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
;
61 /* must hold xtime_lock */
62 void timekeeping_leap_insert(int leapsecond
)
64 xtime
.tv_sec
+= leapsecond
;
65 wall_to_monotonic
.tv_sec
-= leapsecond
;
66 update_vsyscall(&xtime
, clock
);
69 #ifdef CONFIG_GENERIC_TIME
71 * clocksource_forward_now - update clock to the current time
73 * Forward the current clock to update its state since the last call to
74 * update_wall_time(). This is useful before significant clock changes,
75 * as it avoids having to deal with this time offset explicitly.
77 static void clocksource_forward_now(void)
79 cycle_t cycle_now
, cycle_delta
;
82 cycle_now
= clock
->read(clock
);
83 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
84 clock
->cycle_last
= cycle_now
;
86 nsec
= cyc2ns(clock
, cycle_delta
);
88 /* If arch requires, add in gettimeoffset() */
89 nsec
+= arch_gettimeoffset();
91 timespec_add_ns(&xtime
, nsec
);
93 nsec
= ((s64
)cycle_delta
* clock
->mult_orig
) >> clock
->shift
;
94 clock
->raw_time
.tv_nsec
+= nsec
;
98 * getnstimeofday - Returns the time of day in a timespec
99 * @ts: pointer to the timespec to be set
101 * Returns the time of day in a timespec.
103 void getnstimeofday(struct timespec
*ts
)
105 cycle_t cycle_now
, cycle_delta
;
109 WARN_ON(timekeeping_suspended
);
112 seq
= read_seqbegin(&xtime_lock
);
116 /* read clocksource: */
117 cycle_now
= clock
->read(clock
);
119 /* calculate the delta since the last update_wall_time: */
120 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
122 /* convert to nanoseconds: */
123 nsecs
= cyc2ns(clock
, cycle_delta
);
125 /* If arch requires, add in gettimeoffset() */
126 nsecs
+= arch_gettimeoffset();
128 } while (read_seqretry(&xtime_lock
, seq
));
130 timespec_add_ns(ts
, nsecs
);
133 EXPORT_SYMBOL(getnstimeofday
);
135 ktime_t
ktime_get(void)
137 cycle_t cycle_now
, cycle_delta
;
141 WARN_ON(timekeeping_suspended
);
144 seq
= read_seqbegin(&xtime_lock
);
145 secs
= xtime
.tv_sec
+ wall_to_monotonic
.tv_sec
;
146 nsecs
= xtime
.tv_nsec
+ wall_to_monotonic
.tv_nsec
;
148 /* read clocksource: */
149 cycle_now
= clock
->read(clock
);
151 /* calculate the delta since the last update_wall_time: */
152 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
154 /* convert to nanoseconds: */
155 nsecs
+= cyc2ns(clock
, cycle_delta
);
157 } while (read_seqretry(&xtime_lock
, seq
));
159 * Use ktime_set/ktime_add_ns to create a proper ktime on
160 * 32-bit architectures without CONFIG_KTIME_SCALAR.
162 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
164 EXPORT_SYMBOL_GPL(ktime_get
);
167 * ktime_get_ts - get the monotonic clock in timespec format
168 * @ts: pointer to timespec variable
170 * The function calculates the monotonic clock from the realtime
171 * clock and the wall_to_monotonic offset and stores the result
172 * in normalized timespec format in the variable pointed to by @ts.
