2 * linux/kernel/time/clocksource.c
4 * This file contains the functions which manage clocksource drivers.
6 * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 * o Allow clocksource drivers to be unregistered
26 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
28 #include <linux/device.h>
29 #include <linux/clocksource.h>
30 #include <linux/init.h>
31 #include <linux/module.h>
32 #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
33 #include <linux/tick.h>
34 #include <linux/kthread.h>
36 #include "tick-internal.h"
37 #include "timekeeping_internal.h"
40 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
41 * @mult: pointer to mult variable
42 * @shift: pointer to shift variable
43 * @from: frequency to convert from
44 * @to: frequency to convert to
45 * @maxsec: guaranteed runtime conversion range in seconds
47 * The function evaluates the shift/mult pair for the scaled math
48 * operations of clocksources and clockevents.
50 * @to and @from are frequency values in HZ. For clock sources @to is
51 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
52 * event @to is the counter frequency and @from is NSEC_PER_SEC.
54 * The @maxsec conversion range argument controls the time frame in
55 * seconds which must be covered by the runtime conversion with the
56 * calculated mult and shift factors. This guarantees that no 64bit
57 * overflow happens when the input value of the conversion is
58 * multiplied with the calculated mult factor. Larger ranges may
59 * reduce the conversion accuracy by chosing smaller mult and shift
63 clocks_calc_mult_shift(u32
*mult
, u32
*shift
, u32 from
, u32 to
, u32 maxsec
)
69 * Calculate the shift factor which is limiting the conversion
72 tmp
= ((u64
)maxsec
* from
) >> 32;
79 * Find the conversion shift/mult pair which has the best
80 * accuracy and fits the maxsec conversion range:
82 for (sft
= 32; sft
> 0; sft
--) {
83 tmp
= (u64
) to
<< sft
;
86 if ((tmp
>> sftacc
) == 0)
92 EXPORT_SYMBOL_GPL(clocks_calc_mult_shift
);
94 /*[Clocksource internal variables]---------
96 * currently selected clocksource.
98 * linked list with the registered clocksources
100 * protects manipulations to curr_clocksource and the clocksource_list
102 * Name of the user-specified clocksource.
104 static struct clocksource
*curr_clocksource
;
105 static LIST_HEAD(clocksource_list
);
106 static DEFINE_MUTEX(clocksource_mutex
);
107 static char override_name
[CS_NAME_LEN
];
108 static int finished_booting
;
110 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
111 static void clocksource_watchdog_work(struct work_struct
*work
);
112 static void clocksource_select(void);
114 static LIST_HEAD(watchdog_list
);
115 static struct clocksource
*watchdog
;
116 static struct timer_list watchdog_timer
;
117 static DECLARE_WORK(watchdog_work
, clocksource_watchdog_work
);
118 static DEFINE_SPINLOCK(watchdog_lock
);
119 static int watchdog_running
;
120 static atomic_t watchdog_reset_pending
;
122 static int clocksource_watchdog_kthread(void *data
);
123 static void __clocksource_change_rating(struct clocksource
*cs
, int rating
);
126 * Interval: 0.5sec Threshold: 0.0625s
128 #define WATCHDOG_INTERVAL (HZ >> 1)
129 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
131 static void clocksource_watchdog_work(struct work_struct
*work
)
134 * If kthread_run fails the next watchdog scan over the
135 * watchdog_list will find the unstable clock again.
137 kthread_run(clocksource_watchdog_kthread
, NULL
, "kwatchdog");
140 static void __clocksource_unstable(struct clocksource
*cs
)
142 cs
->flags
&= ~(CLOCK_SOURCE_VALID_FOR_HRES
| CLOCK_SOURCE_WATCHDOG
);
143 cs
->flags
|= CLOCK_SOURCE_UNSTABLE
;
145 if (cs
->mark_unstable
)
146 cs
->mark_unstable(cs
);
148 if (finished_booting
)
149 schedule_work(&watchdog_work
);
153 * clocksource_mark_unstable - mark clocksource unstable via watchdog
154 * @cs: clocksource to be marked unstable
156 * This function is called instead of clocksource_change_rating from
157 * cpu hotplug code to avoid a deadlock between the clocksource mutex
158 * and the cpu hotplug mutex. It defers the update of the clocksource
159 * to the watchdog thread.
