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 : * Interval: 0.5sec.
100 : */
101 : #define WATCHDOG_INTERVAL (HZ >> 1)
102 :
103 : /*
104 : * Threshold: 0.0312s, when doubled: 0.0625s.
105 : * Also a default for cs->uncertainty_margin when registering clocks.
106 : */
107 : #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
108 :
109 : /*
110 : * Maximum permissible delay between two readouts of the watchdog
111 : * clocksource surrounding a read of the clocksource being validated.
112 : * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
113 : * a lower bound for cs->uncertainty_margin values when registering clocks.
114 : *
115 : * The default of 500 parts per million is based on NTP's limits.
116 : * If a clocksource is good enough for NTP, it is good enough for us!
117 : */
118 : #ifdef CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
119 : #define MAX_SKEW_USEC CONFIG_CLOCKSOURCE_WATCHDOG_MAX_SKEW_US
120 : #else
121 : #define MAX_SKEW_USEC (125 * WATCHDOG_INTERVAL / HZ)
122 : #endif
123 :
124 : #define WATCHDOG_MAX_SKEW (MAX_SKEW_USEC * NSEC_PER_USEC)
125 :
126 : #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
127 : static void clocksource_watchdog_work(struct work_struct *work);
128 : static void clocksource_select(void);
129 :
130 : static LIST_HEAD(watchdog_list);
131 : static struct clocksource *watchdog;
132 : static struct timer_list watchdog_timer;
133 : static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
134 : static DEFINE_SPINLOCK(watchdog_lock);
135 : static int watchdog_running;
136 : static atomic_t watchdog_reset_pending;
137 :
138 : static inline void clocksource_watchdog_lock(unsigned long *flags)
139 : {
140 : spin_lock_irqsave(&watchdog_lock, *flags);
141 : }
142 :
143 : static inline void clocksource_watchdog_unlock(unsigned long *flags)
144 : {
145 : spin_unlock_irqrestore(&watchdog_lock, *flags);
146 : }
147 :
148 : static int clocksource_watchdog_kthread(void *data);
149 : static void __clocksource_change_rating(struct clocksource *cs, int rating);
150 :
151 : static void clocksource_watchdog_work(struct work_struct *work)
152 : {
153 : /*
154 : * We cannot directly run clocksource_watchdog_kthread() here, because
155 : * clocksource_select() calls timekeeping_notify() which uses
156 : * stop_machine(). One cannot use stop_machine() from a workqueue() due
157 : * lock inversions wrt CPU hotplug.
158 : *
159 : * Also, we only ever run this work once or twice during the lifetime
160 : * of the kernel, so there is no point in creating a more permanent
161 : * kthread for this.
162 : *
163 : * If kthread_run fails the next watchdog scan over the
164 : * watchdog_list will find the unstable clock again.
165 : */
166 : kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
167 : }
168 :
169 : static void __clocksource_unstable(struct clocksource *cs)
170 : {
171 : cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
172 : cs->flags |= CLOCK_SOURCE_UNSTABLE;
173 :
174 : /*
175 : * If the clocksource is registered clocksource_watchdog_kthread() will
176 : * re-rate and re-select.
177 : */
178 : if (list_empty(&cs->list)) {
179 : cs->rating = 0;
180 : return;
181 : }
182 :
183 : if (cs->mark_unstable)
184 : cs->mark_unstable(cs);
185 :
186 : /* kick clocksource_watchdog_kthread() */
187 : if (finished_booting)
188 : schedule_work(&watchdog_work);
189 : }
190 :
191 : /**
192 : * clocksource_mark_unstable - mark clocksource unstable via watchdog
193 : * @cs: clocksource to be marked unstable
194 : *
195 : * This function is called by the x86 TSC code to mark clocksources as unstable;
196 : * it defers demotion and re-selection to a kthread.
197 : */
198 : void clocksource_mark_unstable(struct clocksource *cs)
199 : {
200 : unsigned long flags;
201 :
202 : spin_lock_irqsave(&watchdog_lock, flags);
203 : if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
204 : if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
205 : list_add(&cs->wd_list, &watchdog_list);
206 : __clocksource_unstable(cs);
207 : }
208 : spin_unlock_irqrestore(&watchdog_lock, flags);
209 : }
210 :
211 : ulong max_cswd_read_retries = 2;
212 : module_param(max_cswd_read_retries, ulong, 0644);
213 : EXPORT_SYMBOL_GPL(max_cswd_read_retries);
214 : static int verify_n_cpus = 8;
215 : module_param(verify_n_cpus, int, 0644);
216 :
217 : enum wd_read_status {
218 : WD_READ_SUCCESS,
219 : WD_READ_UNSTABLE,
220 : WD_READ_SKIP
221 : };
222 :
223 : static enum wd_read_status cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
224 : {
225 : unsigned int nretries;
226 : u64 wd_end, wd_end2, wd_delta;
227 : int64_t wd_delay, wd_seq_delay;
228 :
229 : for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
230 : local_irq_disable();
231 : *wdnow = watchdog->read(watchdog);
232 : *csnow = cs->read(cs);
233 : wd_end = watchdog->read(watchdog);
234 : wd_end2 = watchdog->read(watchdog);
235 : local_irq_enable();
236 :
237 : wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
238 : wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
239 : watchdog->shift);
240 : if (wd_delay <= WATCHDOG_MAX_SKEW) {
241 : if (nretries > 1 || nretries >= max_cswd_read_retries) {
242 : pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
243 : smp_processor_id(), watchdog->name, nretries);
244 : }
245 : return WD_READ_SUCCESS;
246 : }
247 :
248 : /*
249 : * Now compute delay in consecutive watchdog read to see if
250 : * there is too much external interferences that cause
251 : * significant delay in reading both clocksource and watchdog.
252 : *
253 : * If consecutive WD read-back delay > WATCHDOG_MAX_SKEW/2,
254 : * report system busy, reinit the watchdog and skip the current
255 : * watchdog test.
