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. */
32 /* Number of clock cycles in one NTP interval. */
33 cycle_t cycle_interval
;
34 /* Number of clock shifted nano seconds in one NTP interval. */
36 /* shifted nano seconds left over when rounding cycle_interval */
38 /* Raw nano seconds accumulated per NTP interval. */
41 /* Current CLOCK_REALTIME time in seconds */
43 /* Clock shifted nano seconds */
46 /* Difference between accumulated time and NTP time in ntp
47 * shifted nano seconds. */
49 /* Shift conversion between clock shifted nano seconds and
50 * ntp shifted nano seconds. */
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 /* Offset clock monotonic -> clock realtime */
70 /* time spent in suspend */
71 struct timespec total_sleep_time
;
72 /* Offset clock monotonic -> clock boottime */
74 /* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
75 struct timespec raw_time
;
76 /* Seqlock for all timekeeper values */
80 static struct timekeeper timekeeper
;
83 * This read-write spinlock protects us from races in SMP while
86 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(xtime_lock
);
88 /* flag for if timekeeping is suspended */
89 int __read_mostly timekeeping_suspended
;
91 static inline void tk_normalize_xtime(struct timekeeper
*tk
)
93 while (tk
->xtime_nsec
>= ((u64
)NSEC_PER_SEC
<< tk
->shift
)) {
94 tk
->xtime_nsec
-= (u64
)NSEC_PER_SEC
<< tk
->shift
;
99 static struct timespec
tk_xtime(struct timekeeper
*tk
)
103 ts
.tv_sec
= tk
->xtime_sec
;
104 ts
.tv_nsec
= (long)(tk
->xtime_nsec
>> tk
->shift
);
108 static void tk_set_xtime(struct timekeeper
*tk
, const struct timespec
*ts
)
110 tk
->xtime_sec
= ts
->tv_sec
;
111 tk
->xtime_nsec
= (u64
)ts
->tv_nsec
<< tk
->shift
;
114 static void tk_xtime_add(struct timekeeper
*tk
, const struct timespec
*ts
)
116 tk
->xtime_sec
+= ts
->tv_sec
;
117 tk
->xtime_nsec
+= (u64
)ts
->tv_nsec
<< tk
->shift
;
120 static void tk_set_wall_to_mono(struct timekeeper
*tk
, struct timespec wtm
)
125 * Verify consistency of: offset_real = -wall_to_monotonic
126 * before modifying anything
128 set_normalized_timespec(&tmp
, -tk
->wall_to_monotonic
.tv_sec
,
129 -tk
->wall_to_monotonic
.tv_nsec
);
130 WARN_ON_ONCE(tk
->offs_real
.tv64
!= timespec_to_ktime(tmp
).tv64
);
131 tk
->wall_to_monotonic
= wtm
;
132 set_normalized_timespec(&tmp
, -wtm
.tv_sec
, -wtm
.tv_nsec
);
133 tk
->offs_real
= timespec_to_ktime(tmp
);
136 static void tk_set_sleep_time(struct timekeeper
*tk
, struct timespec t
)
138 /* Verify consistency before modifying */
139 WARN_ON_ONCE(tk
->offs_boot
.tv64
!= timespec_to_ktime(tk
->total_sleep_time
).tv64
);
141 tk
->total_sleep_time
= t
;
142 tk
->offs_boot
= timespec_to_ktime(t
);
146 * timekeeper_setup_internals - Set up internals to use clocksource clock.
148 * @clock: Pointer to clocksource.
150 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
151 * pair and interval request.
153 * Unless you're the timekeeping code, you should not be using this!
155 static void tk_setup_internals(struct timekeeper
*tk
, struct clocksource
*clock
)
158 u64 tmp
, ntpinterval
;
159 struct clocksource
*old_clock
;
161 old_clock
= tk
->clock
;
163 clock
->cycle_last
= clock
->read(clock
);
165 /* Do the ns -> cycle conversion first, using original mult */
166 tmp
= NTP_INTERVAL_LENGTH
;
167 tmp
<<= clock
->shift
;
169 tmp
+= clock
->mult
/2;
170 do_div(tmp
, clock
->mult
);
174 interval
= (cycle_t
) tmp
;
175 tk
->cycle_interval
= interval
;
177 /* Go back from cycles -> shifted ns */
178 tk
->xtime_interval
= (u64
) interval
* clock
->mult
;
179 tk
->xtime_remainder
= ntpinterval
- tk
->xtime_interval
;
181 ((u64
) interval
* clock
->mult
) >> clock
->shift
;
183 /* if changing clocks, convert xtime_nsec shift units */
185 int shift_change
= clock
->shift
- old_clock
->shift
;
186 if (shift_change
< 0)
187 tk
->xtime_nsec
>>= -shift_change
;
189 tk
->xtime_nsec
<<= shift_change
;
191 tk
->shift
= clock
->shift
;
194 tk
->ntp_error_shift
= NTP_SCALE_SHIFT
- clock
->shift
;
197 * The timekeeper keeps its own mult values for the currently
198 * active clocksource. These value will be adjusted via NTP
199 * to counteract clock drifting.