161 void clocksource_mark_unstable(struct clocksource
*cs
)
165 spin_lock_irqsave(&watchdog_lock
, flags
);
166 if (!(cs
->flags
& CLOCK_SOURCE_UNSTABLE
)) {
167 if (list_empty(&cs
->wd_list
))
168 list_add(&cs
->wd_list
, &watchdog_list
);
169 __clocksource_unstable(cs
);
171 spin_unlock_irqrestore(&watchdog_lock
, flags
);
174 static void clocksource_watchdog(unsigned long data
)
176 struct clocksource
*cs
;
177 u64 csnow
, wdnow
, cslast
, wdlast
, delta
;
178 int64_t wd_nsec
, cs_nsec
;
179 int next_cpu
, reset_pending
;
181 spin_lock(&watchdog_lock
);
182 if (!watchdog_running
)
185 reset_pending
= atomic_read(&watchdog_reset_pending
);
187 list_for_each_entry(cs
, &watchdog_list
, wd_list
) {
189 /* Clocksource already marked unstable? */
190 if (cs
->flags
& CLOCK_SOURCE_UNSTABLE
) {
191 if (finished_booting
)
192 schedule_work(&watchdog_work
);
197 csnow
= cs
->read(cs
);
198 wdnow
= watchdog
->read(watchdog
);
201 /* Clocksource initialized ? */
202 if (!(cs
->flags
& CLOCK_SOURCE_WATCHDOG
) ||
203 atomic_read(&watchdog_reset_pending
)) {
204 cs
->flags
|= CLOCK_SOURCE_WATCHDOG
;
210 delta
= clocksource_delta(wdnow
, cs
->wd_last
, watchdog
->mask
);
211 wd_nsec
= clocksource_cyc2ns(delta
, watchdog
->mult
,
214 delta
= clocksource_delta(csnow
, cs
->cs_last
, cs
->mask
);
215 cs_nsec
= clocksource_cyc2ns(delta
, cs
->mult
, cs
->shift
);
216 wdlast
= cs
->wd_last
; /* save these in case we print them */
217 cslast
= cs
->cs_last
;
221 if (atomic_read(&watchdog_reset_pending
))
224 /* Check the deviation from the watchdog clocksource. */
225 if (abs(cs_nsec
- wd_nsec
) > WATCHDOG_THRESHOLD
) {
226 pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
227 smp_processor_id(), cs
->name
);
228 pr_warn(" '%s' wd_now: %llx wd_last: %llx mask: %llx\n",
229 watchdog
->name
, wdnow
, wdlast
, watchdog
->mask
);
230 pr_warn(" '%s' cs_now: %llx cs_last: %llx mask: %llx\n",
231 cs
->name
, csnow
, cslast
, cs
->mask
);
232 __clocksource_unstable(cs
);
236 if (cs
== curr_clocksource
&& cs
->tick_stable
)
239 if (!(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
) &&
240 (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) &&
241 (watchdog
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)) {
242 /* Mark it valid for high-res. */
243 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
246 * clocksource_done_booting() will sort it if
247 * finished_booting is not set yet.
249 if (!finished_booting
)
253 * If this is not the current clocksource let
254 * the watchdog thread reselect it. Due to the
255 * change to high res this clocksource might
256 * be preferred now. If it is the current
257 * clocksource let the tick code know about
260 if (cs
!= curr_clocksource
) {
261 cs
->flags
|= CLOCK_SOURCE_RESELECT
;
262 schedule_work(&watchdog_work
);
270 * We only clear the watchdog_reset_pending, when we did a
271 * full cycle through all clocksources.
