clocksource.c 23 KB

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  1. /*
  2. * linux/kernel/time/clocksource.c
  3. *
  4. * This file contains the functions which manage clocksource drivers.
  5. *
  6. * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
  7. *
  8. * This program is free software; you can redistribute it and/or modify
  9. * it under the terms of the GNU General Public License as published by
  10. * the Free Software Foundation; either version 2 of the License, or
  11. * (at your option) any later version.
  12. *
  13. * This program is distributed in the hope that it will be useful,
  14. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16. * GNU General Public License for more details.
  17. *
  18. * You should have received a copy of the GNU General Public License
  19. * along with this program; if not, write to the Free Software
  20. * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21. *
  22. * TODO WishList:
  23. * o Allow clocksource drivers to be unregistered
  24. */
  25. #include <linux/clocksource.h>
  26. #include <linux/sysdev.h>
  27. #include <linux/init.h>
  28. #include <linux/module.h>
  29. #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
  30. #include <linux/tick.h>
  31. #include <linux/kthread.h>
  32. void timecounter_init(struct timecounter *tc,
  33. const struct cyclecounter *cc,
  34. u64 start_tstamp)
  35. {
  36. tc->cc = cc;
  37. tc->cycle_last = cc->read(cc);
  38. tc->nsec = start_tstamp;
  39. }
  40. EXPORT_SYMBOL_GPL(timecounter_init);
  41. /**
  42. * timecounter_read_delta - get nanoseconds since last call of this function
  43. * @tc: Pointer to time counter
  44. *
  45. * When the underlying cycle counter runs over, this will be handled
  46. * correctly as long as it does not run over more than once between
  47. * calls.
  48. *
  49. * The first call to this function for a new time counter initializes
  50. * the time tracking and returns an undefined result.
  51. */
  52. static u64 timecounter_read_delta(struct timecounter *tc)
  53. {
  54. cycle_t cycle_now, cycle_delta;
  55. u64 ns_offset;
  56. /* read cycle counter: */
  57. cycle_now = tc->cc->read(tc->cc);
  58. /* calculate the delta since the last timecounter_read_delta(): */
  59. cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
  60. /* convert to nanoseconds: */
  61. ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta);
  62. /* update time stamp of timecounter_read_delta() call: */
  63. tc->cycle_last = cycle_now;
  64. return ns_offset;
  65. }
  66. u64 timecounter_read(struct timecounter *tc)
  67. {
  68. u64 nsec;
  69. /* increment time by nanoseconds since last call */
  70. nsec = timecounter_read_delta(tc);
  71. nsec += tc->nsec;
  72. tc->nsec = nsec;
  73. return nsec;
  74. }
  75. EXPORT_SYMBOL_GPL(timecounter_read);
  76. u64 timecounter_cyc2time(struct timecounter *tc,
  77. cycle_t cycle_tstamp)
  78. {
  79. u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
  80. u64 nsec;
  81. /*
  82. * Instead of always treating cycle_tstamp as more recent
  83. * than tc->cycle_last, detect when it is too far in the
  84. * future and treat it as old time stamp instead.
  85. */
  86. if (cycle_delta > tc->cc->mask / 2) {
  87. cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
  88. nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta);
  89. } else {
  90. nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec;
  91. }
  92. return nsec;
  93. }
  94. EXPORT_SYMBOL_GPL(timecounter_cyc2time);
  95. /**
  96. * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
  97. * @mult: pointer to mult variable
  98. * @shift: pointer to shift variable
  99. * @from: frequency to convert from
  100. * @to: frequency to convert to
  101. * @minsec: guaranteed runtime conversion range in seconds
  102. *
  103. * The function evaluates the shift/mult pair for the scaled math
  104. * operations of clocksources and clockevents.
  105. *
  106. * @to and @from are frequency values in HZ. For clock sources @to is
  107. * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
  108. * event @to is the counter frequency and @from is NSEC_PER_SEC.
