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/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>
24 /* Structure holding internal timekeeping values. */
26 /* Current clocksource used for timekeeping. */
27 struct clocksource
*clock
;
28 /* NTP adjusted clock multiplier */
30 /* The shift value of the current clocksource. */
33 /* Number of clock cycles in one NTP interval. */
34 cycle_t cycle_interval
;
35 /* Number of clock shifted nano seconds in one NTP interval. */
37 /* shifted nano seconds left over when rounding cycle_interval */
39 /* Raw nano seconds accumulated per NTP interval. */
42 /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */
44 /* Difference between accumulated time and NTP time in ntp
45 * shifted nano seconds. */
47 /* Shift conversion between clock shifted nano seconds and
48 * ntp shifted nano seconds. */
51 /* The current time */
52 struct timespec xtime
;
54 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
55 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
56 * at zero at system boot time, so wall_to_monotonic will be negative,
57 * however, we will ALWAYS keep the tv_nsec part positive so we can use
58 * the usual normalization.
60 * wall_to_monotonic is moved after resume from suspend for the
61 * monotonic time not to jump. We need to add total_sleep_time to
62 * wall_to_monotonic to get the real boot based time offset.
64 * - wall_to_monotonic is no longer the boot time, getboottime must be
67 struct timespec wall_to_monotonic
;
68 /* time spent in suspend */
69 struct timespec total_sleep_time
;
70 /* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
71 struct timespec raw_time
;
73 /* Seqlock for all timekeeper values */
77 static struct timekeeper timekeeper
;
80 * This read-write spinlock protects us from races in SMP while
83 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(xtime_lock
);
86 /* flag for if timekeeping is suspended */
87 int __read_mostly timekeeping_suspended
;
92 * timekeeper_setup_internals - Set up internals to use clocksource clock.
94 * @clock: Pointer to clocksource.
96 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
97 * pair and interval request.
99 * Unless you're the timekeeping code, you should not be using this!
101 static void timekeeper_setup_internals(struct clocksource
*clock
)
104 u64 tmp
, ntpinterval
;
106 timekeeper
.clock
= clock
;
107 clock
->cycle_last
= clock
->read(clock
);
109 /* Do the ns -> cycle conversion first, using original mult */
110 tmp
= NTP_INTERVAL_LENGTH
;
111 tmp
<<= clock
->shift
;
113 tmp
+= clock
->mult
/2;
114 do_div(tmp
, clock
->mult
);
118 interval
= (cycle_t
) tmp
;
119 timekeeper
.cycle_interval
= interval
;
121 /* Go back from cycles -> shifted ns */
122 timekeeper
.xtime_interval
= (u64
) interval
* clock
->mult
;
123 timekeeper
.xtime_remainder
= ntpinterval
- timekeeper
.xtime_interval
;
124 timekeeper
.raw_interval
=
125 ((u64
) interval
* clock
->mult
) >> clock
->shift
;
127 timekeeper
.xtime_nsec
= 0;
128 timekeeper
.shift
= clock
->shift
;
130 timekeeper
.ntp_error
= 0;
131 timekeeper
.ntp_error_shift
= NTP_SCALE_SHIFT
- clock
->shift
;
134 * The timekeeper keeps its own mult values for the currently
135 * active clocksource. These value will be adjusted via NTP
136 * to counteract clock drifting.
138 timekeeper
.mult
= clock
->mult
;
141 /* Timekeeper helper functions. */
142 static inline s64
timekeeping_get_ns(void)
144 cycle_t cycle_now
, cycle_delta
;
145 struct clocksource
*clock
;
147 /* read clocksource: */
148 clock
= timekeeper
.clock
;
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 /* return delta convert to nanoseconds using ntp adjusted mult. */
155 return clocksource_cyc2ns(cycle_delta
, timekeeper
.mult
,
159 static inline s64
timekeeping_get_ns_raw(void)
161 cycle_t cycle_now
, cycle_delta
;
162 struct clocksource
*clock
;
164 /* read clocksource: */
165 clock
= timekeeper
.clock
;
166 cycle_now
= clock
->read(clock
);
168 /* calculate the delta since the last update_wall_time: */
169 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
171 /* return delta convert to nanoseconds. */
172 return clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
175 /* must hold write on timekeeper.lock */
176 static void timekeeping_update(bool clearntp
)
179 timekeeper
.ntp_error
= 0;
182 update_vsyscall(&timekeeper
.xtime
, &timekeeper
.wall_to_monotonic
,
183 timekeeper
.clock
, timekeeper
.mult
);
188 * timekeeping_forward_now - update clock to the current time
190 * Forward the current clock to update its state since the last call to
191 * update_wall_time(). This is useful before significant clock changes,
192 * as it avoids having to deal with this time offset explicitly.
