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 /* The shift value of the current clocksource. */
31 /* Number of clock cycles in one NTP interval. */
32 cycle_t cycle_interval
;
33 /* Number of clock shifted nano seconds in one NTP interval. */
35 /* shifted nano seconds left over when rounding cycle_interval */
37 /* Raw nano seconds accumulated per NTP interval. */
40 /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */
42 /* Difference between accumulated time and NTP time in ntp
43 * shifted nano seconds. */
45 /* Shift conversion between clock shifted nano seconds and
46 * ntp shifted nano seconds. */
48 /* NTP adjusted clock multiplier */
52 static struct timekeeper timekeeper
;
55 * timekeeper_setup_internals - Set up internals to use clocksource clock.
57 * @clock: Pointer to clocksource.
59 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
60 * pair and interval request.
62 * Unless you're the timekeeping code, you should not be using this!
64 static void timekeeper_setup_internals(struct clocksource
*clock
)
69 timekeeper
.clock
= clock
;
70 clock
->cycle_last
= clock
->read(clock
);
72 /* Do the ns -> cycle conversion first, using original mult */
73 tmp
= NTP_INTERVAL_LENGTH
;
77 do_div(tmp
, clock
->mult
);
81 interval
= (cycle_t
) tmp
;
82 timekeeper
.cycle_interval
= interval
;
84 /* Go back from cycles -> shifted ns */
85 timekeeper
.xtime_interval
= (u64
) interval
* clock
->mult
;
86 timekeeper
.xtime_remainder
= ntpinterval
- timekeeper
.xtime_interval
;
87 timekeeper
.raw_interval
=
88 ((u64
) interval
* clock
->mult
) >> clock
->shift
;
90 timekeeper
.xtime_nsec
= 0;
91 timekeeper
.shift
= clock
->shift
;
93 timekeeper
.ntp_error
= 0;
94 timekeeper
.ntp_error_shift
= NTP_SCALE_SHIFT
- clock
->shift
;
97 * The timekeeper keeps its own mult values for the currently
98 * active clocksource. These value will be adjusted via NTP
99 * to counteract clock drifting.
101 timekeeper
.mult
= clock
->mult
;
104 /* Timekeeper helper functions. */
105 static inline s64
timekeeping_get_ns(void)
107 cycle_t cycle_now
, cycle_delta
;
108 struct clocksource
*clock
;
110 /* read clocksource: */
111 clock
= timekeeper
.clock
;
112 cycle_now
= clock
->read(clock
);
114 /* calculate the delta since the last update_wall_time: */
115 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
117 /* return delta convert to nanoseconds using ntp adjusted mult. */
118 return clocksource_cyc2ns(cycle_delta
, timekeeper
.mult
,
122 static inline s64
timekeeping_get_ns_raw(void)
124 cycle_t cycle_now
, cycle_delta
;
125 struct clocksource
*clock
;
127 /* read clocksource: */
128 clock
= timekeeper
.clock
;
129 cycle_now
= clock
->read(clock
);
131 /* calculate the delta since the last update_wall_time: */
132 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
134 /* return delta convert to nanoseconds using ntp adjusted mult. */
135 return clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
139 * This read-write spinlock protects us from races in SMP while
140 * playing with xtime.
142 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(xtime_lock
);
147 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
148 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
149 * at zero at system boot time, so wall_to_monotonic will be negative,
150 * however, we will ALWAYS keep the tv_nsec part positive so we can use
151 * the usual normalization.
153 * wall_to_monotonic is moved after resume from suspend for the monotonic
154 * time not to jump. We need to add total_sleep_time to wall_to_monotonic
155 * to get the real boot based time offset.
