projects/linux·blob v3.3 · refs

1245 lines · 32.8 KiB

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/sched.h>
17#include <linux/syscore_ops.h>
18#include <linux/clocksource.h>
19#include <linux/jiffies.h>
20#include <linux/time.h>
21#include <linux/tick.h>
22#include <linux/stop_machine.h>
23
24/* Structure holding internal timekeeping values. */
25struct timekeeper {
26 /* Current clocksource used for timekeeping. */
27 struct clocksource *clock;
28 /* The shift value of the current clocksource. */
29 int shift;
30
31 /* Number of clock cycles in one NTP interval. */
32 cycle_t cycle_interval;
33 /* Number of clock shifted nano seconds in one NTP interval. */
34 u64 xtime_interval;
35 /* shifted nano seconds left over when rounding cycle_interval */
36 s64 xtime_remainder;
37 /* Raw nano seconds accumulated per NTP interval. */
38 u32 raw_interval;
39
40 /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */
41 u64 xtime_nsec;
42 /* Difference between accumulated time and NTP time in ntp
43 * shifted nano seconds. */
44 s64 ntp_error;
45 /* Shift conversion between clock shifted nano seconds and
46 * ntp shifted nano seconds. */
47 int ntp_error_shift;
48 /* NTP adjusted clock multiplier */
49 u32 mult;
50};
51
52static struct timekeeper timekeeper;
53
54/**
55 * timekeeper_setup_internals - Set up internals to use clocksource clock.
56 *
57 * @clock: Pointer to clocksource.
58 *
59 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
60 * pair and interval request.
61 *
62 * Unless you're the timekeeping code, you should not be using this!
63 */
64static void timekeeper_setup_internals(struct clocksource *clock)
65{
66 cycle_t interval;
67 u64 tmp, ntpinterval;
68
69 timekeeper.clock = clock;
70 clock->cycle_last = clock->read(clock);
71
72 /* Do the ns -> cycle conversion first, using original mult */
73 tmp = NTP_INTERVAL_LENGTH;
74 tmp <<= clock->shift;
75 ntpinterval = tmp;
76 tmp += clock->mult/2;
77 do_div(tmp, clock->mult);
78 if (tmp == 0)
79 tmp = 1;
80
81 interval = (cycle_t) tmp;
82 timekeeper.cycle_interval = interval;
83
84 /* Go back from cycles -> shifted ns */
85 timekeeper.xtime_interval = (u64) interval * clock->mult;
86 timekeeper.xtime_remainder = ntpinterval - timekeeper.xtime_interval;
87 timekeeper.raw_interval =
88 ((u64) interval * clock->mult) >> clock->shift;
89
90 timekeeper.xtime_nsec = 0;
91 timekeeper.shift = clock->shift;
92
93 timekeeper.ntp_error = 0;
94 timekeeper.ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
95
96 /*
97 * The timekeeper keeps its own mult values for the currently
98 * active clocksource. These value will be adjusted via NTP
99 * to counteract clock drifting.
100 */
101 timekeeper.mult = clock->mult;
102}
103
104/* Timekeeper helper functions. */
105static inline s64 timekeeping_get_ns(void)
106{
107 cycle_t cycle_now, cycle_delta;
108 struct clocksource *clock;
109
110 /* read clocksource: */
111 clock = timekeeper.clock;
112 cycle_now = clock->read(clock);
113
114 /* calculate the delta since the last update_wall_time: */
115 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
116
117 /* return delta convert to nanoseconds using ntp adjusted mult. */
118 return clocksource_cyc2ns(cycle_delta, timekeeper.mult,
119 timekeeper.shift);
120}
121
122static inline s64 timekeeping_get_ns_raw(void)
123{
124 cycle_t cycle_now, cycle_delta;
125 struct clocksource *clock;
126
127 /* read clocksource: */
128 clock = timekeeper.clock;
129 cycle_now = clock->read(clock);
130
131 /* calculate the delta since the last update_wall_time: */
132 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
133
134 /* return delta convert to nanoseconds. */
135 return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
136}
137
138/*
139 * This read-write spinlock protects us from races in SMP while
140 * playing with xtime.
141 */
142__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
143
144
145/*
146 * The current time
147 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
148 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
149 * at zero at system boot time, so wall_to_monotonic will be negative,
150 * however, we will ALWAYS keep the tv_nsec part positive so we can use
151 * the usual normalization.
152 *
153 * wall_to_monotonic is moved after resume from suspend for the monotonic
154 * time not to jump. We need to add total_sleep_time to wall_to_monotonic
155 * to get the real boot based time offset.
156 *
157 * - wall_to_monotonic is no longer the boot time, getboottime must be
158 * used instead.