194 static void timekeeping_forward_now(void)
196 cycle_t cycle_now
, cycle_delta
;
197 struct clocksource
*clock
;
200 clock
= timekeeper
.clock
;
201 cycle_now
= clock
->read(clock
);
202 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
203 clock
->cycle_last
= cycle_now
;
205 nsec
= clocksource_cyc2ns(cycle_delta
, timekeeper
.mult
,
208 /* If arch requires, add in gettimeoffset() */
209 nsec
+= arch_gettimeoffset();
211 timespec_add_ns(&timekeeper
.xtime
, nsec
);
213 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
214 timespec_add_ns(&timekeeper
.raw_time
, nsec
);
218 * getnstimeofday - Returns the time of day in a timespec
219 * @ts: pointer to the timespec to be set
221 * Returns the time of day in a timespec.
223 void getnstimeofday(struct timespec
*ts
)
228 WARN_ON(timekeeping_suspended
);
231 seq
= read_seqbegin(&timekeeper
.lock
);
233 *ts
= timekeeper
.xtime
;
234 nsecs
= timekeeping_get_ns();
236 /* If arch requires, add in gettimeoffset() */
237 nsecs
+= arch_gettimeoffset();
239 } while (read_seqretry(&timekeeper
.lock
, seq
));
241 timespec_add_ns(ts
, nsecs
);
244 EXPORT_SYMBOL(getnstimeofday
);
246 ktime_t
ktime_get(void)
251 WARN_ON(timekeeping_suspended
);
254 seq
= read_seqbegin(&timekeeper
.lock
);
255 secs
= timekeeper
.xtime
.tv_sec
+
256 timekeeper
.wall_to_monotonic
.tv_sec
;
257 nsecs
= timekeeper
.xtime
.tv_nsec
+
258 timekeeper
.wall_to_monotonic
.tv_nsec
;
259 nsecs
+= timekeeping_get_ns();
260 /* If arch requires, add in gettimeoffset() */
261 nsecs
+= arch_gettimeoffset();
263 } while (read_seqretry(&timekeeper
.lock
, seq
));
265 * Use ktime_set/ktime_add_ns to create a proper ktime on
266 * 32-bit architectures without CONFIG_KTIME_SCALAR.
268 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
270 EXPORT_SYMBOL_GPL(ktime_get
);
273 * ktime_get_ts - get the monotonic clock in timespec format
274 * @ts: pointer to timespec variable
276 * The function calculates the monotonic clock from the realtime
277 * clock and the wall_to_monotonic offset and stores the result
278 * in normalized timespec format in the variable pointed to by @ts.
280 void ktime_get_ts(struct timespec
*ts
)
282 struct timespec tomono
;
286 WARN_ON(timekeeping_suspended
);
289 seq
= read_seqbegin(&timekeeper
.lock
);
290 *ts
= timekeeper
.xtime
;
291 tomono
= timekeeper
.wall_to_monotonic
;
292 nsecs
= timekeeping_get_ns();
293 /* If arch requires, add in gettimeoffset() */
294 nsecs
+= arch_gettimeoffset();
296 } while (read_seqretry(&timekeeper
.lock
, seq
));
298 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
299 ts
->tv_nsec
+ tomono
.tv_nsec
+ nsecs
);
301 EXPORT_SYMBOL_GPL(ktime_get_ts
);
303 #ifdef CONFIG_NTP_PPS
306 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
307 * @ts_raw: pointer to the timespec to be set to raw monotonic time
308 * @ts_real: pointer to the timespec to be set to the time of day
310 * This function reads both the time of day and raw monotonic time at the
311 * same time atomically and stores the resulting timestamps in timespec
314 void getnstime_raw_and_real(struct timespec
*ts_raw
, struct timespec
*ts_real
)
317 s64 nsecs_raw
, nsecs_real
;
319 WARN_ON_ONCE(timekeeping_suspended
);
324 seq
= read_seqbegin(&timekeeper
.lock
);
326 *ts_raw
= timekeeper
.raw_time
;
327 *ts_real
= timekeeper
.xtime
;
329 nsecs_raw
= timekeeping_get_ns_raw();
330 nsecs_real
= timekeeping_get_ns();
332 /* If arch requires, add in gettimeoffset() */
333 arch_offset
= arch_gettimeoffset();
334 nsecs_raw
+= arch_offset
;
335 nsecs_real
+= arch_offset
;
337 } while (read_seqretry(&timekeeper
.lock
, seq
));
339 timespec_add_ns(ts_raw
, nsecs_raw
);
340 timespec_add_ns(ts_real
, nsecs_real
);
342 EXPORT_SYMBOL(getnstime_raw_and_real
);
344 #endif /* CONFIG_NTP_PPS */
347 * do_gettimeofday - Returns the time of day in a timeval
348 * @tv: pointer to the timeval to be set
350 * NOTE: Users should be converted to using getnstimeofday()
352 void do_gettimeofday(struct timeval
*tv
