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/timekeeper_internal.h>
12 #include <linux/module.h>
13 #include <linux/interrupt.h>
14 #include <linux/percpu.h>
15 #include <linux/init.h>
17 #include <linux/sched.h>
18 #include <linux/syscore_ops.h>
19 #include <linux/clocksource.h>
20 #include <linux/jiffies.h>
21 #include <linux/time.h>
22 #include <linux/tick.h>
23 #include <linux/stop_machine.h>
26 static struct timekeeper timekeeper
;
29 * This read-write spinlock protects us from races in SMP while
32 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(xtime_lock
);
34 /* flag for if timekeeping is suspended */
35 int __read_mostly timekeeping_suspended
;
37 static inline void tk_normalize_xtime(struct timekeeper
*tk
)
39 while (tk
->xtime_nsec
>= ((u64
)NSEC_PER_SEC
<< tk
->shift
)) {
40 tk
->xtime_nsec
-= (u64
)NSEC_PER_SEC
<< tk
->shift
;
45 static struct timespec
tk_xtime(struct timekeeper
*tk
)
49 ts
.tv_sec
= tk
->xtime_sec
;
50 ts
.tv_nsec
= (long)(tk
->xtime_nsec
>> tk
->shift
);
54 static void tk_set_xtime(struct timekeeper
*tk
, const struct timespec
*ts
)
56 tk
->xtime_sec
= ts
->tv_sec
;
57 tk
->xtime_nsec
= (u64
)ts
->tv_nsec
<< tk
->shift
;
60 static void tk_xtime_add(struct timekeeper
*tk
, const struct timespec
*ts
)
62 tk
->xtime_sec
+= ts
->tv_sec
;
63 tk
->xtime_nsec
+= (u64
)ts
->tv_nsec
<< tk
->shift
;
64 tk_normalize_xtime(tk
);
67 static void tk_set_wall_to_mono(struct timekeeper
*tk
, struct timespec wtm
)
72 * Verify consistency of: offset_real = -wall_to_monotonic
73 * before modifying anything
75 set_normalized_timespec(&tmp
, -tk
->wall_to_monotonic
.tv_sec
,
76 -tk
->wall_to_monotonic
.tv_nsec
);
77 WARN_ON_ONCE(tk
->offs_real
.tv64
!= timespec_to_ktime(tmp
).tv64
);
78 tk
->wall_to_monotonic
= wtm
;
79 set_normalized_timespec(&tmp
, -wtm
.tv_sec
, -wtm
.tv_nsec
);
80 tk
->offs_real
= timespec_to_ktime(tmp
);
83 static void tk_set_sleep_time(struct timekeeper
*tk
, struct timespec t
)
85 /* Verify consistency before modifying */
86 WARN_ON_ONCE(tk
->offs_boot
.tv64
!= timespec_to_ktime(tk
->total_sleep_time
).tv64
);
88 tk
->total_sleep_time
= t
;
89 tk
->offs_boot
= timespec_to_ktime(t
);
93 * timekeeper_setup_internals - Set up internals to use clocksource clock.
95 * @clock: Pointer to clocksource.
97 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
98 * pair and interval request.
100 * Unless you're the timekeeping code, you should not be using this!
102 static void tk_setup_internals(struct timekeeper
*tk
, struct clocksource
*clock
)
105 u64 tmp
, ntpinterval
;
106 struct clocksource
*old_clock
;
108 old_clock
= tk
->clock
;
110 clock
->cycle_last
= clock
->read(clock
);
112 /* Do the ns -> cycle conversion first, using original mult */
113 tmp
= NTP_INTERVAL_LENGTH
;
114 tmp
<<= clock
->shift
;
116 tmp
+= clock
->mult
/2;
117 do_div(tmp
, clock
->mult
);
121 interval
= (cycle_t
) tmp
;
122 tk
->cycle_interval
= interval
;
124 /* Go back from cycles -> shifted ns */
125 tk
->xtime_interval
= (u64
) interval
* clock
->mult
;
126 tk
->xtime_remainder
= ntpinterval
- tk
->xtime_interval
;
128 ((u64
) interval
* clock
->mult
) >> clock
->shift
;
130 /* if changing clocks, convert xtime_nsec shift units */
132 int shift_change
= clock
->shift
- old_clock
->shift
;
133 if (shift_change
< 0)
134 tk
->xtime_nsec
>>= -shift_change
;
136 tk
->xtime_nsec
<<= shift_change
;
138 tk
->shift
= clock
->shift
;
141 tk
->ntp_error_shift
= NTP_SCALE_SHIFT
- clock
->shift
;
144 * The timekeeper keeps its own mult values for the currently
145 * active clocksource. These value will be adjusted via NTP
146 * to counteract clock drifting.