157 * - wall_to_monotonic is no longer the boot time, getboottime must be
160 static struct timespec xtime
__attribute__ ((aligned (16)));
161 static struct timespec wall_to_monotonic
__attribute__ ((aligned (16)));
162 static struct timespec total_sleep_time
;
165 * The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
167 static struct timespec raw_time
;
169 /* flag for if timekeeping is suspended */
170 int __read_mostly timekeeping_suspended
;
172 /* must hold xtime_lock */
173 void timekeeping_leap_insert(int leapsecond
)
175 xtime
.tv_sec
+= leapsecond
;
176 wall_to_monotonic
.tv_sec
-= leapsecond
;
177 update_vsyscall(&xtime
, &wall_to_monotonic
, timekeeper
.clock
,
182 * timekeeping_forward_now - update clock to the current time
184 * Forward the current clock to update its state since the last call to
185 * update_wall_time(). This is useful before significant clock changes,
186 * as it avoids having to deal with this time offset explicitly.
188 static void timekeeping_forward_now(void)
190 cycle_t cycle_now
, cycle_delta
;
191 struct clocksource
*clock
;
194 clock
= timekeeper
.clock
;
195 cycle_now
= clock
->read(clock
);
196 cycle_delta
= (cycle_now
- clock
->cycle_last
) & clock
->mask
;
197 clock
->cycle_last
= cycle_now
;
199 nsec
= clocksource_cyc2ns(cycle_delta
, timekeeper
.mult
,
202 /* If arch requires, add in gettimeoffset() */
203 nsec
+= arch_gettimeoffset();
205 timespec_add_ns(&xtime
, nsec
);
207 nsec
= clocksource_cyc2ns(cycle_delta
, clock
->mult
, clock
->shift
);
208 timespec_add_ns(&raw_time
, nsec
);
212 * getnstimeofday - Returns the time of day in a timespec
213 * @ts: pointer to the timespec to be set
215 * Returns the time of day in a timespec.
217 void getnstimeofday(struct timespec
*ts
)
222 WARN_ON(timekeeping_suspended
);
225 seq
= read_seqbegin(&xtime_lock
);
228 nsecs
= timekeeping_get_ns();
230 /* If arch requires, add in gettimeoffset() */
231 nsecs
+= arch_gettimeoffset();
233 } while (read_seqretry(&xtime_lock
, seq
));
235 timespec_add_ns(ts
, nsecs
);
238 EXPORT_SYMBOL(getnstimeofday
);
240 ktime_t
ktime_get(void)
245 WARN_ON(timekeeping_suspended
);
248 seq
= read_seqbegin(&xtime_lock
);
249 secs
= xtime
.tv_sec
+ wall_to_monotonic
.tv_sec
;
250 nsecs
= xtime
.tv_nsec
+ wall_to_monotonic
.tv_nsec
;
251 nsecs
+= timekeeping_get_ns();
252 /* If arch requires, add in gettimeoffset() */
253 nsecs
+= arch_gettimeoffset();
255 } while (read_seqretry(&xtime_lock
, seq
));
257 * Use ktime_set/ktime_add_ns to create a proper ktime on
258 * 32-bit architectures without CONFIG_KTIME_SCALAR.
260 return ktime_add_ns(ktime_set(secs
, 0), nsecs
);
262 EXPORT_SYMBOL_GPL(ktime_get
);
265 * ktime_get_ts - get the monotonic clock in timespec format
266 * @ts: pointer to timespec variable
268 * The function calculates the monotonic clock from the realtime
269 * clock and the wall_to_monotonic offset and stores the result
270 * in normalized timespec format in the variable pointed to by @ts.