)
356 getnstimeofday(&now
);
357 tv
->tv_sec
= now
.tv_sec
;
358 tv
->tv_usec
= now
.tv_nsec
/1000;
361 EXPORT_SYMBOL(do_gettimeofday
);
363 * do_settimeofday - Sets the time of day
364 * @tv: pointer to the timespec variable containing the new time
366 * Sets the time of day to the new time and update NTP and notify hrtimers
368 int do_settimeofday(const struct timespec
*tv
)
370 struct timespec ts_delta
;
373 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
376 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
378 timekeeping_forward_now();
380 ts_delta
.tv_sec
= tv
->tv_sec
- timekeeper
.xtime
.tv_sec
;
381 ts_delta
.tv_nsec
= tv
->tv_nsec
- timekeeper
.xtime
.tv_nsec
;
382 timekeeper
.wall_to_monotonic
=
383 timespec_sub(timekeeper
.wall_to_monotonic
, ts_delta
);
385 timekeeper
.xtime
= *tv
;
386 timekeeping_update(true);
388 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
390 /* signal hrtimers about time change */
396 EXPORT_SYMBOL(do_settimeofday
);
400 * timekeeping_inject_offset - Adds or subtracts from the current time.
401 * @tv: pointer to the timespec variable containing the offset
403 * Adds or subtracts an offset value from the current time.
405 int timekeeping_inject_offset(struct timespec
*ts
)
409 if ((unsigned long)ts
->tv_nsec
>= NSEC_PER_SEC
)
412 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
414 timekeeping_forward_now();
416 timekeeper
.xtime
= timespec_add(timekeeper
.xtime
, *ts
);
417 timekeeper
.wall_to_monotonic
=
418 timespec_sub(timekeeper
.wall_to_monotonic
, *ts
);
420 timekeeping_update(true);
422 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
424 /* signal hrtimers about time change */
429 EXPORT_SYMBOL(timekeeping_inject_offset
);
432 * change_clocksource - Swaps clocksources if a new one is available
434 * Accumulates current time interval and initializes new clocksource
436 static int change_clocksource(void *data
)
438 struct clocksource
*new, *old
;
441 new = (struct clocksource
*) data
;
443 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
445 timekeeping_forward_now();
446 if (!new->enable
|| new->enable(new) == 0) {
447 old
= timekeeper
.clock
;
448 timekeeper_setup_internals(new);
452 timekeeping_update(true);
454 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
460 * timekeeping_notify - Install a new clock source
461 * @clock: pointer to the clock source
463 * This function is called from clocksource.c after a new, better clock
464 * source has been registered. The caller holds the clocksource_mutex.
466 void timekeeping_notify(struct clocksource
*clock
)
468 if (timekeeper
.clock
== clock
)
470 stop_machine(change_clocksource
, clock
, NULL
);
475 * ktime_get_real - get the real (wall-) time in ktime_t format
477 * returns the time in ktime_t format
479 ktime_t
ktime_get_real(void)
483 getnstimeofday(&now
);
485 return timespec_to_ktime(now
);
487 EXPORT_SYMBOL_GPL(ktime_get_real
);
490 * getrawmonotonic - Returns the raw monotonic time in a timespec
491 * @ts: pointer to the timespec to be set
493 * Returns the raw monotonic time (completely un-modified by ntp)
495 void getrawmonotonic(struct timespec
*ts
)
501 seq
= read_seqbegin(&timekeeper
.lock
);
502 nsecs
= timekeeping_get_ns_raw();
503 *ts
= timekeeper
.raw_time
;
505 } while (read_seqretry(&timekeeper
.lock
, seq
));
507 timespec_add_ns(ts
, nsecs
);
509 EXPORT_SYMBOL(getrawmonotonic
);
513 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
515 int timekeeping_valid_for_hres(void)
521 seq
= read_seqbegin(&timekeeper
.lock
);
523 ret
= timekeeper
.clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
525 } while (read_seqretry(&timekeeper
.lock
, seq
));
531 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
533 u64
timekeeping_max_deferment(void)
538 seq
= read_seqbegin(&timekeeper
.lock
);
540 ret
= timekeeper
.clock
->max_idle_ns
;
542 } while (read_seqretry(&timekeeper
.lock
, seq
));
548 * read_persistent_clock - Return time from the persistent clock.
