2 * linux/kernel/time/timekeeping.c
4 * Kernel timekeeping code and accessor functions
6 * This code was moved from linux/kernel/timer.c.
7 * Please see that file for copyright and history logs.
11 #include <linux/module.h>
12 #include <linux/interrupt.h>
13 #include <linux/percpu.h>
14 #include <linux/init.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>
24 * This read-write spinlock protects us from races in SMP while
27 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(xtime_lock
);
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.
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.
42 * - wall_to_monotonic is no longer the boot time, getboottime must be
45 struct timespec xtime
__attribute__ ((aligned (16)));
46 struct timespec wall_to_monotonic
__attribute__ ((aligned (16)));
47 static unsigned long total_sleep_time
; /* seconds */
49 /* flag for if timekeeping is suspended */
50 int __read_mostly timekeeping_suspended
;
52 static struct timespec xtime_cache
__attribute__ ((aligned (16)));
53 void update_xtime_cache(u64 nsec
)
56 timespec_add_ns(&xtime_cache
, nsec
);
59 struct clocksource
*clock
;
62 #ifdef CONFIG_GENERIC_TIME
64 * clocksource_forward_now - update clock to the current time
66 * Forward the current clock to update its state since the last call to
67 * update_wall_time(). This is useful before significant clock changes,
68 * as it avoids having to deal with this time offset explicitly.
70 static void clocksource_forward_now(void)
72 cycle_t cycle_now
, cycle_delta
;
75 cycle_now
= clocksource_read(clock
);
76 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
77 clock
->cycle_last
= cycle_now
;
79 nsec
= cyc2ns(clock
, cycle_delta
);
81 /* If arch requires, add in gettimeoffset() */
82 nsec
+= arch_gettimeoffset();
84 timespec_add_ns(&xtime
, nsec
);
86 nsec
= ((s64
)cycle_delta
* clock
->mult_orig
) >> clock
->shift
;
87 clock
->raw_time
.tv_nsec
+= nsec
;
91 * getnstimeofday - Returns the time of day in a timespec
92 * @ts: pointer to the timespec to be set
94 * Returns the time of day in a timespec.
96 void getnstimeofday(struct timespec
*ts
)
98 cycle_t cycle_now
, cycle_delta
;
102 WARN_ON(timekeeping_suspended
);
105 seq
= read_seqbegin(&xtime_lock
);
109 /* read clocksource: */
110 cycle_now
= clocksource_read(clock
);
112 /* calculate the delta since the last update_wall_time: */
113 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
115 /* convert to nanoseconds: */
116 nsecs
= cyc2ns(clock
, cycle_delta
);
118 /* If arch requires, add in gettimeoffset() */
119 nsecs
+= arch_gettimeoffset();
121 } while (read_seqretry(&xtime_lock
, seq
));
123 timespec_add_ns(ts
, nsecs
);
126 EXPORT_SYMBOL(getnstimeofday
);
128 ktime_t
ktime_get(void)
130 cycle_t cycle_now
, cycle_delta
;
134 WARN_ON(timekeeping_suspended
);
137 seq
= read_seqbegin(&xtime_lock
);
138 secs
= xtime
.tv_sec
+ wall_to_monotonic
.tv_sec
;
139 nsecs
= xtime
.tv_nsec
+ wall_to_monotonic
.tv_nsec
;
141 /* read clocksource: */
142 cycle_now
= clocksource_read(clock
);
144 /* calculate the delta since the last update_wall_time: */
145 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
147 /* convert to nanoseconds: */
148 nsecs
+= cyc2ns(clock
, cycle_delta
);
150 } while (read_seqretry(&xtime_lock
, seq
));
152 * Use ktime_set/ktime_add_ns to create a proper ktime on
153 * 32-bit architectures without CONFIG_KTIME_SCALAR.
155 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
157 EXPORT_SYMBOL_GPL(ktime_get
);
160 * ktime_get_ts - get the monotonic clock in timespec format
161 * @ts: pointer to timespec variable
163 * The function calculates the monotonic clock from the realtime
164 * clock and the wall_to_monotonic offset and stores the result
165 * in normalized timespec format in the variable pointed to by @ts.