  109. *
  110. * The @minsec conversion range argument controls the time frame in
  111. * seconds which must be covered by the runtime conversion with the
  112. * calculated mult and shift factors. This guarantees that no 64bit
  113. * overflow happens when the input value of the conversion is
  114. * multiplied with the calculated mult factor. Larger ranges may
  115. * reduce the conversion accuracy by chosing smaller mult and shift
  116. * factors.
  117. */
  118. void
  119. clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec)
  120. {
  121. u64 tmp;
  122. u32 sft, sftacc= 32;
  123. /*
  124. * Calculate the shift factor which is limiting the conversion
  125. * range:
  126. */
  127. tmp = ((u64)minsec * from) >> 32;
  128. while (tmp) {
  129. tmp >>=1;
  130. sftacc--;
  131. }
  132. /*
  133. * Find the conversion shift/mult pair which has the best
  134. * accuracy and fits the maxsec conversion range:
  135. */
  136. for (sft = 32; sft > 0; sft--) {
  137. tmp = (u64) to << sft;
  138. do_div(tmp, from);
  139. if ((tmp >> sftacc) == 0)
  140. break;
  141. }
  142. *mult = tmp;
  143. *shift = sft;
  144. }
  145. /*[Clocksource internal variables]---------
  146. * curr_clocksource:
  147. * currently selected clocksource.
  148. * clocksource_list:
  149. * linked list with the registered clocksources
  150. * clocksource_mutex:
  151. * protects manipulations to curr_clocksource and the clocksource_list
  152. * override_name:
  153. * Name of the user-specified clocksource.
  154. */
  155. static struct clocksource *curr_clocksource;
  156. static LIST_HEAD(clocksource_list);
  157. static DEFINE_MUTEX(clocksource_mutex);
  158. static char override_name[32];
  159. static int finished_booting;
  160. #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
  161. static void clocksource_watchdog_work(struct work_struct *work);
  162. static LIST_HEAD(watchdog_list);
  163. static struct clocksource *watchdog;
  164. static struct timer_list watchdog_timer;
  165. static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
  166. static DEFINE_SPINLOCK(watchdog_lock);
  167. static cycle_t watchdog_last;
  168. static int watchdog_running;
  169. static int clocksource_watchdog_kthread(void *data);
  170. static void __clocksource_change_rating(struct clocksource *cs, int rating);
  171. /*
  172. * Interval: 0.5sec Threshold: 0.0625s
  173. */
  174. #define WATCHDOG_INTERVAL (HZ >> 1)
  175. #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
  176. static void clocksource_watchdog_work(struct work_struct *work)
  177. {
  178. /*
  179. * If kthread_run fails the next watchdog scan over the
  180. * watchdog_list will find the unstable clock again.
  181. */
  182. kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
  183. }
  184. static void __clocksource_unstable(struct clocksource *cs)
  185. {
  186. cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
  187. cs->flags |= CLOCK_SOURCE_UNSTABLE;
  188. if (finished_booting)
  189. schedule_work(&watchdog_work);
  190. }
  191. static void clocksource_unstable(struct clocksource *cs, int64_t delta)
  192. {
  193. printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
  194. cs->name, delta);
  195. __clocksource_unstable(cs);
  196. }
  197. /**
  198. * clocksource_mark_unstable - mark clocksource unstable via watchdog
  199. * @cs: clocksource to be marked unstable
  200. *
  201. * This function is called instead of clocksource_change_rating from
  202. * cpu hotplug code to avoid a deadlock between the clocksource mutex
  203. * and the cpu hotplug mutex. It defers the update of the clocksource
  204. * to the watchdog thread.