272 void ktime_get_ts(struct timespec
*ts
)
274 struct timespec tomono
;
278 WARN_ON(timekeeping_suspended
);
281 seq
= read_seqbegin(&xtime_lock
);
283 tomono
= wall_to_monotonic
;
284 nsecs
= timekeeping_get_ns();
285 /* If arch requires, add in gettimeoffset() */
286 nsecs
+= arch_gettimeoffset();
288 } while (read_seqretry(&xtime_lock
, seq
));
290 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
291 ts
->tv_nsec
+ tomono
.tv_nsec
+ nsecs
);
293 EXPORT_SYMBOL_GPL(ktime_get_ts
);
295 #ifdef CONFIG_NTP_PPS
298 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
299 * @ts_raw: pointer to the timespec to be set to raw monotonic time
300 * @ts_real: pointer to the timespec to be set to the time of day
302 * This function reads both the time of day and raw monotonic time at the
303 * same time atomically and stores the resulting timestamps in timespec
306 void getnstime_raw_and_real(struct timespec
*ts_raw
, struct timespec
*ts_real
)
309 s64 nsecs_raw
, nsecs_real
;
311 WARN_ON_ONCE(timekeeping_suspended
);
316 seq
= read_seqbegin(&xtime_lock
);
321 nsecs_raw
= timekeeping_get_ns_raw();
322 nsecs_real
= timekeeping_get_ns();
324 /* If arch requires, add in gettimeoffset() */
325 arch_offset
= arch_gettimeoffset();
326 nsecs_raw
+= arch_offset
;
327 nsecs_real
+= arch_offset
;
329 } while (read_seqretry(&xtime_lock
, seq
));
331 timespec_add_ns(ts_raw
, nsecs_raw
);
332 timespec_add_ns(ts_real
, nsecs_real
);
334 EXPORT_SYMBOL(getnstime_raw_and_real
);
336 #endif /* CONFIG_NTP_PPS */
339 * do_gettimeofday - Returns the time of day in a timeval
340 * @tv: pointer to the timeval to be set
342 * NOTE: Users should be converted to using getnstimeofday()
344 void do_gettimeofday(struct timeval
*tv
)
348 getnstimeofday(&now
);
349 tv
->tv_sec
= now
.tv_sec
;
350 tv
->tv_usec
= now
.tv_nsec
/1000;
353 EXPORT_SYMBOL(do_gettimeofday
);
355 * do_settimeofday - Sets the time of day
356 * @tv: pointer to the timespec variable containing the new time
358 * Sets the time of day to the new time and update NTP and notify hrtimers
360 int do_settimeofday(const struct timespec
*tv
)
362 struct timespec ts_delta
;
365 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
368 write_seqlock_irqsave(&xtime_lock
, flags
);
370 timekeeping_forward_now();
372 ts_delta
.tv_sec
= tv
->tv_sec
- xtime
.tv_sec
;
373 ts_delta
.tv_nsec
= tv
->tv_nsec
- xtime
.tv_nsec
;
374 wall_to_monotonic
= timespec_sub(wall_to_monotonic
, ts_delta
);
378 timekeeper
.ntp_error
= 0;
381 update_vsyscall(&xtime
, &wall_to_monotonic
, timekeeper
.clock
,
384 write_sequnlock_irqrestore(&xtime_lock
, flags
);
386 /* signal hrtimers about time change */
392 EXPORT_SYMBOL(do_settimeofday
);
396 * timekeeping_inject_offset - Adds or subtracts from the current time.
397 * @tv: pointer to the timespec variable containing the offset
399 * Adds or subtracts an offset value from the current time.
401 int timekeeping_inject_offset(struct timespec
*ts
)
405 if ((unsigned long)ts
->tv_nsec
>= NSEC_PER_SEC
)
408 write_seqlock_irqsave(&xtime_lock
, flags
);
410 timekeeping_forward_now();
412 xtime
= timespec_add(xtime
, *ts
);
413 wall_to_monotonic
= timespec_sub(wall_to_monotonic
, *ts
);
415 timekeeper
.ntp_error
= 0;
418 update_vsyscall(&xtime
, &wall_to_monotonic
, timekeeper
.clock
,
421 write_sequnlock_irqrestore(&xtime_lock
, flags
);
423 /* signal hrtimers about time change */
428 EXPORT_SYMBOL(timekeeping_inject_offset
);
431 * change_clocksource - Swaps clocksources if a new one is available
433 * Accumulates current time interval and initializes new clocksource
435 static int change_clocksource(void *data
)
437 struct clocksource
*new, *old
;
439 new = (struct clocksource
*) data
;
441 timekeeping_forward_now();
442 if (!new->enable
|| new->enable(new) == 0) {
443 old
= timekeeper
.clock
;
444 timekeeper_setup_internals(new);
452 * timekeeping_notify - Install a new clock source
453 * @clock: pointer to the clock source
455 * This function is called from clocksource.c after a new, better clock
456 * source has been registered. The caller holds the clocksource_mutex.