167 void ktime_get_ts(struct timespec
*ts
)
169 cycle_t cycle_now
, cycle_delta
;
170 struct timespec tomono
;
174 WARN_ON(timekeeping_suspended
);
177 seq
= read_seqbegin(&xtime_lock
);
179 tomono
= wall_to_monotonic
;
181 /* read clocksource: */
182 cycle_now
= clocksource_read(clock
);
184 /* calculate the delta since the last update_wall_time: */
185 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
187 /* convert to nanoseconds: */
188 nsecs
= cyc2ns(clock
, cycle_delta
);
190 } while (read_seqretry(&xtime_lock
, seq
));
192 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
193 ts
->tv_nsec
+ tomono
.tv_nsec
+ nsecs
);
195 EXPORT_SYMBOL_GPL(ktime_get_ts
);
198 * do_gettimeofday - Returns the time of day in a timeval
199 * @tv: pointer to the timeval to be set
201 * NOTE: Users should be converted to using getnstimeofday()
203 void do_gettimeofday(struct timeval
*tv
)
207 getnstimeofday(&now
);
208 tv
->tv_sec
= now
.tv_sec
;
209 tv
->tv_usec
= now
.tv_nsec
/1000;
212 EXPORT_SYMBOL(do_gettimeofday
);
214 * do_settimeofday - Sets the time of day
215 * @tv: pointer to the timespec variable containing the new time
217 * Sets the time of day to the new time and update NTP and notify hrtimers
219 int do_settimeofday(struct timespec
*tv
)
221 struct timespec ts_delta
;
224 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
227 write_seqlock_irqsave(&xtime_lock
, flags
);
229 clocksource_forward_now();
231 ts_delta
.tv_sec
= tv
->tv_sec
- xtime
.tv_sec
;
232 ts_delta
.tv_nsec
= tv
->tv_nsec
- xtime
.tv_nsec
;
233 wall_to_monotonic
= timespec_sub(wall_to_monotonic
, ts_delta
);
237 update_xtime_cache(0);
242 update_vsyscall(&xtime
, clock
);
244 write_sequnlock_irqrestore(&xtime_lock
, flags
);
246 /* signal hrtimers about time change */
252 EXPORT_SYMBOL(do_settimeofday
);
255 * change_clocksource - Swaps clocksources if a new one is available
257 * Accumulates current time interval and initializes new clocksource
259 static void change_clocksource(void)
261 struct clocksource
*new, *old
;
263 new = clocksource_get_next();
268 clocksource_forward_now();
270 if (clocksource_enable(new))
273 new->raw_time
= clock
->raw_time
;
276 clocksource_disable(old
);
278 clock
->cycle_last
= 0;
279 clock
->cycle_last
= clocksource_read(clock
);
281 clock
->xtime_nsec
= 0;
282 clocksource_calculate_interval(clock
, NTP_INTERVAL_LENGTH
);
287 * We're holding xtime lock and waking up klogd would deadlock
288 * us on enqueue. So no printing!
289 printk(KERN_INFO "Time: %s clocksource has been installed.\n",
293 #else /* GENERIC_TIME */
294 static inline void clocksource_forward_now(void) { }
295 static inline void change_clocksource(void) { }
298 * ktime_get - get the monotonic time in ktime_t format
300 * returns the time in ktime_t format
302 ktime_t
ktime_get(void)
308 return timespec_to_ktime(now
);
310 EXPORT_SYMBOL_GPL(ktime_get
);
313 * ktime_get_ts - get the monotonic clock in timespec format
314 * @ts: pointer to timespec variable
316 * The function calculates the monotonic clock from the realtime
317 * clock and the wall_to_monotonic offset and stores the result
318 * in normalized timespec format in the variable pointed to by @ts.