174 void ktime_get_ts(struct timespec
*ts
)
176 cycle_t cycle_now
, cycle_delta
;
177 struct timespec tomono
;
181 WARN_ON(timekeeping_suspended
);
184 seq
= read_seqbegin(&xtime_lock
);
186 tomono
= wall_to_monotonic
;
188 /* read clocksource: */
189 cycle_now
= clock
->read(clock
);
191 /* calculate the delta since the last update_wall_time: */
192 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
194 /* convert to nanoseconds: */
195 nsecs
= cyc2ns(clock
, cycle_delta
);
197 } while (read_seqretry(&xtime_lock
, seq
));
199 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
200 ts
->tv_nsec
+ tomono
.tv_nsec
+ nsecs
);
202 EXPORT_SYMBOL_GPL(ktime_get_ts
);
205 * do_gettimeofday - Returns the time of day in a timeval
206 * @tv: pointer to the timeval to be set
208 * NOTE: Users should be converted to using getnstimeofday()
210 void do_gettimeofday(struct timeval
*tv
)
214 getnstimeofday(&now
);
215 tv
->tv_sec
= now
.tv_sec
;
216 tv
->tv_usec
= now
.tv_nsec
/1000;
219 EXPORT_SYMBOL(do_gettimeofday
);
221 * do_settimeofday - Sets the time of day
222 * @tv: pointer to the timespec variable containing the new time
224 * Sets the time of day to the new time and update NTP and notify hrtimers
226 int do_settimeofday(struct timespec
*tv
)
228 struct timespec ts_delta
;
231 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
234 write_seqlock_irqsave(&xtime_lock
, flags
);
236 clocksource_forward_now();
238 ts_delta
.tv_sec
= tv
->tv_sec
- xtime
.tv_sec
;
239 ts_delta
.tv_nsec
= tv
->tv_nsec
- xtime
.tv_nsec
;
240 wall_to_monotonic
= timespec_sub(wall_to_monotonic
, ts_delta
);
244 update_xtime_cache(0);
249 update_vsyscall(&xtime
, clock
);
251 write_sequnlock_irqrestore(&xtime_lock
, flags
);
253 /* signal hrtimers about time change */
259 EXPORT_SYMBOL(do_settimeofday
);
262 * change_clocksource - Swaps clocksources if a new one is available
264 * Accumulates current time interval and initializes new clocksource
266 static void change_clocksource(void)
268 struct clocksource
*new, *old
;
270 new = clocksource_get_next();
275 clocksource_forward_now();
277 if (new->enable
&& !new->enable(new))
280 * The frequency may have changed while the clocksource
281 * was disabled. If so the code in ->enable() must update
282 * the mult value to reflect the new frequency. Make sure
283 * mult_orig follows this change.
285 new->mult_orig
= new->mult
;
287 new->raw_time
= clock
->raw_time
;
291 * Save mult_orig in mult so that the value can be restored
292 * regardless if ->enable() updates the value of mult or not.
294 old
->mult
= old
->mult_orig
;
298 clock
->cycle_last
= clock
->read(clock
);
300 clock
->xtime_nsec
= 0;
301 clocksource_calculate_interval(clock
, NTP_INTERVAL_LENGTH
);
306 * We're holding xtime lock and waking up klogd would deadlock
307 * us on enqueue. So no printing!
308 printk(KERN_INFO "Time: %s clocksource has been installed.\n",
312 #else /* GENERIC_TIME */
313 static inline void clocksource_forward_now(void) { }
314 static inline void change_clocksource(void) { }
317 * ktime_get - get the monotonic time in ktime_t format
319 * returns the time in ktime_t format
321 ktime_t
ktime_get(void)
327 return timespec_to_ktime(now
);
329 EXPORT_SYMBOL_GPL(ktime_get
);
332 * ktime_get_ts - get the monotonic clock in timespec format
333 * @ts: pointer to timespec variable
335 * The function calculates the monotonic clock from the realtime
336 * clock and the wall_to_monotonic offset and stores the result
337 * in normalized timespec format in the variable pointed to by @ts.