256 : */
257 : wd_delta = clocksource_delta(wd_end2, wd_end, watchdog->mask);
258 : wd_seq_delay = clocksource_cyc2ns(wd_delta, watchdog->mult, watchdog->shift);
259 : if (wd_seq_delay > WATCHDOG_MAX_SKEW/2)
260 : goto skip_test;
261 : }
262 :
263 : pr_warn("timekeeping watchdog on CPU%d: wd-%s-wd excessive read-back delay of %lldns vs. limit of %ldns, wd-wd read-back delay only %lldns, attempt %d, marking %s unstable\n",
264 : smp_processor_id(), cs->name, wd_delay, WATCHDOG_MAX_SKEW, wd_seq_delay, nretries, cs->name);
265 : return WD_READ_UNSTABLE;
266 :
267 : skip_test:
268 : pr_info("timekeeping watchdog on CPU%d: %s wd-wd read-back delay of %lldns\n",
269 : smp_processor_id(), watchdog->name, wd_seq_delay);
270 : pr_info("wd-%s-wd read-back delay of %lldns, clock-skew test skipped!\n",
271 : cs->name, wd_delay);
272 : return WD_READ_SKIP;
273 : }
274 :
275 : static u64 csnow_mid;
276 : static cpumask_t cpus_ahead;
277 : static cpumask_t cpus_behind;
278 : static cpumask_t cpus_chosen;
279 :
280 : static void clocksource_verify_choose_cpus(void)
281 : {
282 : int cpu, i, n = verify_n_cpus;
283 :
284 : if (n < 0) {
285 : /* Check all of the CPUs. */
286 : cpumask_copy(&cpus_chosen, cpu_online_mask);
287 : cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
288 : return;
289 : }
290 :
291 : /* If no checking desired, or no other CPU to check, leave. */
292 : cpumask_clear(&cpus_chosen);
293 : if (n == 0 || num_online_cpus() <= 1)
294 : return;
295 :
296 : /* Make sure to select at least one CPU other than the current CPU. */
297 : cpu = cpumask_first(cpu_online_mask);
298 : if (cpu == smp_processor_id())
299 : cpu = cpumask_next(cpu, cpu_online_mask);
300 : if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
301 : return;
302 : cpumask_set_cpu(cpu, &cpus_chosen);
303 :
304 : /* Force a sane value for the boot parameter. */
305 : if (n > nr_cpu_ids)
306 : n = nr_cpu_ids;
307 :
308 : /*
309 : * Randomly select the specified number of CPUs. If the same
310 : * CPU is selected multiple times, that CPU is checked only once,
311 : * and no replacement CPU is selected. This gracefully handles
312 : * situations where verify_n_cpus is greater than the number of
313 : * CPUs that are currently online.
314 : */
315 : for (i = 1; i < n; i++) {
316 : cpu = get_random_u32_below(nr_cpu_ids);
317 : cpu = cpumask_next(cpu - 1, cpu_online_mask);
318 : if (cpu >= nr_cpu_ids)
319 : cpu = cpumask_first(cpu_online_mask);
320 : if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
321 : cpumask_set_cpu(cpu, &cpus_chosen);
322 : }
323 :
324 : /* Don't verify ourselves. */
325 : cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
326 : }
327 :
328 : static void clocksource_verify_one_cpu(void *csin)
329 : {
330 : struct clocksource *cs = (struct clocksource *)csin;
331 :
332 : csnow_mid = cs->read(cs);
333 : }
334 :
335 : void clocksource_verify_percpu(struct clocksource *cs)
336 : {
337 : int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
338 : u64 csnow_begin, csnow_end;
339 : int cpu, testcpu;
340 : s64 delta;
341 :
342 : if (verify_n_cpus == 0)
343 : return;
344 : cpumask_clear(&cpus_ahead);
345 : cpumask_clear(&cpus_behind);
346 : cpus_read_lock();
347 : preempt_disable();
348 : clocksource_verify_choose_cpus();
349 : if (cpumask_empty(&cpus_chosen)) {
350 : preempt_enable();
351 : cpus_read_unlock();
352 : pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
353 : return;
354 : }
355 : testcpu = smp_processor_id();
356 : pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
357 : for_each_cpu(cpu, &cpus_chosen) {
358 : if (cpu == testcpu)
359 : continue;
360 : csnow_begin = cs->read(cs);
361 : smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
362 : csnow_end = cs->read(cs);
363 : delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
364 : if (delta < 0)
365 : cpumask_set_cpu(cpu, &cpus_behind);
366 : delta = (csnow_end - csnow_mid) & cs->mask;
367 : if (delta < 0)
368 : cpumask_set_cpu(cpu, &cpus_ahead);
369 : delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
370 : cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
371 : if (cs_nsec > cs_nsec_max)
372 : cs_nsec_max = cs_nsec;
373 : if (cs_nsec < cs_nsec_min)
374 : cs_nsec_min = cs_nsec;
375 : }
376 : preempt_enable();
377 : cpus_read_unlock();
378 : if (!cpumask_empty(&cpus_ahead))
379 : pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
380 : cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
381 : if (!cpumask_empty(&cpus_behind))
382 : pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n",
383 : cpumask_pr_args(&cpus_behind), testcpu, cs->name);
384 : if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
385 : pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n",
386 : testcpu, cs_nsec_min, cs_nsec_max, cs->name);
387 : }
388 : EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
389 :
390 : static inline void clocksource_reset_watchdog(void)
391 : {
392 : struct clocksource *cs;
393 :
394 : list_for_each_entry(cs, &watchdog_list, wd_list)
395 : cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
396 : }
397 :
398 :
399 : static void clocksource_watchdog(struct timer_list *unused)
400 : {
401 : u64 csnow, wdnow, cslast, wdlast, delta;
402 : int next_cpu, reset_pending;
403 : int64_t wd_nsec, cs_nsec;
404 : struct clocksource *cs;
405 : enum wd_read_status read_ret;
406 : unsigned long extra_wait = 0;
407 : u32 md;
408 :
409 : spin_lock(&watchdog_lock);
410 : if (!watchdog_running)
411 : goto out;
412 :
413 : reset_pending = atomic_read(&watchdog_reset_pending);
414 :
415 : list_for_each_entry(cs, &watchdog_list, wd_list) {
416 :
417 : /* Clocksource already marked unstable? */
418 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
419 : if (finished_booting)
420 : schedule_work(&watchdog_work);
421 : continue;
422 : }
423 :
424 : read_ret = cs_watchdog_read(cs, &csnow, &wdnow);
425 :
426 : if (read_ret == WD_READ_UNSTABLE) {
427 : /* Clock readout unreliable, so give it up. */
428 : __clocksource_unstable(cs);
429 : continue;
430 : }
431 :
432 : /*
433 : * When WD_READ_SKIP is returned, it means the system is likely
434 : * under very heavy load, where the latency of reading
435 : * watchdog/clocksource is very big, and affect the accuracy of
436 : * watchdog check. So give system some space and suspend the
437 : * watchdog check for 5 minutes.
