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
)
298 WARN_ON(timekeeping_suspended
);
301 seq
= read_seqbegin(&timekeeper
.lock
);
303 ts
->tv_sec
= timekeeper
.xtime_sec
;
304 ts
->tv_nsec
= timekeeping_get_ns(&timekeeper
);
306 } while (read_seqretry(&timekeeper
.lock
, seq
));
308 timespec_add_ns(ts
, nsecs
);
310 EXPORT_SYMBOL(getnstimeofday
);
312 ktime_t
ktime_get(void)
317 WARN_ON(timekeeping_suspended
);
320 seq
= read_seqbegin(&timekeeper
.lock
);
321 secs
= timekeeper
.xtime_sec
+
322 timekeeper
.wall_to_monotonic
.tv_sec
;
323 nsecs
= timekeeping_get_ns(&timekeeper
) +
324 timekeeper
.wall_to_monotonic
.tv_nsec
;
326 } while (read_seqretry(&timekeeper
.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 timespec tomono
;
348 WARN_ON(timekeeping_suspended
);
351 seq
= read_seqbegin(&timekeeper
.lock
);
352 ts
->tv_sec
= timekeeper
.xtime_sec
;
353 ts
->tv_nsec
= timekeeping_get_ns(&timekeeper
);
354 tomono
= timekeeper
.wall_to_monotonic
;
356 } while (read_seqretry(&timekeeper
.lock
, seq
));
358 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
359 ts
->tv_nsec
+ tomono
.tv_nsec
);
361 EXPORT_SYMBOL_GPL(ktime_get_ts
);
363 #ifdef CONFIG_NTP_PPS
366 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
367 * @ts_raw: pointer to the timespec to be set to raw monotonic time
368 * @ts_real: pointer to the timespec to be set to the time of day
370 * This function reads both the time of day and raw monotonic time at the
371 * same time atomically and stores the resulting timestamps in timespec
374 void getnstime_raw_and_real(struct timespec
*ts_raw
, struct timespec
*ts_real
)
377 s64 nsecs_raw
, nsecs_real
;
379 WARN_ON_ONCE(timekeeping_suspended
);
382 seq
= read_seqbegin(&timekeeper
.lock
);
384 *ts_raw
= timekeeper
.raw_time
;
385 ts_real
->tv_sec
= timekeeper
.xtime_sec
;
386 ts_real
->tv_nsec
= 0;
388 nsecs_raw
= timekeeping_get_ns_raw(&timekeeper
);
389 nsecs_real
= timekeeping_get_ns(&timekeeper
);
391 } while (read_seqretry(&timekeeper
.lock
, seq
));
393 timespec_add_ns(ts_raw
, nsecs_raw
);
394 timespec_add_ns(ts_real
, nsecs_real
);
396 EXPORT_SYMBOL(getnstime_raw_and_real
);
398 #endif /* CONFIG_NTP_PPS */
401 * do_gettimeofday - Returns the time of day in a timeval
402 * @tv: pointer to the timeval to be set
404 * NOTE: Users should be converted to using getnstimeofday()
406 void do_gettimeofday(struct timeval
*tv
)
410 getnstimeofday(&now
);
411 tv
->tv_sec
= now
.tv_sec
;
412 tv
->tv_usec
= now
.tv_nsec
/1000;
414 EXPORT_SYMBOL(do_gettimeofday
);
417 * do_settimeofday - Sets the time of day
418 * @tv: pointer to the timespec variable containing the new time
420 * Sets the time of day to the new time and update NTP and notify hrtimers
422 int do_settimeofday(const struct timespec
*tv
)
424 struct timespec ts_delta
, xt
;
427 if ((unsigned long)tv
->tv_nsec
>= NSEC_PER_SEC
)
430 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
432 timekeeping_forward_now(&timekeeper
);
434 xt
= tk_xtime(&timekeeper
);
435 ts_delta
.tv_sec
= tv
->tv_sec
- xt
.tv_sec
;
436 ts_delta
.tv_nsec
= tv
->tv_nsec
- xt
.tv_nsec
;
438 tk_set_wall_to_mono(&timekeeper
,
439 timespec_sub(timekeeper
.wall_to_monotonic
, ts_delta
));
441 tk_set_xtime(&timekeeper
, tv
);
443 timekeeping_update(&timekeeper
, true);
445 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
447 /* signal hrtimers about time change */
452 EXPORT_SYMBOL(do_settimeofday
);
455 * timekeeping_inject_offset - Adds or subtracts from the current time.