339 void ktime_get_ts(struct timespec
*ts
)
341 struct timespec tomono
;
345 seq
= read_seqbegin(&xtime_lock
);
347 tomono
= wall_to_monotonic
;
349 } while (read_seqretry(&xtime_lock
, seq
));
351 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
352 ts
->tv_nsec
+ tomono
.tv_nsec
);
354 EXPORT_SYMBOL_GPL(ktime_get_ts
);
355 #endif /* !GENERIC_TIME */
358 * ktime_get_real - get the real (wall-) time in ktime_t format
360 * returns the time in ktime_t format
362 ktime_t
ktime_get_real(void)
366 getnstimeofday(&now
);
368 return timespec_to_ktime(now
);
370 EXPORT_SYMBOL_GPL(ktime_get_real
);
373 * getrawmonotonic - Returns the raw monotonic time in a timespec
374 * @ts: pointer to the timespec to be set
376 * Returns the raw monotonic time (completely un-modified by ntp)
378 void getrawmonotonic(struct timespec
*ts
)
382 cycle_t cycle_now
, cycle_delta
;
385 seq
= read_seqbegin(&xtime_lock
);
387 /* read clocksource: */
388 cycle_now
= clock
->read(clock
);
390 /* calculate the delta since the last update_wall_time: */
391 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
393 /* convert to nanoseconds: */
394 nsecs
= ((s64
)cycle_delta
* clock
->mult_orig
) >> clock
->shift
;
396 *ts
= clock
->raw_time
;
398 } while (read_seqretry(&xtime_lock
, seq
));
400 timespec_add_ns(ts
, nsecs
);
402 EXPORT_SYMBOL(getrawmonotonic
);
406 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
408 int timekeeping_valid_for_hres(void)
414 seq
= read_seqbegin(&xtime_lock
);
416 ret
= clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
418 } while (read_seqretry(&xtime_lock
, seq
));
424 * read_persistent_clock - Return time in seconds from the persistent clock.
426 * Weak dummy function for arches that do not yet support it.
427 * Returns seconds from epoch using the battery backed persistent clock.
428 * Returns zero if unsupported.
430 * XXX - Do be sure to remove it once all arches implement it.
432 unsigned long __attribute__((weak
)) read_persistent_clock(void)
438 * timekeeping_init - Initializes the clocksource and common timekeeping values
440 void __init
timekeeping_init(void)
443 unsigned long sec
= read_persistent_clock();
445 write_seqlock_irqsave(&xtime_lock
, flags
);
449 clock
= clocksource_get_next();
451 clock
->enable(clock
);
452 /* set mult_orig on enable */
453 clock
->mult_orig
= clock
->mult
;
454 clocksource_calculate_interval(clock
, NTP_INTERVAL_LENGTH
);
455 clock
->cycle_last
= clock
->read(clock
);
459 set_normalized_timespec(&wall_to_monotonic
,
460 -xtime
.tv_sec
, -xtime
.tv_nsec
);
461 update_xtime_cache(0);
462 total_sleep_time
= 0;
463 write_sequnlock_irqrestore(&xtime_lock
, flags
);
466 /* time in seconds when suspend began */
467 static unsigned long timekeeping_suspend_time
;
470 * timekeeping_resume - Resumes the generic timekeeping subsystem.
473 * This is for the generic clocksource timekeeping.
474 * xtime/wall_to_monotonic/jiffies/etc are
475 * still managed by arch specific suspend/resume code.