320 void ktime_get_ts(struct timespec
*ts
)
322 struct timespec tomono
;
326 seq
= read_seqbegin(&xtime_lock
);
328 tomono
= wall_to_monotonic
;
330 } while (read_seqretry(&xtime_lock
, seq
));
332 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
333 ts
->tv_nsec
+ tomono
.tv_nsec
);
335 EXPORT_SYMBOL_GPL(ktime_get_ts
);
336 #endif /* !GENERIC_TIME */
339 * ktime_get_real - get the real (wall-) time in ktime_t format
341 * returns the time in ktime_t format
343 ktime_t
ktime_get_real(void)
347 getnstimeofday(&now
);
349 return timespec_to_ktime(now
);
351 EXPORT_SYMBOL_GPL(ktime_get_real
);
354 * getrawmonotonic - Returns the raw monotonic time in a timespec
355 * @ts: pointer to the timespec to be set
357 * Returns the raw monotonic time (completely un-modified by ntp)
359 void getrawmonotonic(struct timespec
*ts
)
363 cycle_t cycle_now
, cycle_delta
;
366 seq
= read_seqbegin(&xtime_lock
);
368 /* read clocksource: */
369 cycle_now
= clocksource_read(clock
);
371 /* calculate the delta since the last update_wall_time: */
372 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
374 /* convert to nanoseconds: */
375 nsecs
= ((s64
)cycle_delta
* clock
->mult_orig
) >> clock
->shift
;
377 *ts
= clock
->raw_time
;
379 } while (read_seqretry(&xtime_lock
, seq
));
381 timespec_add_ns(ts
, nsecs
);
383 EXPORT_SYMBOL(getrawmonotonic
);
387 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
389 int timekeeping_valid_for_hres(void)
395 seq
= read_seqbegin(&xtime_lock
);
397 ret
= clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
399 } while (read_seqretry(&xtime_lock
, seq
));
405 * read_persistent_clock - Return time in seconds from the persistent clock.
407 * Weak dummy function for arches that do not yet support it.
408 * Returns seconds from epoch using the battery backed persistent clock.
409 * Returns zero if unsupported.
411 * XXX - Do be sure to remove it once all arches implement it.
413 unsigned long __attribute__((weak
)) read_persistent_clock(void)
419 * timekeeping_init - Initializes the clocksource and common timekeeping values
421 void __init
timekeeping_init(void)
424 unsigned long sec
= read_persistent_clock();
426 write_seqlock_irqsave(&xtime_lock
, flags
);
430 clock
= clocksource_get_next();
431 clocksource_enable(clock
);
432 clocksource_calculate_interval(clock
, NTP_INTERVAL_LENGTH
);
433 clock
->cycle_last
= clocksource_read(clock
);
437 set_normalized_timespec(&wall_to_monotonic
,
438 -xtime
.tv_sec
, -xtime
.tv_nsec
);
439 update_xtime_cache(0);
440 total_sleep_time
= 0;
441 write_sequnlock_irqrestore(&xtime_lock
, flags
);
444 /* time in seconds when suspend began */
445 static unsigned long timekeeping_suspend_time
;
448 * timekeeping_resume - Resumes the generic timekeeping subsystem.
451 * This is for the generic clocksource timekeeping.
452 * xtime/wall_to_monotonic/jiffies/etc are
453 * still managed by arch specific suspend/resume code.