274 atomic_dec(&watchdog_reset_pending
);
277 * Cycle through CPUs to check if the CPUs stay synchronized
280 next_cpu
= cpumask_next(raw_smp_processor_id(), cpu_online_mask
);
281 if (next_cpu
>= nr_cpu_ids
)
282 next_cpu
= cpumask_first(cpu_online_mask
);
283 watchdog_timer
.expires
+= WATCHDOG_INTERVAL
;
284 add_timer_on(&watchdog_timer
, next_cpu
);
286 spin_unlock(&watchdog_lock
);
289 static inline void clocksource_start_watchdog(void)
291 if (watchdog_running
|| !watchdog
|| list_empty(&watchdog_list
))
293 init_timer(&watchdog_timer
);
294 watchdog_timer
.function
= clocksource_watchdog
;
295 watchdog_timer
.expires
= jiffies
+ WATCHDOG_INTERVAL
;
296 add_timer_on(&watchdog_timer
, cpumask_first(cpu_online_mask
));
297 watchdog_running
= 1;
300 static inline void clocksource_stop_watchdog(void)
302 if (!watchdog_running
|| (watchdog
&& !list_empty(&watchdog_list
)))
304 del_timer(&watchdog_timer
);
305 watchdog_running
= 0;
308 static inline void clocksource_reset_watchdog(void)
310 struct clocksource
*cs
;
312 list_for_each_entry(cs
, &watchdog_list
, wd_list
)
313 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
316 static void clocksource_resume_watchdog(void)
318 atomic_inc(&watchdog_reset_pending
);
321 static void clocksource_enqueue_watchdog(struct clocksource
*cs
)
325 spin_lock_irqsave(&watchdog_lock
, flags
);
326 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
327 /* cs is a clocksource to be watched. */
328 list_add(&cs
->wd_list
, &watchdog_list
);
329 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
331 /* cs is a watchdog. */
332 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
333 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
335 spin_unlock_irqrestore(&watchdog_lock
, flags
);
338 static void clocksource_select_watchdog(bool fallback
)
340 struct clocksource
*cs
, *old_wd
;
343 spin_lock_irqsave(&watchdog_lock
, flags
);
344 /* save current watchdog */
349 list_for_each_entry(cs
, &clocksource_list
, list
) {
350 /* cs is a clocksource to be watched. */
351 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
)
354 /* Skip current if we were requested for a fallback. */
355 if (fallback
&& cs
== old_wd
)
358 /* Pick the best watchdog. */
359 if (!watchdog
|| cs
->rating
> watchdog
->rating
)
362 /* If we failed to find a fallback restore the old one. */
366 /* If we changed the watchdog we need to reset cycles. */
367 if (watchdog
!= old_wd
)
368 clocksource_reset_watchdog();
370 /* Check if the watchdog timer needs to be started. */
371 clocksource_start_watchdog();
372 spin_unlock_irqrestore(&watchdog_lock
, flags
);
375 static void clocksource_dequeue_watchdog(struct clocksource
*cs
)
379 spin_lock_irqsave(&watchdog_lock
, flags
);
380 if (cs
!= watchdog
) {
381 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
382 /* cs is a watched clocksource. */
383 list_del_init(&cs
->wd_list
);
384 /* Check if the watchdog timer needs to be stopped. */
385 clocksource_stop_watchdog();
388 spin_unlock_irqrestore(&watchdog_lock
, flags
);
391 static int __clocksource_watchdog_kthread(void)
393 struct clocksource
*cs
, *tmp
;
398 spin_lock_irqsave(&watchdog_lock
, flags
);
399 list_for_each_entry_safe(cs
, tmp
, &watchdog_list
, wd_list
) {
400 if (cs
->flags
& CLOCK_SOURCE_UNSTABLE
) {
401 list_del_init(&cs
->wd_list
);
402 list_add(&cs
->wd_list
, &unstable
);
405 if (cs
->flags
& CLOCK_SOURCE_RESELECT
) {
406 cs
->flags
&= ~CLOCK_SOURCE_RESELECT
;
410 /* Check if the watchdog timer needs to be stopped. */
411 clocksource_stop_watchdog();
412 spin_unlock_irqrestore(&watchdog_lock
, flags
);
414 /* Needs to be done outside of watchdog lock */
415 list_for_each_entry_safe(cs
, tmp
, &unstable
, wd_list
) {
416 list_del_init(&cs
->wd_list
);
417 __clocksource_change_rating(cs
, 0);
422 static int clocksource_watchdog_kthread(void *data
)
424 mutex_lock(&clocksource_mutex
);
425 if (__clocksource_watchdog_kthread())
426 clocksource_select();
427 mutex_unlock(&clocksource_mutex
);
431 static bool clocksource_is_watchdog(struct clocksource
*cs
)
433 return cs
== watchdog
;
436 #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
438 static void clocksource_enqueue_watchdog(struct clocksource
*cs
)
440 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
441 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
444 static void clocksource_select_watchdog(bool fallback
) { }
445 static inline void clocksource_dequeue_watchdog(struct clocksource
*cs
) { }
446 static inline void clocksource_resume_watchdog(void) { }
447 static inline int __clocksource_watchdog_kthread(void) { return 0; }
448 static bool clocksource_is_watchdog(struct clocksource
*cs
) { return false; }
449 void clocksource_mark_unstable(struct clocksource
*cs
) { }
451 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
454 * clocksource_suspend - suspend the clocksource(s)
456 void clocksource_suspend(void)
458 struct clocksource
*cs
;
460 list_for_each_entry_reverse(cs
, &clocksource_list
, list
)
466 * clocksource_resume - resume the clocksource(s)
468 void clocksource_resume(void)
470 struct clocksource
*cs
;
472 list_for_each_entry(cs
, &clocksource_list
, list
)
476 clocksource_resume_watchdog();
480 * clocksource_touch_watchdog - Update watchdog
482 * Update the watchdog after exception contexts such as kgdb so as not
483 * to incorrectly trip the watchdog. This might fail when the kernel
484 * was stopped in code which holds watchdog_lock.