201 tk
->mult
= clock
->mult
;
204 /* Timekeeper helper functions. */
205 static inline s64
timekeeping_get_ns(struct timekeeper
*tk
)
207 cycle_t cycle_now
, cycle_delta
;
208 struct clocksource
*clock
;
211 /* read clocksource: */
213 cycle_now
= clock
->read(clock
);
215 /* calculate the delta since the last update_wall_time: */
216 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
218 nsec
= cycle_delta
* tk
->mult
+ tk
->xtime_nsec
;
221 /* If arch requires, add in gettimeoffset() */
222 return nsec
+ arch_gettimeoffset();
225 static inline s64
timekeeping_get_ns_raw(struct timekeeper
*tk
)
227 cycle_t cycle_now
, cycle_delta
;
228 struct clocksource
*clock
;
231 /* read clocksource: */
233 cycle_now
= clock
->read(clock
);
235 /* calculate the delta since the last update_wall_time: */
236 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
238 /* convert delta to nanoseconds. */
239 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
241 /* If arch requires, add in gettimeoffset() */
242 return nsec
+ arch_gettimeoffset();
245 /* must hold write on timekeeper.lock */
246 static void timekeeping_update(struct timekeeper
*tk
, bool clearntp
)
255 update_vsyscall(&xt
, &tk
->wall_to_monotonic
, tk
->clock
, tk
->mult
);
259 * timekeeping_forward_now - update clock to the current time
261 * Forward the current clock to update its state since the last call to
262 * update_wall_time(). This is useful before significant clock changes,
263 * as it avoids having to deal with this time offset explicitly.
265 static void timekeeping_forward_now(struct timekeeper
*tk
)
267 cycle_t cycle_now
, cycle_delta
;
268 struct clocksource
*clock
;
272 cycle_now
= clock
->read(clock
);
273 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
274 clock
->cycle_last
= cycle_now
;
276 tk
->xtime_nsec
+= cycle_delta
* tk
->mult
;
278 /* If arch requires, add in gettimeoffset() */
279 tk
->xtime_nsec
+= arch_gettimeoffset() << tk
->shift
;
281 tk_normalize_xtime(tk
);
283 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
284 timespec_add_ns(&tk
->raw_time
, nsec
);
288 * getnstimeofday - Returns the time of day in a timespec
289 * @ts: pointer to the timespec to be set
291 * Returns the time of day in a timespec.
293 void getnstimeofday(struct timespec
*ts
)
295 struct timekeeper
*tk
= &timekeeper
;
299 WARN_ON(timekeeping_suspended
);
302 seq
= read_seqbegin(&tk
->lock
);
304 ts
->tv_sec
= tk
->xtime_sec
;
305 ts
->tv_nsec
= timekeeping_get_ns(tk
);
307 } while (read_seqretry(&tk
->lock
, seq
));
309 timespec_add_ns(ts
, nsecs
);
311 EXPORT_SYMBOL(getnstimeofday
);
313 ktime_t
ktime_get(void)
315 struct timekeeper
*tk
= &timekeeper
;
319 WARN_ON(timekeeping_suspended
);
322 seq
= read_seqbegin(&tk
->lock
);
323 secs
= tk
->xtime_sec
+ tk
->wall_to_monotonic
.tv_sec
;
324 nsecs
= timekeeping_get_ns(tk
) + tk
->wall_to_monotonic
.tv_nsec
;
326 } while (read_seqretry(&tk
->lock
, seq
));
328 * Use ktime_set/ktime_add_ns to create a proper ktime on
329 * 32-bit architectures without CONFIG_KTIME_SCALAR.
331 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
333 EXPORT_SYMBOL_GPL(ktime_get
);
336 * ktime_get_ts - get the monotonic clock in timespec format
337 * @ts: pointer to timespec variable
339 * The function calculates the monotonic clock from the realtime
340 * clock and the wall_to_monotonic offset and stores the result
341 * in normalized timespec format in the variable pointed to by @ts.