  205. */
  206. void clocksource_mark_unstable(struct clocksource *cs)
  207. {
  208. unsigned long flags;
  209. spin_lock_irqsave(&watchdog_lock, flags);
  210. if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
  211. if (list_empty(&cs->wd_list))
  212. list_add(&cs->wd_list, &watchdog_list);
  213. __clocksource_unstable(cs);
  214. }
  215. spin_unlock_irqrestore(&watchdog_lock, flags);
  216. }
  217. static void clocksource_watchdog(unsigned long data)
  218. {
  219. struct clocksource *cs;
  220. cycle_t csnow, wdnow;
  221. int64_t wd_nsec, cs_nsec;
  222. int next_cpu;
  223. spin_lock(&watchdog_lock);
  224. if (!watchdog_running)
  225. goto out;
  226. wdnow = watchdog->read(watchdog);
  227. wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask,
  228. watchdog->mult, watchdog->shift);
  229. watchdog_last = wdnow;
  230. list_for_each_entry(cs, &watchdog_list, wd_list) {
  231. /* Clocksource already marked unstable? */
  232. if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
  233. if (finished_booting)
  234. schedule_work(&watchdog_work);
  235. continue;
  236. }
  237. csnow = cs->read(cs);
  238. /* Clocksource initialized ? */
  239. if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
  240. cs->flags |= CLOCK_SOURCE_WATCHDOG;
  241. cs->wd_last = csnow;
  242. continue;
  243. }
  244. /* Check the deviation from the watchdog clocksource. */
  245. cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) &
  246. cs->mask, cs->mult, cs->shift);
  247. cs->wd_last = csnow;
  248. if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
  249. clocksource_unstable(cs, cs_nsec - wd_nsec);
  250. continue;
  251. }
  252. if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
  253. (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
  254. (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
  255. cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
  256. /*
  257. * We just marked the clocksource as highres-capable,
  258. * notify the rest of the system as well so that we
  259. * transition into high-res mode:
  260. */
  261. tick_clock_notify();
  262. }
  263. }
  264. /*
  265. * Cycle through CPUs to check if the CPUs stay synchronized
  266. * to each other.
  267. */
  268. next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
  269. if (next_cpu >= nr_cpu_ids)
  270. next_cpu = cpumask_first(cpu_online_mask);
  271. watchdog_timer.expires += WATCHDOG_INTERVAL;
  272. add_timer_on(&watchdog_timer, next_cpu);
  273. out:
  274. spin_unlock(&watchdog_lock);
  275. }
  276. static inline void clocksource_start_watchdog(void)
  277. {
  278. if (watchdog_running || !watchdog || list_empty(&watchdog_list))
  279. return;
  280. init_timer(&watchdog_timer);
  281. watchdog_timer.function = clocksource_watchdog;
  282. watchdog_last = watchdog->read(watchdog);
  283. watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
  284. add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
  285. watchdog_running = 1;
  286. }
  287. static inline void clocksource_stop_watchdog(void)
  288. {
  289. if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
  290. return;
  291. del_timer(&watchdog_timer);
  292. watchdog_running = 0;
  293. }
  294. static inline void clocksource_reset_watchdog(void)
  295. {
  296. struct clocksource *cs;
  297. list_for_each_entry(cs, &watchdog_list, wd_list)
  298. cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
  299. }
  300. static void clocksource_resume_watchdog(void)
  301. {
  302. unsigned long flags;
  303. /*
  304. * We use trylock here to avoid a potential dead lock when
  305. * kgdb calls this code after the kernel has been stopped with
  306. * watchdog_lock held. When watchdog_lock is held we just
  307. * return and accept, that the watchdog might trigger and mark
  308. * the monitored clock source (usually TSC) unstable.
  309. *
  310. * This does not affect the other caller clocksource_resume()
  311. * because at this point the kernel is UP, interrupts are
  312. * disabled and nothing can hold watchdog_lock.