456 * @tv: pointer to the timespec variable containing the offset
458 * Adds or subtracts an offset value from the current time.
460 int timekeeping_inject_offset(struct timespec
*ts
)
464 if ((unsigned long)ts
->tv_nsec
>= NSEC_PER_SEC
)
467 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
469 timekeeping_forward_now(&timekeeper
);
472 tk_xtime_add(&timekeeper
, ts
);
473 tk_set_wall_to_mono(&timekeeper
,
474 timespec_sub(timekeeper
.wall_to_monotonic
, *ts
));
476 timekeeping_update(&timekeeper
, true);
478 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
480 /* signal hrtimers about time change */
485 EXPORT_SYMBOL(timekeeping_inject_offset
);
488 * change_clocksource - Swaps clocksources if a new one is available
490 * Accumulates current time interval and initializes new clocksource
492 static int change_clocksource(void *data
)
494 struct clocksource
*new, *old
;
497 new = (struct clocksource
*) data
;
499 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
501 timekeeping_forward_now(&timekeeper
);
502 if (!new->enable
|| new->enable(new) == 0) {
503 old
= timekeeper
.clock
;
504 tk_setup_internals(&timekeeper
, new);
508 timekeeping_update(&timekeeper
, true);
510 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
516 * timekeeping_notify - Install a new clock source
517 * @clock: pointer to the clock source
519 * This function is called from clocksource.c after a new, better clock
520 * source has been registered. The caller holds the clocksource_mutex.
522 void timekeeping_notify(struct clocksource
*clock
)
524 if (timekeeper
.clock
== clock
)
526 stop_machine(change_clocksource
, clock
, NULL
);
531 * ktime_get_real - get the real (wall-) time in ktime_t format
533 * returns the time in ktime_t format
535 ktime_t
ktime_get_real(void)
539 getnstimeofday(&now
);
541 return timespec_to_ktime(now
);
543 EXPORT_SYMBOL_GPL(ktime_get_real
);
546 * getrawmonotonic - Returns the raw monotonic time in a timespec
547 * @ts: pointer to the timespec to be set
549 * Returns the raw monotonic time (completely un-modified by ntp)
551 void getrawmonotonic(struct timespec
*ts
)
557 seq
= read_seqbegin(&timekeeper
.lock
);
558 nsecs
= timekeeping_get_ns_raw(&timekeeper
);
559 *ts
= timekeeper
.raw_time
;
561 } while (read_seqretry(&timekeeper
.lock
, seq
));
563 timespec_add_ns(ts
, nsecs
);
565 EXPORT_SYMBOL(getrawmonotonic
);
568 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
570 int timekeeping_valid_for_hres(void)
576 seq
= read_seqbegin(&timekeeper
.lock
);
578 ret
= timekeeper
.clock
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
;
580 } while (read_seqretry(&timekeeper
.lock
, seq
));
586 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
588 u64
timekeeping_max_deferment(void)
594 seq
= read_seqbegin(&timekeeper
.lock
);
596 ret
= timekeeper
.clock
->max_idle_ns
;
598 } while (read_seqretry(&timekeeper
.lock
, seq
));
604 * read_persistent_clock - Return time from the persistent clock.
606 * Weak dummy function for arches that do not yet support it.
607 * Reads the time from the battery backed persistent clock.
608 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
610 * XXX - Do be sure to remove it once all arches implement it.
612 void __attribute__((weak
)) read_persistent_clock(struct timespec
*ts
)
619 * read_boot_clock - Return time of the system start.