343 void ktime_get_ts(struct timespec
*ts
)
345 struct timekeeper
*tk
= &timekeeper
;
346 struct timespec tomono
;
349 WARN_ON(timekeeping_suspended
);
352 seq
= read_seqbegin(&tk
->lock
);
353 ts
->tv_sec
= tk
->xtime_sec
;
354 ts
->tv_nsec
= timekeeping_get_ns(tk
);
355 tomono
= tk
->wall_to_monotonic
;
357 } while (read_seqretry(&tk
->lock
, seq
));
359 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
360 ts
->tv_nsec
+ tomono
.tv_nsec
);
362 EXPORT_SYMBOL_GPL(ktime_get_ts
);
364 #ifdef CONFIG_NTP_PPS
367 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
368 * @ts_raw: pointer to the timespec to be set to raw monotonic time
369 * @ts_real: pointer to the timespec to be set to the time of day
371 * This function reads both the time of day and raw monotonic time at the
372 * same time atomically and stores the resulting timestamps in timespec
375 void getnstime_raw_and_real(struct timespec
*ts_raw
, struct timespec
*ts_real
)
377 struct timekeeper
*tk
= &timekeeper
;
379 s64 nsecs_raw
, nsecs_real
;
381 WARN_ON_ONCE(timekeeping_suspended
);
384 seq
= read_seqbegin(&tk
->lock
);
386 *ts_raw
= tk
->raw_time
;
387 ts_real
->tv_sec
= tk
->xtime_sec
;
388 ts_real
->tv_nsec
= 0;
390 nsecs_raw
= timekeeping_get_ns_raw(tk
);
391 nsecs_real
= timekeeping_get_ns(tk
);
393 } while (read_seqretry(&tk
->lock
, seq
));
395 timespec_add_ns(ts_raw
, nsecs_raw
);
396 timespec_add_ns(ts_real
, nsecs_real
);
398 EXPORT_SYMBOL(getnstime_raw_and_real
);
400 #endif /* CONFIG_NTP_PPS */
403 * do_gettimeofday - Returns the time of day in a timeval
404 * @tv: pointer to the timeval to be set
406 * NOTE: Users should be converted to using getnstimeofday()
408 void do_gettimeofday(struct timeval
*tv
)
412 getnstimeofday(&now
);
413 tv
->tv_sec
= now
.tv_sec
;
414 tv
->tv_usec
= now
.tv_nsec
/1000;
416 EXPORT_SYMBOL(do_gettimeofday
);
419 * do_settimeofday - Sets the time of day
420 * @tv: pointer to the timespec variable containing the new time
422 * Sets the time of day to the new time and update NTP and notify hrtimers
424 int do_settimeofday(const struct timespec
*tv
)
426 struct timekeeper
*tk
= &timekeeper
;
427 struct timespec ts_delta
, xt
;
430 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
433 write_seqlock_irqsave(&tk
->lock
, flags
);
435 timekeeping_forward_now(tk
);
438 ts_delta
.tv_sec
= tv
->tv_sec
- xt
.tv_sec
;
439 ts_delta
.tv_nsec
= tv
->tv_nsec
- xt
.tv_nsec
;
441 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, ts_delta
));
443 tk_set_xtime(tk
, tv
);
445 timekeeping_update(tk
, true);
447 write_sequnlock_irqrestore(&tk
->lock
, flags
);
449 /* signal hrtimers about time change */
454 EXPORT_SYMBOL(do_settimeofday
);
457 * timekeeping_inject_offset - Adds or subtracts from the current time.
458 * @tv: pointer to the timespec variable containing the offset
460 * Adds or subtracts an offset value from the current time.
462 int timekeeping_inject_offset(struct timespec
*ts
)
464 struct timekeeper
*tk
= &timekeeper
;
467 if ((unsigned long)ts
->tv_nsec
>= NSEC_PER_SEC
)
470 write_seqlock_irqsave(&tk
->lock
, flags
);
472 timekeeping_forward_now(tk
);
475 tk_xtime_add(tk
, ts
);
476 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, *ts
));
478 timekeeping_update(tk
, true);
480 write_sequnlock_irqrestore(&tk
->lock
, flags
);
482 /* signal hrtimers about time change */
487 EXPORT_SYMBOL(timekeeping_inject_offset
);
490 * change_clocksource - Swaps clocksources if a new one is available
492 * Accumulates current time interval and initializes new clocksource
494 static int change_clocksource(void *data
)
496 struct timekeeper
*tk
= &timekeeper
;
497 struct clocksource
*new, *old
;
500 new = (struct clocksource
*) data
;
502 write_seqlock_irqsave(&tk
->lock
, flags
);
504 timekeeping_forward_now(tk
);
505 if (!new->enable
|| new->enable(new) == 0) {
507 tk_setup_internals(tk
, new);
511 timekeeping_update(tk
, true);
513 write_sequnlock_irqrestore(&tk
->lock
, flags
);
519 * timekeeping_notify - Install a new clock source
520 * @clock: pointer to the clock source
522 * This function is called from clocksource.c after a new, better clock
523 * source has been registered. The caller holds the clocksource_mutex.
525 void timekeeping_notify(struct clocksource
*clock
)
527 struct timekeeper
*tk
= &timekeeper
;
529 if (tk
->clock
== clock
)
531 stop_machine(change_clocksource
, clock
, NULL
);
536 * ktime_get_real - get the real (wall-) time in ktime_t format
538 * returns the time in ktime_t format
540 ktime_t
ktime_get_real(void)
544 getnstimeofday(&now
);
546 return timespec_to_ktime(now
);
548 EXPORT_SYMBOL_GPL(ktime_get_real
);
551 * getrawmonotonic - Returns the raw monotonic time in a timespec
552 * @ts: pointer to the timespec to be set
554 * Returns the raw monotonic time (completely un-modified by ntp)
556 void getrawmonotonic(struct timespec
*ts
)
558 struct timekeeper
*tk
= &timekeeper
;
563 seq
= read_seqbegin(&tk
->lock
);
564 nsecs
= timekeeping_get_ns_raw(tk
);
567 } while (read_seqretry(&tk
->lock
, seq
));
569 timespec_add_ns(ts
, nsecs
);
571 EXPORT_SYMBOL(getrawmonotonic
);
574 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
576 int timekeeping_valid_for_hres(void)
578 struct timekeeper
*tk
= &timekeeper
;
583 seq
= read_seqbegin(&tk
->lock
);
585 ret
= tk
->clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
587 } while (read_seqretry(&tk
->lock
, seq
));
593 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
595 u64
timekeeping_max_deferment(void)
597 struct timekeeper
*tk
= &timekeeper
;
602 seq
= read_seqbegin(&tk
->lock
);
604 ret
= tk
->clock
->max_idle_ns
;
606 } while (read_seqretry(&tk
->lock
, seq
));
612 * read_persistent_clock - Return time from the persistent clock.