  313. */
  314. if (!spin_trylock_irqsave(&watchdog_lock, flags))
  315. return;
  316. clocksource_reset_watchdog();
  317. spin_unlock_irqrestore(&watchdog_lock, flags);
  318. }
  319. static void clocksource_enqueue_watchdog(struct clocksource *cs)
  320. {
  321. unsigned long flags;
  322. spin_lock_irqsave(&watchdog_lock, flags);
  323. if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
  324. /* cs is a clocksource to be watched. */
  325. list_add(&cs->wd_list, &watchdog_list);
  326. cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
  327. } else {
  328. /* cs is a watchdog. */
  329. if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
  330. cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
  331. /* Pick the best watchdog. */
  332. if (!watchdog || cs->rating > watchdog->rating) {
  333. watchdog = cs;
  334. /* Reset watchdog cycles */
  335. clocksource_reset_watchdog();
  336. }
  337. }
  338. /* Check if the watchdog timer needs to be started. */
  339. clocksource_start_watchdog();
  340. spin_unlock_irqrestore(&watchdog_lock, flags);
  341. }
  342. static void clocksource_dequeue_watchdog(struct clocksource *cs)
  343. {
  344. struct clocksource *tmp;
  345. unsigned long flags;
  346. spin_lock_irqsave(&watchdog_lock, flags);
  347. if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
  348. /* cs is a watched clocksource. */
  349. list_del_init(&cs->wd_list);
  350. } else if (cs == watchdog) {
  351. /* Reset watchdog cycles */
  352. clocksource_reset_watchdog();
  353. /* Current watchdog is removed. Find an alternative. */
  354. watchdog = NULL;
  355. list_for_each_entry(tmp, &clocksource_list, list) {
  356. if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
  357. continue;
  358. if (!watchdog || tmp->rating > watchdog->rating)
  359. watchdog = tmp;
  360. }
  361. }
  362. cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
  363. /* Check if the watchdog timer needs to be stopped. */
  364. clocksource_stop_watchdog();
  365. spin_unlock_irqrestore(&watchdog_lock, flags);
  366. }
  367. static int clocksource_watchdog_kthread(void *data)
  368. {
  369. struct clocksource *cs, *tmp;
  370. unsigned long flags;
  371. LIST_HEAD(unstable);
  372. mutex_lock(&clocksource_mutex);
  373. spin_lock_irqsave(&watchdog_lock, flags);
  374. list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
  375. if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
  376. list_del_init(&cs->wd_list);
  377. list_add(&cs->wd_list, &unstable);
  378. }
  379. /* Check if the watchdog timer needs to be stopped. */
  380. clocksource_stop_watchdog();
  381. spin_unlock_irqrestore(&watchdog_lock, flags);
  382. /* Needs to be done outside of watchdog lock */
  383. list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
  384. list_del_init(&cs->wd_list);
  385. __clocksource_change_rating(cs, 0);
  386. }
  387. mutex_unlock(&clocksource_mutex);
  388. return 0;
  389. }
  390. #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
  391. static void clocksource_enqueue_watchdog(struct clocksource *cs)
  392. {
  393. if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
  394. cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
  395. }
  396. static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
  397. static inline void clocksource_resume_watchdog(void) { }
  398. static inline int clocksource_watchdog_kthread(void *data) { return 0; }
  399. #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
  400. /**
  401. * clocksource_resume - resume the clocksource(s)
  402. */
  403. void clocksource_resume(void)
  404. {
  405. struct clocksource *cs;
  406. list_for_each_entry(cs, &clocksource_list, list)
  407. if (cs->resume)
  408. cs->resume();
  409. clocksource_resume_watchdog();
  410. }
  411. /**
  412. * clocksource_touch_watchdog - Update watchdog
  413. *
  414. * Update the watchdog after exception contexts such as kgdb so as not
  415. * to incorrectly trip the watchdog. This might fail when the kernel
  416. * was stopped in code which holds watchdog_lock.
