Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0+
2 : /*
3 : * This file contains the functions which manage clocksource drivers.
4 : *
5 : * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
6 : */
7 :
8 : #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 :
10 : #include <linux/device.h>
11 : #include <linux/clocksource.h>
12 : #include <linux/init.h>
13 : #include <linux/module.h>
14 : #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
15 : #include <linux/tick.h>
16 : #include <linux/kthread.h>
17 : #include <linux/prandom.h>
18 : #include <linux/cpu.h>
19 :
20 : #include "tick-internal.h"
21 : #include "timekeeping_internal.h"
22 :
23 : /**
24 : * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
25 : * @mult: pointer to mult variable
26 : * @shift: pointer to shift variable
27 : * @from: frequency to convert from
28 : * @to: frequency to convert to
29 : * @maxsec: guaranteed runtime conversion range in seconds
30 : *
31 : * The function evaluates the shift/mult pair for the scaled math
32 : * operations of clocksources and clockevents.
33 : *
34 : * @to and @from are frequency values in HZ. For clock sources @to is
35 : * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
36 : * event @to is the counter frequency and @from is NSEC_PER_SEC.
37 : *
38 : * The @maxsec conversion range argument controls the time frame in
39 : * seconds which must be covered by the runtime conversion with the
40 : * calculated mult and shift factors. This guarantees that no 64bit
41 : * overflow happens when the input value of the conversion is
42 : * multiplied with the calculated mult factor. Larger ranges may
43 : * reduce the conversion accuracy by choosing smaller mult and shift
44 : * factors.
45 : */
46 : void
47 0 : clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
48 : {
49 : u64 tmp;
50 1 : u32 sft, sftacc= 32;
51 :
52 : /*
53 : * Calculate the shift factor which is limiting the conversion
54 : * range:
55 : */
56 1 : tmp = ((u64)maxsec * from) >> 32;
57 1 : while (tmp) {
58 0 : tmp >>=1;
59 0 : sftacc--;
60 : }
61 :
62 : /*
63 : * Find the conversion shift/mult pair which has the best
64 : * accuracy and fits the maxsec conversion range:
65 : */
66 9 : for (sft = 32; sft > 0; sft--) {
67 10 : tmp = (u64) to << sft;
68 10 : tmp += from / 2;
69 10 : do_div(tmp, from);
70 10 : if ((tmp >> sftacc) == 0)
71 : break;
72 : }
73 1 : *mult = tmp;
74 1 : *shift = sft;
75 0 : }
76 : EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
77 :
78 : /*[Clocksource internal variables]---------
79 : * curr_clocksource:
80 : * currently selected clocksource.
81 : * suspend_clocksource:
82 : * used to calculate the suspend time.
83 : * clocksource_list:
84 : * linked list with the registered clocksources
85 : * clocksource_mutex:
86 : * protects manipulations to curr_clocksource and the clocksource_list
87 : * override_name:
88 : * Name of the user-specified clocksource.
89 : */
90 : static struct clocksource *curr_clocksource;
91 : static struct clocksource *suspend_clocksource;
92 : static LIST_HEAD(clocksource_list);
93 : static DEFINE_MUTEX(clocksource_mutex);
94 : static char override_name[CS_NAME_LEN];
95 : static int finished_booting;
96 : static u64 suspend_start;
97 :
98 : /*
99 : * Threshold: 0.0312s, when doubled: 0.0625s.
100 : * Also a default for cs->uncertainty_margin when registering clocks.
101 : */
102 : #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
103 :
104 : /*
105 : * Maximum permissible delay between two readouts of the watchdog
106 : * clocksource surrounding a read of the clocksource being validated.
107 : * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
108 : * a lower bound for cs->uncertainty_margin values when registering clocks.
109 : */
110 : #ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
111 : #define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
112 : #else
113 : #define MAX_SKEW_USEC 100
114 : #endif
115 :
116 : #define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
117 :
118 : #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
119 : static void clocksource_watchdog_work(struct work_struct *work);
120 : static void clocksource_select(void);
121 :
122 : static LIST_HEAD(watchdog_list);
123 : static struct clocksource *watchdog;
124 : static struct timer_list watchdog_timer;
125 : static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
126 : static DEFINE_SPINLOCK(watchdog_lock);
127 : static int watchdog_running;
128 : static atomic_t watchdog_reset_pending;
129 :
130 : static inline void clocksource_watchdog_lock(unsigned long *flags)
131 : {
132 : spin_lock_irqsave(&watchdog_lock, *flags);
133 : }
134 :
135 : static inline void clocksource_watchdog_unlock(unsigned long *flags)
136 : {
137 : spin_unlock_irqrestore(&watchdog_lock, *flags);
138 : }
139 :
140 : static int clocksource_watchdog_kthread(void *data);
141 : static void __clocksource_change_rating(struct clocksource *cs, int rating);
142 :
143 : /*
144 : * Interval: 0.5sec.
145 : */
146 : #define WATCHDOG_INTERVAL (HZ >> 1)
147 :
148 : static void clocksource_watchdog_work(struct work_struct *work)
149 : {
150 : /*
151 : * We cannot directly run clocksource_watchdog_kthread() here, because
152 : * clocksource_select() calls timekeeping_notify() which uses
153 : * stop_machine(). One cannot use stop_machine() from a workqueue() due
154 : * lock inversions wrt CPU hotplug.
155 : *
156 : * Also, we only ever run this work once or twice during the lifetime
157 : * of the kernel, so there is no point in creating a more permanent
158 : * kthread for this.
159 : *
160 : * If kthread_run fails the next watchdog scan over the
161 : * watchdog_list will find the unstable clock again.
162 : */
163 : kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
164 : }
165 :
166 : static void __clocksource_unstable(struct clocksource *cs)
167 : {
168 : cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
169 : cs->flags |= CLOCK_SOURCE_UNSTABLE;
170 :
171 : /*
172 : * If the clocksource is registered clocksource_watchdog_kthread() will
173 : * re-rate and re-select.
174 : */
175 : if (list_empty(&cs->list)) {
176 : cs->rating = 0;
177 : return;
178 : }
179 :
180 : if (cs->mark_unstable)
181 : cs->mark_unstable(cs);
182 :
183 : /* kick clocksource_watchdog_kthread() */
184 : if (finished_booting)
185 : schedule_work(&watchdog_work);
186 : }
187 :
188 : /**
189 : * clocksource_mark_unstable - mark clocksource unstable via watchdog
190 : * @cs: clocksource to be marked unstable
191 : *
192 : * This function is called by the x86 TSC code to mark clocksources as unstable;
193 : * it defers demotion and re-selection to a kthread.