148 tk
->mult
= clock
->mult
;
151 /* Timekeeper helper functions. */
152 static inline s64
timekeeping_get_ns(struct timekeeper
*tk
)
154 cycle_t cycle_now
, cycle_delta
;
155 struct clocksource
*clock
;
158 /* read clocksource: */
160 cycle_now
= clock
->read(clock
);
162 /* calculate the delta since the last update_wall_time: */
163 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
165 nsec
= cycle_delta
* tk
->mult
+ tk
->xtime_nsec
;
168 /* If arch requires, add in gettimeoffset() */
169 return nsec
+ arch_gettimeoffset();
172 static inline s64
timekeeping_get_ns_raw(struct timekeeper
*tk
)
174 cycle_t cycle_now
, cycle_delta
;
175 struct clocksource
*clock
;
178 /* read clocksource: */
180 cycle_now
= clock
->read(clock
);
182 /* calculate the delta since the last update_wall_time: */
183 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
185 /* convert delta to nanoseconds. */
186 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
188 /* If arch requires, add in gettimeoffset() */
189 return nsec
+ arch_gettimeoffset();
192 /* must hold write on timekeeper.lock */
193 static void timekeeping_update(struct timekeeper
*tk
, bool clearntp
)
202 update_vsyscall_old(&xt
, &tk
->wall_to_monotonic
, tk
->clock
, tk
->mult
);
206 * timekeeping_forward_now - update clock to the current time
208 * Forward the current clock to update its state since the last call to
209 * update_wall_time(). This is useful before significant clock changes,
210 * as it avoids having to deal with this time offset explicitly.
212 static void timekeeping_forward_now(struct timekeeper
*tk
)
214 cycle_t cycle_now
, cycle_delta
;
215 struct clocksource
*clock
;
219 cycle_now
= clock
->read(clock
);
220 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
221 clock
->cycle_last
= cycle_now
;
223 tk
->xtime_nsec
+= cycle_delta
* tk
->mult
;
225 /* If arch requires, add in gettimeoffset() */
226 tk
->xtime_nsec
+= (u64
)arch_gettimeoffset() << tk
->shift
;
228 tk_normalize_xtime(tk
);
230 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
231 timespec_add_ns(&tk
->raw_time
, nsec
);
235 * getnstimeofday - Returns the time of day in a timespec
236 * @ts: pointer to the timespec to be set
238 * Returns the time of day in a timespec.
240 void getnstimeofday(struct timespec
*ts
)
242 struct timekeeper
*tk
= &timekeeper
;
246 WARN_ON(timekeeping_suspended
);
249 seq
= read_seqbegin(&tk
->lock
);
251 ts
->tv_sec
= tk
->xtime_sec
;
252 nsecs
= timekeeping_get_ns(tk
);
254 } while (read_seqretry(&tk
->lock
, seq
));
257 timespec_add_ns(ts
, nsecs
);
259 EXPORT_SYMBOL(getnstimeofday
);
261 ktime_t
ktime_get(void)
263 struct timekeeper
*tk
= &timekeeper
;
267 WARN_ON(timekeeping_suspended
);
270 seq
= read_seqbegin(&tk
->lock
);
271 secs
= tk
->xtime_sec
+ tk
->wall_to_monotonic
.tv_sec
;
272 nsecs
= timekeeping_get_ns(tk
) + tk
->wall_to_monotonic
.tv_nsec
;
274 } while (read_seqretry(&tk
->lock
, seq
));
276 * Use ktime_set/ktime_add_ns to create a proper ktime on
277 * 32-bit architectures without CONFIG_KTIME_SCALAR.
279 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
281 EXPORT_SYMBOL_GPL(ktime_get
);
284 * ktime_get_ts - get the monotonic clock in timespec format
285 * @ts: pointer to timespec variable
287 * The function calculates the monotonic clock from the realtime
288 * clock and the wall_to_monotonic offset and stores the result
289 * in normalized timespec format in the variable pointed to by @ts.
291 void ktime_get_ts(struct timespec
*ts
)
293 struct timekeeper
*tk
= &timekeeper
;
294 struct timespec tomono
;
298 WARN_ON(timekeeping_suspended
);
301 seq
= read_seqbegin(&tk
->lock
);
302 ts
->tv_sec
= tk
->xtime_sec
;
303 nsec
= timekeeping_get_ns(tk
);
304 tomono
= tk
->wall_to_monotonic
;
306 } while (read_seqretry(&tk
->lock
, seq
));
308 ts
->tv_sec
+= tomono
.tv_sec
;
310 timespec_add_ns(ts
, nsec
+ tomono
.tv_nsec
);
312 EXPORT_SYMBOL_GPL(ktime_get_ts
);
314 #ifdef CONFIG_NTP_PPS
317 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
318 * @ts_raw: pointer to the timespec to be set to raw monotonic time
319 * @ts_real: pointer to the timespec to be set to the time of day
321 * This function reads both the time of day and raw monotonic time at the
322 * same time atomically and stores the resulting timestamps in timespec
325 void getnstime_raw_and_real(struct timespec
*ts_raw
, struct timespec
*ts_real
)
327 struct timekeeper
*tk
= &timekeeper
;
329 s64 nsecs_raw
, nsecs_real
;
331 WARN_ON_ONCE(timekeeping_suspended
);
334 seq
= read_seqbegin(&tk
->lock
);
336 *ts_raw
= tk
->raw_time
;
337 ts_real
->tv_sec
= tk
->xtime_sec
;
338 ts_real
->tv_nsec
= 0;
340 nsecs_raw
= timekeeping_get_ns_raw(tk