438 : */
439 : if (read_ret == WD_READ_SKIP) {
440 : /*
441 : * As the watchdog timer will be suspended, and
442 : * cs->last could keep unchanged for 5 minutes, reset
443 : * the counters.
444 : */
445 : clocksource_reset_watchdog();
446 : extra_wait = HZ * 300;
447 : break;
448 : }
449 :
450 : /* Clocksource initialized ? */
451 : if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
452 : atomic_read(&watchdog_reset_pending)) {
453 : cs->flags |= CLOCK_SOURCE_WATCHDOG;
454 : cs->wd_last = wdnow;
455 : cs->cs_last = csnow;
456 : continue;
457 : }
458 :
459 : delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
460 : wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
461 : watchdog->shift);
462 :
463 : delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
464 : cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
465 : wdlast = cs->wd_last; /* save these in case we print them */
466 : cslast = cs->cs_last;
467 : cs->cs_last = csnow;
468 : cs->wd_last = wdnow;
469 :
470 : if (atomic_read(&watchdog_reset_pending))
471 : continue;
472 :
473 : /* Check the deviation from the watchdog clocksource. */
474 : md = cs->uncertainty_margin + watchdog->uncertainty_margin;
475 : if (abs(cs_nsec - wd_nsec) > md) {
476 : u64 cs_wd_msec;
477 : u64 wd_msec;
478 : u32 wd_rem;
479 :
480 : pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
481 : smp_processor_id(), cs->name);
482 : pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
483 : watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
484 : pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
485 : cs->name, cs_nsec, csnow, cslast, cs->mask);
486 : cs_wd_msec = div_u64_rem(cs_nsec - wd_nsec, 1000U * 1000U, &wd_rem);
487 : wd_msec = div_u64_rem(wd_nsec, 1000U * 1000U, &wd_rem);
488 : pr_warn(" Clocksource '%s' skewed %lld ns (%lld ms) over watchdog '%s' interval of %lld ns (%lld ms)\n",
489 : cs->name, cs_nsec - wd_nsec, cs_wd_msec, watchdog->name, wd_nsec, wd_msec);
490 : if (curr_clocksource == cs)
491 : pr_warn(" '%s' is current clocksource.\n", cs->name);
492 : else if (curr_clocksource)
493 : pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name);
494 : else
495 : pr_warn(" No current clocksource.\n");
496 : __clocksource_unstable(cs);
497 : continue;
498 : }
499 :
500 : if (cs == curr_clocksource && cs->tick_stable)
501 : cs->tick_stable(cs);
502 :
503 : if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
504 : (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
505 : (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
506 : /* Mark it valid for high-res. */
507 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
508 :
509 : /*
510 : * clocksource_done_booting() will sort it if
511 : * finished_booting is not set yet.
512 : */
513 : if (!finished_booting)
514 : continue;
515 :
516 : /*
517 : * If this is not the current clocksource let
518 : * the watchdog thread reselect it. Due to the
519 : * change to high res this clocksource might
520 : * be preferred now. If it is the current
521 : * clocksource let the tick code know about
522 : * that change.
523 : */
524 : if (cs != curr_clocksource) {
525 : cs->flags |= CLOCK_SOURCE_RESELECT;
526 : schedule_work(&watchdog_work);
527 : } else {
528 : tick_clock_notify();
529 : }
530 : }
531 : }
532 :
533 : /*
534 : * We only clear the watchdog_reset_pending, when we did a
535 : * full cycle through all clocksources.
536 : */
537 : if (reset_pending)
538 : atomic_dec(&watchdog_reset_pending);
539 :
540 : /*
541 : * Cycle through CPUs to check if the CPUs stay synchronized
542 : * to each other.
543 : */
544 : next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
545 : if (next_cpu >= nr_cpu_ids)
546 : next_cpu = cpumask_first(cpu_online_mask);
547 :
548 : /*
549 : * Arm timer if not already pending: could race with concurrent
550 : * pair clocksource_stop_watchdog() clocksource_start_watchdog().
551 : */
552 : if (!timer_pending(&watchdog_timer)) {
553 : watchdog_timer.expires += WATCHDOG_INTERVAL + extra_wait;
554 : add_timer_on(&watchdog_timer, next_cpu);
555 : }
556 : out:
557 : spin_unlock(&watchdog_lock);
558 : }
559 :
560 : static inline void clocksource_start_watchdog(void)
561 : {
562 : if (watchdog_running || !watchdog || list_empty(&watchdog_list))
563 : return;
564 : timer_setup(&watchdog_timer, clocksource_watchdog, 0);
565 : watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
566 : add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
567 : watchdog_running = 1;
568 : }
569 :
570 : static inline void clocksource_stop_watchdog(void)
571 : {
572 : if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
573 : return;
574 : del_timer(&watchdog_timer);
575 : watchdog_running = 0;
576 : }
577 :
578 : static void clocksource_resume_watchdog(void)
579 : {
580 : atomic_inc(&watchdog_reset_pending);
581 : }
582 :
583 : static void clocksource_enqueue_watchdog(struct clocksource *cs)
584 : {
585 : INIT_LIST_HEAD(&cs->wd_list);
586 :
587 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
588 : /* cs is a clocksource to be watched. */
589 : list_add(&cs->wd_list, &watchdog_list);
590 : cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
591 : } else {
592 : /* cs is a watchdog. */
593 : if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
594 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
595 : }
596 : }
597 :
598 : static void clocksource_select_watchdog(bool fallback)
599 : {
600 : struct clocksource *cs, *old_wd;
601 : unsigned long flags;
602 :
603 : spin_lock_irqsave(&watchdog_lock, flags);
604 : /* save current watchdog */
605 : old_wd = watchdog;
606 : if (fallback)
607 : watchdog = NULL;
608 :
609 : list_for_each_entry(cs, &clocksource_list, list) {
610 : /* cs is a clocksource to be watched. */
611 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
612 : continue;
613 :
614 : /* Skip current if we were requested for a fallback. */
615 : if (fallback && cs == old_wd)
616 : continue;
617 :
618 : /* Pick the best watchdog. */
619 : if (!watchdog || cs->rating > watchdog->rating)
620 : watchdog = cs;
621 : }
622 : /* If we failed to find a fallback restore the old one. */