194 : */
195 : void clocksource_mark_unstable(struct clocksource *cs)
196 : {
197 : unsigned long flags;
198 :
199 : spin_lock_irqsave(&watchdog_lock, flags);
200 : if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
201 : if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
202 : list_add(&cs->wd_list, &watchdog_list);
203 : __clocksource_unstable(cs);
204 : }
205 : spin_unlock_irqrestore(&watchdog_lock, flags);
206 : }
207 :
208 : ulong max_cswd_read_retries = 2;
209 : module_param(max_cswd_read_retries, ulong, 0644);
210 : EXPORT_SYMBOL_GPL(max_cswd_read_retries);
211 : static int verify_n_cpus = 8;
212 : module_param(verify_n_cpus, int, 0644);
213 :
214 : enum wd_read_status {
215 : WD_READ_SUCCESS,
216 : WD_READ_UNSTABLE,
217 : WD_READ_SKIP
218 : };
219 :
220 : static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
221 : {
222 : unsigned int nretries;
223 : u64 wd_end, wd_end2, wd_delta;
224 : int64_t wd_delay, wd_seq_delay;
225 :
226 : for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
227 : local_irq_disable();
228 : *wdnow = watchdog->read(watchdog);
229 : *csnow = cs->read(cs);
230 : wd_end = watchdog->read(watchdog);
231 : wd_end2 = watchdog->read(watchdog);
232 : local_irq_enable();
233 :
234 : wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
235 : wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
236 : watchdog->shift);
237 : if (wd_delay <= WATCHDOG_MAX_SKEW) {
238 : if (nretries > 1 || nretries >= max_cswd_read_retries) {
239 : pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
240 : smp_processor_id(), watchdog->name, nretries);
241 : }
242 : return WD_READ_SUCCESS;
243 : }
244 :
245 : /*
246 : * Now compute delay in consecutive watchdog read to see if
247 : * there is too much external interferences that cause
248 : * significant delay in reading both clocksource and watchdog.
249 : *
250 : * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
251 : * report system busy, reinit the watchdog and skip the current
252 : * watchdog test.
253 : */
254 : wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
255 : wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
256 : if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
257 : goto skip_test;
258 : }
259 :
260 : pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
261 : smp_processor_id(), watchdog->name, wd_delay, nretries);
262 : return WD_READ_UNSTABLE;
263 :
264 : skip_test:
265 : pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
266 : smp_processor_id(), watchdog->name, wd_seq_delay);
267 : pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
268 : cs->name, wd_delay);
269 : return WD_READ_SKIP;
270 : }
271 :
272 : static u64 csnow_mid;
273 : static cpumask_t cpus_ahead;
274 : static cpumask_t cpus_behind;
275 : static cpumask_t cpus_chosen;
276 :
277 : static void clocksource_verify_choose_cpus(void)
278 : {
279 : int cpu, i, n = verify_n_cpus;
280 :
281 : if (n < 0) {
282 : /* Check all of the CPUs. */
283 : cpumask_copy(&cpus_chosen, cpu_online_mask);
284 : cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
285 : return;
286 : }
287 :
288 : /* If no checking desired, or no other CPU to check, leave. */
289 : cpumask_clear(&cpus_chosen);
290 : if (n == 0 || num_online_cpus() <= 1)
291 : return;
292 :
293 : /* Make sure to select at least one CPU other than the current CPU. */
294 : cpu = cpumask_first(cpu_online_mask);
295 : if (cpu == smp_processor_id())
296 : cpu = cpumask_next(cpu, cpu_online_mask);
297 : if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
298 : return;
299 : cpumask_set_cpu(cpu, &cpus_chosen);
300 :
301 : /* Force a sane value for the boot parameter. */
302 : if (n > nr_cpu_ids)
303 : n = nr_cpu_ids;
304 :
305 : /*
306 : * Randomly select the specified number of CPUs. If the same
307 : * CPU is selected multiple times, that CPU is checked only once,
308 : * and no replacement CPU is selected. This gracefully handles
309 : * situations where verify_n_cpus is greater than the number of
310 : * CPUs that are currently online.
311 : */
312 : for (i = 1; i < n; i++) {
313 : cpu = prandom_u32() % nr_cpu_ids;
314 : cpu = cpumask_next(cpu - 1, cpu_online_mask);
315 : if (cpu >= nr_cpu_ids)
316 : cpu = cpumask_first(cpu_online_mask);
317 : if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
318 : cpumask_set_cpu(cpu, &cpus_chosen);
319 : }
320 :
321 : /* Don't verify ourselves. */
322 : cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
323 : }
324 :
325 : static void clocksource_verify_one_cpu(void *csin)
326 : {
327 : struct clocksource *cs = (struct clocksource *)csin;
328 :
329 : csnow_mid = cs->read(cs);
330 : }
331 :
332 : void clocksource_verify_percpu(struct clocksource *cs)
333 : {
334 : int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
335 : u64 csnow_begin, csnow_end;
336 : int cpu, testcpu;
337 : s64 delta;
338 :
339 : if (verify_n_cpus == 0)
340 : return;
341 : cpumask_clear(&cpus_ahead);
342 : cpumask_clear(&cpus_behind);
343 : cpus_read_lock();
344 : preempt_disable();
345 : clocksource_verify_choose_cpus();
346 : if (cpumask_weight(&cpus_chosen) == 0) {
347 : preempt_enable();
348 : cpus_read_unlock();
349 : pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
350 : return;
351 : }
352 : testcpu = smp_processor_id();
353 : pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
354 : for_each_cpu(cpu, &cpus_chosen) {
355 : if (cpu == testcpu)
356 : continue;