);
341 nsecs_real
= timekeeping_get_ns(tk
);
343 } while (read_seqretry(&tk
->lock
, seq
));
345 timespec_add_ns(ts_raw
, nsecs_raw
);
346 timespec_add_ns(ts_real
, nsecs_real
);
348 EXPORT_SYMBOL(getnstime_raw_and_real
);
350 #endif /* CONFIG_NTP_PPS */
353 * do_gettimeofday - Returns the time of day in a timeval
354 * @tv: pointer to the timeval to be set
356 * NOTE: Users should be converted to using getnstimeofday()
358 void do_gettimeofday(struct timeval
*tv
)
362 getnstimeofday(&now
);
363 tv
->tv_sec
= now
.tv_sec
;
364 tv
->tv_usec
= now
.tv_nsec
/1000;
366 EXPORT_SYMBOL(do_gettimeofday
);
369 * do_settimeofday - Sets the time of day
370 * @tv: pointer to the timespec variable containing the new time
372 * Sets the time of day to the new time and update NTP and notify hrtimers
374 int do_settimeofday(const struct timespec
*tv
)
376 struct timekeeper
*tk
= &timekeeper
;
377 struct timespec ts_delta
, xt
;
380 if (!timespec_valid_strict(tv
))
383 write_seqlock_irqsave(&tk
->lock
, flags
);
385 timekeeping_forward_now(tk
);
388 ts_delta
.tv_sec
= tv
->tv_sec
- xt
.tv_sec
;
389 ts_delta
.tv_nsec
= tv
->tv_nsec
- xt
.tv_nsec
;
391 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, ts_delta
));
393 tk_set_xtime(tk
, tv
);
395 timekeeping_update(tk
, true);
397 write_sequnlock_irqrestore(&tk
->lock
, flags
);
399 /* signal hrtimers about time change */
404 EXPORT_SYMBOL(do_settimeofday
);
407 * timekeeping_inject_offset - Adds or subtracts from the current time.
408 * @tv: pointer to the timespec variable containing the offset
410 * Adds or subtracts an offset value from the current time.
412 int timekeeping_inject_offset(struct timespec
*ts
)
414 struct timekeeper
*tk
= &timekeeper
;
419 if ((unsigned long)ts
->tv_nsec
>= NSEC_PER_SEC
)
422 write_seqlock_irqsave(&tk
->lock
, flags
);
424 timekeeping_forward_now(tk
);
426 /* Make sure the proposed value is valid */
427 tmp
= timespec_add(tk_xtime(tk
), *ts
);
428 if (!timespec_valid_strict(&tmp
)) {
433 tk_xtime_add(tk
, ts
);
434 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, *ts
));
436 error
: /* even if we error out, we forwarded the time, so call update */
437 timekeeping_update(tk
, true);
439 write_sequnlock_irqrestore(&tk
->lock
, flags
);
441 /* signal hrtimers about time change */
446 EXPORT_SYMBOL(timekeeping_inject_offset
);
449 * change_clocksource - Swaps clocksources if a new one is available
451 * Accumulates current time interval and initializes new clocksource
453 static int change_clocksource(void *data
)
455 struct timekeeper
*tk
= &timekeeper
;
456 struct clocksource
*new, *old
;
459 new = (struct clocksource
*) data
;
461 write_seqlock_irqsave(&tk
->lock
, flags
);
463 timekeeping_forward_now(tk
);
464 if (!new->enable
|| new->enable(new) == 0) {
466 tk_setup_internals(tk
, new);
470 timekeeping_update(tk
, true);
472 write_sequnlock_irqrestore(&tk
->lock
, flags
);
478 * timekeeping_notify - Install a new clock source
479 * @clock: pointer to the clock source
481 * This function is called from clocksource.c after a new, better clock
482 * source has been registered. The caller holds the clocksource_mutex.
484 void timekeeping_notify(struct clocksource
*clock
)
486 struct timekeeper
*tk
= &timekeeper
;
488 if (tk
->clock
== clock
)
490 stop_machine(change_clocksource
, clock
, NULL
);
495 * ktime_get_real - get the real (wall-) time in ktime_t format
497 * returns the time in ktime_t format
499 ktime_t
ktime_get_real(void)
503 getnstimeofday(&now
);
505 return timespec_to_ktime(now
);
507 EXPORT_SYMBOL_GPL(ktime_get_real
);
510 * getrawmonotonic - Returns the raw monotonic time in a timespec
511 * @ts: pointer to the timespec to be set
513 * Returns the raw monotonic time (completely un-modified by ntp)
515 void getrawmonotonic(struct timespec
*ts
)
517 struct timekeeper
*tk
= &timekeeper
;
522 seq
= read_seqbegin(&tk
->lock
);
523 nsecs
= timekeeping_get_ns_raw(tk
);
526 } while (read_seqretry(&tk
->lock
, seq
));
528 timespec_add_ns(ts
, nsecs
);
530 EXPORT_SYMBOL(getrawmonotonic
);
533 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
535 int timekeeping_valid_for_hres(void)
537 struct timekeeper
*tk
= &timekeeper
;
542 seq
= read_seqbegin(&tk
->lock
);
544 ret
= tk
->clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
546 } while (read_seqretry(&tk
->lock
, seq
));
552 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
554 u64
timekeeping_max_deferment(void)
556 struct timekeeper
*tk
= &timekeeper
;
561 seq
= read_seqbegin(&tk
->lock
);
563 ret
= tk
->clock
->max_idle_ns
;
565 } while (read_seqretry(&tk
->lock
, seq
));
571 * read_persistent_clock - Return time from the persistent clock.
