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734efb46 JS |
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 | * o get rid of clocksource_jiffies extern | |
25 | */ | |
26 | ||
27 | #include <linux/clocksource.h> | |
28 | #include <linux/sysdev.h> | |
29 | #include <linux/init.h> | |
30 | #include <linux/module.h> | |
dc29a365 | 31 | #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ |
79bf2bb3 | 32 | #include <linux/tick.h> |
734efb46 JS |
33 | |
34 | /* XXX - Would like a better way for initializing curr_clocksource */ | |
35 | extern struct clocksource clocksource_jiffies; | |
36 | ||
37 | /*[Clocksource internal variables]--------- | |
38 | * curr_clocksource: | |
39 | * currently selected clocksource. Initialized to clocksource_jiffies. | |
40 | * next_clocksource: | |
41 | * pending next selected clocksource. | |
42 | * clocksource_list: | |
43 | * linked list with the registered clocksources | |
44 | * clocksource_lock: | |
45 | * protects manipulations to curr_clocksource and next_clocksource | |
46 | * and the clocksource_list | |
47 | * override_name: | |
48 | * Name of the user-specified clocksource. | |
49 | */ | |
50 | static struct clocksource *curr_clocksource = &clocksource_jiffies; | |
51 | static struct clocksource *next_clocksource; | |
92c7e002 | 52 | static struct clocksource *clocksource_override; |
734efb46 JS |
53 | static LIST_HEAD(clocksource_list); |
54 | static DEFINE_SPINLOCK(clocksource_lock); | |
55 | static char override_name[32]; | |
56 | static int finished_booting; | |
57 | ||
6bb74df4 | 58 | /* clocksource_done_booting - Called near the end of core bootup |
734efb46 | 59 | * |
6bb74df4 JS |
60 | * Hack to avoid lots of clocksource churn at boot time. |
61 | * We use fs_initcall because we want this to start before | |
62 | * device_initcall but after subsys_initcall. | |
734efb46 | 63 | */ |
ad596171 | 64 | static int __init clocksource_done_booting(void) |
734efb46 JS |
65 | { |
66 | finished_booting = 1; | |
67 | return 0; | |
68 | } | |
6bb74df4 | 69 | fs_initcall(clocksource_done_booting); |
734efb46 | 70 | |
5d8b34fd TG |
71 | #ifdef CONFIG_CLOCKSOURCE_WATCHDOG |
72 | static LIST_HEAD(watchdog_list); | |
73 | static struct clocksource *watchdog; | |
74 | static struct timer_list watchdog_timer; | |
75 | static DEFINE_SPINLOCK(watchdog_lock); | |
76 | static cycle_t watchdog_last; | |
8f89441b | 77 | static unsigned long watchdog_resumed; |
b52f52a0 | 78 | |
5d8b34fd | 79 | /* |
35c35d1a | 80 | * Interval: 0.5sec Threshold: 0.0625s |
5d8b34fd TG |
81 | */ |
82 | #define WATCHDOG_INTERVAL (HZ >> 1) | |
35c35d1a | 83 | #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) |
5d8b34fd TG |
84 | |
85 | static void clocksource_ratewd(struct clocksource *cs, int64_t delta) | |
86 | { | |
35c35d1a | 87 | if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD) |
5d8b34fd TG |
88 | return; |
89 | ||
90 | printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", | |
91 | cs->name, delta); | |
92 | cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); | |
93 | clocksource_change_rating(cs, 0); | |
5d8b34fd TG |
94 | list_del(&cs->wd_list); |
95 | } | |
96 | ||
97 | static void clocksource_watchdog(unsigned long data) | |
98 | { | |
99 | struct clocksource *cs, *tmp; | |
100 | cycle_t csnow, wdnow; | |
101 | int64_t wd_nsec, cs_nsec; | |
b52f52a0 | 102 | int resumed; |
5d8b34fd TG |
103 | |
104 | spin_lock(&watchdog_lock); | |
105 | ||
8f89441b | 106 | resumed = test_and_clear_bit(0, &watchdog_resumed); |
b52f52a0 | 107 | |
5d8b34fd TG |
108 | wdnow = watchdog->read(); |
109 | wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask); | |
110 | watchdog_last = wdnow; | |
111 | ||
112 | list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { | |
113 | csnow = cs->read(); | |
b52f52a0 TG |
114 | |
115 | if (unlikely(resumed)) { | |
116 | cs->wd_last = csnow; | |
117 | continue; | |
118 | } | |
119 | ||
5d8b34fd TG |
120 | /* Initialized ? */ |