357 : csnow_begin = cs->read(cs);
358 : smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
359 : csnow_end = cs->read(cs);
360 : delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
361 : if (delta < 0)
362 : cpumask_set_cpu(cpu, &cpus_behind);
363 : delta = (csnow_end - csnow_mid) & cs->mask;
364 : if (delta < 0)
365 : cpumask_set_cpu(cpu, &cpus_ahead);
366 : delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
367 : cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
368 : if (cs_nsec > cs_nsec_max)
369 : cs_nsec_max = cs_nsec;
370 : if (cs_nsec < cs_nsec_min)
371 : cs_nsec_min = cs_nsec;
372 : }
373 : preempt_enable();
374 : cpus_read_unlock();
375 : if (!cpumask_empty(&cpus_ahead))
376 : pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
377 : cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
378 : if (!cpumask_empty(&cpus_behind))
379 : pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n",
380 : cpumask_pr_args(&cpus_behind), testcpu, cs->name);
381 : if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
382 : pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n",
383 : testcpu, cs_nsec_min, cs_nsec_max, cs->name);
384 : }
385 : EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
386 :
387 : static void clocksource_watchdog(struct timer_list *unused)
388 : {
389 : u64 csnow, wdnow, cslast, wdlast, delta;
390 : int next_cpu, reset_pending;
391 : int64_t wd_nsec, cs_nsec;
392 : struct clocksource *cs;
393 : enum wd_read_status read_ret;
394 : u32 md;
395 :
396 : spin_lock(&watchdog_lock);
397 : if (!watchdog_running)
398 : goto out;
399 :
400 : reset_pending = atomic_read(&watchdog_reset_pending);
401 :
402 : list_for_each_entry(cs, &watchdog_list, wd_list) {
403 :
404 : /* Clocksource already marked unstable? */
405 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
406 : if (finished_booting)
407 : schedule_work(&watchdog_work);
408 : continue;
409 : }
410 :
411 : read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
412 :
413 : if (read_ret != WD_READ_SUCCESS) {
414 : if (read_ret == WD_READ_UNSTABLE)
415 : /* Clock readout unreliable, so give it up. */
416 : __clocksource_unstable(cs);
417 : continue;
418 : }
419 :
420 : /* Clocksource initialized ? */
421 : if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
422 : atomic_read(&watchdog_reset_pending)) {
423 : cs->flags |= CLOCK_SOURCE_WATCHDOG;
424 : cs->wd_last = wdnow;
425 : cs->cs_last = csnow;
426 : continue;
427 : }
428 :
429 : delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
430 : wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
431 : watchdog->shift);
432 :
433 : delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
434 : cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
435 : wdlast = cs->wd_last; /* save these in case we print them */
436 : cslast = cs->cs_last;
437 : cs->cs_last = csnow;
438 : cs->wd_last = wdnow;
439 :
440 : if (atomic_read(&watchdog_reset_pending))
441 : continue;
442 :
443 : /* Check the deviation from the watchdog clocksource. */
444 : md = cs->uncertainty_margin + watchdog->uncertainty_margin;
445 : if (abs(cs_nsec - wd_nsec) > md) {
446 : pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
447 : smp_processor_id(), cs->name);
448 : pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
449 : watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
450 : pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
451 : cs->name, cs_nsec, csnow, cslast, cs->mask);
452 : if (curr_clocksource == cs)
453 : pr_warn(" '%s' is current clocksource.\n", cs->name);
454 : else if (curr_clocksource)
455 : pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name);
456 : else
457 : pr_warn(" No current clocksource.\n");
458 : __clocksource_unstable(cs);
459 : continue;
460 : }
461 :
462 : if (cs == curr_clocksource && cs->tick_stable)
463 : cs->tick_stable(cs);
464 :
465 : if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
466 : (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
467 : (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
468 : /* Mark it valid for high-res. */
469 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
470 :
471 : /*
472 : * clocksource_done_booting() will sort it if
473 : * finished_booting is not set yet.
474 : */
475 : if (!finished_booting)
476 : continue;
477 :
478 : /*
479 : * If this is not the current clocksource let
480 : * the watchdog thread reselect it. Due to the
481 : * change to high res this clocksource might
482 : * be preferred now. If it is the current
483 : * clocksource let the tick code know about
484 : * that change.
485 : */
486 : if (cs != curr_clocksource) {
487 : cs->flags |= CLOCK_SOURCE_RESELECT;
488 : schedule_work(&watchdog_work);
489 : } else {
490 : tick_clock_notify();
491 : }
492 : }
493 : }
494 :
495 : /*
496 : * We only clear the watchdog_reset_pending, when we did a
497 : * full cycle through all clocksources.
498 : */
499 : if (reset_pending)
500 : atomic_dec(&watchdog_reset_pending);
501 :
502 : /*
503 : * Cycle through CPUs to check if the CPUs stay synchronized
504 : * to each other.
505 : */
506 : next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
507 : if (next_cpu >= nr_cpu_ids)
508 : next_cpu = cpumask_first(cpu_online_mask);
509 :
510 : /*
511 : * Arm timer if not already pending: could race with concurrent
512 : * pair clocksource_stop_watchdog() clocksource_start_watchdog().