477 static int timekeeping_resume(struct sys_device
*dev
)
480 unsigned long now
= read_persistent_clock();
482 clocksource_resume();
484 write_seqlock_irqsave(&xtime_lock
, flags
);
486 if (now
&& (now
> timekeeping_suspend_time
)) {
487 unsigned long sleep_length
= now
- timekeeping_suspend_time
;
489 xtime
.tv_sec
+= sleep_length
;
490 wall_to_monotonic
.tv_sec
-= sleep_length
;
491 total_sleep_time
+= sleep_length
;
493 update_xtime_cache(0);
494 /* re-base the last cycle value */
495 clock
->cycle_last
= clock
->read(clock
);
497 timekeeping_suspended
= 0;
498 write_sequnlock_irqrestore(&xtime_lock
, flags
);
500 touch_softlockup_watchdog();
502 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
504 /* Resume hrtimers */
505 hres_timers_resume();
510 static int timekeeping_suspend(struct sys_device
*dev
, pm_message_t state
)
514 timekeeping_suspend_time
= read_persistent_clock();
516 write_seqlock_irqsave(&xtime_lock
, flags
);
517 clocksource_forward_now();
518 timekeeping_suspended
= 1;
519 write_sequnlock_irqrestore(&xtime_lock
, flags
);
521 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
526 /* sysfs resume/suspend bits for timekeeping */
527 static struct sysdev_class timekeeping_sysclass
= {
528 .name
= "timekeeping",
529 .resume
= timekeeping_resume
,
530 .suspend
= timekeeping_suspend
,
533 static struct sys_device device_timer
= {
535 .cls
= &timekeeping_sysclass
,
538 static int __init
timekeeping_init_device(void)
540 int error
= sysdev_class_register(&timekeeping_sysclass
);
542 error
= sysdev_register(&device_timer
);
546 device_initcall(timekeeping_init_device
);
549 * If the error is already larger, we look ahead even further
550 * to compensate for late or lost adjustments.
552 static __always_inline
int clocksource_bigadjust(s64 error
, s64
*interval
,
560 * Use the current error value to determine how much to look ahead.
561 * The larger the error the slower we adjust for it to avoid problems
562 * with losing too many ticks, otherwise we would overadjust and
563 * produce an even larger error. The smaller the adjustment the
564 * faster we try to adjust for it, as lost ticks can do less harm
565 * here. This is tuned so that an error of about 1 msec is adjusted
566 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
568 error2
= clock
->error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
569 error2
= abs(error2
);
570 for (look_ahead
= 0; error2
> 0; look_ahead
++)
574 * Now calculate the error in (1 << look_ahead) ticks, but first
575 * remove the single look ahead already included in the error.
577 tick_error
= tick_length
>> (NTP_SCALE_SHIFT
- clock
->shift
+ 1);
578 tick_error
-= clock
->xtime_interval
>> 1;
579 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
581 /* Finally calculate the adjustment shift value. */
586 *interval
= -*interval
;
590 for (adj
= 0; error
> i
; adj
++)
599 * Adjust the multiplier to reduce the error value,
600 * this is optimized for the most common adjustments of -1,0,1,
601 * for other values we can do a bit more work.
603 static void clocksource_adjust(s64 offset
)
605 s64 error
, interval
= clock
->cycle_interval
;
608 error
= clock
->error
>> (NTP_SCALE_SHIFT
- clock
->shift
- 1);
609 if (error
> interval
) {
611 if (likely(error
<= interval
))
614 adj
= clocksource_bigadjust(error
, &interval
, &offset
);
615 } else if (error
< -interval
) {
617 if (likely(error
>= -interval
)) {
619 interval
= -interval
;
622 adj
= clocksource_bigadjust(error
, &interval
, &offset
);
627 clock
->xtime_interval
+= interval
;
628 clock
->xtime_nsec
-= offset
;
629 clock
->error
-= (interval
- offset
) <<
630 (NTP_SCALE_SHIFT
- clock
->shift
);
634 * update_wall_time - Uses the current clocksource to increment the wall time
636 * Called from the timer interrupt, must hold a write on xtime_lock.
638 void update_wall_time(void)
642 /* Make sure we're fully resumed: */
643 if (unlikely(timekeeping_suspended
))
646 #ifdef CONFIG_GENERIC_TIME
647 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
649 offset
= clock
->cycle_interval
;
651 clock
->xtime_nsec
= (s64
)xtime
.tv_nsec
<< clock
->shift
;
653 /* normally this loop will run just once, however in the
654 * case of lost or late ticks, it will accumulate correctly.