121 | if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) { | |
122 | if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && | |
123 | (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { | |
124 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; | |
79bf2bb3 TG |
125 | /* |
126 | * We just marked the clocksource as | |
127 | * highres-capable, notify the rest of the | |
128 | * system as well so that we transition | |
129 | * into high-res mode: | |
130 | */ | |
131 | tick_clock_notify(); | |
5d8b34fd TG |
132 | } |
133 | cs->flags |= CLOCK_SOURCE_WATCHDOG; | |
134 | cs->wd_last = csnow; | |
135 | } else { | |
136 | cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask); | |
137 | cs->wd_last = csnow; | |
138 | /* Check the delta. Might remove from the list ! */ | |
139 | clocksource_ratewd(cs, cs_nsec - wd_nsec); | |
140 | } | |
141 | } | |
142 | ||
143 | if (!list_empty(&watchdog_list)) { | |
3150e63d AM |
144 | __mod_timer(&watchdog_timer, |
145 | watchdog_timer.expires + WATCHDOG_INTERVAL); | |
5d8b34fd TG |
146 | } |
147 | spin_unlock(&watchdog_lock); | |
148 | } | |
b52f52a0 TG |
149 | static void clocksource_resume_watchdog(void) |
150 | { | |
8f89441b | 151 | set_bit(0, &watchdog_resumed); |
b52f52a0 TG |
152 | } |
153 | ||
5d8b34fd TG |
154 | static void clocksource_check_watchdog(struct clocksource *cs) |
155 | { | |
156 | struct clocksource *cse; | |
157 | unsigned long flags; | |
158 | ||
159 | spin_lock_irqsave(&watchdog_lock, flags); | |
160 | if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { | |
161 | int started = !list_empty(&watchdog_list); | |
162 | ||
163 | list_add(&cs->wd_list, &watchdog_list); | |
164 | if (!started && watchdog) { | |
165 | watchdog_last = watchdog->read(); | |
166 | watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; | |
3150e63d | 167 | add_timer(&watchdog_timer); |
5d8b34fd | 168 | } |
948ac6d7 TG |
169 | } else { |
170 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) | |
5d8b34fd TG |
171 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
172 | ||
173 | if (!watchdog || cs->rating > watchdog->rating) { | |
174 | if (watchdog) | |
175 | del_timer(&watchdog_timer); | |
176 | watchdog = cs; | |
898a19de | 177 | init_timer(&watchdog_timer); |
5d8b34fd TG |
178 | watchdog_timer.function = clocksource_watchdog; |
179 | ||
180 | /* Reset watchdog cycles */ | |
181 | list_for_each_entry(cse, &watchdog_list, wd_list) | |
182 | cse->flags &= ~CLOCK_SOURCE_WATCHDOG; | |
183 | /* Start if list is not empty */ | |
184 | if (!list_empty(&watchdog_list)) { | |
185 | watchdog_last = watchdog->read(); | |
186 | watchdog_timer.expires = | |
187 | jiffies + WATCHDOG_INTERVAL; | |
3150e63d | 188 | add_timer(&watchdog_timer); |
5d8b34fd TG |
189 | } |
190 | } | |
191 | } | |
192 | spin_unlock_irqrestore(&watchdog_lock, flags); | |
193 | } | |
194 | #else | |
195 | static void clocksource_check_watchdog(struct clocksource *cs) | |
196 | { | |
197 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) | |
198 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; | |
199 | } | |
b52f52a0 TG |
200 | |
201 | static inline void clocksource_resume_watchdog(void) { } | |
5d8b34fd TG |
202 | #endif |
203 | ||
b52f52a0 TG |
204 | /** |
205 | * clocksource_resume - resume the clocksource(s) | |
206 | */ | |
207 | void clocksource_resume(void) | |
208 | { | |
2e197586 | 209 | struct clocksource *cs; |
b52f52a0 TG |
210 | unsigned long flags; |
211 | ||
212 | spin_lock_irqsave(&clocksource_lock, flags); | |
213 | ||
2e197586 | 214 | list_for_each_entry(cs, &clocksource_list, list) { |
b52f52a0 TG |
215 | if (cs->resume) |
216 | cs->resume(); | |
217 | } | |
218 | ||
219 | clocksource_resume_watchdog(); | |
220 | ||
221 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
222 | } | |
223 | ||
734efb46 | 224 | /** |
a2752549 | 225 | * clocksource_get_next - Returns the selected clocksource |
734efb46 JS |
226 | * |
227 | */ | |
a2752549 | 228 | struct clocksource *clocksource_get_next(void) |