455 static int timekeeping_resume(struct sys_device
*dev
)
458 unsigned long now
= read_persistent_clock();
460 clocksource_resume();
462 write_seqlock_irqsave(&xtime_lock
, flags
);
464 if (now
&& (now
> timekeeping_suspend_time
)) {
465 unsigned long sleep_length
= now
- timekeeping_suspend_time
;
467 xtime
.tv_sec
+= sleep_length
;
468 wall_to_monotonic
.tv_sec
-= sleep_length
;
469 total_sleep_time
+= sleep_length
;
471 update_xtime_cache(0);
472 /* re-base the last cycle value */
473 clock
->cycle_last
= 0;
474 clock
->cycle_last
= clocksource_read(clock
);
476 timekeeping_suspended
= 0;
477 write_sequnlock_irqrestore(&xtime_lock
, flags
);
479 touch_softlockup_watchdog();
481 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
483 /* Resume hrtimers */
484 hres_timers_resume();
489 static int timekeeping_suspend(struct sys_device
*dev
, pm_message_t state
)
493 timekeeping_suspend_time
= read_persistent_clock();
495 write_seqlock_irqsave(&xtime_lock
, flags
);
496 clocksource_forward_now();
497 timekeeping_suspended
= 1;
498 write_sequnlock_irqrestore(&xtime_lock
, flags
);
500 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
505 /* sysfs resume/suspend bits for timekeeping */
506 static struct sysdev_class timekeeping_sysclass
= {
507 .name
= "timekeeping",
508 .resume
= timekeeping_resume
,
509 .suspend
= timekeeping_suspend
,
512 static struct sys_device device_timer
= {
514 .cls
= &timekeeping_sysclass
,
517 static int __init
timekeeping_init_device(void)
519 int error
= sysdev_class_register(&timekeeping_sysclass
);
521 error
= sysdev_register(&device_timer
);
525 device_initcall(timekeeping_init_device
);
528 * If the error is already larger, we look ahead even further
529 * to compensate for late or lost adjustments.
531 static __always_inline
int clocksource_bigadjust(s64 error
, s64
*interval
,
539 * Use the current error value to determine how much to look ahead.
540 * The larger the error the slower we adjust for it to avoid problems
541 * with losing too many ticks, otherwise we would overadjust and
542 * produce an even larger error. The smaller the adjustment the
543 * faster we try to adjust for it, as lost ticks can do less harm
544 * here. This is tuned so that an error of about 1 msec is adjusted
545 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
547 error2
= clock
->error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
548 error2
= abs(error2
);
549 for (look_ahead
= 0; error2
> 0; look_ahead
++)
553 * Now calculate the error in (1 << look_ahead) ticks, but first
554 * remove the single look ahead already included in the error.
556 tick_error
= tick_length
>> (NTP_SCALE_SHIFT
- clock
->shift
+ 1);
557 tick_error
-= clock
->xtime_interval
>> 1;
558 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
560 /* Finally calculate the adjustment shift value. */
565 *interval
= -*interval
;
569 for (adj
= 0; error
> i
; adj
++)
578 * Adjust the multiplier to reduce the error value,
579 * this is optimized for the most common adjustments of -1,0,1,
580 * for other values we can do a bit more work.
582 static void clocksource_adjust(s64 offset
)
584 s64 error
, interval
= clock
->cycle_interval
;
587 error
= clock
->error
>> (NTP_SCALE_SHIFT
- clock
->shift
- 1);
588 if (error
> interval
) {
590 if (likely(error
<= interval
))
593 adj
= clocksource_bigadjust(error
, &interval
, &offset
);
594 } else if (error
< -interval
) {
596 if (likely(error
>= -interval
)) {
598 interval
= -interval
;
601 adj
= clocksource_bigadjust(error
, &interval
, &offset
);
606 clock
->xtime_interval
+= interval
;
607 clock
->xtime_nsec
-= offset
;
608 clock
->error
-= (interval
- offset
) <<
609 (NTP_SCALE_SHIFT
- clock
->shift
);
613 * update_wall_time - Uses the current clocksource to increment the wall time
615 * Called from the timer interrupt, must hold a write on xtime_lock.
617 void update_wall_time(void)
621 /* Make sure we're fully resumed: */
622 if (unlikely(timekeeping_suspended
))
625 #ifdef CONFIG_GENERIC_TIME
626 offset
= (clocksource_read(clock
) - clock
->cycle_last
) & clock
->mask
;
628 offset
= clock
->cycle_interval
;
630 clock
->xtime_nsec
= (s64
)xtime
.tv_nsec
<< clock
->shift
;
632 /* normally this loop will run just once, however in the
633 * case of lost or late ticks, it will accumulate correctly.