621 * Weak dummy function for arches that do not yet support it.
622 * Function to read the exact time the system has been started.
623 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
625 * XXX - Do be sure to remove it once all arches implement it.
627 void __attribute__((weak
)) read_boot_clock(struct timespec
*ts
)
634 * timekeeping_init - Initializes the clocksource and common timekeeping values
636 void __init
timekeeping_init(void)
638 struct clocksource
*clock
;
640 struct timespec now
, boot
, tmp
;
642 read_persistent_clock(&now
);
643 read_boot_clock(&boot
);
645 seqlock_init(&timekeeper
.lock
);
649 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
650 clock
= clocksource_default_clock();
652 clock
->enable(clock
);
653 tk_setup_internals(&timekeeper
, clock
);
655 tk_set_xtime(&timekeeper
, &now
);
656 timekeeper
.raw_time
.tv_sec
= 0;
657 timekeeper
.raw_time
.tv_nsec
= 0;
658 if (boot
.tv_sec
== 0 && boot
.tv_nsec
== 0)
659 boot
= tk_xtime(&timekeeper
);
661 set_normalized_timespec(&tmp
, -boot
.tv_sec
, -boot
.tv_nsec
);
662 tk_set_wall_to_mono(&timekeeper
, tmp
);
666 tk_set_sleep_time(&timekeeper
, tmp
);
668 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
671 /* time in seconds when suspend began */
672 static struct timespec timekeeping_suspend_time
;
675 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
676 * @delta: pointer to a timespec delta value
678 * Takes a timespec offset measuring a suspend interval and properly
679 * adds the sleep offset to the timekeeping variables.
681 static void __timekeeping_inject_sleeptime(struct timekeeper
*tk
,
682 struct timespec
*delta
)
684 if (!timespec_valid(delta
)) {
685 printk(KERN_WARNING
"__timekeeping_inject_sleeptime: Invalid "
686 "sleep delta value!\n");
689 tk_xtime_add(tk
, delta
);
690 tk_set_wall_to_mono(tk
, timespec_sub(tk
->wall_to_monotonic
, *delta
));
691 tk_set_sleep_time(tk
, timespec_add(tk
->total_sleep_time
, *delta
));
695 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
696 * @delta: pointer to a timespec delta value
698 * This hook is for architectures that cannot support read_persistent_clock
699 * because their RTC/persistent clock is only accessible when irqs are enabled.
701 * This function should only be called by rtc_resume(), and allows
702 * a suspend offset to be injected into the timekeeping values.
704 void timekeeping_inject_sleeptime(struct timespec
*delta
)
709 /* Make sure we don't set the clock twice */
710 read_persistent_clock(&ts
);
711 if (!(ts
.tv_sec
== 0 && ts
.tv_nsec
== 0))
714 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
716 timekeeping_forward_now(&timekeeper
);
718 __timekeeping_inject_sleeptime(&timekeeper
, delta
);
720 timekeeping_update(&timekeeper
, true);
722 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
724 /* signal hrtimers about time change */
729 * timekeeping_resume - Resumes the generic timekeeping subsystem.
731 * This is for the generic clocksource timekeeping.
732 * xtime/wall_to_monotonic/jiffies/etc are
733 * still managed by arch specific suspend/resume code.
735 static void timekeeping_resume(void)
740 read_persistent_clock(&ts
);
742 clocksource_resume();
744 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
746 if (timespec_compare(&ts
, &timekeeping_suspend_time
) > 0) {
747 ts
= timespec_sub(ts
, timekeeping_suspend_time
);
748 __timekeeping_inject_sleeptime(&timekeeper
, &ts
);
750 /* re-base the last cycle value */
751 timekeeper
.clock
->cycle_last
= timekeeper
.clock
->read(timekeeper
.clock
);
752 timekeeper
.ntp_error
= 0;
753 timekeeping_suspended
= 0;
754 timekeeping_update(&timekeeper
, false);
755 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
757 touch_softlockup_watchdog();
759 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME
, NULL
);
761 /* Resume hrtimers */
765 static int timekeeping_suspend(void)
768 struct timespec delta
, delta_delta
;
769 static struct timespec old_delta
;
771 read_persistent_clock(&timekeeping_suspend_time
);
773 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
774 timekeeping_forward_now(&timekeeper
);
775 timekeeping_suspended
= 1;
778 * To avoid drift caused by repeated suspend/resumes,
779 * which each can add ~1 second drift error,
780 * try to compensate so the difference in system time
781 * and persistent_clock time stays close to constant.