159 */
160static struct timespec xtime __attribute__ ((aligned (16)));
161static struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
162static struct timespec total_sleep_time;
163
164/*
165 * The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
166 */
167static struct timespec raw_time;
168
169/* flag for if timekeeping is suspended */
170int __read_mostly timekeeping_suspended;
171
172/* must hold xtime_lock */
173void timekeeping_leap_insert(int leapsecond)
174{
175 xtime.tv_sec += leapsecond;
176 wall_to_monotonic.tv_sec -= leapsecond;
177 update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
178 timekeeper.mult);
179}
180
181/**
182 * timekeeping_forward_now - update clock to the current time
183 *
184 * Forward the current clock to update its state since the last call to
185 * update_wall_time(). This is useful before significant clock changes,
186 * as it avoids having to deal with this time offset explicitly.
187 */
188static void timekeeping_forward_now(void)
189{
190 cycle_t cycle_now, cycle_delta;
191 struct clocksource *clock;
192 s64 nsec;
193
194 clock = timekeeper.clock;
195 cycle_now = clock->read(clock);
196 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
197 clock->cycle_last = cycle_now;
198
199 nsec = clocksource_cyc2ns(cycle_delta, timekeeper.mult,
200 timekeeper.shift);
201
202 /* If arch requires, add in gettimeoffset() */
203 nsec += arch_gettimeoffset();
204
205 timespec_add_ns(&xtime, nsec);
206
207 nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
208 timespec_add_ns(&raw_time, nsec);
209}
210
211/**
212 * getnstimeofday - Returns the time of day in a timespec
213 * @ts: pointer to the timespec to be set
214 *
215 * Returns the time of day in a timespec.
216 */
217void getnstimeofday(struct timespec *ts)
218{
219 unsigned long seq;
220 s64 nsecs;
221
222 WARN_ON(timekeeping_suspended);
223
224 do {
225 seq = read_seqbegin(&xtime_lock);
226
227 *ts = xtime;
228 nsecs = timekeeping_get_ns();
229
230 /* If arch requires, add in gettimeoffset() */
231 nsecs += arch_gettimeoffset();
232
233 } while (read_seqretry(&xtime_lock, seq));
234
235 timespec_add_ns(ts, nsecs);
236}
237
238EXPORT_SYMBOL(getnstimeofday);
239
240ktime_t ktime_get(void)
241{
242 unsigned int seq;
243 s64 secs, nsecs;
244
245 WARN_ON(timekeeping_suspended);
246
247 do {
248 seq = read_seqbegin(&xtime_lock);
249 secs = xtime.tv_sec + wall_to_monotonic.tv_sec;
250 nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
251 nsecs += timekeeping_get_ns();
252 /* If arch requires, add in gettimeoffset() */
253 nsecs += arch_gettimeoffset();
254
255 } while (read_seqretry(&xtime_lock, seq));
256 /*
257 * Use ktime_set/ktime_add_ns to create a proper ktime on
258 * 32-bit architectures without CONFIG_KTIME_SCALAR.
259 */
260 return ktime_add_ns(ktime_set(secs, 0), nsecs);
261}
262EXPORT_SYMBOL_GPL(ktime_get);
263
264/**
265 * ktime_get_ts - get the monotonic clock in timespec format
266 * @ts: pointer to timespec variable
267 *
268 * The function calculates the monotonic clock from the realtime
269 * clock and the wall_to_monotonic offset and stores the result
270 * in normalized timespec format in the variable pointed to by @ts.
271 */
272void ktime_get_ts(struct timespec *ts)
273{
274 struct timespec tomono;
275 unsigned int seq;
276 s64 nsecs;
277
278 WARN_ON(timekeeping_suspended);
279
280 do {
281 seq = read_seqbegin(&xtime_lock);
282 *ts = xtime;
283 tomono = wall_to_monotonic;
284 nsecs = timekeeping_get_ns();
285 /* If arch requires, add in gettimeoffset() */
286 nsecs += arch_gettimeoffset();
287
288 } while (read_seqretry(&xtime_lock, seq));
289
290 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
291 ts->tv_nsec + tomono.tv_nsec + nsecs);
292}
293EXPORT_SYMBOL_GPL(ktime_get_ts);
294
295#ifdef CONFIG_NTP_PPS
296
297/**
298 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
299 * @ts_raw: pointer to the timespec to be set to raw monotonic time
300 * @ts_real: pointer to the timespec to be set to the time of day
301 *
302 * This function reads both the time of day and raw monotonic time at the
303 * same time atomically and stores the resulting timestamps in timespec
304 * format.