635 while (offset
>= clock
->cycle_interval
) {
636 /* accumulate one interval */
637 offset
-= clock
->cycle_interval
;
638 clock
->cycle_last
+= clock
->cycle_interval
;
640 clock
->xtime_nsec
+= clock
->xtime_interval
;
641 if (clock
->xtime_nsec
>= (u64
)NSEC_PER_SEC
<< clock
->shift
) {
642 clock
->xtime_nsec
-= (u64
)NSEC_PER_SEC
<< clock
->shift
;
647 clock
->raw_time
.tv_nsec
+= clock
->raw_interval
;
648 if (clock
->raw_time
.tv_nsec
>= NSEC_PER_SEC
) {
649 clock
->raw_time
.tv_nsec
-= NSEC_PER_SEC
;
650 clock
->raw_time
.tv_sec
++;
653 /* accumulate error between NTP and clock interval */
654 clock
->error
+= tick_length
;
655 clock
->error
-= clock
->xtime_interval
<< (NTP_SCALE_SHIFT
- clock
->shift
);
658 /* correct the clock when NTP error is too big */
659 clocksource_adjust(offset
);
662 * Since in the loop above, we accumulate any amount of time
663 * in xtime_nsec over a second into xtime.tv_sec, its possible for
664 * xtime_nsec to be fairly small after the loop. Further, if we're
665 * slightly speeding the clocksource up in clocksource_adjust(),
666 * its possible the required corrective factor to xtime_nsec could
667 * cause it to underflow.
669 * Now, we cannot simply roll the accumulated second back, since
670 * the NTP subsystem has been notified via second_overflow. So
671 * instead we push xtime_nsec forward by the amount we underflowed,
672 * and add that amount into the error.
674 * We'll correct this error next time through this function, when
675 * xtime_nsec is not as small.
677 if (unlikely((s64
)clock
->xtime_nsec
< 0)) {
678 s64 neg
= -(s64
)clock
->xtime_nsec
;
679 clock
->xtime_nsec
= 0;
680 clock
->error
+= neg
<< (NTP_SCALE_SHIFT
- clock
->shift
);
683 /* store full nanoseconds into xtime after rounding it up and
684 * add the remainder to the error difference.
686 xtime
.tv_nsec
= ((s64
)clock
->xtime_nsec
>> clock
->shift
) + 1;
687 clock
->xtime_nsec
-= (s64
)xtime
.tv_nsec
<< clock
->shift
;
688 clock
->error
+= clock
->xtime_nsec
<< (NTP_SCALE_SHIFT
- clock
->shift
);
690 update_xtime_cache(cyc2ns(clock
, offset
));
692 /* check to see if there is a new clocksource to use */
693 change_clocksource();
694 update_vsyscall(&xtime
, clock
);
698 * getboottime - Return the real time of system boot.
699 * @ts: pointer to the timespec to be set
701 * Returns the time of day in a timespec.
703 * This is based on the wall_to_monotonic offset and the total suspend
704 * time. Calls to settimeofday will affect the value returned (which
705 * basically means that however wrong your real time clock is at boot time,
706 * you get the right time here).
708 void getboottime(struct timespec
*ts
)
710 set_normalized_timespec(ts
,
711 - (wall_to_monotonic
.tv_sec
+ total_sleep_time
),
712 - wall_to_monotonic
.tv_nsec
);
716 * monotonic_to_bootbased - Convert the monotonic time to boot based.
717 * @ts: pointer to the timespec to be converted
719 void monotonic_to_bootbased(struct timespec
*ts
)
721 ts
->tv_sec
+= total_sleep_time
;
724 unsigned long get_seconds(void)
726 return xtime_cache
.tv_sec
;
728 EXPORT_SYMBOL(get_seconds
);
731 struct timespec
current_kernel_time(void)
737 seq
= read_seqbegin(&xtime_lock
);
740 } while (read_seqretry(&xtime_lock
, seq
));
744 EXPORT_SYMBOL(current_kernel_time
);