458 void timekeeping_notify(struct clocksource
*clock
)
460 if (timekeeper
.clock
== clock
)
462 stop_machine(change_clocksource
, clock
, NULL
);
467 * ktime_get_real - get the real (wall-) time in ktime_t format
469 * returns the time in ktime_t format
471 ktime_t
ktime_get_real(void)
475 getnstimeofday(&now
);
477 return timespec_to_ktime(now
);
479 EXPORT_SYMBOL_GPL(ktime_get_real
);
482 * getrawmonotonic - Returns the raw monotonic time in a timespec
483 * @ts: pointer to the timespec to be set
485 * Returns the raw monotonic time (completely un-modified by ntp)
487 void getrawmonotonic(struct timespec
*ts
)
493 seq
= read_seqbegin(&xtime_lock
);
494 nsecs
= timekeeping_get_ns_raw();
497 } while (read_seqretry(&xtime_lock
, seq
));
499 timespec_add_ns(ts
, nsecs
);
501 EXPORT_SYMBOL(getrawmonotonic
);
505 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
507 int timekeeping_valid_for_hres(void)
513 seq
= read_seqbegin(&xtime_lock
);
515 ret
= timekeeper
.clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
517 } while (read_seqretry(&xtime_lock
, seq
));
523 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
525 * Caller must observe xtime_lock via read_seqbegin/read_seqretry to
526 * ensure that the clocksource does not change!
528 u64
timekeeping_max_deferment(void)
530 return timekeeper
.clock
->max_idle_ns
;
534 * read_persistent_clock - Return time from the persistent clock.
536 * Weak dummy function for arches that do not yet support it.
537 * Reads the time from the battery backed persistent clock.
538 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
540 * XXX - Do be sure to remove it once all arches implement it.
542 void __attribute__((weak
)) read_persistent_clock(struct timespec
*ts
)
549 * read_boot_clock - Return time of the system start.
551 * Weak dummy function for arches that do not yet support it.
552 * Function to read the exact time the system has been started.
553 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
555 * XXX - Do be sure to remove it once all arches implement it.
557 void __attribute__((weak
)) read_boot_clock(struct timespec
*ts
)
564 * timekeeping_init - Initializes the clocksource and common timekeeping values
566 void __init
timekeeping_init(void)
568 struct clocksource
*clock
;
570 struct timespec now
, boot
;
572 read_persistent_clock(&now
);
573 read_boot_clock(&boot
);
575 write_seqlock_irqsave(&xtime_lock
, flags
);
579 clock
= clocksource_default_clock();
581 clock
->enable(clock
);
582 timekeeper_setup_internals(clock
);
584 xtime
.tv_sec
= now
.tv_sec
;
585 xtime
.tv_nsec
= now
.tv_nsec
;
587 raw_time
.tv_nsec
= 0;
588 if (boot
.tv_sec
== 0 && boot
.tv_nsec
== 0) {
589 boot
.tv_sec
= xtime
.tv_sec
;
590 boot
.tv_nsec
= xtime
.tv_nsec
;
592 set_normalized_timespec(&wall_to_monotonic
,
593 -boot
.tv_sec
, -boot
.tv_nsec
);
594 total_sleep_time
.tv_sec
= 0;
595 total_sleep_time
.tv_nsec
= 0;
596 write_sequnlock_irqrestore(&xtime_lock
, flags
);
599 /* time in seconds when suspend began */
600 static struct timespec timekeeping_suspend_time
;
603 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
604 * @delta: pointer to a timespec delta value
606 * Takes a timespec offset measuring a suspend interval and properly
607 * adds the sleep offset to the timekeeping variables.