513 : */
514 : if (!timer_pending(&watchdog_timer)) {
515 : watchdog_timer.expires += WATCHDOG_INTERVAL;
516 : add_timer_on(&watchdog_timer, next_cpu);
517 : }
518 : out:
519 : spin_unlock(&watchdog_lock);
520 : }
521 :
522 : static inline void clocksource_start_watchdog(void)
523 : {
524 : if (watchdog_running || !watchdog || list_empty(&watchdog_list))
525 : return;
526 : timer_setup(&watchdog_timer, clocksource_watchdog, 0);
527 : watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
528 : add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
529 : watchdog_running = 1;
530 : }
531 :
532 : static inline void clocksource_stop_watchdog(void)
533 : {
534 : if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
535 : return;
536 : del_timer(&watchdog_timer);
537 : watchdog_running = 0;
538 : }
539 :
540 : static inline void clocksource_reset_watchdog(void)
541 : {
542 : struct clocksource *cs;
543 :
544 : list_for_each_entry(cs, &watchdog_list, wd_list)
545 : cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
546 : }
547 :
548 : static void clocksource_resume_watchdog(void)
549 : {
550 : atomic_inc(&watchdog_reset_pending);
551 : }
552 :
553 : static void clocksource_enqueue_watchdog(struct clocksource *cs)
554 : {
555 : INIT_LIST_HEAD(&cs->wd_list);
556 :
557 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
558 : /* cs is a clocksource to be watched. */
559 : list_add(&cs->wd_list, &watchdog_list);
560 : cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
561 : } else {
562 : /* cs is a watchdog. */
563 : if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
564 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
565 : }
566 : }
567 :
568 : static void clocksource_select_watchdog(bool fallback)
569 : {
570 : struct clocksource *cs, *old_wd;
571 : unsigned long flags;
572 :
573 : spin_lock_irqsave(&watchdog_lock, flags);
574 : /* save current watchdog */
575 : old_wd = watchdog;
576 : if (fallback)
577 : watchdog = NULL;
578 :
579 : list_for_each_entry(cs, &clocksource_list, list) {
580 : /* cs is a clocksource to be watched. */
581 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
582 : continue;
583 :
584 : /* Skip current if we were requested for a fallback. */
585 : if (fallback && cs == old_wd)
586 : continue;
587 :
588 : /* Pick the best watchdog. */
589 : if (!watchdog || cs->rating > watchdog->rating)
590 : watchdog = cs;
591 : }
592 : /* If we failed to find a fallback restore the old one. */
593 : if (!watchdog)
594 : watchdog = old_wd;
595 :
596 : /* If we changed the watchdog we need to reset cycles. */
597 : if (watchdog != old_wd)
598 : clocksource_reset_watchdog();
599 :
600 : /* Check if the watchdog timer needs to be started. */
601 : clocksource_start_watchdog();
602 : spin_unlock_irqrestore(&watchdog_lock, flags);
603 : }
604 :
605 : static void clocksource_dequeue_watchdog(struct clocksource *cs)
606 : {
607 : if (cs != watchdog) {
608 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
609 : /* cs is a watched clocksource. */
610 : list_del_init(&cs->wd_list);
611 : /* Check if the watchdog timer needs to be stopped. */
612 : clocksource_stop_watchdog();
613 : }
614 : }
615 : }
616 :
617 : static int __clocksource_watchdog_kthread(void)
618 : {
619 : struct clocksource *cs, *tmp;
620 : unsigned long flags;
621 : int select = 0;
622 :
623 : /* Do any required per-CPU skew verification. */
624 : if (curr_clocksource &&
625 : curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
626 : curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
627 : clocksource_verify_percpu(curr_clocksource);
628 :
629 : spin_lock_irqsave(&watchdog_lock, flags);
630 : list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
631 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
632 : list_del_init(&cs->wd_list);
633 : __clocksource_change_rating(cs, 0);
634 : select = 1;
635 : }
636 : if (cs->flags & CLOCK_SOURCE_RESELECT) {
637 : cs->flags &= ~CLOCK_SOURCE_RESELECT;
638 : select = 1;
639 : }
640 : }
641 : /* Check if the watchdog timer needs to be stopped. */
642 : clocksource_stop_watchdog();
643 : spin_unlock_irqrestore(&watchdog_lock, flags);
644 :
645 : return select;
646 : }
647 :
648 : static int clocksource_watchdog_kthread(void *data)
649 : {
650 : mutex_lock(&clocksource_mutex);
651 : if (__clocksource_watchdog_kthread())
652 : clocksource_select();
653 : mutex_unlock(&clocksource_mutex);
654 : return 0;
655 : }
656 :
657 : static bool clocksource_is_watchdog(struct clocksource *cs)
658 : {
659 : return cs == watchdog;
660 : }
661 :
662 : #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
663 :
664 : static void clocksource_enqueue_watchdog(struct clocksource *cs)
665 : {
666 2 : if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
667 1 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
668 : }
669 :
670 : static void clocksource_select_watchdog(bool fallback) { }
671 : static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
672 : static inline void clocksource_resume_watchdog(void) { }
673 : static inline int __clocksource_watchdog_kthread(void) { return 0; }
674 : static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
675 0 : void clocksource_mark_unstable(struct clocksource *cs) { }
676 :
677 : static inline void clocksource_watchdog_lock(unsigned long *flags) { }
678 : static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
679 :
680 : #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
681 :
682 : static bool clocksource_is_suspend(struct clocksource *cs)
683 : {
684 0 : return cs == suspend_clocksource;
685 : }
686 :
687 2 : static void __clocksource_suspend_select(struct clocksource *cs)
688 : {
689 : /*
690 : * Skip the clocksource which will be stopped in suspend state.
691 : */
692 2 : if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
693 : return;
694 :
695 : /*
696 : * The nonstop clocksource can be selected as the suspend clocksource to
697 : * calculate the suspend time, so it should not supply suspend/resume
698 : * interfaces to suspend the nonstop clocksource when system suspends.
699 : */
700 0 : if (cs->suspend || cs->resume) {
701 0 : pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
702 : cs->name);
703 : }
704 :
705 : /* Pick the best rating. */
706 0 : if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
707 0 : suspend_clocksource = cs;
708 : }
709 :
710 : /**
711 : * clocksource_suspend_select - Select the best clocksource for suspend timing
712 : * @fallback: if select a fallback clocksource
713 : */
714 0 : static void clocksource_suspend_select(bool fallback)
715 : {
716 : struct clocksource *cs, *old_suspend;
717 :
718 0 : old_suspend = suspend_clocksource;
719 0 : if (fallback)
720 0 : suspend_clocksource = NULL;
721 :
722 0 : list_for_each_entry(cs, &clocksource_list, list) {
723 : /* Skip current if we were requested for a fallback. */
724 0 : if (fallback && cs == old_suspend)
725 0 : continue;
726 :
727 0 : __clocksource_suspend_select(cs);
728 : }
729 0 : }
730 :
731 : /**
732 : * clocksource_start_suspend_timing - Start measuring the suspend timing
733 : * @cs: current clocksource from timekeeping
734 : * @start_cycles: current cycles from timekeeping
735 : *
736 : * This function will save the start cycle values of suspend timer to calculate
737 : * the suspend time when resuming system.
738 : *
739 : * This function is called late in the suspend process from timekeeping_suspend(),
740 : * that means processes are frozen, non-boot cpus and interrupts are disabled
741 : * now. It is therefore possible to start the suspend timer without taking the
742 : * clocksource mutex.
743 : */
744 0 : void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
745 : {
746 0 : if (!suspend_clocksource)
747 : return;
748 :
749 : /*
750 : * If current clocksource is the suspend timer, we should use the
751 : * tkr_mono.cycle_last value as suspend_start to avoid same reading
752 : * from suspend timer.