305 */
306void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
307{
308 unsigned long seq;
309 s64 nsecs_raw, nsecs_real;
310
311 WARN_ON_ONCE(timekeeping_suspended);
312
313 do {
314 u32 arch_offset;
315
316 seq = read_seqbegin(&xtime_lock);
317
318 *ts_raw = raw_time;
319 *ts_real = xtime;
320
321 nsecs_raw = timekeeping_get_ns_raw();
322 nsecs_real = timekeeping_get_ns();
323
324 /* If arch requires, add in gettimeoffset() */
325 arch_offset = arch_gettimeoffset();
326 nsecs_raw += arch_offset;
327 nsecs_real += arch_offset;
328
329 } while (read_seqretry(&xtime_lock, seq));
330
331 timespec_add_ns(ts_raw, nsecs_raw);
332 timespec_add_ns(ts_real, nsecs_real);
333}
334EXPORT_SYMBOL(getnstime_raw_and_real);
335
336#endif /* CONFIG_NTP_PPS */
337
338/**
339 * do_gettimeofday - Returns the time of day in a timeval
340 * @tv: pointer to the timeval to be set
341 *
342 * NOTE: Users should be converted to using getnstimeofday()
343 */
344void do_gettimeofday(struct timeval *tv)
345{
346 struct timespec now;
347
348 getnstimeofday(&now);
349 tv->tv_sec = now.tv_sec;
350 tv->tv_usec = now.tv_nsec/1000;
351}
352
353EXPORT_SYMBOL(do_gettimeofday);
354/**
355 * do_settimeofday - Sets the time of day
356 * @tv: pointer to the timespec variable containing the new time
357 *
358 * Sets the time of day to the new time and update NTP and notify hrtimers
359 */
360int do_settimeofday(const struct timespec *tv)
361{
362 struct timespec ts_delta;
363 unsigned long flags;
364
365 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
366 return -EINVAL;
367
368 write_seqlock_irqsave(&xtime_lock, flags);
369
370 timekeeping_forward_now();
371
372 ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec;
373 ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec;
374 wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta);
375
376 xtime = *tv;
377
378 timekeeper.ntp_error = 0;
379 ntp_clear();
380
381 update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
382 timekeeper.mult);
383
384 write_sequnlock_irqrestore(&xtime_lock, flags);
385
386 /* signal hrtimers about time change */
387 clock_was_set();
388
389 return 0;
390}
391
392EXPORT_SYMBOL(do_settimeofday);
393
394
395/**
396 * timekeeping_inject_offset - Adds or subtracts from the current time.
397 * @tv: pointer to the timespec variable containing the offset
398 *
399 * Adds or subtracts an offset value from the current time.
400 */
401int timekeeping_inject_offset(struct timespec *ts)
402{
403 unsigned long flags;
404
405 if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
406 return -EINVAL;
407
408 write_seqlock_irqsave(&xtime_lock, flags);
409
410 timekeeping_forward_now();
411
412 xtime = timespec_add(xtime, *ts);
413 wall_to_monotonic = timespec_sub(wall_to_monotonic, *ts);
414
415 timekeeper.ntp_error = 0;
416 ntp_clear();
417
418 update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
419 timekeeper.mult);
420
421 write_sequnlock_irqrestore(&xtime_lock, flags);
422
423 /* signal hrtimers about time change */
424 clock_was_set();
425
426 return 0;
427}
428EXPORT_SYMBOL(timekeeping_inject_offset);
429
430/**
431 * change_clocksource - Swaps clocksources if a new one is available
432 *
433 * Accumulates current time interval and initializes new clocksource
434 */
435static int change_clocksource(void *data)
436{
437 struct clocksource *new, *old;
438
439 new = (struct clocksource *) data;
440
441 timekeeping_forward_now();
442 if (!new->enable || new->enable(new) == 0) {
443 old = timekeeper.clock;
444 timekeeper_setup_internals(new);
445 if (old->disable)
446 old->disable(old);
447 }
448 return 0;
449}
450
451/**
452 * timekeeping_notify - Install a new clock source
453 * @clock: pointer to the clock source
454 *
455 * This function is called from clocksource.c after a new, better clock
456 * source has been registered. The caller holds the clocksource_mutex.
457 */
458void timekeeping_notify(struct clocksource *clock)
459{
460 if (timekeeper.clock == clock)
461 return;
462 stop_machine(change_clocksource, clock, NULL);
463 tick_clock_notify();
464}
465
466/**
467 * ktime_get_real - get the real (wall-) time in ktime_t format
468 *
469 * returns the time in ktime_t format
470 */
471ktime_t ktime_get_real(void)
472{
473 struct timespec now;
474
475 getnstimeofday(&now);
476
477 return timespec_to_ktime(now);
478}
479EXPORT_SYMBOL_GPL(ktime_get_real);
480
481/**
482 * getrawmonotonic - Returns the raw monotonic time in a timespec
483 * @ts: pointer to the timespec to be set
484 *
485 * Returns the raw monotonic time (completely un-modified by ntp)
486 */
487void getrawmonotonic(struct timespec *ts)
488{
489 unsigned long seq;
490 s64 nsecs;
491
492 do {
493 seq = read_seqbegin(&xtime_lock);
494 nsecs = timekeeping_get_ns_raw();
495 *ts = raw_time;
496
497 } while (read_seqretry(&xtime_lock, seq));
498
499 timespec_add_ns(ts, nsecs);
500}
501EXPORT_SYMBOL(getrawmonotonic);
502
503
504/**
505 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
506 */
507int timekeeping_valid_for_hres(void)
508{
509 unsigned long seq;
510 int ret;
511
512 do {
513 seq = read_seqbegin(&xtime_lock);
514
515 ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
516
517 } while (read_seqretry(&xtime_lock, seq));
518
519 return ret;
520}
521
522/**
523 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
524 *
525 * Caller must observe xtime_lock via read_seqbegin/read_seqretry to
526 * ensure that the clocksource does not change!