614 * Weak dummy function for arches that do not yet support it.
615 * Reads the time from the battery backed persistent clock.
616 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
618 * XXX - Do be sure to remove it once all arches implement it.
620 void __attribute__((weak
)) read_persistent_clock(struct timespec
*ts
)
627 * read_boot_clock - Return time of the system start.
629 * Weak dummy function for arches that do not yet support it.
630 * Function to read the exact time the system has been started.
631 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
633 * XXX - Do be sure to remove it once all arches implement it.
635 void __attribute__((weak
)) read_boot_clock(struct timespec
*ts
)
642 * timekeeping_init - Initializes the clocksource and common timekeeping values
644 void __init
timekeeping_init(void)
646 struct timekeeper
*tk
= &timekeeper
;
647 struct clocksource
*clock
;
649 struct timespec now
, boot
, tmp
;
651 read_persistent_clock(&now
);
652 read_boot_clock(&boot
);
654 seqlock_init(&tk
->lock
);
658 write_seqlock_irqsave(&tk
->lock
, flags
);
659 clock
= clocksource_default_clock();
661 clock
->enable(clock
);
662 tk_setup_internals(tk
, clock
);
664 tk_set_xtime(tk
, &now
);
665 tk
->raw_time
.tv_sec
= 0;
666 tk
->raw_time
.tv_nsec
= 0;
667 if (boot
.tv_sec
== 0 && boot
.tv_nsec
== 0)
670 set_normalized_timespec(&tmp
, -boot
.tv_sec
, -boot
.tv_nsec
);
671 tk_set_wall_to_mono(tk
, tmp
);
675 tk_set_sleep_time(tk
, tmp
);
677 write_sequnlock_irqrestore(&tk
->lock
, flags
);
680 /* time in seconds when suspend began */
681 static struct timespec timekeeping_suspend_time
;
684 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
685 * @delta: pointer to a timespec delta value
687 * Takes a timespec offset measuring a suspend interval and properly
688 * adds the sleep offset to the timekeeping variables.
690 static void __timekeeping_inject_sleeptime(struct timekeeper
*tk
,
691 struct timespec
*delta
)
693 if (!timespec_valid(delta
)) {
694 printk(KERN_WARNING
"__timekeeping_inject_sleeptime: Invalid "
695 "sleep delta value!\n");
698 tk_xtime_add(tk
, delta
);
699 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, *delta
));
700 tk_set_sleep_time(tk
, timespec_add(tk
->total_sleep_time
, *delta
));
704 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
705 * @delta: pointer to a timespec delta value
707 * This hook is for architectures that cannot support read_persistent_clock
708 * because their RTC/persistent clock is only accessible when irqs are enabled.
710 * This function should only be called by rtc_resume(), and allows
711 * a suspend offset to be injected into the timekeeping values.
713 void timekeeping_inject_sleeptime(struct timespec
*delta
)
715 struct timekeeper
*tk
= &timekeeper
;
719 /* Make sure we don't set the clock twice */
720 read_persistent_clock(&ts
);
721 if (!(ts
.tv_sec
== 0 && ts
.tv_nsec
== 0))
724 write_seqlock_irqsave(&tk
->lock
, flags
);
726 timekeeping_forward_now(tk
);
728 __timekeeping_inject_sleeptime(tk
, delta
);
730 timekeeping_update(tk
, true);
732 write_sequnlock_irqrestore(&tk
->lock
, flags
);
734 /* signal hrtimers about time change */
739 * timekeeping_resume - Resumes the generic timekeeping subsystem.
741 * This is for the generic clocksource timekeeping.
742 * xtime/wall_to_monotonic/jiffies/etc are
743 * still managed by arch specific suspend/resume code.