783 delta
= timespec_sub(tk_xtime(&timekeeper
), timekeeping_suspend_time
);
784 delta_delta
= timespec_sub(delta
, old_delta
);
785 if (abs(delta_delta
.tv_sec
) >= 2) {
787 * if delta_delta is too large, assume time correction
788 * has occured and set old_delta to the current delta.
792 /* Otherwise try to adjust old_system to compensate */
793 timekeeping_suspend_time
=
794 timespec_add(timekeeping_suspend_time
, delta_delta
);
796 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
798 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND
, NULL
);
799 clocksource_suspend();
804 /* sysfs resume/suspend bits for timekeeping */
805 static struct syscore_ops timekeeping_syscore_ops
= {
806 .resume
= timekeeping_resume
,
807 .suspend
= timekeeping_suspend
,
810 static int __init
timekeeping_init_ops(void)
812 register_syscore_ops(&timekeeping_syscore_ops
);
816 device_initcall(timekeeping_init_ops
);
819 * If the error is already larger, we look ahead even further
820 * to compensate for late or lost adjustments.
822 static __always_inline
int timekeeping_bigadjust(struct timekeeper
*tk
,
823 s64 error
, s64
*interval
,
831 * Use the current error value to determine how much to look ahead.
832 * The larger the error the slower we adjust for it to avoid problems
833 * with losing too many ticks, otherwise we would overadjust and
834 * produce an even larger error. The smaller the adjustment the
835 * faster we try to adjust for it, as lost ticks can do less harm
836 * here. This is tuned so that an error of about 1 msec is adjusted
837 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
839 error2
= tk
->ntp_error
>> (NTP_SCALE_SHIFT
+ 22 - 2 * SHIFT_HZ
);
840 error2
= abs(error2
);
841 for (look_ahead
= 0; error2
> 0; look_ahead
++)
845 * Now calculate the error in (1 << look_ahead) ticks, but first
846 * remove the single look ahead already included in the error.
848 tick_error
= ntp_tick_length() >> (tk
->ntp_error_shift
+ 1);
849 tick_error
-= tk
->xtime_interval
>> 1;
850 error
= ((error
- tick_error
) >> look_ahead
) + tick_error
;
852 /* Finally calculate the adjustment shift value. */
857 *interval
= -*interval
;
861 for (adj
= 0; error
> i
; adj
++)
870 * Adjust the multiplier to reduce the error value,
871 * this is optimized for the most common adjustments of -1,0,1,
872 * for other values we can do a bit more work.
874 static void timekeeping_adjust(struct timekeeper
*tk
, s64 offset
)
876 s64 error
, interval
= tk
->cycle_interval
;
880 * The point of this is to check if the error is greater than half
883 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
885 * Note we subtract one in the shift, so that error is really error*2.
886 * This "saves" dividing(shifting) interval twice, but keeps the
887 * (error > interval) comparison as still measuring if error is
888 * larger than half an interval.
890 * Note: It does not "save" on aggravation when reading the code.
892 error
= tk
->ntp_error
>> (tk
->ntp_error_shift
- 1);
893 if (error
> interval
) {
895 * We now divide error by 4(via shift), which checks if
896 * the error is greater than twice the interval.
897 * If it is greater, we need a bigadjust, if its smaller,
898 * we can adjust by 1.
902 * XXX - In update_wall_time, we round up to the next
903 * nanosecond, and store the amount rounded up into
904 * the error. This causes the likely below to be unlikely.