609 static void __timekeeping_inject_sleeptime(struct timespec
*delta
)
611 xtime
= timespec_add(xtime
, *delta
);
612 wall_to_monotonic
= timespec_sub(wall_to_monotonic
, *delta
);
613 total_sleep_time
= timespec_add(total_sleep_time
, *delta
);
618 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
619 * @delta: pointer to a timespec delta value
621 * This hook is for architectures that cannot support read_persistent_clock
622 * because their RTC/persistent clock is only accessible when irqs are enabled.
624 * This function should only be called by rtc_resume(), and allows
625 * a suspend offset to be injected into the timekeeping values.
627 void timekeeping_inject_sleeptime(struct timespec
*delta
)
632 /* Make sure we don't set the clock twice */
633 read_persistent_clock(&ts
);
634 if (!(ts
.tv_sec
== 0 && ts
.tv_nsec
== 0))
637 write_seqlock_irqsave(&xtime_lock
, flags
);
638 timekeeping_forward_now();
640 __timekeeping_inject_sleeptime(delta
);
642 timekeeper
.ntp_error
= 0;
644 update_vsyscall(&xtime
, &wall_to_monotonic
, timekeeper
.clock
,
647 write_sequnlock_irqrestore(&xtime_lock
, flags
);
649 /* signal hrtimers about time change */
655 * timekeeping_resume - Resumes the generic timekeeping subsystem.
657 * This is for the generic clocksource timekeeping.
658 * xtime/wall_to_monotonic/jiffies/etc are
659 * still managed by arch specific suspend/resume code.
661 static void timekeeping_resume(void)
666 read_persistent_clock(&ts
);
668 clocksource_resume();
670 write_seqlock_irqsave(&xtime_lock
, flags
);
672 if (timespec_compare(&ts
, &timekeeping_suspend_time
) > 0) {
673 ts
= timespec_sub(ts
, timekeeping_suspend_time
);
674 __timekeeping_inject_sleeptime(&ts
);
676 /* re-base the last cycle value */
677 timekeeper
.clock
->cycle_last
= timekeeper
.clock
->read(timekeeper
.clock
);
678 timekeeper
.ntp_error
= 0;
679 timekeeping_suspended
= 0;
680 write_sequnlock_irqrestore(&xtime_lock
, flags
);
682 touch_softlockup_watchdog();
684 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
686 /* Resume hrtimers */
690 static int timekeeping_suspend(void)
694 read_persistent_clock(&timekeeping_suspend_time
);
696 write_seqlock_irqsave(&xtime_lock
, flags
);
697 timekeeping_forward_now();
698 timekeeping_suspended
= 1;
699 write_sequnlock_irqrestore(&xtime_lock
, flags
);
701 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
702 clocksource_suspend();
707 /* sysfs resume/suspend bits for timekeeping */
708 static struct syscore_ops timekeeping_syscore_ops
= {
709 .resume
= timekeeping_resume
,
710 .suspend
= timekeeping_suspend
,
713 static int __init
timekeeping_init_ops(void)
715 register_syscore_ops(&timekeeping_syscore_ops
);
719 device_initcall(timekeeping_init_ops
);
722 * If the error is already larger, we look ahead even further
723 * to compensate for late or lost adjustments.
725 static __always_inline
int timekeeping_bigadjust(s64 error
, s64
*interval
,
733 * Use the current error value to determine how much to look ahead.
734 * The larger the error the slower we adjust for it to avoid problems
735 * with losing too many ticks, otherwise we would overadjust and
736 * produce an even larger error. The smaller the adjustment the
737 * faster we try to adjust for it, as lost ticks can do less harm
738 * here. This is tuned so that an error of about 1 msec is adjusted
739 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
741 error2
= timekeeper
.ntp_error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
742 error2
= abs(error2
);
743 for (look_ahead
= 0; error2
> 0; look_ahead
++)
747 * Now calculate the error in (1 << look_ahead) ticks, but first
748 * remove the single look ahead already included in the error.