527 */
528u64 timekeeping_max_deferment(void)
529{
530 return timekeeper.clock->max_idle_ns;
531}
532
533/**
534 * read_persistent_clock - Return time from the persistent clock.
535 *
536 * Weak dummy function for arches that do not yet support it.
537 * Reads the time from the battery backed persistent clock.
538 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
539 *
540 * XXX - Do be sure to remove it once all arches implement it.
541 */
542void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
543{
544 ts->tv_sec = 0;
545 ts->tv_nsec = 0;
546}
547
548/**
549 * read_boot_clock - Return time of the system start.
550 *
551 * Weak dummy function for arches that do not yet support it.
552 * Function to read the exact time the system has been started.
553 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
554 *
555 * XXX - Do be sure to remove it once all arches implement it.
556 */
557void __attribute__((weak)) read_boot_clock(struct timespec *ts)
558{
559 ts->tv_sec = 0;
560 ts->tv_nsec = 0;
561}
562
563/*
564 * timekeeping_init - Initializes the clocksource and common timekeeping values
565 */
566void __init timekeeping_init(void)
567{
568 struct clocksource *clock;
569 unsigned long flags;
570 struct timespec now, boot;
571
572 read_persistent_clock(&now);
573 read_boot_clock(&boot);
574
575 write_seqlock_irqsave(&xtime_lock, flags);
576
577 ntp_init();
578
579 clock = clocksource_default_clock();
580 if (clock->enable)
581 clock->enable(clock);
582 timekeeper_setup_internals(clock);
583
584 xtime.tv_sec = now.tv_sec;
585 xtime.tv_nsec = now.tv_nsec;
586 raw_time.tv_sec = 0;
587 raw_time.tv_nsec = 0;
588 if (boot.tv_sec == 0 && boot.tv_nsec == 0) {
589 boot.tv_sec = xtime.tv_sec;
590 boot.tv_nsec = xtime.tv_nsec;
591 }
592 set_normalized_timespec(&wall_to_monotonic,
593 -boot.tv_sec, -boot.tv_nsec);
594 total_sleep_time.tv_sec = 0;
595 total_sleep_time.tv_nsec = 0;
596 write_sequnlock_irqrestore(&xtime_lock, flags);
597}
598
599/* time in seconds when suspend began */
600static struct timespec timekeeping_suspend_time;
601
602/**
603 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
604 * @delta: pointer to a timespec delta value
605 *
606 * Takes a timespec offset measuring a suspend interval and properly
607 * adds the sleep offset to the timekeeping variables.
608 */
609static void __timekeeping_inject_sleeptime(struct timespec *delta)
610{
611 if (!timespec_valid(delta)) {
612 printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
613 "sleep delta value!\n");
614 return;
615 }
616
617 xtime = timespec_add(xtime, *delta);
618 wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
619 total_sleep_time = timespec_add(total_sleep_time, *delta);
620}
621
622
623/**
624 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
625 * @delta: pointer to a timespec delta value
626 *
627 * This hook is for architectures that cannot support read_persistent_clock
628 * because their RTC/persistent clock is only accessible when irqs are enabled.
629 *
630 * This function should only be called by rtc_resume(), and allows
631 * a suspend offset to be injected into the timekeeping values.
632 */
633void timekeeping_inject_sleeptime(struct timespec *delta)
634{
635 unsigned long flags;
636 struct timespec ts;
637
638 /* Make sure we don't set the clock twice */
639 read_persistent_clock(&ts);
640 if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
641 return;
642
643 write_seqlock_irqsave(&xtime_lock, flags);
644 timekeeping_forward_now();
645
646 __timekeeping_inject_sleeptime(delta);
647
648 timekeeper.ntp_error = 0;
649 ntp_clear();
650 update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
651 timekeeper.mult);
652
653 write_sequnlock_irqrestore(&xtime_lock, flags);
654
655 /* signal hrtimers about time change */
656 clock_was_set();
657}
658
659
660/**
661 * timekeeping_resume - Resumes the generic timekeeping subsystem.
662 *
663 * This is for the generic clocksource timekeeping.
664 * xtime/wall_to_monotonic/jiffies/etc are
665 * still managed by arch specific suspend/resume code.