906 * The proper fix is to avoid rounding up by using
907 * the high precision timekeeper.xtime_nsec instead of
908 * xtime.tv_nsec everywhere. Fixing this will take some
911 if (likely(error
<= interval
))
914 adj
= timekeeping_bigadjust(tk
, error
, &interval
,
916 } else if (error
< -interval
) {
917 /* See comment above, this is just switched for the negative */
919 if (likely(error
>= -interval
)) {
921 interval
= -interval
;
924 adj
= timekeeping_bigadjust(tk
, error
, &interval
,
929 if (unlikely(tk
->clock
->maxadj
&&
930 (tk
->mult
+ adj
> tk
->clock
->mult
+ tk
->clock
->maxadj
))) {
931 printk_once(KERN_WARNING
932 "Adjusting %s more than 11%% (%ld vs %ld)\n",
933 tk
->clock
->name
, (long)tk
->mult
+ adj
,
934 (long)tk
->clock
->mult
+ tk
->clock
->maxadj
);
937 * So the following can be confusing.
939 * To keep things simple, lets assume adj == 1 for now.
941 * When adj != 1, remember that the interval and offset values
942 * have been appropriately scaled so the math is the same.
944 * The basic idea here is that we're increasing the multiplier
945 * by one, this causes the xtime_interval to be incremented by
946 * one cycle_interval. This is because:
947 * xtime_interval = cycle_interval * mult
948 * So if mult is being incremented by one:
949 * xtime_interval = cycle_interval * (mult + 1)
951 * xtime_interval = (cycle_interval * mult) + cycle_interval
952 * Which can be shortened to:
953 * xtime_interval += cycle_interval
955 * So offset stores the non-accumulated cycles. Thus the current
956 * time (in shifted nanoseconds) is:
957 * now = (offset * adj) + xtime_nsec
958 * Now, even though we're adjusting the clock frequency, we have
959 * to keep time consistent. In other words, we can't jump back
960 * in time, and we also want to avoid jumping forward in time.
962 * So given the same offset value, we need the time to be the same
963 * both before and after the freq adjustment.
964 * now = (offset * adj_1) + xtime_nsec_1
965 * now = (offset * adj_2) + xtime_nsec_2
967 * (offset * adj_1) + xtime_nsec_1 =
968 * (offset * adj_2) + xtime_nsec_2
972 * (offset * adj_1) + xtime_nsec_1 =
973 * (offset * (adj_1+1)) + xtime_nsec_2
974 * (offset * adj_1) + xtime_nsec_1 =
975 * (offset * adj_1) + offset + xtime_nsec_2
976 * Canceling the sides:
977 * xtime_nsec_1 = offset + xtime_nsec_2
979 * xtime_nsec_2 = xtime_nsec_1 - offset
980 * Which simplfies to:
981 * xtime_nsec -= offset
983 * XXX - TODO: Doc ntp_error calculation.
986 tk
->xtime_interval
+= interval
;
987 tk
->xtime_nsec
-= offset
;
988 tk
->ntp_error
-= (interval
- offset
) << tk
->ntp_error_shift
;
991 * It may be possible that when we entered this function, xtime_nsec
992 * was very small. Further, if we're slightly speeding the clocksource
993 * in the code above, its possible the required corrective factor to
994 * xtime_nsec could cause it to underflow.
996 * Now, since we already accumulated the second, cannot simply roll
997 * the accumulated second back, since the NTP subsystem has been
998 * notified via second_overflow. So instead we push xtime_nsec forward
999 * by the amount we underflowed, and add that amount into the error.
1001 * We'll correct this error next time through this function, when
1002 * xtime_nsec is not as small.
1004 if (unlikely((s64
)tk
->xtime_nsec
< 0)) {
1005 s64 neg
= -(s64
)tk
->xtime_nsec
;
1007 tk
->ntp_error
+= neg
<< tk
->ntp_error_shift
;
1013 * accumulate_nsecs_to_secs - Accumulates nsecs into secs
1015 * Helper function that accumulates a the nsecs greater then a second
1016 * from the xtime_nsec field to the xtime_secs field.