750 tick_error
= tick_length
>> (timekeeper
.ntp_error_shift
+ 1);
751 tick_error
-= timekeeper
.xtime_interval
>> 1;
752 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
754 /* Finally calculate the adjustment shift value. */
759 *interval
= -*interval
;
763 for (adj
= 0; error
> i
; adj
++)
772 * Adjust the multiplier to reduce the error value,
773 * this is optimized for the most common adjustments of -1,0,1,
774 * for other values we can do a bit more work.
776 static void timekeeping_adjust(s64 offset
)
778 s64 error
, interval
= timekeeper
.cycle_interval
;
781 error
= timekeeper
.ntp_error
>> (timekeeper
.ntp_error_shift
- 1);
782 if (error
> interval
) {
784 if (likely(error
<= interval
))
787 adj
= timekeeping_bigadjust(error
, &interval
, &offset
);
788 } else if (error
< -interval
) {
790 if (likely(error
>= -interval
)) {
792 interval
= -interval
;
795 adj
= timekeeping_bigadjust(error
, &interval
, &offset
);
799 timekeeper
.mult
+= adj
;
800 timekeeper
.xtime_interval
+= interval
;
801 timekeeper
.xtime_nsec
-= offset
;
802 timekeeper
.ntp_error
-= (interval
- offset
) <<
803 timekeeper
.ntp_error_shift
;
808 * logarithmic_accumulation - shifted accumulation of cycles
810 * This functions accumulates a shifted interval of cycles into
811 * into a shifted interval nanoseconds. Allows for O(log) accumulation
814 * Returns the unconsumed cycles.
816 static cycle_t
logarithmic_accumulation(cycle_t offset
, int shift
)
818 u64 nsecps
= (u64
)NSEC_PER_SEC
<< timekeeper
.shift
;
821 /* If the offset is smaller then a shifted interval, do nothing */
822 if (offset
< timekeeper
.cycle_interval
<<shift
)
825 /* Accumulate one shifted interval */
826 offset
-= timekeeper
.cycle_interval
<< shift
;
827 timekeeper
.clock
->cycle_last
+= timekeeper
.cycle_interval
<< shift
;
829 timekeeper
.xtime_nsec
+= timekeeper
.xtime_interval
<< shift
;
830 while (timekeeper
.xtime_nsec
>= nsecps
) {
831 timekeeper
.xtime_nsec
-= nsecps
;
836 /* Accumulate raw time */
837 raw_nsecs
= timekeeper
.raw_interval
<< shift
;
838 raw_nsecs
+= raw_time
.tv_nsec
;
839 if (raw_nsecs
>= NSEC_PER_SEC
) {
840 u64 raw_secs
= raw_nsecs
;
841 raw_nsecs
= do_div(raw_secs
, NSEC_PER_SEC
);
842 raw_time
.tv_sec
+= raw_secs
;
844 raw_time
.tv_nsec
= raw_nsecs
;
846 /* Accumulate error between NTP and clock interval */
847 timekeeper
.ntp_error
+= tick_length
<< shift
;
848 timekeeper
.ntp_error
-=
849 (timekeeper
.xtime_interval
+ timekeeper
.xtime_remainder
) <<
850 (timekeeper
.ntp_error_shift
+ shift
);
857 * update_wall_time - Uses the current clocksource to increment the wall time
859 * Called from the timer interrupt, must hold a write on xtime_lock.