550 * Weak dummy function for arches that do not yet support it.
551 * Reads the time from the battery backed persistent clock.
552 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
554 * XXX - Do be sure to remove it once all arches implement it.
556 void __attribute__((weak
)) read_persistent_clock(struct timespec
*ts
)
563 * read_boot_clock - Return time of the system start.
565 * Weak dummy function for arches that do not yet support it.
566 * Function to read the exact time the system has been started.
567 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
569 * XXX - Do be sure to remove it once all arches implement it.
571 void __attribute__((weak
)) read_boot_clock(struct timespec
*ts
)
578 * timekeeping_init - Initializes the clocksource and common timekeeping values
580 void __init
timekeeping_init(void)
582 struct clocksource
*clock
;
584 struct timespec now
, boot
;
586 read_persistent_clock(&now
);
587 read_boot_clock(&boot
);
589 seqlock_init(&timekeeper
.lock
);
593 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
594 clock
= clocksource_default_clock();
596 clock
->enable(clock
);
597 timekeeper_setup_internals(clock
);
599 timekeeper
.xtime
.tv_sec
= now
.tv_sec
;
600 timekeeper
.xtime
.tv_nsec
= now
.tv_nsec
;
601 timekeeper
.raw_time
.tv_sec
= 0;
602 timekeeper
.raw_time
.tv_nsec
= 0;
603 if (boot
.tv_sec
== 0 && boot
.tv_nsec
== 0) {
604 boot
.tv_sec
= timekeeper
.xtime
.tv_sec
;
605 boot
.tv_nsec
= timekeeper
.xtime
.tv_nsec
;
607 set_normalized_timespec(&timekeeper
.wall_to_monotonic
,
608 -boot
.tv_sec
, -boot
.tv_nsec
);
609 timekeeper
.total_sleep_time
.tv_sec
= 0;
610 timekeeper
.total_sleep_time
.tv_nsec
= 0;
611 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
614 /* time in seconds when suspend began */
615 static struct timespec timekeeping_suspend_time
;
618 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
619 * @delta: pointer to a timespec delta value
621 * Takes a timespec offset measuring a suspend interval and properly
622 * adds the sleep offset to the timekeeping variables.
624 static void __timekeeping_inject_sleeptime(struct timespec
*delta
)
626 if (!timespec_valid(delta
)) {
627 printk(KERN_WARNING
"__timekeeping_inject_sleeptime: Invalid "
628 "sleep delta value!\n");
632 timekeeper
.xtime
= timespec_add(timekeeper
.xtime
, *delta
);
633 timekeeper
.wall_to_monotonic
=
634 timespec_sub(timekeeper
.wall_to_monotonic
, *delta
);
635 timekeeper
.total_sleep_time
= timespec_add(
636 timekeeper
.total_sleep_time
, *delta
);
641 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
642 * @delta: pointer to a timespec delta value
644 * This hook is for architectures that cannot support read_persistent_clock
645 * because their RTC/persistent clock is only accessible when irqs are enabled.
647 * This function should only be called by rtc_resume(), and allows
648 * a suspend offset to be injected into the timekeeping values.
650 void timekeeping_inject_sleeptime(struct timespec
*delta
)
655 /* Make sure we don't set the clock twice */
656 read_persistent_clock(&ts
);
657 if (!(ts
.tv_sec
== 0 && ts
.tv_nsec
== 0))
660 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
662 timekeeping_forward_now();
664 __timekeeping_inject_sleeptime(delta
);
666 timekeeping_update(true);
668 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
670 /* signal hrtimers about time change */
676 * timekeeping_resume - Resumes the generic timekeeping subsystem.
678 * This is for the generic clocksource timekeeping.
679 * xtime/wall_to_monotonic/jiffies/etc are
680 * still managed by arch specific suspend/resume code.
682 static void timekeeping_resume(void)
687 read_persistent_clock(&ts
);
689 clocksource_resume();
691 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
693 if (timespec_compare(&ts
, &timekeeping_suspend_time
) > 0) {
694 ts
= timespec_sub(ts
, timekeeping_suspend_time
);
695 __timekeeping_inject_sleeptime(&ts
);
697 /* re-base the last cycle value */
698 timekeeper
.clock
->cycle_last
= timekeeper
.clock
->read(timekeeper
.clock
);
699 timekeeper
.ntp_error
= 0;
700 timekeeping_suspended
= 0;
701 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
703 touch_softlockup_watchdog();
705 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
707 /* Resume hrtimers */
711 static int timekeeping_suspend(void)
714 struct timespec delta
, delta_delta
;
715 static struct timespec old_delta
;
717 read_persistent_clock(&timekeeping_suspend_time
);
719 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
720 timekeeping_forward_now();
721 timekeeping_suspended
= 1;
724 * To avoid drift caused by repeated suspend/resumes,
725 * which each can add ~1 second drift error,
726 * try to compensate so the difference in system time
727 * and persistent_clock time stays close to constant.