573 * Weak dummy function for arches that do not yet support it.
574 * Reads the time from the battery backed persistent clock.
575 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
577 * XXX - Do be sure to remove it once all arches implement it.
579 void __attribute__((weak
)) read_persistent_clock(struct timespec
*ts
)
586 * read_boot_clock - Return time of the system start.
588 * Weak dummy function for arches that do not yet support it.
589 * Function to read the exact time the system has been started.
590 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
592 * XXX - Do be sure to remove it once all arches implement it.
594 void __attribute__((weak
)) read_boot_clock(struct timespec
*ts
)
601 * timekeeping_init - Initializes the clocksource and common timekeeping values
603 void __init
timekeeping_init(void)
605 struct timekeeper
*tk
= &timekeeper
;
606 struct clocksource
*clock
;
608 struct timespec now
, boot
, tmp
;
610 read_persistent_clock(&now
);
611 if (!timespec_valid_strict(&now
)) {
612 pr_warn("WARNING: Persistent clock returned invalid value!\n"
613 " Check your CMOS/BIOS settings.\n");
618 read_boot_clock(&boot
);
619 if (!timespec_valid_strict(&boot
)) {
620 pr_warn("WARNING: Boot clock returned invalid value!\n"
621 " Check your CMOS/BIOS settings.\n");
626 seqlock_init(&tk
->lock
);
630 write_seqlock_irqsave(&tk
->lock
, flags
);
631 clock
= clocksource_default_clock();
633 clock
->enable(clock
);
634 tk_setup_internals(tk
, clock
);
636 tk_set_xtime(tk
, &now
);
637 tk
->raw_time
.tv_sec
= 0;
638 tk
->raw_time
.tv_nsec
= 0;
639 if (boot
.tv_sec
== 0 && boot
.tv_nsec
== 0)
642 set_normalized_timespec(&tmp
, -boot
.tv_sec
, -boot
.tv_nsec
);
643 tk_set_wall_to_mono(tk
, tmp
);
647 tk_set_sleep_time(tk
, tmp
);
649 write_sequnlock_irqrestore(&tk
->lock
, flags
);
652 /* time in seconds when suspend began */
653 static struct timespec timekeeping_suspend_time
;
656 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
657 * @delta: pointer to a timespec delta value
659 * Takes a timespec offset measuring a suspend interval and properly
660 * adds the sleep offset to the timekeeping variables.
662 static void __timekeeping_inject_sleeptime(struct timekeeper
*tk
,
663 struct timespec
*delta
)
665 if (!timespec_valid_strict(delta
)) {
666 printk(KERN_WARNING
"__timekeeping_inject_sleeptime: Invalid "
667 "sleep delta value!\n");
670 tk_xtime_add(tk
, delta
);
671 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, *delta
));
672 tk_set_sleep_time(tk
, timespec_add(tk
->total_sleep_time
, *delta
));
676 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
677 * @delta: pointer to a timespec delta value
679 * This hook is for architectures that cannot support read_persistent_clock
680 * because their RTC/persistent clock is only accessible when irqs are enabled.
682 * This function should only be called by rtc_resume(), and allows
683 * a suspend offset to be injected into the timekeeping values.
685 void timekeeping_inject_sleeptime(struct timespec
*delta
)
687 struct timekeeper
*tk
= &timekeeper
;
691 /* Make sure we don't set the clock twice */
692 read_persistent_clock(&ts
);
693 if (!(ts
.tv_sec
== 0 && ts
.tv_nsec
== 0))
696 write_seqlock_irqsave(&tk
->lock
, flags
);
698 timekeeping_forward_now(tk
);
700 __timekeeping_inject_sleeptime(tk
, delta
);
702 timekeeping_update(tk
, true);
704 write_sequnlock_irqrestore(&tk
->lock
, flags
);
706 /* signal hrtimers about time change */
711 * timekeeping_resume - Resumes the generic timekeeping subsystem.
713 * This is for the generic clocksource timekeeping.
714 * xtime/wall_to_monotonic/jiffies/etc are
715 * still managed by arch specific suspend/resume code.