486 void clocksource_touch_watchdog(void)
488 clocksource_resume_watchdog();
492 * clocksource_max_adjustment- Returns max adjustment amount
493 * @cs: Pointer to clocksource
496 static u32
clocksource_max_adjustment(struct clocksource
*cs
)
500 * We won't try to correct for more than 11% adjustments (110,000 ppm),
502 ret
= (u64
)cs
->mult
* 11;
508 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
509 * @mult: cycle to nanosecond multiplier
510 * @shift: cycle to nanosecond divisor (power of two)
511 * @maxadj: maximum adjustment value to mult (~11%)
512 * @mask: bitmask for two's complement subtraction of non 64 bit counters
513 * @max_cyc: maximum cycle value before potential overflow (does not include
516 * NOTE: This function includes a safety margin of 50%, in other words, we
517 * return half the number of nanoseconds the hardware counter can technically
518 * cover. This is done so that we can potentially detect problems caused by
519 * delayed timers or bad hardware, which might result in time intervals that
520 * are larger than what the math used can handle without overflows.
522 u64
clocks_calc_max_nsecs(u32 mult
, u32 shift
, u32 maxadj
, u64 mask
, u64
*max_cyc
)
524 u64 max_nsecs
, max_cycles
;
527 * Calculate the maximum number of cycles that we can pass to the
528 * cyc2ns() function without overflowing a 64-bit result.
530 max_cycles
= ULLONG_MAX
;
531 do_div(max_cycles
, mult
+maxadj
);
534 * The actual maximum number of cycles we can defer the clocksource is
535 * determined by the minimum of max_cycles and mask.
536 * Note: Here we subtract the maxadj to make sure we don't sleep for
537 * too long if there's a large negative adjustment.
539 max_cycles
= min(max_cycles
, mask
);
540 max_nsecs
= clocksource_cyc2ns(max_cycles
, mult
- maxadj
, shift
);
542 /* return the max_cycles value as well if requested */
544 *max_cyc
= max_cycles
;
546 /* Return 50% of the actual maximum, so we can detect bad values */
553 * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
554 * @cs: Pointer to clocksource to be updated
557 static inline void clocksource_update_max_deferment(struct clocksource
*cs
)
559 cs
->max_idle_ns
= clocks_calc_max_nsecs(cs
->mult
, cs
->shift
,
560 cs
->maxadj
, cs
->mask
,
564 #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
566 static struct clocksource
*clocksource_find_best(bool oneshot
, bool skipcur
)
568 struct clocksource
*cs
;
570 if (!finished_booting
|| list_empty(&clocksource_list
))
574 * We pick the clocksource with the highest rating. If oneshot
575 * mode is active, we pick the highres valid clocksource with
578 list_for_each_entry(cs
, &clocksource_list
, list
) {
579 if (skipcur
&& cs
== curr_clocksource
)
581 if (oneshot
&& !(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
))
588 static void __clocksource_select(bool skipcur
)
590 bool oneshot
= tick_oneshot_mode_active();
591 struct clocksource
*best
, *cs
;
593 /* Find the best suitable clocksource */
594 best
= clocksource_find_best(oneshot
, skipcur
);
598 /* Check for the override clocksource. */
599 list_for_each_entry(cs
, &clocksource_list
, list
) {
600 if (skipcur
&& cs
== curr_clocksource
)
602 if (strcmp(cs
->name
, override_name
) != 0)
605 * Check to make sure we don't switch to a non-highres
606 * capable clocksource if the tick code is in oneshot
607 * mode (highres or nohz)
609 if (!(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
) && oneshot
) {
610 /* Override clocksource cannot be used. */
611 if (cs
->flags
& CLOCK_SOURCE_UNSTABLE
) {
612 pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
614 override_name
[0] = 0;
617 * The override cannot be currently verified.