861 static void update_wall_time(void)
863 struct clocksource
*clock
;
865 int shift
= 0, maxshift
;
867 /* Make sure we're fully resumed: */
868 if (unlikely(timekeeping_suspended
))
871 clock
= timekeeper
.clock
;
873 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
874 offset
= timekeeper
.cycle_interval
;
876 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
878 timekeeper
.xtime_nsec
= (s64
)xtime
.tv_nsec
<< timekeeper
.shift
;
881 * With NO_HZ we may have to accumulate many cycle_intervals
882 * (think "ticks") worth of time at once. To do this efficiently,
883 * we calculate the largest doubling multiple of cycle_intervals
884 * that is smaller then the offset. We then accumulate that
885 * chunk in one go, and then try to consume the next smaller
888 shift
= ilog2(offset
) - ilog2(timekeeper
.cycle_interval
);
889 shift
= max(0, shift
);
890 /* Bound shift to one less then what overflows tick_length */
891 maxshift
= (8*sizeof(tick_length
) - (ilog2(tick_length
)+1)) - 1;
892 shift
= min(shift
, maxshift
);
893 while (offset
>= timekeeper
.cycle_interval
) {
894 offset
= logarithmic_accumulation(offset
, shift
);
895 if(offset
< timekeeper
.cycle_interval
<<shift
)
899 /* correct the clock when NTP error is too big */
900 timekeeping_adjust(offset
);
903 * Since in the loop above, we accumulate any amount of time
904 * in xtime_nsec over a second into xtime.tv_sec, its possible for
905 * xtime_nsec to be fairly small after the loop. Further, if we're
906 * slightly speeding the clocksource up in timekeeping_adjust(),
907 * its possible the required corrective factor to xtime_nsec could
908 * cause it to underflow.
910 * Now, we cannot simply roll the accumulated second back, since
911 * the NTP subsystem has been notified via second_overflow. So
912 * instead we push xtime_nsec forward by the amount we underflowed,
913 * and add that amount into the error.
915 * We'll correct this error next time through this function, when
916 * xtime_nsec is not as small.
918 if (unlikely((s64
)timekeeper
.xtime_nsec
< 0)) {
919 s64 neg
= -(s64
)timekeeper
.xtime_nsec
;
920 timekeeper
.xtime_nsec
= 0;
921 timekeeper
.ntp_error
+= neg
<< timekeeper
.ntp_error_shift
;
926 * Store full nanoseconds into xtime after rounding it up and
927 * add the remainder to the error difference.
929 xtime
.tv_nsec
= ((s64
) timekeeper
.xtime_nsec
>> timekeeper
.shift
) + 1;
930 timekeeper
.xtime_nsec
-= (s64
) xtime
.tv_nsec
<< timekeeper
.shift
;
931 timekeeper
.ntp_error
+= timekeeper
.xtime_nsec
<<
932 timekeeper
.ntp_error_shift
;
935 * Finally, make sure that after the rounding
936 * xtime.tv_nsec isn't larger then NSEC_PER_SEC
938 if (unlikely(xtime
.tv_nsec
>= NSEC_PER_SEC
)) {
939 xtime
.tv_nsec
-= NSEC_PER_SEC
;
944 /* check to see if there is a new clocksource to use */
945 update_vsyscall(&xtime
, &wall_to_monotonic
, timekeeper
.clock
,
950 * getboottime - Return the real time of system boot.
951 * @ts: pointer to the timespec to be set
953 * Returns the wall-time of boot in a timespec.
955 * This is based on the wall_to_monotonic offset and the total suspend
956 * time. Calls to settimeofday will affect the value returned (which
957 * basically means that however wrong your real time clock is at boot time,
958 * you get the right time here).
960 void getboottime(struct timespec
*ts
)
962 struct timespec boottime
= {
963 .tv_sec
= wall_to_monotonic
.tv_sec
+ total_sleep_time
.tv_sec
,
964 .tv_nsec
= wall_to_monotonic
.tv_nsec
+ total_sleep_time
.tv_nsec
967 set_normalized_timespec(ts
, -boottime
.tv_sec
, -boottime
.tv_nsec
);
969 EXPORT_SYMBOL_GPL(getboottime
);
973 * get_monotonic_boottime - Returns monotonic time since boot
974 * @ts: pointer to the timespec to be set
976 * Returns the monotonic time since boot in a timespec.