745 static void timekeeping_resume(void)
747 struct timekeeper
*tk
= &timekeeper
;
751 read_persistent_clock(&ts
);
753 clocksource_resume();
755 write_seqlock_irqsave(&tk
->lock
, flags
);
757 if (timespec_compare(&ts
, &timekeeping_suspend_time
) > 0) {
758 ts
= timespec_sub(ts
, timekeeping_suspend_time
);
759 __timekeeping_inject_sleeptime(tk
, &ts
);
761 /* re-base the last cycle value */
762 tk
->clock
->cycle_last
= tk
->clock
->read(tk
->clock
);
764 timekeeping_suspended
= 0;
765 timekeeping_update(tk
, false);
766 write_sequnlock_irqrestore(&tk
->lock
, flags
);
768 touch_softlockup_watchdog();
770 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
772 /* Resume hrtimers */
776 static int timekeeping_suspend(void)
778 struct timekeeper
*tk
= &timekeeper
;
780 struct timespec delta
, delta_delta
;
781 static struct timespec old_delta
;
783 read_persistent_clock(&timekeeping_suspend_time
);
785 write_seqlock_irqsave(&tk
->lock
, flags
);
786 timekeeping_forward_now(tk
);
787 timekeeping_suspended
= 1;
790 * To avoid drift caused by repeated suspend/resumes,
791 * which each can add ~1 second drift error,
792 * try to compensate so the difference in system time
793 * and persistent_clock time stays close to constant.
795 delta
= timespec_sub(tk_xtime(tk
), timekeeping_suspend_time
);
796 delta_delta
= timespec_sub(delta
, old_delta
);
797 if (abs(delta_delta
.tv_sec
) >= 2) {
799 * if delta_delta is too large, assume time correction
800 * has occured and set old_delta to the current delta.
804 /* Otherwise try to adjust old_system to compensate */
805 timekeeping_suspend_time
=
806 timespec_add(timekeeping_suspend_time
, delta_delta
);
808 write_sequnlock_irqrestore(&tk
->lock
, flags
);
810 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
811 clocksource_suspend();
816 /* sysfs resume/suspend bits for timekeeping */
817 static struct syscore_ops timekeeping_syscore_ops
= {
818 .resume
= timekeeping_resume
,
819 .suspend
= timekeeping_suspend
,
822 static int __init
timekeeping_init_ops(void)
824 register_syscore_ops(&timekeeping_syscore_ops
);
828 device_initcall(timekeeping_init_ops
);
831 * If the error is already larger, we look ahead even further
832 * to compensate for late or lost adjustments.
834 static __always_inline
int timekeeping_bigadjust(struct timekeeper
*tk
,
835 s64 error
, s64
*interval
,
843 * Use the current error value to determine how much to look ahead.
844 * The larger the error the slower we adjust for it to avoid problems
845 * with losing too many ticks, otherwise we would overadjust and
846 * produce an even larger error. The smaller the adjustment the
847 * faster we try to adjust for it, as lost ticks can do less harm
848 * here. This is tuned so that an error of about 1 msec is adjusted
849 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
851 error2
= tk
->ntp_error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
852 error2
= abs(error2
);
853 for (look_ahead
= 0; error2
> 0; look_ahead
++)
857 * Now calculate the error in (1 << look_ahead) ticks, but first
858 * remove the single look ahead already included in the error.
860 tick_error
= ntp_tick_length() >> (tk
->ntp_error_shift
+ 1);
861 tick_error
-= tk
->xtime_interval
>> 1;
862 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
864 /* Finally calculate the adjustment shift value. */
869 *interval
= -*interval
;
873 for (adj
= 0; error
> i
; adj
++)
882 * Adjust the multiplier to reduce the error value,
883 * this is optimized for the most common adjustments of -1,0,1,
884 * for other values we can do a bit more work.
886 static void timekeeping_adjust(struct timekeeper
*tk
, s64 offset
)
888 s64 error
, interval
= tk
->cycle_interval
;
892 * The point of this is to check if the error is greater than half
895 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
897 * Note we subtract one in the shift, so that error is really error*2.
898 * This "saves" dividing(shifting) interval twice, but keeps the
899 * (error > interval) comparison as still measuring if error is
900 * larger than half an interval.
902 * Note: It does not "save" on aggravation when reading the code.
904 error
= tk
->ntp_error
>> (tk
->ntp_error_shift
- 1);
905 if (error
> interval
) {
907 * We now divide error by 4(via shift), which checks if
908 * the error is greater than twice the interval.
909 * If it is greater, we need a bigadjust, if its smaller,
910 * we can adjust by 1.
914 * XXX - In update_wall_time, we round up to the next
915 * nanosecond, and store the amount rounded up into
916 * the error. This causes the likely below to be unlikely.
918 * The proper fix is to avoid rounding up by using
919 * the high precision tk->xtime_nsec instead of
920 * xtime.tv_nsec everywhere. Fixing this will take some
923 if (likely(error
<= interval
))
926 adj
= timekeeping_bigadjust(tk
, error
, &interval
, &offset
);
928 if (error
< -interval
) {
929 /* See comment above, this is just switched for the negative */
931 if (likely(error
>= -interval
)) {
933 interval
= -interval
;
936 adj
= timekeeping_bigadjust(tk
, error
, &interval
, &offset
);
943 if (unlikely(tk
->clock
->maxadj
&&
944 (tk
->mult
+ adj
> tk
->clock
->mult
+ tk
->clock
->maxadj
))) {
945 printk_once(KERN_WARNING
946 "Adjusting %s more than 11%% (%ld vs %ld)\n",
947 tk
->clock
->name
, (long)tk
->mult
+ adj
,
948 (long)tk
->clock
->mult
+ tk
->clock
->maxadj
);
951 * So the following can be confusing.