729 delta
= timespec_sub(timekeeper
.xtime
, timekeeping_suspend_time
);
730 delta_delta
= timespec_sub(delta
, old_delta
);
731 if (abs(delta_delta
.tv_sec
) >= 2) {
733 * if delta_delta is too large, assume time correction
734 * has occured and set old_delta to the current delta.
738 /* Otherwise try to adjust old_system to compensate */
739 timekeeping_suspend_time
=
740 timespec_add(timekeeping_suspend_time
, delta_delta
);
742 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
744 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
745 clocksource_suspend();
750 /* sysfs resume/suspend bits for timekeeping */
751 static struct syscore_ops timekeeping_syscore_ops
= {
752 .resume
= timekeeping_resume
,
753 .suspend
= timekeeping_suspend
,
756 static int __init
timekeeping_init_ops(void)
758 register_syscore_ops(&timekeeping_syscore_ops
);
762 device_initcall(timekeeping_init_ops
);
765 * If the error is already larger, we look ahead even further
766 * to compensate for late or lost adjustments.
768 static __always_inline
int timekeeping_bigadjust(s64 error
, s64
*interval
,
776 * Use the current error value to determine how much to look ahead.
777 * The larger the error the slower we adjust for it to avoid problems
778 * with losing too many ticks, otherwise we would overadjust and
779 * produce an even larger error. The smaller the adjustment the
780 * faster we try to adjust for it, as lost ticks can do less harm
781 * here. This is tuned so that an error of about 1 msec is adjusted
782 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
784 error2
= timekeeper
.ntp_error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
785 error2
= abs(error2
);
786 for (look_ahead
= 0; error2
> 0; look_ahead
++)
790 * Now calculate the error in (1 << look_ahead) ticks, but first
791 * remove the single look ahead already included in the error.
793 tick_error
= ntp_tick_length() >> (timekeeper
.ntp_error_shift
+ 1);
794 tick_error
-= timekeeper
.xtime_interval
>> 1;
795 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
797 /* Finally calculate the adjustment shift value. */
802 *interval
= -*interval
;
806 for (adj
= 0; error
> i
; adj
++)
815 * Adjust the multiplier to reduce the error value,
816 * this is optimized for the most common adjustments of -1,0,1,
817 * for other values we can do a bit more work.
819 static void timekeeping_adjust(s64 offset
)
821 s64 error
, interval
= timekeeper
.cycle_interval
;
825 * The point of this is to check if the error is greater than half
828 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
830 * Note we subtract one in the shift, so that error is really error*2.
831 * This "saves" dividing(shifting) interval twice, but keeps the
832 * (error > interval) comparison as still measuring if error is
833 * larger than half an interval.
835 * Note: It does not "save" on aggravation when reading the code.
837 error
= timekeeper
.ntp_error
>> (timekeeper
.ntp_error_shift
- 1);
838 if (error
> interval
) {
840 * We now divide error by 4(via shift), which checks if
841 * the error is greater than twice the interval.
842 * If it is greater, we need a bigadjust, if its smaller,
843 * we can adjust by 1.
847 * XXX - In update_wall_time, we round up to the next
848 * nanosecond, and store the amount rounded up into
849 * the error. This causes the likely below to be unlikely.
851 * The proper fix is to avoid rounding up by using
852 * the high precision timekeeper.xtime_nsec instead of
853 * xtime.tv_nsec everywhere. Fixing this will take some
856 if (likely(error
<= interval
))
859 adj
= timekeeping_bigadjust(error
, &interval
, &offset
);
860 } else if (error
< -interval
) {
861 /* See comment above, this is just switched for the negative */
863 if (likely(error
>= -interval
)) {
865 interval
= -interval
;
868 adj
= timekeeping_bigadjust(error
, &interval
, &offset
);
869 } else /* No adjustment needed */
872 if (unlikely(timekeeper
.clock
->maxadj
&&
873 (timekeeper
.mult
+ adj
>
874 timekeeper
.clock
->mult
+ timekeeper
.clock
->maxadj
))) {
875 printk_once(KERN_WARNING
876 "Adjusting %s more than 11%% (%ld vs %ld)\n",
877 timekeeper
.clock
->name
, (long)timekeeper
.mult
+ adj
,
878 (long)timekeeper
.clock
->mult
+
879 timekeeper
.clock
->maxadj
);
882 * So the following can be confusing.