753 : */
754 0 : if (clocksource_is_suspend(cs)) {
755 0 : suspend_start = start_cycles;
756 0 : return;
757 : }
758 :
759 0 : if (suspend_clocksource->enable &&
760 0 : suspend_clocksource->enable(suspend_clocksource)) {
761 0 : pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
762 : return;
763 : }
764 :
765 0 : suspend_start = suspend_clocksource->read(suspend_clocksource);
766 : }
767 :
768 : /**
769 : * clocksource_stop_suspend_timing - Stop measuring the suspend timing
770 : * @cs: current clocksource from timekeeping
771 : * @cycle_now: current cycles from timekeeping
772 : *
773 : * This function will calculate the suspend time from suspend timer.
774 : *
775 : * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
776 : *
777 : * This function is called early in the resume process from timekeeping_resume(),
778 : * that means there is only one cpu, no processes are running and the interrupts
779 : * are disabled. It is therefore possible to stop the suspend timer without
780 : * taking the clocksource mutex.
781 : */
782 0 : u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
783 : {
784 0 : u64 now, delta, nsec = 0;
785 :
786 0 : if (!suspend_clocksource)
787 : return 0;
788 :
789 : /*
790 : * If current clocksource is the suspend timer, we should use the
791 : * tkr_mono.cycle_last value from timekeeping as current cycle to
792 : * avoid same reading from suspend timer.
793 : */
794 0 : if (clocksource_is_suspend(cs))
795 : now = cycle_now;
796 : else
797 0 : now = suspend_clocksource->read(suspend_clocksource);
798 :
799 0 : if (now > suspend_start) {
800 0 : delta = clocksource_delta(now, suspend_start,
801 0 : suspend_clocksource->mask);
802 0 : nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
803 : suspend_clocksource->shift);
804 : }
805 :
806 : /*
807 : * Disable the suspend timer to save power if current clocksource is
808 : * not the suspend timer.
809 : */
810 0 : if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
811 0 : suspend_clocksource->disable(suspend_clocksource);
812 :
813 : return nsec;
814 : }
815 :
816 : /**
817 : * clocksource_suspend - suspend the clocksource(s)
818 : */
819 0 : void clocksource_suspend(void)
820 : {
821 : struct clocksource *cs;
822 :
823 0 : list_for_each_entry_reverse(cs, &clocksource_list, list)
824 0 : if (cs->suspend)
825 0 : cs->suspend(cs);
826 0 : }
827 :
828 : /**
829 : * clocksource_resume - resume the clocksource(s)
830 : */
831 0 : void clocksource_resume(void)
832 : {
833 : struct clocksource *cs;
834 :
835 0 : list_for_each_entry(cs, &clocksource_list, list)
836 0 : if (cs->resume)
837 0 : cs->resume(cs);
838 :
839 : clocksource_resume_watchdog();
840 0 : }
841 :
842 : /**
843 : * clocksource_touch_watchdog - Update watchdog
844 : *
845 : * Update the watchdog after exception contexts such as kgdb so as not
846 : * to incorrectly trip the watchdog. This might fail when the kernel
847 : * was stopped in code which holds watchdog_lock.
848 : */
849 0 : void clocksource_touch_watchdog(void)
850 : {
851 : clocksource_resume_watchdog();
852 0 : }
853 :
854 : /**
855 : * clocksource_max_adjustment- Returns max adjustment amount
856 : * @cs: Pointer to clocksource
857 : *
858 : */
859 : static u32 clocksource_max_adjustment(struct clocksource *cs)
860 : {
861 : u64 ret;
862 : /*
863 : * We won't try to correct for more than 11% adjustments (110,000 ppm),
864 : */
865 2 : ret = (u64)cs->mult * 11;
866 2 : do_div(ret,100);
867 2 : return (u32)ret;
868 : }
869 :
870 : /**
871 : * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
872 : * @mult: cycle to nanosecond multiplier
873 : * @shift: cycle to nanosecond divisor (power of two)
874 : * @maxadj: maximum adjustment value to mult (~11%)
875 : * @mask: bitmask for two's complement subtraction of non 64 bit counters
876 : * @max_cyc: maximum cycle value before potential overflow (does not include
877 : * any safety margin)
878 : *
879 : * NOTE: This function includes a safety margin of 50%, in other words, we
880 : * return half the number of nanoseconds the hardware counter can technically
881 : * cover. This is done so that we can potentially detect problems caused by
882 : * delayed timers or bad hardware, which might result in time intervals that
883 : * are larger than what the math used can handle without overflows.
884 : */
885 0 : u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
886 : {
887 : u64 max_nsecs, max_cycles;
888 :
889 : /*
890 : * Calculate the maximum number of cycles that we can pass to the
891 : * cyc2ns() function without overflowing a 64-bit result.
892 : */
893 2 : max_cycles = ULLONG_MAX;
894 2 : do_div(max_cycles, mult+maxadj);
895 :
896 : /*
897 : * The actual maximum number of cycles we can defer the clocksource is
898 : * determined by the minimum of max_cycles and mask.
899 : * Note: Here we subtract the maxadj to make sure we don't sleep for
900 : * too long if there's a large negative adjustment.
901 : */
902 2 : max_cycles = min(max_cycles, mask);
903 4 : max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
904 :
905 : /* return the max_cycles value as well if requested */
906 2 : if (max_cyc)
907 2 : *max_cyc = max_cycles;
908 :
909 : /* Return 50% of the actual maximum, so we can detect bad values */
910 2 : max_nsecs >>= 1;
911 :
912 0 : return max_nsecs;
913 : }
914 :
915 : /**
916 : * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
917 : * @cs: Pointer to clocksource to be updated
918 : *
919 : */
920 : static inline void clocksource_update_max_deferment(struct clocksource *cs)
921 : {
922 4 : cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
923 : cs->maxadj, cs->mask,
924 : &cs->max_cycles);
925 : }
926 :
927 3 : static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
928 : {
929 : struct clocksource *cs;
930 :
931 4 : if (!finished_booting || list_empty(&clocksource_list))
932 : return NULL;
933 :
934 : /*
935 : * We pick the clocksource with the highest rating. If oneshot
936 : * mode is active, we pick the highres valid clocksource with
937 : * the best rating.