666 */
667static void timekeeping_resume(void)
668{
669 unsigned long flags;
670 struct timespec ts;
671
672 read_persistent_clock(&ts);
673
674 clocksource_resume();
675
676 write_seqlock_irqsave(&xtime_lock, flags);
677
678 if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
679 ts = timespec_sub(ts, timekeeping_suspend_time);
680 __timekeeping_inject_sleeptime(&ts);
681 }
682 /* re-base the last cycle value */
683 timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
684 timekeeper.ntp_error = 0;
685 timekeeping_suspended = 0;
686 write_sequnlock_irqrestore(&xtime_lock, flags);
687
688 touch_softlockup_watchdog();
689
690 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
691
692 /* Resume hrtimers */
693 hrtimers_resume();
694}
695
696static int timekeeping_suspend(void)
697{
698 unsigned long flags;
699 struct timespec delta, delta_delta;
700 static struct timespec old_delta;
701
702 read_persistent_clock(&timekeeping_suspend_time);
703
704 write_seqlock_irqsave(&xtime_lock, flags);
705 timekeeping_forward_now();
706 timekeeping_suspended = 1;
707
708 /*
709 * To avoid drift caused by repeated suspend/resumes,
710 * which each can add ~1 second drift error,
711 * try to compensate so the difference in system time
712 * and persistent_clock time stays close to constant.
713 */
714 delta = timespec_sub(xtime, timekeeping_suspend_time);
715 delta_delta = timespec_sub(delta, old_delta);
716 if (abs(delta_delta.tv_sec) >= 2) {
717 /*
718 * if delta_delta is too large, assume time correction
719 * has occured and set old_delta to the current delta.
720 */
721 old_delta = delta;
722 } else {
723 /* Otherwise try to adjust old_system to compensate */
724 timekeeping_suspend_time =
725 timespec_add(timekeeping_suspend_time, delta_delta);
726 }
727 write_sequnlock_irqrestore(&xtime_lock, flags);
728
729 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
730 clocksource_suspend();
731
732 return 0;
733}
734
735/* sysfs resume/suspend bits for timekeeping */
736static struct syscore_ops timekeeping_syscore_ops = {
737 .resume = timekeeping_resume,
738 .suspend = timekeeping_suspend,
739};
740
741static int __init timekeeping_init_ops(void)
742{
743 register_syscore_ops(&timekeeping_syscore_ops);
744 return 0;
745}
746
747device_initcall(timekeeping_init_ops);
748
749/*
750 * If the error is already larger, we look ahead even further
751 * to compensate for late or lost adjustments.
752 */
753static __always_inline int timekeeping_bigadjust(s64 error, s64 *interval,
754 s64 *offset)
755{
756 s64 tick_error, i;
757 u32 look_ahead, adj;
758 s32 error2, mult;
759
760 /*
761 * Use the current error value to determine how much to look ahead.
762 * The larger the error the slower we adjust for it to avoid problems
763 * with losing too many ticks, otherwise we would overadjust and
764 * produce an even larger error. The smaller the adjustment the
765 * faster we try to adjust for it, as lost ticks can do less harm
766 * here. This is tuned so that an error of about 1 msec is adjusted
767 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
768 */
769 error2 = timekeeper.ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ);
770 error2 = abs(error2);
771 for (look_ahead = 0; error2 > 0; look_ahead++)
772 error2 >>= 2;
773
774 /*
775 * Now calculate the error in (1 << look_ahead) ticks, but first
776 * remove the single look ahead already included in the error.
777 */
778 tick_error = tick_length >> (timekeeper.ntp_error_shift + 1);
779 tick_error -= timekeeper.xtime_interval >> 1;
780 error = ((error - tick_error) >> look_ahead) + tick_error;
781
782 /* Finally calculate the adjustment shift value. */
783 i = *interval;
784 mult = 1;
785 if (error < 0) {
786 error = -error;
787 *interval = -*interval;
788 *offset = -*offset;
789 mult = -1;
790 }
791 for (adj = 0; error > i; adj++)
792 error >>= 1;
793
794 *interval <<= adj;
795 *offset <<= adj;
796 return mult << adj;
797}
798
799/*
800 * Adjust the multiplier to reduce the error value,
801 * this is optimized for the most common adjustments of -1,0,1,
802 * for other values we can do a bit more work.
803 */
804static void timekeeping_adjust(s64 offset)
805{
806 s64 error, interval = timekeeper.cycle_interval;
807 int adj;
808
809 /*
810 * The point of this is to check if the error is greater then half
811 * an interval.
812 *
813 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
814 *
815 * Note we subtract one in the shift, so that error is really error*2.
816 * This "saves" dividing(shifting) interval twice, but keeps the
817 * (error > interval) comparison as still measuring if error is
818 * larger then half an interval.
819 *
820 * Note: It does not "save" on aggravation when reading the code.