618 * Deferring to let the watchdog check.
620 pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
624 /* Override clocksource can be used. */
629 if (curr_clocksource
!= best
&& !timekeeping_notify(best
)) {
630 pr_info("Switched to clocksource %s\n", best
->name
);
631 curr_clocksource
= best
;
636 * clocksource_select - Select the best clocksource available
638 * Private function. Must hold clocksource_mutex when called.
640 * Select the clocksource with the best rating, or the clocksource,
641 * which is selected by userspace override.
643 static void clocksource_select(void)
645 __clocksource_select(false);
648 static void clocksource_select_fallback(void)
650 __clocksource_select(true);
653 #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
654 static inline void clocksource_select(void) { }
655 static inline void clocksource_select_fallback(void) { }
660 * clocksource_done_booting - Called near the end of core bootup
662 * Hack to avoid lots of clocksource churn at boot time.
663 * We use fs_initcall because we want this to start before
664 * device_initcall but after subsys_initcall.
666 static int __init
clocksource_done_booting(void)
668 mutex_lock(&clocksource_mutex
);
669 curr_clocksource
= clocksource_default_clock();
670 finished_booting
= 1;
672 * Run the watchdog first to eliminate unstable clock sources
674 __clocksource_watchdog_kthread();
675 clocksource_select();
676 mutex_unlock(&clocksource_mutex
);
679 fs_initcall(clocksource_done_booting
);
682 * Enqueue the clocksource sorted by rating
684 static void clocksource_enqueue(struct clocksource
*cs
)
686 struct list_head
*entry
= &clocksource_list
;
687 struct clocksource
*tmp
;
689 list_for_each_entry(tmp
, &clocksource_list
, list
) {
690 /* Keep track of the place, where to insert */
691 if (tmp
->rating
< cs
->rating
)
695 list_add(&cs
->list
, entry
);
699 * __clocksource_update_freq_scale - Used update clocksource with new freq
700 * @cs: clocksource to be registered
701 * @scale: Scale factor multiplied against freq to get clocksource hz
702 * @freq: clocksource frequency (cycles per second) divided by scale
704 * This should only be called from the clocksource->enable() method.
706 * This *SHOULD NOT* be called directly! Please use the
707 * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
710 void __clocksource_update_freq_scale(struct clocksource
*cs
, u32 scale
, u32 freq
)
715 * Default clocksources are *special* and self-define their mult/shift.
716 * But, you're not special, so you should specify a freq value.
720 * Calc the maximum number of seconds which we can run before
721 * wrapping around. For clocksources which have a mask > 32-bit
722 * we need to limit the max sleep time to have a good
723 * conversion precision. 10 minutes is still a reasonable
724 * amount. That results in a shift value of 24 for a
725 * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
726 * ~ 0.06ppm granularity for NTP.
733 else if (sec
> 600 && cs
->mask
> UINT_MAX
)
736 clocks_calc_mult_shift(&cs
->mult
, &cs
->shift
, freq
,
737 NSEC_PER_SEC
/ scale
, sec
* scale
);
740 * Ensure clocksources that have large 'mult' values don't overflow
743 cs
->maxadj
= clocksource_max_adjustment(cs
);
744 while (freq
&& ((cs
->mult
+ cs
->maxadj
< cs
->mult
)
745 || (cs
->mult
- cs
->maxadj
> cs
->mult
))) {
748 cs
->maxadj
= clocksource_max_adjustment(cs
);
752 * Only warn for *special* clocksources that self-define
753 * their mult/shift values and don't specify a freq.