938 : */
939 1 : list_for_each_entry(cs, &clocksource_list, list) {
940 1 : if (skipcur && cs == curr_clocksource)
941 0 : continue;
942 1 : if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
943 0 : continue;
944 : return cs;
945 : }
946 : return NULL;
947 : }
948 :
949 3 : static void __clocksource_select(bool skipcur)
950 : {
951 3 : bool oneshot = tick_oneshot_mode_active();
952 : struct clocksource *best, *cs;
953 :
954 : /* Find the best suitable clocksource */
955 3 : best = clocksource_find_best(oneshot, skipcur);
956 3 : if (!best)
957 : return;
958 :
959 1 : if (!strlen(override_name))
960 : goto found;
961 :
962 : /* Check for the override clocksource. */
963 0 : list_for_each_entry(cs, &clocksource_list, list) {
964 0 : if (skipcur && cs == curr_clocksource)
965 0 : continue;
966 0 : if (strcmp(cs->name, override_name) != 0)
967 0 : continue;
968 : /*
969 : * Check to make sure we don't switch to a non-highres
970 : * capable clocksource if the tick code is in oneshot
971 : * mode (highres or nohz)
972 : */
973 : if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
974 : /* Override clocksource cannot be used. */
975 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
976 : pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
977 : cs->name);
978 : override_name[0] = 0;
979 : } else {
980 : /*
981 : * The override cannot be currently verified.
982 : * Deferring to let the watchdog check.
983 : */
984 : pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
985 : cs->name);
986 : }
987 : } else
988 : /* Override clocksource can be used. */
989 : best = cs;
990 : break;
991 : }
992 :
993 : found:
994 1 : if (curr_clocksource != best && !timekeeping_notify(best)) {
995 1 : pr_info("Switched to clocksource %s\n", best->name);
996 1 : curr_clocksource = best;
997 : }
998 : }
999 :
1000 : /**
1001 : * clocksource_select - Select the best clocksource available
1002 : *
1003 : * Private function. Must hold clocksource_mutex when called.
1004 : *
1005 : * Select the clocksource with the best rating, or the clocksource,
1006 : * which is selected by userspace override.
1007 : */
1008 : static void clocksource_select(void)
1009 : {
1010 3 : __clocksource_select(false);
1011 : }
1012 :
1013 : static void clocksource_select_fallback(void)
1014 : {
1015 0 : __clocksource_select(true);
1016 : }
1017 :
1018 : /*
1019 : * clocksource_done_booting - Called near the end of core bootup
1020 : *
1021 : * Hack to avoid lots of clocksource churn at boot time.
1022 : * We use fs_initcall because we want this to start before
1023 : * device_initcall but after subsys_initcall.
1024 : */
1025 1 : static int __init clocksource_done_booting(void)
1026 : {
1027 1 : mutex_lock(&clocksource_mutex);
1028 1 : curr_clocksource = clocksource_default_clock();
1029 1 : finished_booting = 1;
1030 : /*
1031 : * Run the watchdog first to eliminate unstable clock sources
1032 : */
1033 : __clocksource_watchdog_kthread();
1034 : clocksource_select();
1035 1 : mutex_unlock(&clocksource_mutex);
1036 1 : return 0;
1037 : }
1038 : fs_initcall(clocksource_done_booting);
1039 :
1040 : /*
1041 : * Enqueue the clocksource sorted by rating
1042 : */
1043 : static void clocksource_enqueue(struct clocksource *cs)
1044 : {
1045 2 : struct list_head *entry = &clocksource_list;
1046 : struct clocksource *tmp;
1047 :
1048 3 : list_for_each_entry(tmp, &clocksource_list, list) {
1049 : /* Keep track of the place, where to insert */
1050 1 : if (tmp->rating < cs->rating)
1051 : break;
1052 1 : entry = &tmp->list;
1053 : }
1054 4 : list_add(&cs->list, entry);
1055 : }
1056 :
1057 : /**
1058 : * __clocksource_update_freq_scale - Used update clocksource with new freq
1059 : * @cs: clocksource to be registered
1060 : * @scale: Scale factor multiplied against freq to get clocksource hz
1061 : * @freq: clocksource frequency (cycles per second) divided by scale
1062 : *
1063 : * This should only be called from the clocksource->enable() method.
1064 : *
1065 : * This *SHOULD NOT* be called directly! Please use the
1066 : * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
1067 : * functions.
1068 : */
1069 2 : void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
1070 : {
1071 : u64 sec;
1072 :
1073 : /*
1074 : * Default clocksources are *special* and self-define their mult/shift.
1075 : * But, you're not special, so you should specify a freq value.
1076 : */
1077 2 : if (freq) {
1078 : /*
1079 : * Calc the maximum number of seconds which we can run before
1080 : * wrapping around. For clocksources which have a mask > 32-bit
1081 : * we need to limit the max sleep time to have a good
1082 : * conversion precision. 10 minutes is still a reasonable
1083 : * amount. That results in a shift value of 24 for a
1084 : * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
1085 : * ~ 0.06ppm granularity for NTP.
1086 : */
1087 1 : sec = cs->mask;
1088 1 : do_div(sec, freq);
1089 1 : do_div(sec, scale);
1090 1 : if (!sec)
1091 : sec = 1;
1092 1 : else if (sec > 600 && cs->mask > UINT_MAX)
1093 1 : sec = 600;
1094 :
1095 2 : clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
1096 1 : NSEC_PER_SEC / scale, sec * scale);
1097 : }
1098 :
1099 : /*
1100 : * If the uncertainty margin is not specified, calculate it.
1101 : * If both scale and freq are non-zero, calculate the clock
1102 : * period, but bound below at 2*WATCHDOG_MAX_SKEW. However,
1103 : * if either of scale or freq is zero, be very conservative and
1104 : * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the
1105 : * uncertainty margin. Allow stupidly small uncertainty margins
1106 : * to be specified by the caller for testing purposes, but warn
1107 : * to discourage production use of this capability.
1108 : */
1109 2 : if (scale && freq && !cs->uncertainty_margin) {
1110 1 : cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq);
1111 1 : if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW)
1112 1 : cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW;
1113 1 : } else if (!cs->uncertainty_margin) {
1114 0 : cs->uncertainty_margin = WATCHDOG_THRESHOLD;
1115 : }
1116 2 : WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW);
1117 :
1118 : /*
1119 : * Ensure clocksources that have large 'mult' values don't overflow
1120 : * when adjusted.
1121 : */
1122 4 : cs->maxadj = clocksource_max_adjustment(cs);
1123 4 : while (freq && ((cs->mult + cs->maxadj < cs->mult)
1124 1 : || (cs->mult - cs->maxadj > cs->mult))) {
1125 0 : cs->mult >>= 1;
1126 0 : cs->shift--;
1127 0 : cs->maxadj = clocksource_max_adjustment(cs);
1128 : }
1129 :
1130 : /*
1131 : * Only warn for *special* clocksources that self-define
1132 : * their mult/shift values and don't specify a freq.