821 */
822 error = timekeeper.ntp_error >> (timekeeper.ntp_error_shift - 1);
823 if (error > interval) {
824 /*
825 * We now divide error by 4(via shift), which checks if
826 * the error is greater then twice the interval.
827 * If it is greater, we need a bigadjust, if its smaller,
828 * we can adjust by 1.
829 */
830 error >>= 2;
831 /*
832 * XXX - In update_wall_time, we round up to the next
833 * nanosecond, and store the amount rounded up into
834 * the error. This causes the likely below to be unlikely.
835 *
836 * The proper fix is to avoid rounding up by using
837 * the high precision timekeeper.xtime_nsec instead of
838 * xtime.tv_nsec everywhere. Fixing this will take some
839 * time.
840 */
841 if (likely(error <= interval))
842 adj = 1;
843 else
844 adj = timekeeping_bigadjust(error, &interval, &offset);
845 } else if (error < -interval) {
846 /* See comment above, this is just switched for the negative */
847 error >>= 2;
848 if (likely(error >= -interval)) {
849 adj = -1;
850 interval = -interval;
851 offset = -offset;
852 } else
853 adj = timekeeping_bigadjust(error, &interval, &offset);
854 } else /* No adjustment needed */
855 return;
856
857 WARN_ONCE(timekeeper.clock->maxadj &&
858 (timekeeper.mult + adj > timekeeper.clock->mult +
859 timekeeper.clock->maxadj),
860 "Adjusting %s more then 11%% (%ld vs %ld)\n",
861 timekeeper.clock->name, (long)timekeeper.mult + adj,
862 (long)timekeeper.clock->mult +
863 timekeeper.clock->maxadj);
864 /*
865 * So the following can be confusing.
866 *
867 * To keep things simple, lets assume adj == 1 for now.
868 *
869 * When adj != 1, remember that the interval and offset values
870 * have been appropriately scaled so the math is the same.
871 *
872 * The basic idea here is that we're increasing the multiplier
873 * by one, this causes the xtime_interval to be incremented by
874 * one cycle_interval. This is because:
875 * xtime_interval = cycle_interval * mult
876 * So if mult is being incremented by one:
877 * xtime_interval = cycle_interval * (mult + 1)
878 * Its the same as:
879 * xtime_interval = (cycle_interval * mult) + cycle_interval
880 * Which can be shortened to:
881 * xtime_interval += cycle_interval
882 *
883 * So offset stores the non-accumulated cycles. Thus the current
884 * time (in shifted nanoseconds) is:
885 * now = (offset * adj) + xtime_nsec
886 * Now, even though we're adjusting the clock frequency, we have
887 * to keep time consistent. In other words, we can't jump back
888 * in time, and we also want to avoid jumping forward in time.
889 *
890 * So given the same offset value, we need the time to be the same
891 * both before and after the freq adjustment.
892 * now = (offset * adj_1) + xtime_nsec_1
893 * now = (offset * adj_2) + xtime_nsec_2
894 * So:
895 * (offset * adj_1) + xtime_nsec_1 =
896 * (offset * adj_2) + xtime_nsec_2
897 * And we know:
898 * adj_2 = adj_1 + 1
899 * So:
900 * (offset * adj_1) + xtime_nsec_1 =
901 * (offset * (adj_1+1)) + xtime_nsec_2
902 * (offset * adj_1) + xtime_nsec_1 =
903 * (offset * adj_1) + offset + xtime_nsec_2
904 * Canceling the sides:
905 * xtime_nsec_1 = offset + xtime_nsec_2
906 * Which gives us:
907 * xtime_nsec_2 = xtime_nsec_1 - offset
908 * Which simplfies to:
909 * xtime_nsec -= offset
910 *
911 * XXX - TODO: Doc ntp_error calculation.
912 */
913 timekeeper.mult += adj;
914 timekeeper.xtime_interval += interval;
915 timekeeper.xtime_nsec -= offset;
916 timekeeper.ntp_error -= (interval - offset) <<
917 timekeeper.ntp_error_shift;
918}
919
920
921/**
922 * logarithmic_accumulation - shifted accumulation of cycles
923 *
924 * This functions accumulates a shifted interval of cycles into
925 * into a shifted interval nanoseconds. Allows for O(log) accumulation
926 * loop.
927 *
928 * Returns the unconsumed cycles.