623 : if (!watchdog)
624 : watchdog = old_wd;
625 :
626 : /* If we changed the watchdog we need to reset cycles. */
627 : if (watchdog != old_wd)
628 : clocksource_reset_watchdog();
629 :
630 : /* Check if the watchdog timer needs to be started. */
631 : clocksource_start_watchdog();
632 : spin_unlock_irqrestore(&watchdog_lock, flags);
633 : }
634 :
635 : static void clocksource_dequeue_watchdog(struct clocksource *cs)
636 : {
637 : if (cs != watchdog) {
638 : if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
639 : /* cs is a watched clocksource. */
640 : list_del_init(&cs->wd_list);
641 : /* Check if the watchdog timer needs to be stopped. */
642 : clocksource_stop_watchdog();
643 : }
644 : }
645 : }
646 :
647 : static int __clocksource_watchdog_kthread(void)
648 : {
649 : struct clocksource *cs, *tmp;
650 : unsigned long flags;
651 : int select = 0;
652 :
653 : /* Do any required per-CPU skew verification. */
654 : if (curr_clocksource &&
655 : curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
656 : curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
657 : clocksource_verify_percpu(curr_clocksource);
658 :
659 : spin_lock_irqsave(&watchdog_lock, flags);
660 : list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
661 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
662 : list_del_init(&cs->wd_list);
663 : __clocksource_change_rating(cs, 0);
664 : select = 1;
665 : }
666 : if (cs->flags & CLOCK_SOURCE_RESELECT) {
667 : cs->flags &= ~CLOCK_SOURCE_RESELECT;
668 : select = 1;
669 : }
670 : }
671 : /* Check if the watchdog timer needs to be stopped. */
672 : clocksource_stop_watchdog();
673 : spin_unlock_irqrestore(&watchdog_lock, flags);
674 :
675 : return select;
676 : }
677 :
678 : static int clocksource_watchdog_kthread(void *data)
679 : {
680 : mutex_lock(&clocksource_mutex);
681 : if (__clocksource_watchdog_kthread())
682 : clocksource_select();
683 : mutex_unlock(&clocksource_mutex);
684 : return 0;
685 : }
686 :
687 : static bool clocksource_is_watchdog(struct clocksource *cs)
688 : {
689 : return cs == watchdog;
690 : }
691 :
692 : #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
693 :
694 : static void clocksource_enqueue_watchdog(struct clocksource *cs)
695 : {
696 2 : if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
697 1 : cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
698 : }
699 :
700 : static void clocksource_select_watchdog(bool fallback) { }
701 : static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
702 : static inline void clocksource_resume_watchdog(void) { }
703 : static inline int __clocksource_watchdog_kthread(void) { return 0; }
704 : static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
705 0 : void clocksource_mark_unstable(struct clocksource *cs) { }
706 :
707 : static inline void clocksource_watchdog_lock(unsigned long *flags) { }
708 : static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
709 :
710 : #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
711 :
712 : static bool clocksource_is_suspend(struct clocksource *cs)
713 : {
714 0 : return cs == suspend_clocksource;
715 : }
716 :
717 2 : static void __clocksource_suspend_select(struct clocksource *cs)
718 : {
719 : /*
720 : * Skip the clocksource which will be stopped in suspend state.
721 : */
722 2 : if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
723 : return;
724 :
725 : /*
726 : * The nonstop clocksource can be selected as the suspend clocksource to
727 : * calculate the suspend time, so it should not supply suspend/resume
728 : * interfaces to suspend the nonstop clocksource when system suspends.
729 : */
730 0 : if (cs->suspend || cs->resume) {
731 0 : pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
732 : cs->name);
733 : }
734 :
735 : /* Pick the best rating. */
736 0 : if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
737 0 : suspend_clocksource = cs;
738 : }
739 :
740 : /**
741 : * clocksource_suspend_select - Select the best clocksource for suspend timing
742 : * @fallback: if select a fallback clocksource
743 : */
744 0 : static void clocksource_suspend_select(bool fallback)
745 : {
746 : struct clocksource *cs, *old_suspend;
747 :
748 0 : old_suspend = suspend_clocksource;
749 0 : if (fallback)
750 0 : suspend_clocksource = NULL;
751 :
752 0 : list_for_each_entry(cs, &clocksource_list, list) {
753 : /* Skip current if we were requested for a fallback. */
754 0 : if (fallback && cs == old_suspend)
755 0 : continue;
756 :
757 0 : __clocksource_suspend_select(cs);
758 : }
759 0 : }
760 :
761 : /**
762 : * clocksource_start_suspend_timing - Start measuring the suspend timing
763 : * @cs: current clocksource from timekeeping
764 : * @start_cycles: current cycles from timekeeping
765 : *
766 : * This function will save the start cycle values of suspend timer to calculate
767 : * the suspend time when resuming system.
768 : *
769 : * This function is called late in the suspend process from timekeeping_suspend(),
770 : * that means processes are frozen, non-boot cpus and interrupts are disabled
771 : * now. It is therefore possible to start the suspend timer without taking the
772 : * clocksource mutex.
773 : */
774 0 : void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
775 : {
776 0 : if (!suspend_clocksource)
777 : return;
778 :
779 : /*
780 : * If current clocksource is the suspend timer, we should use the
781 : * tkr_mono.cycle_last value as suspend_start to avoid same reading
782 : * from suspend timer.
783 : */
784 0 : if (clocksource_is_suspend(cs)) {
785 0 : suspend_start = start_cycles;
786 0 : return;
787 : }
788 :
789 0 : if (suspend_clocksource->enable &&
790 0 : suspend_clocksource->enable(suspend_clocksource)) {
791 0 : pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
792 : return;
793 : }
794 :
795 0 : suspend_start = suspend_clocksource->read(suspend_clocksource);
796 : }
797 :
798 : /**
799 : * clocksource_stop_suspend_timing - Stop measuring the suspend timing
800 : * @cs: current clocksource from timekeeping
801 : * @cycle_now: current cycles from timekeeping
802 : *
803 : * This function will calculate the suspend time from suspend timer.