656 while (offset
>= clock
->cycle_interval
) {
657 /* accumulate one interval */
658 offset
-= clock
->cycle_interval
;
659 clock
->cycle_last
+= clock
->cycle_interval
;
661 clock
->xtime_nsec
+= clock
->xtime_interval
;
662 if (clock
->xtime_nsec
>= (u64
)NSEC_PER_SEC
<< clock
->shift
) {
663 clock
->xtime_nsec
-= (u64
)NSEC_PER_SEC
<< clock
->shift
;
668 clock
->raw_time
.tv_nsec
+= clock
->raw_interval
;
669 if (clock
->raw_time
.tv_nsec
>= NSEC_PER_SEC
) {
670 clock
->raw_time
.tv_nsec
-= NSEC_PER_SEC
;
671 clock
->raw_time
.tv_sec
++;
674 /* accumulate error between NTP and clock interval */
675 clock
->error
+= tick_length
;
676 clock
->error
-= clock
->xtime_interval
<< (NTP_SCALE_SHIFT
- clock
->shift
);
679 /* correct the clock when NTP error is too big */
680 clocksource_adjust(offset
);
683 * Since in the loop above, we accumulate any amount of time
684 * in xtime_nsec over a second into xtime.tv_sec, its possible for
685 * xtime_nsec to be fairly small after the loop. Further, if we're
686 * slightly speeding the clocksource up in clocksource_adjust(),
687 * its possible the required corrective factor to xtime_nsec could
688 * cause it to underflow.
690 * Now, we cannot simply roll the accumulated second back, since
691 * the NTP subsystem has been notified via second_overflow. So
692 * instead we push xtime_nsec forward by the amount we underflowed,
693 * and add that amount into the error.
695 * We'll correct this error next time through this function, when
696 * xtime_nsec is not as small.
698 if (unlikely((s64
)clock
->xtime_nsec
< 0)) {
699 s64 neg
= -(s64
)clock
->xtime_nsec
;
700 clock
->xtime_nsec
= 0;
701 clock
->error
+= neg
<< (NTP_SCALE_SHIFT
- clock
->shift
);
704 /* store full nanoseconds into xtime after rounding it up and
705 * add the remainder to the error difference.
707 xtime
.tv_nsec
= ((s64
)clock
->xtime_nsec
>> clock
->shift
) + 1;
708 clock
->xtime_nsec
-= (s64
)xtime
.tv_nsec
<< clock
->shift
;
709 clock
->error
+= clock
->xtime_nsec
<< (NTP_SCALE_SHIFT
- clock
->shift
);
711 update_xtime_cache(cyc2ns(clock
, offset
));
713 /* check to see if there is a new clocksource to use */
714 change_clocksource();
715 update_vsyscall(&xtime
, clock
);
719 * getboottime - Return the real time of system boot.
720 * @ts: pointer to the timespec to be set
722 * Returns the time of day in a timespec.
724 * This is based on the wall_to_monotonic offset and the total suspend
725 * time. Calls to settimeofday will affect the value returned (which
726 * basically means that however wrong your real time clock is at boot time,
727 * you get the right time here).
729 void getboottime(struct timespec
*ts
)
731 set_normalized_timespec(ts
,
732 - (wall_to_monotonic
.tv_sec
+ total_sleep_time
),
733 - wall_to_monotonic
.tv_nsec
);
737 * monotonic_to_bootbased - Convert the monotonic time to boot based.
738 * @ts: pointer to the timespec to be converted
740 void monotonic_to_bootbased(struct timespec
*ts
)
742 ts
->tv_sec
+= total_sleep_time
;
745 unsigned long get_seconds(void)
747 return xtime_cache
.tv_sec
;
749 EXPORT_SYMBOL(get_seconds
);
752 struct timespec
current_kernel_time(void)
758 seq
= read_seqbegin(&xtime_lock
);
761 } while (read_seqretry(&xtime_lock
, seq
));
765 EXPORT_SYMBOL(current_kernel_time
);