717 static void timekeeping_resume(void)
719 struct timekeeper
*tk
= &timekeeper
;
723 read_persistent_clock(&ts
);
725 clocksource_resume();
727 write_seqlock_irqsave(&tk
->lock
, flags
);
729 if (timespec_compare(&ts
, &timekeeping_suspend_time
) > 0) {
730 ts
= timespec_sub(ts
, timekeeping_suspend_time
);
731 __timekeeping_inject_sleeptime(tk
, &ts
);
733 /* re-base the last cycle value */
734 tk
->clock
->cycle_last
= tk
->clock
->read(tk
->clock
);
736 timekeeping_suspended
= 0;
737 timekeeping_update(tk
, false);
738 write_sequnlock_irqrestore(&tk
->lock
, flags
);
740 touch_softlockup_watchdog();
742 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
744 /* Resume hrtimers */
748 static int timekeeping_suspend(void)
750 struct timekeeper
*tk
= &timekeeper
;
752 struct timespec delta
, delta_delta
;
753 static struct timespec old_delta
;
755 read_persistent_clock(&timekeeping_suspend_time
);
757 write_seqlock_irqsave(&tk
->lock
, flags
);
758 timekeeping_forward_now(tk
);
759 timekeeping_suspended
= 1;
762 * To avoid drift caused by repeated suspend/resumes,
763 * which each can add ~1 second drift error,
764 * try to compensate so the difference in system time
765 * and persistent_clock time stays close to constant.
767 delta
= timespec_sub(tk_xtime(tk
), timekeeping_suspend_time
);
768 delta_delta
= timespec_sub(delta
, old_delta
);
769 if (abs(delta_delta
.tv_sec
) >= 2) {
771 * if delta_delta is too large, assume time correction
772 * has occured and set old_delta to the current delta.
776 /* Otherwise try to adjust old_system to compensate */
777 timekeeping_suspend_time
=
778 timespec_add(timekeeping_suspend_time
, delta_delta
);
780 write_sequnlock_irqrestore(&tk
->lock
, flags
);
782 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
783 clocksource_suspend();
788 /* sysfs resume/suspend bits for timekeeping */
789 static struct syscore_ops timekeeping_syscore_ops
= {
790 .resume
= timekeeping_resume
,
791 .suspend
= timekeeping_suspend
,
794 static int __init
timekeeping_init_ops(void)
796 register_syscore_ops(&timekeeping_syscore_ops
);
800 device_initcall(timekeeping_init_ops
);
803 * If the error is already larger, we look ahead even further
804 * to compensate for late or lost adjustments.
806 static __always_inline
int timekeeping_bigadjust(struct timekeeper
*tk
,
807 s64 error
, s64
*interval
,
815 * Use the current error value to determine how much to look ahead.
816 * The larger the error the slower we adjust for it to avoid problems
817 * with losing too many ticks, otherwise we would overadjust and
818 * produce an even larger error. The smaller the adjustment the
819 * faster we try to adjust for it, as lost ticks can do less harm
820 * here. This is tuned so that an error of about 1 msec is adjusted
821 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
823 error2
= tk
->ntp_error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
824 error2
= abs(error2
);
825 for (look_ahead
= 0; error2
> 0; look_ahead
++)
829 * Now calculate the error in (1 << look_ahead) ticks, but first
830 * remove the single look ahead already included in the error.
832 tick_error
= ntp_tick_length() >> (tk
->ntp_error_shift
+ 1);
833 tick_error
-= tk
->xtime_interval
>> 1;
834 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
836 /* Finally calculate the adjustment shift value. */
841 *interval
= -*interval
;
845 for (adj
= 0; error
> i
; adj
++)
854 * Adjust the multiplier to reduce the error value,
855 * this is optimized for the most common adjustments of -1,0,1,
856 * for other values we can do a bit more work.
858 static void timekeeping_adjust(struct timekeeper
*tk
, s64 offset
)
860 s64 error
, interval
= tk
->cycle_interval
;
864 * The point of this is to check if the error is greater than half
867 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
869 * Note we subtract one in the shift, so that error is really error*2.
870 * This "saves" dividing(shifting) interval twice, but keeps the
871 * (error > interval) comparison as still measuring if error is
872 * larger than half an interval.
874 * Note: It does not "save" on aggravation when reading the code.
876 error
= tk
->ntp_error
>> (tk
->ntp_error_shift
- 1);
877 if (error
> interval
) {
879 * We now divide error by 4(via shift), which checks if
880 * the error is greater than twice the interval.
881 * If it is greater, we need a bigadjust, if its smaller,
882 * we can adjust by 1.
886 * XXX - In update_wall_time, we round up to the next
887 * nanosecond, and store the amount rounded up into
888 * the error. This causes the likely below to be unlikely.
890 * The proper fix is to avoid rounding up by using
891 * the high precision tk->xtime_nsec instead of
892 * xtime.tv_nsec everywhere. Fixing this will take some
895 if (likely(error
<= interval
))
898 adj
= timekeeping_bigadjust(tk
, error
, &interval
, &offset
);
900 if (error
< -interval
) {
901 /* See comment above, this is just switched for the negative */
903 if (likely(error
>= -interval
)) {
905 interval
= -interval
;
908 adj
= timekeeping_bigadjust(tk
, error
, &interval
, &offset
);
915 if (unlikely(tk
->clock
->maxadj
&&
916 (tk
->mult
+ adj
> tk
->clock
->mult
+ tk
->clock
->maxadj
))) {
917 printk_once(KERN_WARNING
918 "Adjusting %s more than 11%% (%ld vs %ld)\n",
919 tk
->clock
->name
, (long)tk
->mult
+ adj
,
920 (long)tk
->clock
->mult
+ tk
->clock
->maxadj
);
923 * So the following can be confusing.