  417. */
  418. void clocksource_touch_watchdog(void)
  419. {
  420. clocksource_resume_watchdog();
  421. }
  422. /**
  423. * clocksource_max_deferment - Returns max time the clocksource can be deferred
  424. * @cs: Pointer to clocksource
  425. *
  426. */
  427. static u64 clocksource_max_deferment(struct clocksource *cs)
  428. {
  429. u64 max_nsecs, max_cycles;
  430. /*
  431. * Calculate the maximum number of cycles that we can pass to the
  432. * cyc2ns function without overflowing a 64-bit signed result. The
  433. * maximum number of cycles is equal to ULLONG_MAX/cs->mult which
  434. * is equivalent to the below.
  435. * max_cycles < (2^63)/cs->mult
  436. * max_cycles < 2^(log2((2^63)/cs->mult))
  437. * max_cycles < 2^(log2(2^63) - log2(cs->mult))
  438. * max_cycles < 2^(63 - log2(cs->mult))
  439. * max_cycles < 1 << (63 - log2(cs->mult))
  440. * Please note that we add 1 to the result of the log2 to account for
  441. * any rounding errors, ensure the above inequality is satisfied and
  442. * no overflow will occur.
  443. */
  444. max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1));
  445. /*
  446. * The actual maximum number of cycles we can defer the clocksource is
  447. * determined by the minimum of max_cycles and cs->mask.
  448. */
  449. max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
  450. max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift);
  451. /*
  452. * To ensure that the clocksource does not wrap whilst we are idle,
  453. * limit the time the clocksource can be deferred by 12.5%. Please
  454. * note a margin of 12.5% is used because this can be computed with
  455. * a shift, versus say 10% which would require division.
  456. */
  457. return max_nsecs - (max_nsecs >> 5);
  458. }
  459. #ifdef CONFIG_GENERIC_TIME
  460. /**
  461. * clocksource_select - Select the best clocksource available
  462. *
  463. * Private function. Must hold clocksource_mutex when called.
  464. *
  465. * Select the clocksource with the best rating, or the clocksource,
  466. * which is selected by userspace override.
  467. */
  468. static void clocksource_select(void)
  469. {
  470. struct clocksource *best, *cs;
  471. if (!finished_booting || list_empty(&clocksource_list))
  472. return;
  473. /* First clocksource on the list has the best rating. */
  474. best = list_first_entry(&clocksource_list, struct clocksource, list);
  475. /* Check for the override clocksource. */
  476. list_for_each_entry(cs, &clocksource_list, list) {
  477. if (strcmp(cs->name, override_name) != 0)
  478. continue;
  479. /*
  480. * Check to make sure we don't switch to a non-highres
  481. * capable clocksource if the tick code is in oneshot
  482. * mode (highres or nohz)
  483. */
  484. if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
  485. tick_oneshot_mode_active()) {
  486. /* Override clocksource cannot be used. */
  487. printk(KERN_WARNING "Override clocksource %s is not "
  488. "HRT compatible. Cannot switch while in "
  489. "HRT/NOHZ mode\n", cs->name);
  490. override_name[0] = 0;
  491. } else
  492. /* Override clocksource can be used. */
  493. best = cs;
  494. break;
  495. }
  496. if (curr_clocksource != best) {
  497. printk(KERN_INFO "Switching to clocksource %s\n", best->name);
  498. curr_clocksource = best;
  499. timekeeping_notify(curr_clocksource);
  500. }
  501. }
  502. #else /* CONFIG_GENERIC_TIME */
  503. static inline void clocksource_select(void) { }
  504. #endif
  505. /*
  506. * clocksource_done_booting - Called near the end of core bootup
  507. *
  508. * Hack to avoid lots of clocksource churn at boot time.
  509. * We use fs_initcall because we want this to start before
  510. * device_initcall but after subsys_initcall.