929 */
930static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
931{
932 u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift;
933 u64 raw_nsecs;
934
935 /* If the offset is smaller then a shifted interval, do nothing */
936 if (offset < timekeeper.cycle_interval<<shift)
937 return offset;
938
939 /* Accumulate one shifted interval */
940 offset -= timekeeper.cycle_interval << shift;
941 timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift;
942
943 timekeeper.xtime_nsec += timekeeper.xtime_interval << shift;
944 while (timekeeper.xtime_nsec >= nsecps) {
945 timekeeper.xtime_nsec -= nsecps;
946 xtime.tv_sec++;
947 second_overflow();
948 }
949
950 /* Accumulate raw time */
951 raw_nsecs = timekeeper.raw_interval << shift;
952 raw_nsecs += raw_time.tv_nsec;
953 if (raw_nsecs >= NSEC_PER_SEC) {
954 u64 raw_secs = raw_nsecs;
955 raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
956 raw_time.tv_sec += raw_secs;
957 }
958 raw_time.tv_nsec = raw_nsecs;
959
960 /* Accumulate error between NTP and clock interval */
961 timekeeper.ntp_error += tick_length << shift;
962 timekeeper.ntp_error -=
963 (timekeeper.xtime_interval + timekeeper.xtime_remainder) <<
964 (timekeeper.ntp_error_shift + shift);
965
966 return offset;
967}
968
969
970/**
971 * update_wall_time - Uses the current clocksource to increment the wall time
972 *
973 * Called from the timer interrupt, must hold a write on xtime_lock.
974 */
975static void update_wall_time(void)
976{
977 struct clocksource *clock;
978 cycle_t offset;
979 int shift = 0, maxshift;
980
981 /* Make sure we're fully resumed: */
982 if (unlikely(timekeeping_suspended))
983 return;
984
985 clock = timekeeper.clock;
986
987#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
988 offset = timekeeper.cycle_interval;
989#else
990 offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
991#endif
992 timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift;
993
994 /*
995 * With NO_HZ we may have to accumulate many cycle_intervals
996 * (think "ticks") worth of time at once. To do this efficiently,
997 * we calculate the largest doubling multiple of cycle_intervals
998 * that is smaller then the offset. We then accumulate that
999 * chunk in one go, and then try to consume the next smaller
1000 * doubled multiple.
1001 */
1002 shift = ilog2(offset) - ilog2(timekeeper.cycle_interval);
1003 shift = max(0, shift);
1004 /* Bound shift to one less then what overflows tick_length */
1005 maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1;
1006 shift = min(shift, maxshift);
1007 while (offset >= timekeeper.cycle_interval) {
1008 offset = logarithmic_accumulation(offset, shift);
1009 if(offset < timekeeper.cycle_interval<<shift)
1010 shift--;
1011 }
1012
1013 /* correct the clock when NTP error is too big */
1014 timekeeping_adjust(offset);
1015
1016 /*
1017 * Since in the loop above, we accumulate any amount of time
1018 * in xtime_nsec over a second into xtime.tv_sec, its possible for
1019 * xtime_nsec to be fairly small after the loop. Further, if we're
1020 * slightly speeding the clocksource up in timekeeping_adjust(),
1021 * its possible the required corrective factor to xtime_nsec could
1022 * cause it to underflow.
1023 *
1024 * Now, we cannot simply roll the accumulated second back, since
1025 * the NTP subsystem has been notified via second_overflow. So
1026 * instead we push xtime_nsec forward by the amount we underflowed,
1027 * and add that amount into the error.
1028 *
1029 * We'll correct this error next time through this function, when
1030 * xtime_nsec is not as small.
1031 */
1032 if (unlikely((s64)timekeeper.xtime_nsec < 0)) {
1033 s64 neg = -(s64)timekeeper.xtime_nsec;
1034 timekeeper.xtime_nsec = 0;
1035 timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
1036 }
1037
1038
1039 /*
1040 * Store full nanoseconds into xtime after rounding it up and
1041 * add the remainder to the error difference.
1042 */
1043 xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1;
1044 timekeeper.xtime_nsec -= (s64) xtime.tv_nsec << timekeeper.shift;
1045 timekeeper.ntp_error += timekeeper.xtime_nsec <<
1046 timekeeper.ntp_error_shift;
1047
1048 /*
1049 * Finally, make sure that after the rounding
1050 * xtime.tv_nsec isn't larger then NSEC_PER_SEC
1051 */
1052 if (unlikely(xtime.tv_nsec >= NSEC_PER_SEC)) {
1053 xtime.tv_nsec -= NSEC_PER_SEC;
1054 xtime.tv_sec++;
1055 second_overflow();
1056 }
1057
1058 /* check to see if there is a new clocksource to use */
1059 update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
1060 timekeeper.mult);
1061}
1062
1063/**
1064 * getboottime - Return the real time of system boot.
1065 * @ts: pointer to the timespec to be set
1066 *
1067 * Returns the wall-time of boot in a timespec.
1068 *
1069 * This is based on the wall_to_monotonic offset and the total suspend
1070 * time. Calls to settimeofday will affect the value returned (which
1071 * basically means that however wrong your real time clock is at boot time,
1072 * you get the right time here).