978 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
979 * includes the time spent in suspend.
981 void get_monotonic_boottime(struct timespec
*ts
)
983 struct timespec tomono
, sleep
;
987 WARN_ON(timekeeping_suspended
);
990 seq
= read_seqbegin(&xtime_lock
);
992 tomono
= wall_to_monotonic
;
993 sleep
= total_sleep_time
;
994 nsecs
= timekeeping_get_ns();
996 } while (read_seqretry(&xtime_lock
, seq
));
998 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
+ sleep
.tv_sec
,
999 ts
->tv_nsec
+ tomono
.tv_nsec
+ sleep
.tv_nsec
+ nsecs
);
1001 EXPORT_SYMBOL_GPL(get_monotonic_boottime
);
1004 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1006 * Returns the monotonic time since boot in a ktime
1008 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1009 * includes the time spent in suspend.
1011 ktime_t
ktime_get_boottime(void)
1015 get_monotonic_boottime(&ts
);
1016 return timespec_to_ktime(ts
);
1018 EXPORT_SYMBOL_GPL(ktime_get_boottime
);
1021 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1022 * @ts: pointer to the timespec to be converted
1024 void monotonic_to_bootbased(struct timespec
*ts
)
1026 *ts
= timespec_add(*ts
, total_sleep_time
);
1028 EXPORT_SYMBOL_GPL(monotonic_to_bootbased
);
1030 unsigned long get_seconds(void)
1032 return xtime
.tv_sec
;
1034 EXPORT_SYMBOL(get_seconds
);
1036 struct timespec
__current_kernel_time(void)
1041 struct timespec
current_kernel_time(void)
1043 struct timespec now
;
1047 seq
= read_seqbegin(&xtime_lock
);
1050 } while (read_seqretry(&xtime_lock
, seq
));
1054 EXPORT_SYMBOL(current_kernel_time
);
1056 struct timespec
get_monotonic_coarse(void)
1058 struct timespec now
, mono
;
1062 seq
= read_seqbegin(&xtime_lock
);
1065 mono
= wall_to_monotonic
;
1066 } while (read_seqretry(&xtime_lock
, seq
));
1068 set_normalized_timespec(&now
, now
.tv_sec
+ mono
.tv_sec
,
1069 now
.tv_nsec
+ mono
.tv_nsec
);
1074 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1075 * without sampling the sequence number in xtime_lock.
1076 * jiffies is defined in the linker script...
1078 void do_timer(unsigned long ticks
)
1080 jiffies_64
+= ticks
;
1082 calc_global_load(ticks
);
1086 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1087 * and sleep offsets.
1088 * @xtim: pointer to timespec to be set with xtime
1089 * @wtom: pointer to timespec to be set with wall_to_monotonic
1090 * @sleep: pointer to timespec to be set with time in suspend
1092 void get_xtime_and_monotonic_and_sleep_offset(struct timespec
*xtim
,
1093 struct timespec
*wtom
, struct timespec
*sleep
)
1098 seq
= read_seqbegin(&xtime_lock
);
1100 *wtom
= wall_to_monotonic
;
1101 *sleep
= total_sleep_time
;
1102 } while (read_seqretry(&xtime_lock
, seq
));
1106 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1108 ktime_t
ktime_get_monotonic_offset(void)
1111 struct timespec wtom
;
1114 seq
= read_seqbegin(&xtime_lock
);
1115 wtom
= wall_to_monotonic
;
1116 } while (read_seqretry(&xtime_lock
, seq
));
1117 return timespec_to_ktime(wtom
);
1121 * xtime_update() - advances the timekeeping infrastructure
1122 * @ticks: number of ticks, that have elapsed since the last call.
1124 * Must be called with interrupts disabled.
1126 void xtime_update(unsigned long ticks
)
1128 write_seqlock(&xtime_lock
);
1130 write_sequnlock(&xtime_lock
);