  511. */
  512. static int __init clocksource_done_booting(void)
  513. {
  514. finished_booting = 1;
  515. /*
  516. * Run the watchdog first to eliminate unstable clock sources
  517. */
  518. clocksource_watchdog_kthread(NULL);
  519. mutex_lock(&clocksource_mutex);
  520. clocksource_select();
  521. mutex_unlock(&clocksource_mutex);
  522. return 0;
  523. }
  524. fs_initcall(clocksource_done_booting);
  525. /*
  526. * Enqueue the clocksource sorted by rating
  527. */
  528. static void clocksource_enqueue(struct clocksource *cs)
  529. {
  530. struct list_head *entry = &clocksource_list;
  531. struct clocksource *tmp;
  532. list_for_each_entry(tmp, &clocksource_list, list)
  533. /* Keep track of the place, where to insert */
  534. if (tmp->rating >= cs->rating)
  535. entry = &tmp->list;
  536. list_add(&cs->list, entry);
  537. }
  538. /**
  539. * clocksource_register - Used to install new clocksources
  540. * @t: clocksource to be registered
  541. *
  542. * Returns -EBUSY if registration fails, zero otherwise.
  543. */
  544. int clocksource_register(struct clocksource *cs)
  545. {
  546. /* calculate max idle time permitted for this clocksource */
  547. cs->max_idle_ns = clocksource_max_deferment(cs);
  548. mutex_lock(&clocksource_mutex);
  549. clocksource_enqueue(cs);
  550. clocksource_select();
  551. clocksource_enqueue_watchdog(cs);
  552. mutex_unlock(&clocksource_mutex);
  553. return 0;
  554. }
  555. EXPORT_SYMBOL(clocksource_register);
  556. static void __clocksource_change_rating(struct clocksource *cs, int rating)
  557. {
  558. list_del(&cs->list);
  559. cs->rating = rating;
  560. clocksource_enqueue(cs);
  561. clocksource_select();
  562. }
  563. /**
  564. * clocksource_change_rating - Change the rating of a registered clocksource
  565. */
  566. void clocksource_change_rating(struct clocksource *cs, int rating)
  567. {
  568. mutex_lock(&clocksource_mutex);
  569. __clocksource_change_rating(cs, rating);
  570. mutex_unlock(&clocksource_mutex);
  571. }
  572. EXPORT_SYMBOL(clocksource_change_rating);
  573. /**
  574. * clocksource_unregister - remove a registered clocksource
  575. */
  576. void clocksource_unregister(struct clocksource *cs)
  577. {
  578. mutex_lock(&clocksource_mutex);
  579. clocksource_dequeue_watchdog(cs);
  580. list_del(&cs->list);
  581. clocksource_select();
  582. mutex_unlock(&clocksource_mutex);
  583. }
  584. EXPORT_SYMBOL(clocksource_unregister);
  585. #ifdef CONFIG_SYSFS
  586. /**
  587. * sysfs_show_current_clocksources - sysfs interface for current clocksource
  588. * @dev: unused
  589. * @buf: char buffer to be filled with clocksource list
  590. *
  591. * Provides sysfs interface for listing current clocksource.
  592. */
  593. static ssize_t
  594. sysfs_show_current_clocksources(struct sys_device *dev,
  595. struct sysdev_attribute *attr, char *buf)
  596. {
  597. ssize_t count = 0;
  598. mutex_lock(&clocksource_mutex);
  599. count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
  600. mutex_unlock(&clocksource_mutex);
  601. return count;
  602. }
  603. /**
  604. * sysfs_override_clocksource - interface for manually overriding clocksource
  605. * @dev: unused
  606. * @buf: name of override clocksource
  607. * @count: length of buffer
  608. *
  609. * Takes input from sysfs interface for manually overriding the default
  610. * clocksource selection.