804 : *
805 : * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
806 : *
807 : * This function is called early in the resume process from timekeeping_resume(),
808 : * that means there is only one cpu, no processes are running and the interrupts
809 : * are disabled. It is therefore possible to stop the suspend timer without
810 : * taking the clocksource mutex.
811 : */
812 0 : u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
813 : {
814 0 : u64 now, delta, nsec = 0;
815 :
816 0 : if (!suspend_clocksource)
817 : return 0;
818 :
819 : /*
820 : * If current clocksource is the suspend timer, we should use the
821 : * tkr_mono.cycle_last value from timekeeping as current cycle to
822 : * avoid same reading from suspend timer.
823 : */
824 0 : if (clocksource_is_suspend(cs))
825 : now = cycle_now;
826 : else
827 0 : now = suspend_clocksource->read(suspend_clocksource);
828 :
829 0 : if (now > suspend_start) {
830 0 : delta = clocksource_delta(now, suspend_start,
831 0 : suspend_clocksource->mask);
832 0 : nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
833 : suspend_clocksource->shift);
834 : }
835 :
836 : /*
837 : * Disable the suspend timer to save power if current clocksource is
838 : * not the suspend timer.
839 : */
840 0 : if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
841 0 : suspend_clocksource->disable(suspend_clocksource);
842 :
843 : return nsec;
844 : }
845 :
846 : /**
847 : * clocksource_suspend - suspend the clocksource(s)
848 : */
849 0 : void clocksource_suspend(void)
850 : {
851 : struct clocksource *cs;
852 :
853 0 : list_for_each_entry_reverse(cs, &clocksource_list, list)
854 0 : if (cs->suspend)
855 0 : cs->suspend(cs);
856 0 : }
857 :
858 : /**
859 : * clocksource_resume - resume the clocksource(s)
860 : */
861 0 : void clocksource_resume(void)
862 : {
863 : struct clocksource *cs;
864 :
865 0 : list_for_each_entry(cs, &clocksource_list, list)
866 0 : if (cs->resume)
867 0 : cs->resume(cs);
868 :
869 : clocksource_resume_watchdog();
870 0 : }
871 :
872 : /**
873 : * clocksource_touch_watchdog - Update watchdog
874 : *
875 : * Update the watchdog after exception contexts such as kgdb so as not
876 : * to incorrectly trip the watchdog. This might fail when the kernel
877 : * was stopped in code which holds watchdog_lock.
878 : */
879 0 : void clocksource_touch_watchdog(void)
880 : {
881 : clocksource_resume_watchdog();
882 0 : }
883 :
884 : /**
885 : * clocksource_max_adjustment- Returns max adjustment amount
886 : * @cs: Pointer to clocksource
887 : *
888 : */
889 : static u32 clocksource_max_adjustment(struct clocksource *cs)
890 : {
891 : u64 ret;
892 : /*
893 : * We won't try to correct for more than 11% adjustments (110,000 ppm),
894 : */
895 2 : ret = (u64)cs->mult * 11;
896 2 : do_div(ret,100);
897 2 : return (u32)ret;
898 : }
899 :
900 : /**
901 : * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
902 : * @mult: cycle to nanosecond multiplier
903 : * @shift: cycle to nanosecond divisor (power of two)
904 : * @maxadj: maximum adjustment value to mult (~11%)
905 : * @mask: bitmask for two's complement subtraction of non 64 bit counters
906 : * @max_cyc: maximum cycle value before potential overflow (does not include
907 : * any safety margin)
908 : *
909 : * NOTE: This function includes a safety margin of 50%, in other words, we
910 : * return half the number of nanoseconds the hardware counter can technically
911 : * cover. This is done so that we can potentially detect problems caused by
912 : * delayed timers or bad hardware, which might result in time intervals that
913 : * are larger than what the math used can handle without overflows.
914 : */
915 0 : u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
916 : {
917 : u64 max_nsecs, max_cycles;
918 :
919 : /*
920 : * Calculate the maximum number of cycles that we can pass to the
921 : * cyc2ns() function without overflowing a 64-bit result.
922 : */
923 2 : max_cycles = ULLONG_MAX;
924 2 : do_div(max_cycles, mult+maxadj);
925 :
926 : /*
927 : * The actual maximum number of cycles we can defer the clocksource is
928 : * determined by the minimum of max_cycles and mask.
929 : * Note: Here we subtract the maxadj to make sure we don't sleep for
930 : * too long if there's a large negative adjustment.
931 : */
932 2 : max_cycles = min(max_cycles, mask);
933 4 : max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
934 :
935 : /* return the max_cycles value as well if requested */
936 2 : if (max_cyc)
937 2 : *max_cyc = max_cycles;
938 :
939 : /* Return 50% of the actual maximum, so we can detect bad values */
940 2 : max_nsecs >>= 1;
941 :
942 0 : return max_nsecs;
943 : }
944 :
945 : /**
946 : * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
947 : * @cs: Pointer to clocksource to be updated
948 : *
949 : */
950 : static inline void clocksource_update_max_deferment(struct clocksource *cs)
951 : {
952 4 : cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
953 : cs->maxadj, cs->mask,
954 : &cs->max_cycles);
955 : }
956 :
957 3 : static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
958 : {
959 : struct clocksource *cs;
960 :
961 4 : if (!finished_booting || list_empty(&clocksource_list))
962 : return NULL;
963 :
964 : /*
965 : * We pick the clocksource with the highest rating. If oneshot
966 : * mode is active, we pick the highres valid clocksource with
967 : * the best rating.
968 : */
969 1 : list_for_each_entry(cs, &clocksource_list, list) {
970 1 : if (skipcur && cs == curr_clocksource)
971 0 : continue;
972 1 : if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
973 0 : continue;
974 : return cs;
975 : }
976 : return NULL;
977 : }
978 :
979 3 : static void __clocksource_select(bool skipcur)
980 : {
981 3 : bool oneshot = tick_oneshot_mode_active();
982 : struct clocksource *best, *cs;
983 :
984 : /* Find the best suitable clocksource */
985 3 : best = clocksource_find_best(oneshot, skipcur);
986 3 : if (!best)
987 : return;
988 :
989 1 : if (!strlen(override_name))
990 : goto found;
991 :
992 : /* Check for the override clocksource. */
993 0 : list_for_each_entry(cs, &clocksource_list, list) {
994 0 : if (skipcur && cs == curr_clocksource)
995 0 : continue;
996 0 : if (strcmp(cs->name, override_name) != 0)
997 0 : continue;
998 : /*
999 : * Check to make sure we don't switch to a non-highres
1000 : * capable clocksource if the tick code is in oneshot
1001 : * mode (highres or nohz)
1002 : */
1003 : if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
1004 : /* Override clocksource cannot be used. */
1005 : if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
1006 : pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
1007 : cs->name);
1008 : override_name[0] = 0;
1009 : } else {
1010 : /*
1011 : * The override cannot be currently verified.