1017 * It also calls into the NTP code to handle leapsecond processing.
1020 static inline void accumulate_nsecs_to_secs(struct timekeeper
*tk
)
1022 u64 nsecps
= (u64
)NSEC_PER_SEC
<< tk
->shift
;
1024 while (tk
->xtime_nsec
>= nsecps
) {
1027 tk
->xtime_nsec
-= nsecps
;
1030 /* Figure out if its a leap sec and apply if needed */
1031 leap
= second_overflow(tk
->xtime_sec
);
1032 if (unlikely(leap
)) {
1035 tk
->xtime_sec
+= leap
;
1039 tk_set_wall_to_mono(tk
,
1040 timespec_sub(tk
->wall_to_monotonic
, ts
));
1042 clock_was_set_delayed();
1048 * logarithmic_accumulation - shifted accumulation of cycles
1050 * This functions accumulates a shifted interval of cycles into
1051 * into a shifted interval nanoseconds. Allows for O(log) accumulation
1054 * Returns the unconsumed cycles.
1056 static cycle_t
logarithmic_accumulation(struct timekeeper
*tk
, cycle_t offset
,
1061 /* If the offset is smaller then a shifted interval, do nothing */
1062 if (offset
< tk
->cycle_interval
<<shift
)
1065 /* Accumulate one shifted interval */
1066 offset
-= tk
->cycle_interval
<< shift
;
1067 tk
->clock
->cycle_last
+= tk
->cycle_interval
<< shift
;
1069 tk
->xtime_nsec
+= tk
->xtime_interval
<< shift
;
1070 accumulate_nsecs_to_secs(tk
);
1072 /* Accumulate raw time */
1073 raw_nsecs
= tk
->raw_interval
<< shift
;
1074 raw_nsecs
+= tk
->raw_time
.tv_nsec
;
1075 if (raw_nsecs
>= NSEC_PER_SEC
) {
1076 u64 raw_secs
= raw_nsecs
;
1077 raw_nsecs
= do_div(raw_secs
, NSEC_PER_SEC
);
1078 tk
->raw_time
.tv_sec
+= raw_secs
;
1080 tk
->raw_time
.tv_nsec
= raw_nsecs
;
1082 /* Accumulate error between NTP and clock interval */
1083 tk
->ntp_error
+= ntp_tick_length() << shift
;
1084 tk
->ntp_error
-= (tk
->xtime_interval
+ tk
->xtime_remainder
) <<
1085 (tk
->ntp_error_shift
+ shift
);
1091 * update_wall_time - Uses the current clocksource to increment the wall time
1094 static void update_wall_time(void)
1096 struct clocksource
*clock
;
1098 int shift
= 0, maxshift
;
1099 unsigned long flags
;
1102 write_seqlock_irqsave(&timekeeper
.lock
, flags
);
1104 /* Make sure we're fully resumed: */
1105 if (unlikely(timekeeping_suspended
))
1108 clock
= timekeeper
.clock
;
1110 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1111 offset
= timekeeper
.cycle_interval
;
1113 offset
= (clock
->read(clock
) - clock
->cycle_last
) & clock
->mask
;
1117 * With NO_HZ we may have to accumulate many cycle_intervals
1118 * (think "ticks") worth of time at once. To do this efficiently,
1119 * we calculate the largest doubling multiple of cycle_intervals
1120 * that is smaller than the offset. We then accumulate that
1121 * chunk in one go, and then try to consume the next smaller
1124 shift
= ilog2(offset
) - ilog2(timekeeper
.cycle_interval
);
1125 shift
= max(0, shift
);
1126 /* Bound shift to one less than what overflows tick_length */
1127 maxshift
= (64 - (ilog2(ntp_tick_length())+1)) - 1;
1128 shift
= min(shift
, maxshift
);
1129 while (offset
>= timekeeper
.cycle_interval
) {
1130 offset
= logarithmic_accumulation(&timekeeper
, offset
, shift
);
1131 if(offset
< timekeeper
.cycle_interval
<<shift
)
1135 /* correct the clock when NTP error is too big */
1136 timekeeping_adjust(&timekeeper
, offset
);
1140 * Store only full nanoseconds into xtime_nsec after rounding
1141 * it up and add the remainder to the error difference.