755 WARN_ONCE(cs
->mult
+ cs
->maxadj
< cs
->mult
,
756 "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
759 clocksource_update_max_deferment(cs
);
761 pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
762 cs
->name
, cs
->mask
, cs
->max_cycles
, cs
->max_idle_ns
);
764 EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale
);
767 * __clocksource_register_scale - Used to install new clocksources
768 * @cs: clocksource to be registered
769 * @scale: Scale factor multiplied against freq to get clocksource hz
770 * @freq: clocksource frequency (cycles per second) divided by scale
772 * Returns -EBUSY if registration fails, zero otherwise.
774 * This *SHOULD NOT* be called directly! Please use the
775 * clocksource_register_hz() or clocksource_register_khz helper functions.
777 int __clocksource_register_scale(struct clocksource
*cs
, u32 scale
, u32 freq
)
780 /* Initialize mult/shift and max_idle_ns */
781 __clocksource_update_freq_scale(cs
, scale
, freq
);
783 /* Add clocksource to the clocksource list */
784 mutex_lock(&clocksource_mutex
);
785 clocksource_enqueue(cs
);
786 clocksource_enqueue_watchdog(cs
);
787 clocksource_select();
788 clocksource_select_watchdog(false);
789 mutex_unlock(&clocksource_mutex
);
792 EXPORT_SYMBOL_GPL(__clocksource_register_scale
);
794 static void __clocksource_change_rating(struct clocksource
*cs
, int rating
)
798 clocksource_enqueue(cs
);
802 * clocksource_change_rating - Change the rating of a registered clocksource
803 * @cs: clocksource to be changed
804 * @rating: new rating
806 void clocksource_change_rating(struct clocksource
*cs
, int rating
)
808 mutex_lock(&clocksource_mutex
);
809 __clocksource_change_rating(cs
, rating
);
810 clocksource_select();
811 clocksource_select_watchdog(false);
812 mutex_unlock(&clocksource_mutex
);
814 EXPORT_SYMBOL(clocksource_change_rating
);
817 * Unbind clocksource @cs. Called with clocksource_mutex held
819 static int clocksource_unbind(struct clocksource
*cs
)
821 if (clocksource_is_watchdog(cs
)) {
822 /* Select and try to install a replacement watchdog. */
823 clocksource_select_watchdog(true);
824 if (clocksource_is_watchdog(cs
))
828 if (cs
== curr_clocksource
) {
829 /* Select and try to install a replacement clock source */
830 clocksource_select_fallback();
831 if (curr_clocksource
== cs
)
834 clocksource_dequeue_watchdog(cs
);
835 list_del_init(&cs
->list
);
840 * clocksource_unregister - remove a registered clocksource
841 * @cs: clocksource to be unregistered
843 int clocksource_unregister(struct clocksource
*cs
)
847 mutex_lock(&clocksource_mutex
);
848 if (!list_empty(&cs
->list
))
849 ret
= clocksource_unbind(cs
);
850 mutex_unlock(&clocksource_mutex
);
853 EXPORT_SYMBOL(clocksource_unregister
);
857 * sysfs_show_current_clocksources - sysfs interface for current clocksource
860 * @buf: char buffer to be filled with clocksource list
862 * Provides sysfs interface for listing current clocksource.
865 sysfs_show_current_clocksources(struct device
*dev
,
866 struct device_attribute
*attr
, char *buf
)
870 mutex_lock(&clocksource_mutex
);
871 count
= snprintf(buf
, PAGE_SIZE
, "%s\n", curr_clocksource
->name
);
872 mutex_unlock(&clocksource_mutex
);
877 ssize_t
sysfs_get_uname(const char *buf
, char *dst
, size_t cnt
)
881 /* strings from sysfs write are not 0 terminated! */
882 if (!cnt
|| cnt
>= CS_NAME_LEN
)
886 if (buf
[cnt
-1] == '\n')
889 memcpy(dst
, buf
, cnt
);
895 * sysfs_override_clocksource - interface for manually overriding clocksource
898 * @buf: name of override clocksource
899 * @count: length of buffer
901 * Takes input from sysfs interface for manually overriding the default
902 * clocksource selection.