1012 : * Deferring to let the watchdog check.
1013 : */
1014 : pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
1015 : cs->name);
1016 : }
1017 : } else
1018 : /* Override clocksource can be used. */
1019 : best = cs;
1020 : break;
1021 : }
1022 :
1023 : found:
1024 1 : if (curr_clocksource != best && !timekeeping_notify(best)) {
1025 1 : pr_info("Switched to clocksource %s\n", best->name);
1026 1 : curr_clocksource = best;
1027 : }
1028 : }
1029 :
1030 : /**
1031 : * clocksource_select - Select the best clocksource available
1032 : *
1033 : * Private function. Must hold clocksource_mutex when called.
1034 : *
1035 : * Select the clocksource with the best rating, or the clocksource,
1036 : * which is selected by userspace override.
1037 : */
1038 : static void clocksource_select(void)
1039 : {
1040 3 : __clocksource_select(false);
1041 : }
1042 :
1043 : static void clocksource_select_fallback(void)
1044 : {
1045 0 : __clocksource_select(true);
1046 : }
1047 :
1048 : /*
1049 : * clocksource_done_booting - Called near the end of core bootup
1050 : *
1051 : * Hack to avoid lots of clocksource churn at boot time.
1052 : * We use fs_initcall because we want this to start before
1053 : * device_initcall but after subsys_initcall.
1054 : */
1055 1 : static int __init clocksource_done_booting(void)
1056 : {
1057 1 : mutex_lock(&clocksource_mutex);
1058 1 : curr_clocksource = clocksource_default_clock();
1059 1 : finished_booting = 1;
1060 : /*
1061 : * Run the watchdog first to eliminate unstable clock sources
1062 : */
1063 : __clocksource_watchdog_kthread();
1064 : clocksource_select();
1065 1 : mutex_unlock(&clocksource_mutex);
1066 1 : return 0;
1067 : }
1068 : fs_initcall(clocksource_done_booting);
1069 :
1070 : /*
1071 : * Enqueue the clocksource sorted by rating
1072 : */
1073 : static void clocksource_enqueue(struct clocksource *cs)
1074 : {
1075 2 : struct list_head *entry = &clocksource_list;
1076 : struct clocksource *tmp;
1077 :
1078 3 : list_for_each_entry(tmp, &clocksource_list, list) {
1079 : /* Keep track of the place, where to insert */
1080 1 : if (tmp->rating < cs->rating)
1081 : break;
1082 1 : entry = &tmp->list;
1083 : }
1084 4 : list_add(&cs->list, entry);
1085 : }
1086 :
1087 : /**
1088 : * __clocksource_update_freq_scale - Used update clocksource with new freq
1089 : * @cs: clocksource to be registered
1090 : * @scale: Scale factor multiplied against freq to get clocksource hz
1091 : * @freq: clocksource frequency (cycles per second) divided by scale
1092 : *
1093 : * This should only be called from the clocksource->enable() method.
1094 : *
1095 : * This *SHOULD NOT* be called directly! Please use the
1096 : * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
1097 : * functions.
1098 : */
1099 2 : void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
1100 : {
1101 : u64 sec;
1102 :
1103 : /*
1104 : * Default clocksources are *special* and self-define their mult/shift.
1105 : * But, you're not special, so you should specify a freq value.
1106 : */
1107 2 : if (freq) {
1108 : /*
1109 : * Calc the maximum number of seconds which we can run before
1110 : * wrapping around. For clocksources which have a mask > 32-bit
1111 : * we need to limit the max sleep time to have a good
1112 : * conversion precision. 10 minutes is still a reasonable
1113 : * amount. That results in a shift value of 24 for a
1114 : * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
1115 : * ~ 0.06ppm granularity for NTP.
1116 : */
1117 1 : sec = cs->mask;
1118 1 : do_div(sec, freq);
1119 1 : do_div(sec, scale);
1120 1 : if (!sec)
1121 : sec = 1;
1122 1 : else if (sec > 600 && cs->mask > UINT_MAX)
1123 1 : sec = 600;
1124 :
1125 2 : clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
1126 1 : NSEC_PER_SEC / scale, sec * scale);
1127 : }
1128 :
1129 : /*
1130 : * If the uncertainty margin is not specified, calculate it.
1131 : * If both scale and freq are non-zero, calculate the clock
1132 : * period, but bound below at 2*WATCHDOG_MAX_SKEW. However,
1133 : * if either of scale or freq is zero, be very conservative and
1134 : * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the
1135 : * uncertainty margin. Allow stupidly small uncertainty margins
1136 : * to be specified by the caller for testing purposes, but warn
1137 : * to discourage production use of this capability.
1138 : */
1139 2 : if (scale && freq && !cs->uncertainty_margin) {
1140 1 : cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq);
1141 1 : if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW)
1142 1 : cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW;
1143 1 : } else if (!cs->uncertainty_margin) {
1144 0 : cs->uncertainty_margin = WATCHDOG_THRESHOLD;
1145 : }
1146 2 : WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW);
1147 :
1148 : /*
1149 : * Ensure clocksources that have large 'mult' values don't overflow
1150 : * when adjusted.
1151 : */
1152 4 : cs->maxadj = clocksource_max_adjustment(cs);
1153 4 : while (freq && ((cs->mult + cs->maxadj < cs->mult)
1154 1 : || (cs->mult - cs->maxadj > cs->mult))) {
1155 0 : cs->mult >>= 1;
1156 0 : cs->shift--;
1157 0 : cs->maxadj = clocksource_max_adjustment(cs);
1158 : }
1159 :
1160 : /*
1161 : * Only warn for *special* clocksources that self-define
1162 : * their mult/shift values and don't specify a freq.