925 * To keep things simple, lets assume adj == 1 for now.
927 * When adj != 1, remember that the interval and offset values
928 * have been appropriately scaled so the math is the same.
930 * The basic idea here is that we're increasing the multiplier
931 * by one, this causes the xtime_interval to be incremented by
932 * one cycle_interval. This is because:
933 * xtime_interval = cycle_interval * mult
934 * So if mult is being incremented by one:
935 * xtime_interval = cycle_interval * (mult + 1)
937 * xtime_interval = (cycle_interval * mult) + cycle_interval
938 * Which can be shortened to:
939 * xtime_interval += cycle_interval
941 * So offset stores the non-accumulated cycles. Thus the current
942 * time (in shifted nanoseconds) is:
943 * now = (offset * adj) + xtime_nsec
944 * Now, even though we're adjusting the clock frequency, we have
945 * to keep time consistent. In other words, we can't jump back
946 * in time, and we also want to avoid jumping forward in time.
948 * So given the same offset value, we need the time to be the same
949 * both before and after the freq adjustment.
950 * now = (offset * adj_1) + xtime_nsec_1
951 * now = (offset * adj_2) + xtime_nsec_2
953 * (offset * adj_1) + xtime_nsec_1 =
954 * (offset * adj_2) + xtime_nsec_2
958 * (offset * adj_1) + xtime_nsec_1 =
959 * (offset * (adj_1+1)) + xtime_nsec_2
960 * (offset * adj_1) + xtime_nsec_1 =
961 * (offset * adj_1) + offset + xtime_nsec_2
962 * Canceling the sides:
963 * xtime_nsec_1 = offset + xtime_nsec_2
965 * xtime_nsec_2 = xtime_nsec_1 - offset
966 * Which simplfies to:
967 * xtime_nsec -= offset
969 * XXX - TODO: Doc ntp_error calculation.
972 tk
->xtime_interval
+= interval
;
973 tk
->xtime_nsec
-= offset
;
974 tk
->ntp_error
-= (interval
- offset
) << tk
->ntp_error_shift
;
978 * It may be possible that when we entered this function, xtime_nsec
979 * was very small. Further, if we're slightly speeding the clocksource
980 * in the code above, its possible the required corrective factor to
981 * xtime_nsec could cause it to underflow.
983 * Now, since we already accumulated the second, cannot simply roll
984 * the accumulated second back, since the NTP subsystem has been
985 * notified via second_overflow. So instead we push xtime_nsec forward
986 * by the amount we underflowed, and add that amount into the error.
988 * We'll correct this error next time through this function, when
989 * xtime_nsec is not as small.
991 if (unlikely((s64
)tk
->xtime_nsec
< 0)) {
992 s64 neg
= -(s64
)tk
->xtime_nsec
;
994 tk
->ntp_error
+= neg
<< tk
->ntp_error_shift
;
1000 * accumulate_nsecs_to_secs - Accumulates nsecs into secs
1002 * Helper function that accumulates a the nsecs greater then a second
1003 * from the xtime_nsec field to the xtime_secs field.
1004 * It also calls into the NTP code to handle leapsecond processing.
1007 static inline void accumulate_nsecs_to_secs(struct timekeeper
*tk
)
1009 u64 nsecps
= (u64
)NSEC_PER_SEC
<< tk
->shift
;
1011 while (tk
->xtime_nsec
>= nsecps
) {
1014 tk
->xtime_nsec
-= nsecps
;
1017 /* Figure out if its a leap sec and apply if needed */
1018 leap
= second_overflow(tk
->xtime_sec
);
1019 if (unlikely(leap
)) {
1022 tk
->xtime_sec
+= leap
;
1026 tk_set_wall_to_mono(tk
,
1027 timespec_sub(tk
->wall_to_monotonic
, ts
));
1029 clock_was_set_delayed();
1035 * logarithmic_accumulation - shifted accumulation of cycles
1037 * This functions accumulates a shifted interval of cycles into
1038 * into a shifted interval nanoseconds. Allows for O(log) accumulation
1041 * Returns the unconsumed cycles.