1073 */
1074void getboottime(struct timespec *ts)
1075{
1076 struct timespec boottime = {
1077 .tv_sec = wall_to_monotonic.tv_sec + total_sleep_time.tv_sec,
1078 .tv_nsec = wall_to_monotonic.tv_nsec + total_sleep_time.tv_nsec
1079 };
1080
1081 set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
1082}
1083EXPORT_SYMBOL_GPL(getboottime);
1084
1085
1086/**
1087 * get_monotonic_boottime - Returns monotonic time since boot
1088 * @ts: pointer to the timespec to be set
1089 *
1090 * Returns the monotonic time since boot in a timespec.
1091 *
1092 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1093 * includes the time spent in suspend.
1094 */
1095void get_monotonic_boottime(struct timespec *ts)
1096{
1097 struct timespec tomono, sleep;
1098 unsigned int seq;
1099 s64 nsecs;
1100
1101 WARN_ON(timekeeping_suspended);
1102
1103 do {
1104 seq = read_seqbegin(&xtime_lock);
1105 *ts = xtime;
1106 tomono = wall_to_monotonic;
1107 sleep = total_sleep_time;
1108 nsecs = timekeeping_get_ns();
1109
1110 } while (read_seqretry(&xtime_lock, seq));
1111
1112 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
1113 ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs);
1114}
1115EXPORT_SYMBOL_GPL(get_monotonic_boottime);
1116
1117/**
1118 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1119 *
1120 * Returns the monotonic time since boot in a ktime
1121 *
1122 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1123 * includes the time spent in suspend.
1124 */
1125ktime_t ktime_get_boottime(void)
1126{
1127 struct timespec ts;
1128
1129 get_monotonic_boottime(&ts);
1130 return timespec_to_ktime(ts);
1131}
1132EXPORT_SYMBOL_GPL(ktime_get_boottime);
1133
1134/**
1135 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1136 * @ts: pointer to the timespec to be converted
1137 */
1138void monotonic_to_bootbased(struct timespec *ts)
1139{
1140 *ts = timespec_add(*ts, total_sleep_time);
1141}
1142EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
1143
1144unsigned long get_seconds(void)
1145{
1146 return xtime.tv_sec;
1147}
1148EXPORT_SYMBOL(get_seconds);
1149
1150struct timespec __current_kernel_time(void)
1151{
1152 return xtime;
1153}
1154
1155struct timespec current_kernel_time(void)
1156{
1157 struct timespec now;
1158 unsigned long seq;
1159
1160 do {
1161 seq = read_seqbegin(&xtime_lock);
1162
1163 now = xtime;
1164 } while (read_seqretry(&xtime_lock, seq));
1165
1166 return now;
1167}
1168EXPORT_SYMBOL(current_kernel_time);
1169
1170struct timespec get_monotonic_coarse(void)
1171{
1172 struct timespec now, mono;
1173 unsigned long seq;
1174
1175 do {
1176 seq = read_seqbegin(&xtime_lock);
1177
1178 now = xtime;
1179 mono = wall_to_monotonic;
1180 } while (read_seqretry(&xtime_lock, seq));
1181
1182 set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
1183 now.tv_nsec + mono.tv_nsec);
1184 return now;
1185}
1186
1187/*
1188 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1189 * without sampling the sequence number in xtime_lock.
1190 * jiffies is defined in the linker script...
1191 */
1192void do_timer(unsigned long ticks)
1193{
1194 jiffies_64 += ticks;
1195 update_wall_time();
1196 calc_global_load(ticks);
1197}
1198
1199/**
1200 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1201 * and sleep offsets.
1202 * @xtim: pointer to timespec to be set with xtime
1203 * @wtom: pointer to timespec to be set with wall_to_monotonic
1204 * @sleep: pointer to timespec to be set with time in suspend
1205 */
1206void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
1207 struct timespec *wtom, struct timespec *sleep)
1208{
1209 unsigned long seq;
1210
1211 do {
1212 seq = read_seqbegin(&xtime_lock);
1213 *xtim = xtime;
1214 *wtom = wall_to_monotonic;
1215 *sleep = total_sleep_time;
1216 } while (read_seqretry(&xtime_lock, seq));
1217}
1218
1219/**
1220 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1221 */
1222ktime_t ktime_get_monotonic_offset(void)
1223{
1224 unsigned long seq;
1225 struct timespec wtom;
1226
1227 do {
1228 seq = read_seqbegin(&xtime_lock);
1229 wtom = wall_to_monotonic;
1230 } while (read_seqretry(&xtime_lock, seq));
1231 return timespec_to_ktime(wtom);
1232}
1233
1234/**
1235 * xtime_update() - advances the timekeeping infrastructure
1236 * @ticks: number of ticks, that have elapsed since the last call.
1237 *
1238 * Must be called with interrupts disabled.
1239 */
1240void xtime_update(unsigned long ticks)
1241{
1242 write_seqlock(&xtime_lock);
1243 do_timer(ticks);
1244 write_sequnlock(&xtime_lock);
1245}