1133 : */
1134 2 : WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
1135 : "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
1136 : cs->name);
1137 :
1138 2 : clocksource_update_max_deferment(cs);
1139 :
1140 2 : pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
1141 : cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
1142 2 : }
1143 : EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
1144 :
1145 : /**
1146 : * __clocksource_register_scale - Used to install new clocksources
1147 : * @cs: clocksource to be registered
1148 : * @scale: Scale factor multiplied against freq to get clocksource hz
1149 : * @freq: clocksource frequency (cycles per second) divided by scale
1150 : *
1151 : * Returns -EBUSY if registration fails, zero otherwise.
1152 : *
1153 : * This *SHOULD NOT* be called directly! Please use the
1154 : * clocksource_register_hz() or clocksource_register_khz helper functions.
1155 : */
1156 2 : int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
1157 : {
1158 : unsigned long flags;
1159 :
1160 2 : clocksource_arch_init(cs);
1161 :
1162 2 : if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX))
1163 0 : cs->id = CSID_GENERIC;
1164 2 : if (cs->vdso_clock_mode < 0 ||
1165 2 : cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
1166 0 : pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
1167 : cs->name, cs->vdso_clock_mode);
1168 0 : cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
1169 : }
1170 :
1171 : /* Initialize mult/shift and max_idle_ns */
1172 2 : __clocksource_update_freq_scale(cs, scale, freq);
1173 :
1174 : /* Add clocksource to the clocksource list */
1175 2 : mutex_lock(&clocksource_mutex);
1176 :
1177 2 : clocksource_watchdog_lock(&flags);
1178 2 : clocksource_enqueue(cs);
1179 2 : clocksource_enqueue_watchdog(cs);
1180 2 : clocksource_watchdog_unlock(&flags);
1181 :
1182 2 : clocksource_select();
1183 2 : clocksource_select_watchdog(false);
1184 2 : __clocksource_suspend_select(cs);
1185 2 : mutex_unlock(&clocksource_mutex);
1186 2 : return 0;
1187 : }
1188 : EXPORT_SYMBOL_GPL(__clocksource_register_scale);
1189 :
1190 0 : static void __clocksource_change_rating(struct clocksource *cs, int rating)
1191 : {
1192 0 : list_del(&cs->list);
1193 0 : cs->rating = rating;
1194 0 : clocksource_enqueue(cs);
1195 0 : }
1196 :
1197 : /**
1198 : * clocksource_change_rating - Change the rating of a registered clocksource
1199 : * @cs: clocksource to be changed
1200 : * @rating: new rating
1201 : */
1202 0 : void clocksource_change_rating(struct clocksource *cs, int rating)
1203 : {
1204 : unsigned long flags;
1205 :
1206 0 : mutex_lock(&clocksource_mutex);
1207 0 : clocksource_watchdog_lock(&flags);
1208 0 : __clocksource_change_rating(cs, rating);
1209 0 : clocksource_watchdog_unlock(&flags);
1210 :
1211 0 : clocksource_select();
1212 0 : clocksource_select_watchdog(false);
1213 0 : clocksource_suspend_select(false);
1214 0 : mutex_unlock(&clocksource_mutex);
1215 0 : }
1216 : EXPORT_SYMBOL(clocksource_change_rating);
1217 :
1218 : /*
1219 : * Unbind clocksource @cs. Called with clocksource_mutex held
1220 : */
1221 0 : static int clocksource_unbind(struct clocksource *cs)
1222 : {
1223 : unsigned long flags;
1224 :
1225 0 : if (clocksource_is_watchdog(cs)) {
1226 : /* Select and try to install a replacement watchdog. */
1227 : clocksource_select_watchdog(true);
1228 : if (clocksource_is_watchdog(cs))
1229 : return -EBUSY;
1230 : }
1231 :
1232 0 : if (cs == curr_clocksource) {
1233 : /* Select and try to install a replacement clock source */
1234 : clocksource_select_fallback();
1235 0 : if (curr_clocksource == cs)
1236 : return -EBUSY;
1237 : }
1238 :
1239 0 : if (clocksource_is_suspend(cs)) {
1240 : /*
1241 : * Select and try to install a replacement suspend clocksource.
1242 : * If no replacement suspend clocksource, we will just let the
1243 : * clocksource go and have no suspend clocksource.
1244 : */
1245 0 : clocksource_suspend_select(true);
1246 : }
1247 :
1248 0 : clocksource_watchdog_lock(&flags);
1249 0 : clocksource_dequeue_watchdog(cs);
1250 0 : list_del_init(&cs->list);
1251 0 : clocksource_watchdog_unlock(&flags);
1252 :
1253 0 : return 0;
1254 : }
1255 :
1256 : /**
1257 : * clocksource_unregister - remove a registered clocksource
1258 : * @cs: clocksource to be unregistered
1259 : */
1260 0 : int clocksource_unregister(struct clocksource *cs)
1261 : {
1262 0 : int ret = 0;
1263 :
1264 0 : mutex_lock(&clocksource_mutex);
1265 0 : if (!list_empty(&cs->list))
1266 0 : ret = clocksource_unbind(cs);
1267 0 : mutex_unlock(&clocksource_mutex);
1268 0 : return ret;
1269 : }
1270 : EXPORT_SYMBOL(clocksource_unregister);
1271 :
1272 : #ifdef CONFIG_SYSFS
1273 : /**
1274 : * current_clocksource_show - sysfs interface for current clocksource
1275 : * @dev: unused
1276 : * @attr: unused
1277 : * @buf: char buffer to be filled with clocksource list
1278 : *
1279 : * Provides sysfs interface for listing current clocksource.