953 * To keep things simple, lets assume adj == 1 for now.
955 * When adj != 1, remember that the interval and offset values
956 * have been appropriately scaled so the math is the same.
958 * The basic idea here is that we're increasing the multiplier
959 * by one, this causes the xtime_interval to be incremented by
960 * one cycle_interval. This is because:
961 * xtime_interval = cycle_interval * mult
962 * So if mult is being incremented by one:
963 * xtime_interval = cycle_interval * (mult + 1)
965 * xtime_interval = (cycle_interval * mult) + cycle_interval
966 * Which can be shortened to:
967 * xtime_interval += cycle_interval
969 * So offset stores the non-accumulated cycles. Thus the current
970 * time (in shifted nanoseconds) is:
971 * now = (offset * adj) + xtime_nsec
972 * Now, even though we're adjusting the clock frequency, we have
973 * to keep time consistent. In other words, we can't jump back
974 * in time, and we also want to avoid jumping forward in time.
976 * So given the same offset value, we need the time to be the same
977 * both before and after the freq adjustment.
978 * now = (offset * adj_1) + xtime_nsec_1
979 * now = (offset * adj_2) + xtime_nsec_2
981 * (offset * adj_1) + xtime_nsec_1 =
982 * (offset * adj_2) + xtime_nsec_2
986 * (offset * adj_1) + xtime_nsec_1 =
987 * (offset * (adj_1+1)) + xtime_nsec_2
988 * (offset * adj_1) + xtime_nsec_1 =
989 * (offset * adj_1) + offset + xtime_nsec_2
990 * Canceling the sides:
991 * xtime_nsec_1 = offset + xtime_nsec_2
993 * xtime_nsec_2 = xtime_nsec_1 - offset
994 * Which simplfies to:
995 * xtime_nsec -= offset
997 * XXX - TODO: Doc ntp_error calculation.
1000 tk
->xtime_interval
+= interval
;
1001 tk
->xtime_nsec
-= offset
;
1002 tk
->ntp_error
-= (interval
- offset
) << tk
->ntp_error_shift
;
1006 * It may be possible that when we entered this function, xtime_nsec
1007 * was very small. Further, if we're slightly speeding the clocksource
1008 * in the code above, its possible the required corrective factor to
1009 * xtime_nsec could cause it to underflow.
1011 * Now, since we already accumulated the second, cannot simply roll
1012 * the accumulated second back, since the NTP subsystem has been
1013 * notified via second_overflow. So instead we push xtime_nsec forward
1014 * by the amount we underflowed, and add that amount into the error.
1016 * We'll correct this error next time through this function, when
1017 * xtime_nsec is not as small.
1019 if (unlikely((s64
)tk
->xtime_nsec
< 0)) {
1020 s64 neg
= -(s64
)tk
->xtime_nsec
;
1022 tk
->ntp_error
+= neg
<< tk
->ntp_error_shift
;
1028 * accumulate_nsecs_to_secs - Accumulates nsecs into secs
1030 * Helper function that accumulates a the nsecs greater then a second
1031 * from the xtime_nsec field to the xtime_secs field.
1032 * It also calls into the NTP code to handle leapsecond processing.
1035 static inline void accumulate_nsecs_to_secs(struct timekeeper
*tk
)
1037 u64 nsecps
= (u64
)NSEC_PER_SEC
<< tk
->shift
;
1039 while (tk
->xtime_nsec
>= nsecps
) {
1042 tk
->xtime_nsec
-= nsecps
;
1045 /* Figure out if its a leap sec and apply if needed */
1046 leap
= second_overflow(tk
->xtime_sec
);
1047 if (unlikely(leap
)) {
1050 tk
->xtime_sec
+= leap
;
1054 tk_set_wall_to_mono(tk
,
1055 timespec_sub(tk
->wall_to_monotonic
, ts
));
1057 clock_was_set_delayed();
1063 * logarithmic_accumulation - shifted accumulation of cycles
1065 * This functions accumulates a shifted interval of cycles into
1066 * into a shifted interval nanoseconds. Allows for O(log) accumulation
1069 * Returns the unconsumed cycles.