1142 * XXX - This is necessary to avoid small 1ns inconsistnecies caused
1143 * by truncating the remainder in vsyscalls. However, it causes
1144 * additional work to be done in timekeeping_adjust(). Once
1145 * the vsyscall implementations are converted to use xtime_nsec
1146 * (shifted nanoseconds), this can be killed.
1148 remainder
= timekeeper
.xtime_nsec
& ((1 << timekeeper
.shift
) - 1);
1149 timekeeper
.xtime_nsec
-= remainder
;
1150 timekeeper
.xtime_nsec
+= 1 << timekeeper
.shift
;
1151 timekeeper
.ntp_error
+= remainder
<< timekeeper
.ntp_error_shift
;
1154 * Finally, make sure that after the rounding
1155 * xtime_nsec isn't larger than NSEC_PER_SEC
1157 accumulate_nsecs_to_secs(&timekeeper
);
1159 timekeeping_update(&timekeeper
, false);
1162 write_sequnlock_irqrestore(&timekeeper
.lock
, flags
);
1167 * getboottime - Return the real time of system boot.
1168 * @ts: pointer to the timespec to be set
1170 * Returns the wall-time of boot in a timespec.
1172 * This is based on the wall_to_monotonic offset and the total suspend
1173 * time. Calls to settimeofday will affect the value returned (which
1174 * basically means that however wrong your real time clock is at boot time,
1175 * you get the right time here).
1177 void getboottime(struct timespec
*ts
)
1179 struct timespec boottime
= {
1180 .tv_sec
= timekeeper
.wall_to_monotonic
.tv_sec
+
1181 timekeeper
.total_sleep_time
.tv_sec
,
1182 .tv_nsec
= timekeeper
.wall_to_monotonic
.tv_nsec
+
1183 timekeeper
.total_sleep_time
.tv_nsec
1186 set_normalized_timespec(ts
, -boottime
.tv_sec
, -boottime
.tv_nsec
);
1188 EXPORT_SYMBOL_GPL(getboottime
);
1191 * get_monotonic_boottime - Returns monotonic time since boot
1192 * @ts: pointer to the timespec to be set
1194 * Returns the monotonic time since boot in a timespec.
1196 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1197 * includes the time spent in suspend.
1199 void get_monotonic_boottime(struct timespec
*ts
)
1201 struct timespec tomono
, sleep
;
1204 WARN_ON(timekeeping_suspended
);
1207 seq
= read_seqbegin(&timekeeper
.lock
);
1208 ts
->tv_sec
= timekeeper
.xtime_sec
;
1209 ts
->tv_nsec
= timekeeping_get_ns(&timekeeper
);
1210 tomono
= timekeeper
.wall_to_monotonic
;
1211 sleep
= timekeeper
.total_sleep_time
;
1213 } while (read_seqretry(&timekeeper
.lock
, seq
));
1215 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
+ sleep
.tv_sec
,
1216 ts
->tv_nsec
+ tomono
.tv_nsec
+ sleep
.tv_nsec
);
1218 EXPORT_SYMBOL_GPL(get_monotonic_boottime
);
1221 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1223 * Returns the monotonic time since boot in a ktime
1225 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1226 * includes the time spent in suspend.