1043 static cycle_t
logarithmic_accumulation(struct timekeeper
*tk
, cycle_t offset
,
1048 /* If the offset is smaller then a shifted interval, do nothing */
1049 if (offset
< tk
->cycle_interval
<<shift
)
1052 /* Accumulate one shifted interval */
1053 offset
-= tk
->cycle_interval
<< shift
;
1054 tk
->clock
->cycle_last
+= tk
->cycle_interval
<< shift
;
1056 tk
->xtime_nsec
+= tk
->xtime_interval
<< shift
;
1057 accumulate_nsecs_to_secs(tk
);
1059 /* Accumulate raw time */
1060 raw_nsecs
= tk
->raw_interval
<< shift
;
1061 raw_nsecs
+= tk
->raw_time
.tv_nsec
;
1062 if (raw_nsecs
>= NSEC_PER_SEC
) {
1063 u64 raw_secs
= raw_nsecs
;
1064 raw_nsecs
= do_div(raw_secs
, NSEC_PER_SEC
);
1065 tk
->raw_time
.tv_sec
+= raw_secs
;
1067 tk
->raw_time
.tv_nsec
= raw_nsecs
;
1069 /* Accumulate error between NTP and clock interval */
1070 tk
->ntp_error
+= ntp_tick_length() << shift
;
1071 tk
->ntp_error
-= (tk
->xtime_interval
+ tk
->xtime_remainder
) <<
1072 (tk
->ntp_error_shift
+ shift
);
1078 * update_wall_time - Uses the current clocksource to increment the wall time
1081 static void update_wall_time(void)
1083 struct clocksource
*clock
;
1084 struct timekeeper
*tk
= &timekeeper
;
1086 int shift
= 0, maxshift
;
1087 unsigned long flags
;
1090 write_seqlock_irqsave(&tk
->lock
, flags
);
1092 /* Make sure we're fully resumed: */
1093 if (unlikely(timekeeping_suspended
))
1098 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1099 offset
= tk
->cycle_interval
;
1101 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
1104 /* Check if there's really nothing to do */
1105 if (offset
< tk
->cycle_interval
)
1109 * With NO_HZ we may have to accumulate many cycle_intervals
1110 * (think "ticks") worth of time at once. To do this efficiently,
1111 * we calculate the largest doubling multiple of cycle_intervals
1112 * that is smaller than the offset. We then accumulate that
1113 * chunk in one go, and then try to consume the next smaller
1116 shift
= ilog2(offset
) - ilog2(tk
->cycle_interval
);
1117 shift
= max(0, shift
);
1118 /* Bound shift to one less than what overflows tick_length */
1119 maxshift
= (64 - (ilog2(ntp_tick_length())+1)) - 1;
1120 shift
= min(shift
, maxshift
);
1121 while (offset
>= tk
->cycle_interval
) {
1122 offset
= logarithmic_accumulation(tk
, offset
, shift
);
1123 if (offset
< tk
->cycle_interval
<<shift
)
1127 /* correct the clock when NTP error is too big */
1128 timekeeping_adjust(tk
, offset
);
1132 * Store only full nanoseconds into xtime_nsec after rounding
1133 * it up and add the remainder to the error difference.
1134 * XXX - This is necessary to avoid small 1ns inconsistnecies caused
1135 * by truncating the remainder in vsyscalls. However, it causes
1136 * additional work to be done in timekeeping_adjust(). Once
1137 * the vsyscall implementations are converted to use xtime_nsec
1138 * (shifted nanoseconds), this can be killed.
1140 remainder
= tk
->xtime_nsec
& ((1ULL << tk
->shift
) - 1);
1141 tk
->xtime_nsec
-= remainder
;
1142 tk
->xtime_nsec
+= 1ULL << tk
->shift
;
1143 tk
->ntp_error
+= remainder
<< tk
->ntp_error_shift
;
1146 * Finally, make sure that after the rounding
1147 * xtime_nsec isn't larger than NSEC_PER_SEC
1149 accumulate_nsecs_to_secs(tk
);
1151 timekeeping_update(tk
, false);
1154 write_sequnlock_irqrestore(&tk
->lock
, flags
);
1159 * getboottime - Return the real time of system boot.
1160 * @ts: pointer to the timespec to be set
1162 * Returns the wall-time of boot in a timespec.
1164 * This is based on the wall_to_monotonic offset and the total suspend
1165 * time. Calls to settimeofday will affect the value returned (which
1166 * basically means that however wrong your real time clock is at boot time,
1167 * you get the right time here).
1169 void getboottime(struct timespec
*ts
)
1171 struct timekeeper
*tk
= &timekeeper
;
1172 struct timespec boottime
= {
1173 .tv_sec
= tk
->wall_to_monotonic
.tv_sec
+
1174 tk
->total_sleep_time
.tv_sec
,
1175 .tv_nsec
= tk
->wall_to_monotonic
.tv_nsec
+
1176 tk
->total_sleep_time
.tv_nsec
1179 set_normalized_timespec(ts
, -boottime
.tv_sec
, -boottime
.tv_nsec
);
1181 EXPORT_SYMBOL_GPL(getboottime
);
1184 * get_monotonic_boottime - Returns monotonic time since boot
1185 * @ts: pointer to the timespec to be set
1187 * Returns the monotonic time since boot in a timespec.
1189 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1190 * includes the time spent in suspend.
1192 void get_monotonic_boottime(struct timespec
*ts
)
1194 struct timekeeper
*tk
= &timekeeper
;
1195 struct timespec tomono
, sleep
;
1199 WARN_ON(timekeeping_suspended
);
1202 seq
= read_seqbegin(&tk
->lock
);
1203 ts
->tv_sec
= tk
->xtime_sec
;
1204 nsec
= timekeeping_get_ns(tk
);
1205 tomono
= tk
->wall_to_monotonic
;
1206 sleep
= tk
->total_sleep_time
;
1208 } while (read_seqretry(&tk
->lock
, seq
));
1210 ts
->tv_sec
+= tomono
.tv_sec
+ sleep
.tv_sec
;
1212 timespec_add_ns(ts
, nsec
+ tomono
.tv_nsec
+ sleep
.tv_nsec
);
1214 EXPORT_SYMBOL_GPL(get_monotonic_boottime
);
1217 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1219 * Returns the monotonic time since boot in a ktime
1221 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1222 * includes the time spent in suspend.