884 * To keep things simple, lets assume adj == 1 for now.
886 * When adj != 1, remember that the interval and offset values
887 * have been appropriately scaled so the math is the same.
889 * The basic idea here is that we're increasing the multiplier
890 * by one, this causes the xtime_interval to be incremented by
891 * one cycle_interval. This is because:
892 * xtime_interval = cycle_interval * mult
893 * So if mult is being incremented by one:
894 * xtime_interval = cycle_interval * (mult + 1)
896 * xtime_interval = (cycle_interval * mult) + cycle_interval
897 * Which can be shortened to:
898 * xtime_interval += cycle_interval
900 * So offset stores the non-accumulated cycles. Thus the current
901 * time (in shifted nanoseconds) is:
902 * now = (offset * adj) + xtime_nsec
903 * Now, even though we're adjusting the clock frequency, we have
904 * to keep time consistent. In other words, we can't jump back
905 * in time, and we also want to avoid jumping forward in time.
907 * So given the same offset value, we need the time to be the same
908 * both before and after the freq adjustment.
909 * now = (offset * adj_1) + xtime_nsec_1
910 * now = (offset * adj_2) + xtime_nsec_2
912 * (offset * adj_1) + xtime_nsec_1 =
913 * (offset * adj_2) + xtime_nsec_2
917 * (offset * adj_1) + xtime_nsec_1 =
918 * (offset * (adj_1+1)) + xtime_nsec_2
919 * (offset * adj_1) + xtime_nsec_1 =
920 * (offset * adj_1) + offset + xtime_nsec_2
921 * Canceling the sides:
922 * xtime_nsec_1 = offset + xtime_nsec_2
924 * xtime_nsec_2 = xtime_nsec_1 - offset
925 * Which simplfies to:
926 * xtime_nsec -= offset
928 * XXX - TODO: Doc ntp_error calculation.
930 timekeeper
.mult
+= adj
;
931 timekeeper
.xtime_interval
+= interval
;
932 timekeeper
.xtime_nsec
-= offset
;
933 timekeeper
.ntp_error
-= (interval
- offset
) <<
934 timekeeper
.ntp_error_shift
;
939 * logarithmic_accumulation - shifted accumulation of cycles
941 * This functions accumulates a shifted interval of cycles into
942 * into a shifted interval nanoseconds. Allows for O(log) accumulation
945 * Returns the unconsumed cycles.
947 static cycle_t
logarithmic_accumulation(cycle_t offset
, int shift
)
949 u64 nsecps
= (u64
)NSEC_PER_SEC
<< timekeeper
.shift
;
952 /* If the offset is smaller than a shifted interval, do nothing */
953 if (offset
< timekeeper
.cycle_interval
<<shift
)
956 /* Accumulate one shifted interval */
957 offset
-= timekeeper
.cycle_interval
<< shift
;
958 timekeeper
.clock
->cycle_last
+= timekeeper
.cycle_interval
<< shift
;
960 timekeeper
.xtime_nsec
+= timekeeper
.xtime_interval
<< shift
;
961 while (timekeeper
.xtime_nsec
>= nsecps
) {
963 timekeeper
.xtime_nsec
-= nsecps
;
964 timekeeper
.xtime
.tv_sec
++;
965 leap
= second_overflow(timekeeper
.xtime
.tv_sec
);
966 timekeeper
.xtime
.tv_sec
+= leap
;
969 /* Accumulate raw time */
970 raw_nsecs
= timekeeper
.raw_interval
<< shift
;
971 raw_nsecs
+= timekeeper
.raw_time
.tv_nsec
;
972 if (raw_nsecs
>= NSEC_PER_SEC
) {
973 u64 raw_secs
= raw_nsecs
;
974 raw_nsecs
= do_div(raw_secs
, NSEC_PER_SEC
);
975 timekeeper
.raw_time
.tv_sec
+= raw_secs
;
977 timekeeper
.raw_time
.tv_nsec
= raw_nsecs
;
979 /* Accumulate error between NTP and clock interval */
980 timekeeper
.ntp_error
+= ntp_tick_length() << shift
;
981 timekeeper
.ntp_error
-=
982 (timekeeper
.xtime_interval
+ timekeeper
.xtime_remainder
) <<
983 (timekeeper
.ntp_error_shift
+ shift
);
990 * update_wall_time - Uses the current clocksource to increment the wall time
993 static void update_wall_time(void)
995 struct clocksource
*clock
;
997 int shift
= 0, maxshift
;
1000 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
1002 /* Make sure we're fully resumed: */
1003 if (unlikely(timekeeping_suspended
))
1006 clock
= timekeeper
.clock
;