1163 : */
1164 2 : WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
1165 : "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
1166 : cs->name);
1167 :
1168 2 : clocksource_update_max_deferment(cs);
1169 :
1170 2 : pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
1171 : cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
1172 2 : }
1173 : EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
1174 :
1175 : /**
1176 : * __clocksource_register_scale - Used to install new clocksources
1177 : * @cs: clocksource to be registered
1178 : * @scale: Scale factor multiplied against freq to get clocksource hz
1179 : * @freq: clocksource frequency (cycles per second) divided by scale
1180 : *
1181 : * Returns -EBUSY if registration fails, zero otherwise.
1182 : *
1183 : * This *SHOULD NOT* be called directly! Please use the
1184 : * clocksource_register_hz() or clocksource_register_khz helper functions.
1185 : */
1186 2 : int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
1187 : {
1188 : unsigned long flags;
1189 :
1190 2 : clocksource_arch_init(cs);
1191 :
1192 2 : if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX))
1193 0 : cs->id = CSID_GENERIC;
1194 2 : if (cs->vdso_clock_mode < 0 ||
1195 2 : cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
1196 0 : pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
1197 : cs->name, cs->vdso_clock_mode);
1198 0 : cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
1199 : }
1200 :
1201 : /* Initialize mult/shift and max_idle_ns */
1202 2 : __clocksource_update_freq_scale(cs, scale, freq);
1203 :
1204 : /* Add clocksource to the clocksource list */
1205 2 : mutex_lock(&clocksource_mutex);
1206 :
1207 2 : clocksource_watchdog_lock(&flags);
1208 2 : clocksource_enqueue(cs);
1209 2 : clocksource_enqueue_watchdog(cs);
1210 2 : clocksource_watchdog_unlock(&flags);
1211 :
1212 2 : clocksource_select();
1213 2 : clocksource_select_watchdog(false);
1214 2 : __clocksource_suspend_select(cs);
1215 2 : mutex_unlock(&clocksource_mutex);
1216 2 : return 0;
1217 : }
1218 : EXPORT_SYMBOL_GPL(__clocksource_register_scale);
1219 :
1220 0 : static void __clocksource_change_rating(struct clocksource *cs, int rating)
1221 : {
1222 0 : list_del(&cs->list);
1223 0 : cs->rating = rating;
1224 0 : clocksource_enqueue(cs);
1225 0 : }
1226 :
1227 : /**
1228 : * clocksource_change_rating - Change the rating of a registered clocksource
1229 : * @cs: clocksource to be changed
1230 : * @rating: new rating
1231 : */
1232 0 : void clocksource_change_rating(struct clocksource *cs, int rating)
1233 : {
1234 : unsigned long flags;
1235 :
1236 0 : mutex_lock(&clocksource_mutex);
1237 0 : clocksource_watchdog_lock(&flags);
1238 0 : __clocksource_change_rating(cs, rating);
1239 0 : clocksource_watchdog_unlock(&flags);
1240 :
1241 0 : clocksource_select();
1242 0 : clocksource_select_watchdog(false);
1243 0 : clocksource_suspend_select(false);
1244 0 : mutex_unlock(&clocksource_mutex);
1245 0 : }
1246 : EXPORT_SYMBOL(clocksource_change_rating);
1247 :
1248 : /*
1249 : * Unbind clocksource @cs. Called with clocksource_mutex held
1250 : */
1251 0 : static int clocksource_unbind(struct clocksource *cs)
1252 : {
1253 : unsigned long flags;
1254 :
1255 0 : if (clocksource_is_watchdog(cs)) {
1256 : /* Select and try to install a replacement watchdog. */
1257 : clocksource_select_watchdog(true);
1258 : if (clocksource_is_watchdog(cs))
1259 : return -EBUSY;
1260 : }
1261 :
1262 0 : if (cs == curr_clocksource) {
1263 : /* Select and try to install a replacement clock source */
1264 : clocksource_select_fallback();
1265 0 : if (curr_clocksource == cs)
1266 : return -EBUSY;
1267 : }
1268 :
1269 0 : if (clocksource_is_suspend(cs)) {
1270 : /*
1271 : * Select and try to install a replacement suspend clocksource.
1272 : * If no replacement suspend clocksource, we will just let the
1273 : * clocksource go and have no suspend clocksource.
1274 : */
1275 0 : clocksource_suspend_select(true);
1276 : }
1277 :
1278 0 : clocksource_watchdog_lock(&flags);
1279 0 : clocksource_dequeue_watchdog(cs);
1280 0 : list_del_init(&cs->list);
1281 0 : clocksource_watchdog_unlock(&flags);
1282 :
1283 0 : return 0;
1284 : }
1285 :
1286 : /**
1287 : * clocksource_unregister - remove a registered clocksource
1288 : * @cs: clocksource to be unregistered
1289 : */
1290 0 : int clocksource_unregister(struct clocksource *cs)
1291 : {
1292 0 : int ret = 0;
1293 :
1294 0 : mutex_lock(&clocksource_mutex);
1295 0 : if (!list_empty(&cs->list))
1296 0 : ret = clocksource_unbind(cs);
1297 0 : mutex_unlock(&clocksource_mutex);
1298 0 : return ret;
1299 : }
1300 : EXPORT_SYMBOL(clocksource_unregister);
1301 :
1302 : #ifdef CONFIG_SYSFS
1303 : /**
1304 : * current_clocksource_show - sysfs interface for current clocksource
1305 : * @dev: unused
1306 : * @attr: unused
1307 : * @buf: char buffer to be filled with clocksource list
1308 : *
1309 : * Provides sysfs interface for listing current clocksource.
1310 : */
1311 0 : static ssize_t current_clocksource_show(struct device *dev,
1312 : struct device_attribute *attr,
1313 : char *buf)
1314 : {
1315 0 : ssize_t count = 0;
1316 :
1317 0 : mutex_lock(&clocksource_mutex);
1318 0 : count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
1319 0 : mutex_unlock(&clocksource_mutex);
1320 :
1321 0 : return count;
1322 : }
1323 :
1324 0 : ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
1325 : {
1326 0 : size_t ret = cnt;
1327 :
1328 : /* strings from sysfs write are not 0 terminated! */
1329 0 : if (!cnt || cnt >= CS_NAME_LEN)
1330 : return -EINVAL;
1331 :
1332 : /* strip of \n: */
1333 0 : if (buf[cnt-1] == '\n')
1334 0 : cnt--;
1335 0 : if (cnt > 0)
1336 0 : memcpy(dst, buf, cnt);
1337 0 : dst[cnt] = 0;
1338 0 : return ret;
1339 : }
1340 :
1341 : /**
1342 : * current_clocksource_store - interface for manually overriding clocksource
1343 : * @dev: unused
1344 : * @attr: unused
1345 : * @buf: name of override clocksource
1346 : * @count: length of buffer
1347 : *
1348 : * Takes input from sysfs interface for manually overriding the default
1349 : * clocksource selection.