1228 ktime_t
ktime_get_boottime(void)
1232 get_monotonic_boottime(&ts
);
1233 return timespec_to_ktime(ts
);
1235 EXPORT_SYMBOL_GPL(ktime_get_boottime
);
1238 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1239 * @ts: pointer to the timespec to be converted
1241 void monotonic_to_bootbased(struct timespec
*ts
)
1243 *ts
= timespec_add(*ts
, timekeeper
.total_sleep_time
);
1245 EXPORT_SYMBOL_GPL(monotonic_to_bootbased
);
1247 unsigned long get_seconds(void)
1249 return timekeeper
.xtime_sec
;
1251 EXPORT_SYMBOL(get_seconds
);
1253 struct timespec
__current_kernel_time(void)
1255 return tk_xtime(&timekeeper
);
1258 struct timespec
current_kernel_time(void)
1260 struct timespec now
;
1264 seq
= read_seqbegin(&timekeeper
.lock
);
1266 now
= tk_xtime(&timekeeper
);
1267 } while (read_seqretry(&timekeeper
.lock
, seq
));
1271 EXPORT_SYMBOL(current_kernel_time
);
1273 struct timespec
get_monotonic_coarse(void)
1275 struct timespec now
, mono
;
1279 seq
= read_seqbegin(&timekeeper
.lock
);
1281 now
= tk_xtime(&timekeeper
);
1282 mono
= timekeeper
.wall_to_monotonic
;
1283 } while (read_seqretry(&timekeeper
.lock
, seq
));
1285 set_normalized_timespec(&now
, now
.tv_sec
+ mono
.tv_sec
,
1286 now
.tv_nsec
+ mono
.tv_nsec
);
1291 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1292 * without sampling the sequence number in xtime_lock.
1293 * jiffies is defined in the linker script...
1295 void do_timer(unsigned long ticks
)
1297 jiffies_64
+= ticks
;
1299 calc_global_load(ticks
);
1303 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1304 * and sleep offsets.
1305 * @xtim: pointer to timespec to be set with xtime
1306 * @wtom: pointer to timespec to be set with wall_to_monotonic
1307 * @sleep: pointer to timespec to be set with time in suspend
1309 void get_xtime_and_monotonic_and_sleep_offset(struct timespec
*xtim
,
1310 struct timespec
*wtom
, struct timespec
*sleep
)
1315 seq
= read_seqbegin(&timekeeper
.lock
);
1316 *xtim
= tk_xtime(&timekeeper
);
1317 *wtom
= timekeeper
.wall_to_monotonic
;
1318 *sleep
= timekeeper
.total_sleep_time
;
1319 } while (read_seqretry(&timekeeper
.lock
, seq
));
1322 #ifdef CONFIG_HIGH_RES_TIMERS
1324 * ktime_get_update_offsets - hrtimer helper
1325 * @offs_real: pointer to storage for monotonic -> realtime offset
1326 * @offs_boot: pointer to storage for monotonic -> boottime offset
1328 * Returns current monotonic time and updates the offsets
1329 * Called from hrtimer_interupt() or retrigger_next_event()
1331 ktime_t
ktime_get_update_offsets(ktime_t
*offs_real
, ktime_t
*offs_boot
)
1338 seq
= read_seqbegin(&timekeeper
.lock
);
1340 secs
= timekeeper
.xtime_sec
;
1341 nsecs
= timekeeping_get_ns(&timekeeper
);
1343 *offs_real
= timekeeper
.offs_real
;
1344 *offs_boot
= timekeeper
.offs_boot
;
1345 } while (read_seqretry(&timekeeper
.lock
, seq
));
1347 now
= ktime_add_ns(ktime_set(secs
, 0), nsecs
);
1348 now
= ktime_sub(now
, *offs_real
);
1354 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1356 ktime_t
ktime_get_monotonic_offset(void)
1359 struct timespec wtom
;
1362 seq
= read_seqbegin(&timekeeper
.lock
);
1363 wtom
= timekeeper
.wall_to_monotonic
;
1364 } while (read_seqretry(&timekeeper
.lock
, seq
));
1366 return timespec_to_ktime(wtom
);
1368 EXPORT_SYMBOL_GPL(ktime_get_monotonic_offset
);
1371 * xtime_update() - advances the timekeeping infrastructure
1372 * @ticks: number of ticks, that have elapsed since the last call.
1374 * Must be called with interrupts disabled.
1376 void xtime_update(unsigned long ticks
)
1378 write_seqlock(&xtime_lock
);
1380 write_sequnlock(&xtime_lock
);