1224 ktime_t
ktime_get_boottime(void)
1228 get_monotonic_boottime(&ts
);
1229 return timespec_to_ktime(ts
);
1231 EXPORT_SYMBOL_GPL(ktime_get_boottime
);
1234 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1235 * @ts: pointer to the timespec to be converted
1237 void monotonic_to_bootbased(struct timespec
*ts
)
1239 struct timekeeper
*tk
= &timekeeper
;
1241 *ts
= timespec_add(*ts
, tk
->total_sleep_time
);
1243 EXPORT_SYMBOL_GPL(monotonic_to_bootbased
);
1245 unsigned long get_seconds(void)
1247 struct timekeeper
*tk
= &timekeeper
;
1249 return tk
->xtime_sec
;
1251 EXPORT_SYMBOL(get_seconds
);
1253 struct timespec
__current_kernel_time(void)
1255 struct timekeeper
*tk
= &timekeeper
;
1257 return tk_xtime(tk
);
1260 struct timespec
current_kernel_time(void)
1262 struct timekeeper
*tk
= &timekeeper
;
1263 struct timespec now
;
1267 seq
= read_seqbegin(&tk
->lock
);
1270 } while (read_seqretry(&tk
->lock
, seq
));
1274 EXPORT_SYMBOL(current_kernel_time
);
1276 struct timespec
get_monotonic_coarse(void)
1278 struct timekeeper
*tk
= &timekeeper
;
1279 struct timespec now
, mono
;
1283 seq
= read_seqbegin(&tk
->lock
);
1286 mono
= tk
->wall_to_monotonic
;
1287 } while (read_seqretry(&tk
->lock
, seq
));
1289 set_normalized_timespec(&now
, now
.tv_sec
+ mono
.tv_sec
,
1290 now
.tv_nsec
+ mono
.tv_nsec
);
1295 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1296 * without sampling the sequence number in xtime_lock.
1297 * jiffies is defined in the linker script...
1299 void do_timer(unsigned long ticks
)
1301 jiffies_64
+= ticks
;
1303 calc_global_load(ticks
);
1307 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1308 * and sleep offsets.
1309 * @xtim: pointer to timespec to be set with xtime
1310 * @wtom: pointer to timespec to be set with wall_to_monotonic
1311 * @sleep: pointer to timespec to be set with time in suspend
1313 void get_xtime_and_monotonic_and_sleep_offset(struct timespec
*xtim
,
1314 struct timespec
*wtom
, struct timespec
*sleep
)
1316 struct timekeeper
*tk
= &timekeeper
;
1320 seq
= read_seqbegin(&tk
->lock
);
1321 *xtim
= tk_xtime(tk
);
1322 *wtom
= tk
->wall_to_monotonic
;
1323 *sleep
= tk
->total_sleep_time
;
1324 } while (read_seqretry(&tk
->lock
, seq
));
1327 #ifdef CONFIG_HIGH_RES_TIMERS
1329 * ktime_get_update_offsets - hrtimer helper
1330 * @offs_real: pointer to storage for monotonic -> realtime offset
1331 * @offs_boot: pointer to storage for monotonic -> boottime offset
1333 * Returns current monotonic time and updates the offsets
1334 * Called from hrtimer_interupt() or retrigger_next_event()
1336 ktime_t
ktime_get_update_offsets(ktime_t
*offs_real
, ktime_t
*offs_boot
)
1338 struct timekeeper
*tk
= &timekeeper
;
1344 seq
= read_seqbegin(&tk
->lock
);
1346 secs
= tk
->xtime_sec
;
1347 nsecs
= timekeeping_get_ns(tk
);
1349 *offs_real
= tk
->offs_real
;
1350 *offs_boot
= tk
->offs_boot
;
1351 } while (read_seqretry(&tk
->lock
, seq
));
1353 now
= ktime_add_ns(ktime_set(secs
, 0), nsecs
);
1354 now
= ktime_sub(now
, *offs_real
);
1360 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1362 ktime_t
ktime_get_monotonic_offset(void)
1364 struct timekeeper
*tk
= &timekeeper
;
1366 struct timespec wtom
;
1369 seq
= read_seqbegin(&tk
->lock
);
1370 wtom
= tk
->wall_to_monotonic
;
1371 } while (read_seqretry(&tk
->lock
, seq
));
1373 return timespec_to_ktime(wtom
);
1375 EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset
);
1378 * xtime_update() - advances the timekeeping infrastructure
1379 * @ticks: number of ticks, that have elapsed since the last call.
1381 * Must be called with interrupts disabled.
1383 void xtime_update(unsigned long ticks
)
1385 write_seqlock(&xtime_lock
);
1387 write_sequnlock(&xtime_lock
);