1071 static cycle_t
logarithmic_accumulation(struct timekeeper
*tk
, cycle_t offset
,
1076 /* If the offset is smaller then a shifted interval, do nothing */
1077 if (offset
< tk
->cycle_interval
<<shift
)
1080 /* Accumulate one shifted interval */
1081 offset
-= tk
->cycle_interval
<< shift
;
1082 tk
->clock
->cycle_last
+= tk
->cycle_interval
<< shift
;
1084 tk
->xtime_nsec
+= tk
->xtime_interval
<< shift
;
1085 accumulate_nsecs_to_secs(tk
);
1087 /* Accumulate raw time */
1088 raw_nsecs
= tk
->raw_interval
<< shift
;
1089 raw_nsecs
+= tk
->raw_time
.tv_nsec
;
1090 if (raw_nsecs
>= NSEC_PER_SEC
) {
1091 u64 raw_secs
= raw_nsecs
;
1092 raw_nsecs
= do_div(raw_secs
, NSEC_PER_SEC
);
1093 tk
->raw_time
.tv_sec
+= raw_secs
;
1095 tk
->raw_time
.tv_nsec
= raw_nsecs
;
1097 /* Accumulate error between NTP and clock interval */
1098 tk
->ntp_error
+= ntp_tick_length() << shift
;
1099 tk
->ntp_error
-= (tk
->xtime_interval
+ tk
->xtime_remainder
) <<
1100 (tk
->ntp_error_shift
+ shift
);
1106 * update_wall_time - Uses the current clocksource to increment the wall time
1109 static void update_wall_time(void)
1111 struct clocksource
*clock
;
1112 struct timekeeper
*tk
= &timekeeper
;
1114 int shift
= 0, maxshift
;
1115 unsigned long flags
;
1118 write_seqlock_irqsave(&tk
->lock
, flags
);
1120 /* Make sure we're fully resumed: */
1121 if (unlikely(timekeeping_suspended
))
1126 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1127 offset
= tk
->cycle_interval
;
1129 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
1133 * With NO_HZ we may have to accumulate many cycle_intervals
1134 * (think "ticks") worth of time at once. To do this efficiently,
1135 * we calculate the largest doubling multiple of cycle_intervals
1136 * that is smaller than the offset. We then accumulate that
1137 * chunk in one go, and then try to consume the next smaller
1140 shift
= ilog2(offset
) - ilog2(tk
->cycle_interval
);
1141 shift
= max(0, shift
);
1142 /* Bound shift to one less than what overflows tick_length */
1143 maxshift
= (64 - (ilog2(ntp_tick_length())+1)) - 1;
1144 shift
= min(shift
, maxshift
);
1145 while (offset
>= tk
->cycle_interval
) {
1146 offset
= logarithmic_accumulation(tk
, offset
, shift
);
1147 if (offset
< tk
->cycle_interval
<<shift
)
1151 /* correct the clock when NTP error is too big */
1152 timekeeping_adjust(tk
, offset
);
1156 * Store only full nanoseconds into xtime_nsec after rounding
1157 * it up and add the remainder to the error difference.
1158 * XXX - This is necessary to avoid small 1ns inconsistnecies caused
1159 * by truncating the remainder in vsyscalls. However, it causes
1160 * additional work to be done in timekeeping_adjust(). Once
1161 * the vsyscall implementations are converted to use xtime_nsec
1162 * (shifted nanoseconds), this can be killed.
1164 remainder
= tk
->xtime_nsec
& ((1 << tk
->shift
) - 1);
1165 tk
->xtime_nsec
-= remainder
;
1166 tk
->xtime_nsec
+= 1 << tk
->shift
;
1167 tk
->ntp_error
+= remainder
<< tk
->ntp_error_shift
;
1170 * Finally, make sure that after the rounding
1171 * xtime_nsec isn't larger than NSEC_PER_SEC
1173 accumulate_nsecs_to_secs(tk
);
1175 timekeeping_update(tk
, false);
1178 write_sequnlock_irqrestore(&tk
->lock
, flags
);
1183 * getboottime - Return the real time of system boot.
1184 * @ts: pointer to the timespec to be set
1186 * Returns the wall-time of boot in a timespec.
1188 * This is based on the wall_to_monotonic offset and the total suspend
1189 * time. Calls to settimeofday will affect the value returned (which
1190 * basically means that however wrong your real time clock is at boot time,
1191 * you get the right time here).
1193 void getboottime(struct timespec
*ts
)
1195 struct timekeeper
*tk
= &timekeeper
;
1196 struct timespec boottime
= {
1197 .tv_sec
= tk
->wall_to_monotonic
.tv_sec
+
1198 tk
->total_sleep_time
.tv_sec
,
1199 .tv_nsec
= tk
->wall_to_monotonic
.tv_nsec
+
1200 tk
->total_sleep_time
.tv_nsec
1203 set_normalized_timespec(ts
, -boottime
.tv_sec
, -boottime
.tv_nsec
);
1205 EXPORT_SYMBOL_GPL(getboottime
);
1208 * get_monotonic_boottime - Returns monotonic time since boot
1209 * @ts: pointer to the timespec to be set
1211 * Returns the monotonic time since boot in a timespec.
1213 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1214 * includes the time spent in suspend.
1216 void get_monotonic_boottime(struct timespec
*ts
)
1218 struct timekeeper
*tk
= &timekeeper
;
1219 struct timespec tomono
, sleep
;
1222 WARN_ON(timekeeping_suspended
);
1225 seq
= read_seqbegin(&tk
->lock
);
1226 ts
->tv_sec
= tk
->xtime_sec
;
1227 ts
->tv_nsec
= timekeeping_get_ns(tk
);
1228 tomono
= tk
->wall_to_monotonic
;
1229 sleep
= tk
->total_sleep_time
;
1231 } while (read_seqretry(&tk
->lock
, seq
));
1233 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
+ sleep
.tv_sec
,
1234 ts
->tv_nsec
+ tomono
.tv_nsec
+ sleep
.tv_nsec
);
1236 EXPORT_SYMBOL_GPL(get_monotonic_boottime
);
1239 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1241 * Returns the monotonic time since boot in a ktime
1243 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1244 * includes the time spent in suspend.
