |
402 | error >>= 1; | |
403 | ||
404 | *interval <<= adj; | |
405 | *offset <<= adj; | |
406 | return mult << adj; | |
407 | } | |
408 | ||
409 | /* | |
410 | * Adjust the multiplier to reduce the error value, | |
411 | * this is optimized for the most common adjustments of -1,0,1, | |
412 | * for other values we can do a bit more work. | |
413 | */ | |
71120f18 | 414 | static void clocksource_adjust(s64 offset) |
8524070b | 415 | { |
416 | s64 error, interval = clock->cycle_interval; | |
417 | int adj; | |
418 | ||
419 | error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1); | |
420 | if (error > interval) { | |
421 | error >>= 2; | |
422 | if (likely(error <= interval)) | |
423 | adj = 1; | |
424 | else | |
425 | adj = clocksource_bigadjust(error, &interval, &offset); | |
426 | } else if (error < -interval) { | |
427 | error >>= 2; | |
428 | if (likely(error >= -interval)) { | |
429 | adj = -1; | |
430 | interval = -interval; | |
431 | offset = -offset; | |
432 | } else | |
433 | adj = clocksource_bigadjust(error, &interval, &offset); | |
434 | } else | |
435 | return; | |
436 | ||
437 | clock->mult += adj; | |
438 | clock->xtime_interval += interval; | |
439 | clock->xtime_nsec -= offset; | |
440 | clock->error -= (interval - offset) << | |
441 | (TICK_LENGTH_SHIFT - clock->shift); | |
442 | } | |
443 | ||
444 | /** | |
445 | * update_wall_time - Uses the current clocksource to increment the wall time | |
446 | * | |
447 | * Called from the timer interrupt, must hold a write on xtime_lock. | |
448 | */ | |
449 | void update_wall_time(void) | |
450 | { | |
451 | cycle_t offset; | |
452 | ||
453 | /* Make sure we're fully resumed: */ | |
454 | if (unlikely(timekeeping_suspended)) | |
455 | return; | |
456 | ||
457 | #ifdef CONFIG_GENERIC_TIME | |
458 | offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask; | |
459 | #else | |
460 | offset = clock->cycle_interval; | |
461 | #endif | |
462 | clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift; | |
463 | ||
464 | /* normally this loop will run just once, however in the | |
465 | * case of lost or late ticks, it will accumulate correctly. | |
466 | */ | |
467 | while (offset >= clock->cycle_interval) { | |
468 | /* accumulate one interval */ | |
469 | clock->xtime_nsec += clock->xtime_interval; | |
470 | clock->cycle_last += clock->cycle_interval; | |
471 | offset -= clock->cycle_interval; | |
472 | ||
473 | if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) { | |
474 | clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift; | |
475 | xtime.tv_sec++; | |
476 | second_overflow(); | |
477 | } | |
478 | ||
8524070b | 479 | /* accumulate error between NTP and clock interval */ |
480 | clock->error += current_tick_length(); | |
481 | clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift); | |
482 | } | |
483 | ||
484 | /* correct the clock when NTP error is too big */ | |
71120f18 | 485 | clocksource_adjust(offset); |
8524070b | 486 | |
487 | /* store full nanoseconds into xtime */ | |
488 | xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift; | |
489 | clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift; | |
490 | ||
17c38b74 | 491 | update_xtime_cache(cyc2ns(clock, offset)); |
492 | ||
8524070b | 493 | /* check to see if there is a new clocksource to use */ |
494 | change_clocksource(); | |
495 | update_vsyscall(&xtime, clock); | |
496 | } | |
7c3f1a57 TJ |
497 | |
498 | /** | |
499 | * getboottime - Return the real time of system boot. | |
500 | * @ts: pointer to the timespec to be set | |
501 | * | |
502 | * Returns the time of day in a timespec. | |
503 | * | |
504 | * This is based on the wall_to_monotonic offset and the total suspend | |
505 | * time. Calls to settimeofday will affect the value returned (which | |
506 | * basically means that however wrong your real time clock is at boot time, | |
507 | * you get the right time here). | |
508 | */ | |
509 | void getboottime(struct timespec *ts) | |
510 | { | |
511 | set_normalized_timespec(ts, | |
512 | - (wall_to_monotonic.tv_sec + total_sleep_time), | |
513 | - wall_to_monotonic.tv_nsec); | |
514 | } | |
515 | ||
516 | /** | |
517 | * monotonic_to_bootbased - Convert the monotonic time to boot based. | |
518 | * @ts: pointer to the timespec to be converted | |
519 | */ | |
520 | void monotonic_to_bootbased(struct timespec *ts) | |
521 | { | |
522 | ts->tv_sec += total_sleep_time; | |
523 | } | |
2c6b47de | 524 | |
17c38b74 | 525 | unsigned long get_seconds(void) |
526 | { | |
527 | return xtime_cache.tv_sec; | |
528 | } | |
529 | EXPORT_SYMBOL(get_seconds); | |
530 | ||
531 | ||
2c6b47de | 532 | struct timespec current_kernel_time(void) |
533 | { | |
534 | struct timespec now; | |
535 | unsigned long seq; | |
536 | ||
537 | do { | |
538 | seq = read_seqbegin(&xtime_lock); | |
539 | ||
17c38b74 | 540 | now = xtime_cache; |
2c6b47de | 541 | } while (read_seqretry(&xtime_lock, seq)); |
542 | ||
543 | return now; | |
544 | } | |
2c6b47de | 545 | EXPORT_SYMBOL(current_kernel_time); |