  611. */
  612. static ssize_t sysfs_override_clocksource(struct sys_device *dev,
  613. struct sysdev_attribute *attr,
  614. const char *buf, size_t count)
  615. {
  616. size_t ret = count;
  617. /* strings from sysfs write are not 0 terminated! */
  618. if (count >= sizeof(override_name))
  619. return -EINVAL;
  620. /* strip of \n: */
  621. if (buf[count-1] == '\n')
  622. count--;
  623. mutex_lock(&clocksource_mutex);
  624. if (count > 0)
  625. memcpy(override_name, buf, count);
  626. override_name[count] = 0;
  627. clocksource_select();
  628. mutex_unlock(&clocksource_mutex);
  629. return ret;
  630. }
  631. /**
  632. * sysfs_show_available_clocksources - sysfs interface for listing clocksource
  633. * @dev: unused
  634. * @buf: char buffer to be filled with clocksource list
  635. *
  636. * Provides sysfs interface for listing registered clocksources
  637. */
  638. static ssize_t
  639. sysfs_show_available_clocksources(struct sys_device *dev,
  640. struct sysdev_attribute *attr,
  641. char *buf)
  642. {
  643. struct clocksource *src;
  644. ssize_t count = 0;
  645. mutex_lock(&clocksource_mutex);
  646. list_for_each_entry(src, &clocksource_list, list) {
  647. /*
  648. * Don't show non-HRES clocksource if the tick code is
  649. * in one shot mode (highres=on or nohz=on)
  650. */
  651. if (!tick_oneshot_mode_active() ||
  652. (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
  653. count += snprintf(buf + count,
  654. max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
  655. "%s ", src->name);
  656. }
  657. mutex_unlock(&clocksource_mutex);
  658. count += snprintf(buf + count,
  659. max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
  660. return count;
  661. }
  662. /*
  663. * Sysfs setup bits:
  664. */
  665. static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
  666. sysfs_override_clocksource);
  667. static SYSDEV_ATTR(available_clocksource, 0444,
  668. sysfs_show_available_clocksources, NULL);
  669. static struct sysdev_class clocksource_sysclass = {
  670. .name = "clocksource",
  671. };
  672. static struct sys_device device_clocksource = {
  673. .id = 0,
  674. .cls = &clocksource_sysclass,
  675. };
  676. static int __init init_clocksource_sysfs(void)
  677. {
  678. int error = sysdev_class_register(&clocksource_sysclass);
  679. if (!error)
  680. error = sysdev_register(&device_clocksource);
  681. if (!error)
  682. error = sysdev_create_file(
  683. &device_clocksource,
  684. &attr_current_clocksource);
  685. if (!error)
  686. error = sysdev_create_file(
  687. &device_clocksource,
  688. &attr_available_clocksource);
  689. return error;
  690. }
  691. device_initcall(init_clocksource_sysfs);
  692. #endif /* CONFIG_SYSFS */
  693. /**
  694. * boot_override_clocksource - boot clock override
  695. * @str: override name
  696. *
  697. * Takes a clocksource= boot argument and uses it
  698. * as the clocksource override name.
  699. */
  700. static int __init boot_override_clocksource(char* str)
  701. {
  702. mutex_lock(&clocksource_mutex);
  703. if (str)
  704. strlcpy(override_name, str, sizeof(override_name));
  705. mutex_unlock(&clocksource_mutex);
  706. return 1;
  707. }
  708. __setup("clocksource=", boot_override_clocksource);
  709. /**
  710. * boot_override_clock - Compatibility layer for deprecated boot option
  711. * @str: override name
  712. *
  713. * DEPRECATED! Takes a clock= boot argument and uses it
  714. * as the clocksource override name
  715. */
  716. static int __init boot_override_clock(char* str)
  717. {
  718. if (!strcmp(str, "pmtmr")) {
  719. printk("Warning: clock=pmtmr is deprecated. "
  720. "Use clocksource=acpi_pm.\n");
  721. return boot_override_clocksource("acpi_pm");
  722. }
  723. printk("Warning! clock= boot option is deprecated. "
  724. "Use clocksource=xyz\n");
  725. return boot_override_clocksource(str);
  726. }
  727. __setup("clock=", boot_override_clock);