1246 ktime_t
ktime_get_boottime(void)
1250 get_monotonic_boottime(&ts
);
1251 return timespec_to_ktime(ts
);
1253 EXPORT_SYMBOL_GPL(ktime_get_boottime
);
1256 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1257 * @ts: pointer to the timespec to be converted
1259 void monotonic_to_bootbased(struct timespec
*ts
)
1261 struct timekeeper
*tk
= &timekeeper
;
1263 *ts
= timespec_add(*ts
, tk
->total_sleep_time
);
1265 EXPORT_SYMBOL_GPL(monotonic_to_bootbased
);
1267 unsigned long get_seconds(void)
1269 struct timekeeper
*tk
= &timekeeper
;
1271 return tk
->xtime_sec
;
1273 EXPORT_SYMBOL(get_seconds
);
1275 struct timespec
__current_kernel_time(void)
1277 struct timekeeper
*tk
= &timekeeper
;
1279 return tk_xtime(tk
);
1282 struct timespec
current_kernel_time(void)
1284 struct timekeeper
*tk
= &timekeeper
;
1285 struct timespec now
;
1289 seq
= read_seqbegin(&tk
->lock
);
1292 } while (read_seqretry(&tk
->lock
, seq
));
1296 EXPORT_SYMBOL(current_kernel_time
);
1298 struct timespec
get_monotonic_coarse(void)
1300 struct timekeeper
*tk
= &timekeeper
;
1301 struct timespec now
, mono
;
1305 seq
= read_seqbegin(&tk
->lock
);
1308 mono
= tk
->wall_to_monotonic
;
1309 } while (read_seqretry(&tk
->lock
, seq
));
1311 set_normalized_timespec(&now
, now
.tv_sec
+ mono
.tv_sec
,
1312 now
.tv_nsec
+ mono
.tv_nsec
);
1317 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1318 * without sampling the sequence number in xtime_lock.
1319 * jiffies is defined in the linker script...
1321 void do_timer(unsigned long ticks
)
1323 jiffies_64
+= ticks
;
1325 calc_global_load(ticks
);
1329 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1330 * and sleep offsets.
1331 * @xtim: pointer to timespec to be set with xtime
1332 * @wtom: pointer to timespec to be set with wall_to_monotonic
1333 * @sleep: pointer to timespec to be set with time in suspend
1335 void get_xtime_and_monotonic_and_sleep_offset(struct timespec
*xtim
,
1336 struct timespec
*wtom
, struct timespec
*sleep
)
1338 struct timekeeper
*tk
= &timekeeper
;
1342 seq
= read_seqbegin(&tk
->lock
);
1343 *xtim
= tk_xtime(tk
);
1344 *wtom
= tk
->wall_to_monotonic
;
1345 *sleep
= tk
->total_sleep_time
;
1346 } while (read_seqretry(&tk
->lock
, seq
));
1349 #ifdef CONFIG_HIGH_RES_TIMERS
1351 * ktime_get_update_offsets - hrtimer helper
1352 * @offs_real: pointer to storage for monotonic -> realtime offset
1353 * @offs_boot: pointer to storage for monotonic -> boottime offset
1355 * Returns current monotonic time and updates the offsets
1356 * Called from hrtimer_interupt() or retrigger_next_event()
1358 ktime_t
ktime_get_update_offsets(ktime_t
*offs_real
, ktime_t
*offs_boot
)
1360 struct timekeeper
*tk
= &timekeeper
;
1366 seq
= read_seqbegin(&tk
->lock
);
1368 secs
= tk
->xtime_sec
;
1369 nsecs
= timekeeping_get_ns(tk
);
1371 *offs_real
= tk
->offs_real
;
1372 *offs_boot
= tk
->offs_boot
;
1373 } while (read_seqretry(&tk
->lock
, seq
));
1375 now
= ktime_add_ns(ktime_set(secs
, 0), nsecs
);
1376 now
= ktime_sub(now
, *offs_real
);
1382 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1384 ktime_t
ktime_get_monotonic_offset(void)
1386 struct timekeeper
*tk
= &timekeeper
;
1388 struct timespec wtom
;
1391 seq
= read_seqbegin(&tk
->lock
);
1392 wtom
= tk
->wall_to_monotonic
;
1393 } while (read_seqretry(&tk
->lock
, seq
));
1395 return timespec_to_ktime(wtom
);
1397 EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset
);
1400 * xtime_update() - advances the timekeeping infrastructure
1401 * @ticks: number of ticks, that have elapsed since the last call.
1403 * Must be called with interrupts disabled.
1405 void xtime_update(unsigned long ticks
)
1407 write_seqlock(&xtime_lock
);
1409 write_sequnlock(&xtime_lock
);