1008 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1009 offset
= timekeeper
.cycle_interval
;
1011 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
1013 timekeeper
.xtime_nsec
= (s64
)timekeeper
.xtime
.tv_nsec
<<
1017 * With NO_HZ we may have to accumulate many cycle_intervals
1018 * (think "ticks") worth of time at once. To do this efficiently,
1019 * we calculate the largest doubling multiple of cycle_intervals
1020 * that is smaller than the offset. We then accumulate that
1021 * chunk in one go, and then try to consume the next smaller
1024 shift
= ilog2(offset
) - ilog2(timekeeper
.cycle_interval
);
1025 shift
= max(0, shift
);
1026 /* Bound shift to one less than what overflows tick_length */
1027 maxshift
= (64 - (ilog2(ntp_tick_length())+1)) - 1;
1028 shift
= min(shift
, maxshift
);
1029 while (offset
>= timekeeper
.cycle_interval
) {
1030 offset
= logarithmic_accumulation(offset
, shift
);
1031 if(offset
< timekeeper
.cycle_interval
<<shift
)
1035 /* correct the clock when NTP error is too big */
1036 timekeeping_adjust(offset
);
1039 * Since in the loop above, we accumulate any amount of time
1040 * in xtime_nsec over a second into xtime.tv_sec, its possible for
1041 * xtime_nsec to be fairly small after the loop. Further, if we're
1042 * slightly speeding the clocksource up in timekeeping_adjust(),
1043 * its possible the required corrective factor to xtime_nsec could
1044 * cause it to underflow.
1046 * Now, we cannot simply roll the accumulated second back, since
1047 * the NTP subsystem has been notified via second_overflow. So
1048 * instead we push xtime_nsec forward by the amount we underflowed,
1049 * and add that amount into the error.
1051 * We'll correct this error next time through this function, when
1052 * xtime_nsec is not as small.
1054 if (unlikely((s64
)timekeeper
.xtime_nsec
< 0)) {
1055 s64 neg
= -(s64
)timekeeper
.xtime_nsec
;
1056 timekeeper
.xtime_nsec
= 0;
1057 timekeeper
.ntp_error
+= neg
<< timekeeper
.ntp_error_shift
;
1062 * Store full nanoseconds into xtime after rounding it up and
1063 * add the remainder to the error difference.
1065 timekeeper
.xtime
.tv_nsec
= ((s64
)timekeeper
.xtime_nsec
>>
1066 timekeeper
.shift
) + 1;
1067 timekeeper
.xtime_nsec
-= (s64
)timekeeper
.xtime
.tv_nsec
<<
1069 timekeeper
.ntp_error
+= timekeeper
.xtime_nsec
<<
1070 timekeeper
.ntp_error_shift
;
1073 * Finally, make sure that after the rounding
1074 * xtime.tv_nsec isn't larger than NSEC_PER_SEC
1076 if (unlikely(timekeeper
.xtime
.tv_nsec
>= NSEC_PER_SEC
)) {
1078 timekeeper
.xtime
.tv_nsec
-= NSEC_PER_SEC
;
1079 timekeeper
.xtime
.tv_sec
++;
1080 leap
= second_overflow(timekeeper
.xtime
.tv_sec
);
1081 timekeeper
.xtime
.tv_sec
+= leap
;
1084 timekeeping_update(false);
1087 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
1092 * getboottime - Return the real time of system boot.
1093 * @ts: pointer to the timespec to be set
1095 * Returns the wall-time of boot in a timespec.
1097 * This is based on the wall_to_monotonic offset and the total suspend
1098 * time. Calls to settimeofday will affect the value returned (which
1099 * basically means that however wrong your real time clock is at boot time,
1100 * you get the right time here).
1102 void getboottime(struct timespec
*ts
)
1104 struct timespec boottime
= {
1105 .tv_sec
= timekeeper
.wall_to_monotonic
.tv_sec
+
1106 timekeeper
.total_sleep_time
.tv_sec
,
1107 .tv_nsec
= timekeeper
.wall_to_monotonic
.tv_nsec
+
1108 timekeeper
.total_sleep_time
.tv_nsec
1111 set_normalized_timespec(ts
, -boottime
.tv_sec
, -boottime
.tv_nsec
);
1113 EXPORT_SYMBOL_GPL(getboottime
);
1117 * get_monotonic_boottime - Returns monotonic time since boot
1118 * @ts: pointer to the timespec to be set
1120 * Returns the monotonic time since boot in a timespec.