1350 : */
1351 0 : static ssize_t current_clocksource_store(struct device *dev,
1352 : struct device_attribute *attr,
1353 : const char *buf, size_t count)
1354 : {
1355 : ssize_t ret;
1356 :
1357 0 : mutex_lock(&clocksource_mutex);
1358 :
1359 0 : ret = sysfs_get_uname(buf, override_name, count);
1360 0 : if (ret >= 0)
1361 : clocksource_select();
1362 :
1363 0 : mutex_unlock(&clocksource_mutex);
1364 :
1365 0 : return ret;
1366 : }
1367 : static DEVICE_ATTR_RW(current_clocksource);
1368 :
1369 : /**
1370 : * unbind_clocksource_store - interface for manually unbinding clocksource
1371 : * @dev: unused
1372 : * @attr: unused
1373 : * @buf: unused
1374 : * @count: length of buffer
1375 : *
1376 : * Takes input from sysfs interface for manually unbinding a clocksource.
1377 : */
1378 0 : static ssize_t unbind_clocksource_store(struct device *dev,
1379 : struct device_attribute *attr,
1380 : const char *buf, size_t count)
1381 : {
1382 : struct clocksource *cs;
1383 : char name[CS_NAME_LEN];
1384 : ssize_t ret;
1385 :
1386 0 : ret = sysfs_get_uname(buf, name, count);
1387 0 : if (ret < 0)
1388 : return ret;
1389 :
1390 0 : ret = -ENODEV;
1391 0 : mutex_lock(&clocksource_mutex);
1392 0 : list_for_each_entry(cs, &clocksource_list, list) {
1393 0 : if (strcmp(cs->name, name))
1394 0 : continue;
1395 0 : ret = clocksource_unbind(cs);
1396 0 : break;
1397 : }
1398 0 : mutex_unlock(&clocksource_mutex);
1399 :
1400 0 : return ret ? ret : count;
1401 : }
1402 : static DEVICE_ATTR_WO(unbind_clocksource);
1403 :
1404 : /**
1405 : * available_clocksource_show - sysfs interface for listing clocksource
1406 : * @dev: unused
1407 : * @attr: unused
1408 : * @buf: char buffer to be filled with clocksource list
1409 : *
1410 : * Provides sysfs interface for listing registered clocksources
1411 : */
1412 0 : static ssize_t available_clocksource_show(struct device *dev,
1413 : struct device_attribute *attr,
1414 : char *buf)
1415 : {
1416 : struct clocksource *src;
1417 0 : ssize_t count = 0;
1418 :
1419 0 : mutex_lock(&clocksource_mutex);
1420 0 : list_for_each_entry(src, &clocksource_list, list) {
1421 : /*
1422 : * Don't show non-HRES clocksource if the tick code is
1423 : * in one shot mode (highres=on or nohz=on)
1424 : */
1425 : if (!tick_oneshot_mode_active() ||
1426 : (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
1427 0 : count += snprintf(buf + count,
1428 0 : max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
1429 : "%s ", src->name);
1430 : }
1431 0 : mutex_unlock(&clocksource_mutex);
1432 :
1433 0 : count += snprintf(buf + count,
1434 0 : max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
1435 :
1436 0 : return count;
1437 : }
1438 : static DEVICE_ATTR_RO(available_clocksource);
1439 :
1440 : static struct attribute *clocksource_attrs[] = {
1441 : &dev_attr_current_clocksource.attr,
1442 : &dev_attr_unbind_clocksource.attr,
1443 : &dev_attr_available_clocksource.attr,
1444 : NULL
1445 : };
1446 : ATTRIBUTE_GROUPS(clocksource);
1447 :
1448 : static struct bus_type clocksource_subsys = {
1449 : .name = "clocksource",
1450 : .dev_name = "clocksource",
1451 : };
1452 :
1453 : static struct device device_clocksource = {
1454 : .id = 0,
1455 : .bus = &clocksource_subsys,
1456 : .groups = clocksource_groups,
1457 : };
1458 :
1459 1 : static int __init init_clocksource_sysfs(void)
1460 : {
1461 1 : int error = subsys_system_register(&clocksource_subsys, NULL);
1462 :
1463 1 : if (!error)
1464 1 : error = device_register(&device_clocksource);
1465 :
1466 1 : return error;
1467 : }
1468 :
1469 : device_initcall(init_clocksource_sysfs);
1470 : #endif /* CONFIG_SYSFS */
1471 :
1472 : /**
1473 : * boot_override_clocksource - boot clock override
1474 : * @str: override name
1475 : *
1476 : * Takes a clocksource= boot argument and uses it
1477 : * as the clocksource override name.
1478 : */
1479 0 : static int __init boot_override_clocksource(char* str)
1480 : {
1481 0 : mutex_lock(&clocksource_mutex);
1482 0 : if (str)
1483 : strscpy(override_name, str, sizeof(override_name));
1484 0 : mutex_unlock(&clocksource_mutex);
1485 0 : return 1;
1486 : }
1487 :
1488 : __setup("clocksource=", boot_override_clocksource);
1489 :
1490 : /**
1491 : * boot_override_clock - Compatibility layer for deprecated boot option
1492 : * @str: override name
1493 : *
1494 : * DEPRECATED! Takes a clock= boot argument and uses it
1495 : * as the clocksource override name
1496 : */
1497 0 : static int __init boot_override_clock(char* str)
1498 : {
1499 0 : if (!strcmp(str, "pmtmr")) {
1500 0 : pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
1501 0 : return boot_override_clocksource("acpi_pm");
1502 : }
1503 0 : pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
1504 0 : return boot_override_clocksource(str);
1505 : }
1506 :
1507 : __setup("clock=", boot_override_clock);
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