904 static ssize_t
sysfs_override_clocksource(struct device
*dev
,
905 struct device_attribute
*attr
,
906 const char *buf
, size_t count
)
910 mutex_lock(&clocksource_mutex
);
912 ret
= sysfs_get_uname(buf
, override_name
, count
);
914 clocksource_select();
916 mutex_unlock(&clocksource_mutex
);
922 * sysfs_unbind_current_clocksource - interface for manually unbinding clocksource
926 * @count: length of buffer
928 * Takes input from sysfs interface for manually unbinding a clocksource.
930 static ssize_t
sysfs_unbind_clocksource(struct device
*dev
,
931 struct device_attribute
*attr
,
932 const char *buf
, size_t count
)
934 struct clocksource
*cs
;
935 char name
[CS_NAME_LEN
];
938 ret
= sysfs_get_uname(buf
, name
, count
);
943 mutex_lock(&clocksource_mutex
);
944 list_for_each_entry(cs
, &clocksource_list
, list
) {
945 if (strcmp(cs
->name
, name
))
947 ret
= clocksource_unbind(cs
);
950 mutex_unlock(&clocksource_mutex
);
952 return ret
? ret
: count
;
956 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
959 * @buf: char buffer to be filled with clocksource list
961 * Provides sysfs interface for listing registered clocksources
964 sysfs_show_available_clocksources(struct device
*dev
,
965 struct device_attribute
*attr
,
968 struct clocksource
*src
;
971 mutex_lock(&clocksource_mutex
);
972 list_for_each_entry(src
, &clocksource_list
, list
) {
974 * Don't show non-HRES clocksource if the tick code is
975 * in one shot mode (highres=on or nohz=on)
977 if (!tick_oneshot_mode_active() ||
978 (src
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
))
979 count
+= snprintf(buf
+ count
,
980 max((ssize_t
)PAGE_SIZE
- count
, (ssize_t
)0),
983 mutex_unlock(&clocksource_mutex
);
985 count
+= snprintf(buf
+ count
,
986 max((ssize_t
)PAGE_SIZE
- count
, (ssize_t
)0), "\n");
994 static DEVICE_ATTR(current_clocksource
, 0644, sysfs_show_current_clocksources
,
995 sysfs_override_clocksource
);
997 static DEVICE_ATTR(unbind_clocksource
, 0200, NULL
, sysfs_unbind_clocksource
);
999 static DEVICE_ATTR(available_clocksource
, 0444,
1000 sysfs_show_available_clocksources
, NULL
);
1002 static struct bus_type clocksource_subsys
= {
1003 .name
= "clocksource",
1004 .dev_name
= "clocksource",
1007 static struct device device_clocksource
= {
1009 .bus
= &clocksource_subsys
,
1012 static int __init
init_clocksource_sysfs(void)
1014 int error
= subsys_system_register(&clocksource_subsys
, NULL
);
1017 error
= device_register(&device_clocksource
);
1019 error
= device_create_file(
1020 &device_clocksource
,
1021 &dev_attr_current_clocksource
);
1023 error
= device_create_file(&device_clocksource
,
1024 &dev_attr_unbind_clocksource
);
1026 error
= device_create_file(
1027 &device_clocksource
,
1028 &dev_attr_available_clocksource
);
1032 device_initcall(init_clocksource_sysfs
);
1033 #endif /* CONFIG_SYSFS */
1036 * boot_override_clocksource - boot clock override
1037 * @str: override name
1039 * Takes a clocksource= boot argument and uses it
1040 * as the clocksource override name.
1042 static int __init
boot_override_clocksource(char* str
)
1044 mutex_lock(&clocksource_mutex
);
1046 strlcpy(override_name
, str
, sizeof(override_name
));
1047 mutex_unlock(&clocksource_mutex
);
1051 __setup("clocksource=", boot_override_clocksource
);
1054 * boot_override_clock - Compatibility layer for deprecated boot option
1055 * @str: override name
1057 * DEPRECATED! Takes a clock= boot argument and uses it
1058 * as the clocksource override name
1060 static int __init
boot_override_clock(char* str
)
1062 if (!strcmp(str
, "pmtmr")) {
1063 pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
1064 return boot_override_clocksource("acpi_pm");
1066 pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
1067 return boot_override_clocksource(str
);
1070 __setup("clock=", boot_override_clock
);