1122 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1123 * includes the time spent in suspend.
1125 void get_monotonic_boottime(struct timespec
*ts
)
1127 struct timespec tomono
, sleep
;
1131 WARN_ON(timekeeping_suspended
);
1134 seq
= read_seqbegin(&timekeeper
.lock
);
1135 *ts
= timekeeper
.xtime
;
1136 tomono
= timekeeper
.wall_to_monotonic
;
1137 sleep
= timekeeper
.total_sleep_time
;
1138 nsecs
= timekeeping_get_ns();
1140 } while (read_seqretry(&timekeeper
.lock
, seq
));
1142 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
+ sleep
.tv_sec
,
1143 ts
->tv_nsec
+ tomono
.tv_nsec
+ sleep
.tv_nsec
+ nsecs
);
1145 EXPORT_SYMBOL_GPL(get_monotonic_boottime
);
1148 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1150 * Returns the monotonic time since boot in a ktime
1152 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1153 * includes the time spent in suspend.
1155 ktime_t
ktime_get_boottime(void)
1159 get_monotonic_boottime(&ts
);
1160 return timespec_to_ktime(ts
);
1162 EXPORT_SYMBOL_GPL(ktime_get_boottime
);
1165 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1166 * @ts: pointer to the timespec to be converted
1168 void monotonic_to_bootbased(struct timespec
*ts
)
1170 *ts
= timespec_add(*ts
, timekeeper
.total_sleep_time
);
1172 EXPORT_SYMBOL_GPL(monotonic_to_bootbased
);
1174 unsigned long get_seconds(void)
1176 return timekeeper
.xtime
.tv_sec
;
1178 EXPORT_SYMBOL(get_seconds
);
1180 struct timespec
__current_kernel_time(void)
1182 return timekeeper
.xtime
;
1185 struct timespec
current_kernel_time(void)
1187 struct timespec now
;
1191 seq
= read_seqbegin(&timekeeper
.lock
);
1193 now
= timekeeper
.xtime
;
1194 } while (read_seqretry(&timekeeper
.lock
, seq
));
1198 EXPORT_SYMBOL(current_kernel_time
);
1200 struct timespec
get_monotonic_coarse(void)
1202 struct timespec now
, mono
;
1206 seq
= read_seqbegin(&timekeeper
.lock
);
1208 now
= timekeeper
.xtime
;
1209 mono
= timekeeper
.wall_to_monotonic
;
1210 } while (read_seqretry(&timekeeper
.lock
, seq
));
1212 set_normalized_timespec(&now
, now
.tv_sec
+ mono
.tv_sec
,
1213 now
.tv_nsec
+ mono
.tv_nsec
);
1218 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1219 * without sampling the sequence number in xtime_lock.
1220 * jiffies is defined in the linker script...
1222 void do_timer(unsigned long ticks
)
1224 jiffies_64
+= ticks
;
1226 calc_global_load(ticks
);
1230 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1231 * and sleep offsets.
1232 * @xtim: pointer to timespec to be set with xtime
1233 * @wtom: pointer to timespec to be set with wall_to_monotonic
1234 * @sleep: pointer to timespec to be set with time in suspend
1236 void get_xtime_and_monotonic_and_sleep_offset(struct timespec
*xtim
,
1237 struct timespec
*wtom
, struct timespec
*sleep
)
1242 seq
= read_seqbegin(&timekeeper
.lock
);
1243 *xtim
= timekeeper
.xtime
;
1244 *wtom
= timekeeper
.wall_to_monotonic
;
1245 *sleep
= timekeeper
.total_sleep_time
;
1246 } while (read_seqretry(&timekeeper
.lock
, seq
));
1250 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1252 ktime_t
ktime_get_monotonic_offset(void)
1255 struct timespec wtom
;
1258 seq
= read_seqbegin(&timekeeper
.lock
);
1259 wtom
= timekeeper
.wall_to_monotonic
;
1260 } while (read_seqretry(&timekeeper
.lock
, seq
));
1262 return timespec_to_ktime(wtom
);
1264 EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset
);
1268 * xtime_update() - advances the timekeeping infrastructure
1269 * @ticks: number of ticks, that have elapsed since the last call.
1271 * Must be called with interrupts disabled.
1273 void xtime_update(unsigned long ticks
)
1275 write_seqlock(&xtime_lock
);
1277 write_sequnlock(&xtime_lock
);