1280 : */
1281 0 : static ssize_t current_clocksource_show(struct device *dev,
1282 : struct device_attribute *attr,
1283 : char *buf)
1284 : {
1285 0 : ssize_t count = 0;
1286 :
1287 0 : mutex_lock(&clocksource_mutex);
1288 0 : count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
1289 0 : mutex_unlock(&clocksource_mutex);
1290 :
1291 0 : return count;
1292 : }
1293 :
1294 0 : ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
1295 : {
1296 0 : size_t ret = cnt;
1297 :
1298 : /* strings from sysfs write are not 0 terminated! */
1299 0 : if (!cnt || cnt >= CS_NAME_LEN)
1300 : return -EINVAL;
1301 :
1302 : /* strip of \n: */
1303 0 : if (buf[cnt-1] == '\n')
1304 0 : cnt--;
1305 0 : if (cnt > 0)
1306 0 : memcpy(dst, buf, cnt);
1307 0 : dst[cnt] = 0;
1308 0 : return ret;
1309 : }
1310 :
1311 : /**
1312 : * current_clocksource_store - interface for manually overriding clocksource
1313 : * @dev: unused
1314 : * @attr: unused
1315 : * @buf: name of override clocksource
1316 : * @count: length of buffer
1317 : *
1318 : * Takes input from sysfs interface for manually overriding the default
1319 : * clocksource selection.
1320 : */
1321 0 : static ssize_t current_clocksource_store(struct device *dev,
1322 : struct device_attribute *attr,
1323 : const char *buf, size_t count)
1324 : {
1325 : ssize_t ret;
1326 :
1327 0 : mutex_lock(&clocksource_mutex);
1328 :
1329 0 : ret = sysfs_get_uname(buf, override_name, count);
1330 0 : if (ret >= 0)
1331 : clocksource_select();
1332 :
1333 0 : mutex_unlock(&clocksource_mutex);
1334 :
1335 0 : return ret;
1336 : }
1337 : static DEVICE_ATTR_RW(current_clocksource);
1338 :
1339 : /**
1340 : * unbind_clocksource_store - interface for manually unbinding clocksource
1341 : * @dev: unused
1342 : * @attr: unused
1343 : * @buf: unused
1344 : * @count: length of buffer
1345 : *
1346 : * Takes input from sysfs interface for manually unbinding a clocksource.
1347 : */
1348 0 : static ssize_t unbind_clocksource_store(struct device *dev,
1349 : struct device_attribute *attr,
1350 : const char *buf, size_t count)
1351 : {
1352 : struct clocksource *cs;
1353 : char name[CS_NAME_LEN];
1354 : ssize_t ret;
1355 :
1356 0 : ret = sysfs_get_uname(buf, name, count);
1357 0 : if (ret < 0)
1358 : return ret;
1359 :
1360 0 : ret = -ENODEV;
1361 0 : mutex_lock(&clocksource_mutex);
1362 0 : list_for_each_entry(cs, &clocksource_list, list) {
1363 0 : if (strcmp(cs->name, name))
1364 0 : continue;
1365 0 : ret = clocksource_unbind(cs);
1366 0 : break;
1367 : }
1368 0 : mutex_unlock(&clocksource_mutex);
1369 :
1370 0 : return ret ? ret : count;
1371 : }
1372 : static DEVICE_ATTR_WO(unbind_clocksource);
1373 :
1374 : /**
1375 : * available_clocksource_show - sysfs interface for listing clocksource
1376 : * @dev: unused
1377 : * @attr: unused
1378 : * @buf: char buffer to be filled with clocksource list
1379 : *
1380 : * Provides sysfs interface for listing registered clocksources
1381 : */
1382 0 : static ssize_t available_clocksource_show(struct device *dev,
1383 : struct device_attribute *attr,
1384 : char *buf)
1385 : {
1386 : struct clocksource *src;
1387 0 : ssize_t count = 0;
1388 :
1389 0 : mutex_lock(&clocksource_mutex);
1390 0 : list_for_each_entry(src, &clocksource_list, list) {
1391 : /*
1392 : * Don't show non-HRES clocksource if the tick code is
1393 : * in one shot mode (highres=on or nohz=on)
1394 : */
1395 : if (!tick_oneshot_mode_active() ||
1396 : (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
1397 0 : count += snprintf(buf + count,
1398 0 : max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
1399 : "%s ", src->name);
1400 : }
1401 0 : mutex_unlock(&clocksource_mutex);
1402 :
1403 0 : count += snprintf(buf + count,
1404 0 : max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
1405 :
1406 0 : return count;
1407 : }
1408 : static DEVICE_ATTR_RO(available_clocksource);
1409 :
1410 : static struct attribute *clocksource_attrs[] = {
1411 : &dev_attr_current_clocksource.attr,
1412 : &dev_attr_unbind_clocksource.attr,
1413 : &dev_attr_available_clocksource.attr,
1414 : NULL
1415 : };
1416 : ATTRIBUTE_GROUPS(clocksource);
1417 :
1418 : static struct bus_type clocksource_subsys = {
1419 : .name = "clocksource",
1420 : .dev_name = "clocksource",
1421 : };
1422 :
1423 : static struct device device_clocksource = {
1424 : .id = 0,
1425 : .bus = &clocksource_subsys,
1426 : .groups = clocksource_groups,
1427 : };
1428 :
1429 1 : static int __init init_clocksource_sysfs(void)
1430 : {
1431 1 : int error = subsys_system_register(&clocksource_subsys, NULL);
1432 :
1433 1 : if (!error)
1434 1 : error = device_register(&device_clocksource);
1435 :
1436 1 : return error;
1437 : }
1438 :
1439 : device_initcall(init_clocksource_sysfs);
1440 : #endif /* CONFIG_SYSFS */
1441 :
1442 : /**
1443 : * boot_override_clocksource - boot clock override
1444 : * @str: override name
1445 : *
1446 : * Takes a clocksource= boot argument and uses it
1447 : * as the clocksource override name.
1448 : */
1449 0 : static int __init boot_override_clocksource(char* str)
1450 : {
1451 0 : mutex_lock(&clocksource_mutex);
1452 0 : if (str)
1453 0 : strlcpy(override_name, str, sizeof(override_name));
1454 0 : mutex_unlock(&clocksource_mutex);
1455 0 : return 1;
1456 : }
1457 :
1458 : __setup("clocksource=", boot_override_clocksource);
1459 :
1460 : /**
1461 : * boot_override_clock - Compatibility layer for deprecated boot option
1462 : * @str: override name
1463 : *
1464 : * DEPRECATED! Takes a clock= boot argument and uses it
1465 : * as the clocksource override name
1466 : */
1467 0 : static int __init boot_override_clock(char* str)
1468 : {
1469 0 : if (!strcmp(str, "pmtmr")) {
1470 0 : pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
1471 0 : return boot_override_clocksource("acpi_pm");
1472 : }
1473 0 : pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
1474 0 : return boot_override_clocksource(str);
1475 : }
1476 :
1477 : __setup("clock=", boot_override_clock);
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