734efb46 JS |
229 | { |
230 | unsigned long flags; | |
231 | ||
232 | spin_lock_irqsave(&clocksource_lock, flags); | |
233 | if (next_clocksource && finished_booting) { | |
234 | curr_clocksource = next_clocksource; | |
235 | next_clocksource = NULL; | |
236 | } | |
237 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
238 | ||
239 | return curr_clocksource; | |
240 | } | |
241 | ||
242 | /** | |
92c7e002 | 243 | * select_clocksource - Selects the best registered clocksource. |
734efb46 JS |
244 | * |
245 | * Private function. Must hold clocksource_lock when called. | |
246 | * | |
92c7e002 TG |
247 | * Select the clocksource with the best rating, or the clocksource, |
248 | * which is selected by userspace override. | |
734efb46 JS |
249 | */ |
250 | static struct clocksource *select_clocksource(void) | |
251 | { | |
5d8b34fd TG |
252 | struct clocksource *next; |
253 | ||
92c7e002 TG |
254 | if (list_empty(&clocksource_list)) |
255 | return NULL; | |
734efb46 | 256 | |
92c7e002 | 257 | if (clocksource_override) |
5d8b34fd TG |
258 | next = clocksource_override; |
259 | else | |
260 | next = list_entry(clocksource_list.next, struct clocksource, | |
261 | list); | |
734efb46 | 262 | |
5d8b34fd TG |
263 | if (next == curr_clocksource) |
264 | return NULL; | |
265 | ||
266 | return next; | |
734efb46 JS |
267 | } |
268 | ||
92c7e002 TG |
269 | /* |
270 | * Enqueue the clocksource sorted by rating | |
734efb46 | 271 | */ |
92c7e002 | 272 | static int clocksource_enqueue(struct clocksource *c) |
734efb46 | 273 | { |
92c7e002 | 274 | struct list_head *tmp, *entry = &clocksource_list; |
734efb46 JS |
275 | |
276 | list_for_each(tmp, &clocksource_list) { | |
92c7e002 TG |
277 | struct clocksource *cs; |
278 | ||
279 | cs = list_entry(tmp, struct clocksource, list); | |
280 | if (cs == c) | |
281 | return -EBUSY; | |
282 | /* Keep track of the place, where to insert */ | |
283 | if (cs->rating >= c->rating) | |
284 | entry = tmp; | |
734efb46 | 285 | } |
92c7e002 TG |
286 | list_add(&c->list, entry); |
287 | ||
288 | if (strlen(c->name) == strlen(override_name) && | |
289 | !strcmp(c->name, override_name)) | |
290 | clocksource_override = c; | |
734efb46 JS |
291 | |
292 | return 0; | |
293 | } | |
294 | ||
295 | /** | |
a2752549 | 296 | * clocksource_register - Used to install new clocksources |
734efb46 JS |
297 | * @t: clocksource to be registered |
298 | * | |
299 | * Returns -EBUSY if registration fails, zero otherwise. | |
300 | */ | |
a2752549 | 301 | int clocksource_register(struct clocksource *c) |
734efb46 | 302 | { |
734efb46 | 303 | unsigned long flags; |
5d8b34fd | 304 | int ret; |
734efb46 JS |
305 | |
306 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 TG |
307 | ret = clocksource_enqueue(c); |
308 | if (!ret) | |
734efb46 | 309 | next_clocksource = select_clocksource(); |
734efb46 | 310 | spin_unlock_irqrestore(&clocksource_lock, flags); |
5d8b34fd TG |
311 | if (!ret) |
312 | clocksource_check_watchdog(c); | |
734efb46 JS |
313 | return ret; |
314 | } | |
a2752549 | 315 | EXPORT_SYMBOL(clocksource_register); |
734efb46 JS |
316 | |
317 | /** | |
92c7e002 | 318 | * clocksource_change_rating - Change the rating of a registered clocksource |
734efb46 | 319 | * |
734efb46 | 320 | */ |
92c7e002 | 321 | void clocksource_change_rating(struct clocksource *cs, int rating) |
734efb46 JS |
322 | { |
323 | unsigned long flags; | |
324 | ||
325 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 | 326 | list_del(&cs->list); |
5d8b34fd | 327 | cs->rating = rating; |
92c7e002 | 328 | clocksource_enqueue(cs); |
734efb46 JS |
329 | next_clocksource = select_clocksource(); |
330 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
331 | } | |
332 | ||
4713e22c TG |
333 | /** |
334 | * clocksource_unregister - remove a registered clocksource | |
335 | */ | |
336 | void clocksource_unregister(struct clocksource *cs) | |
337 | { | |
338 | unsigned long flags; | |
339 | ||
340 | spin_lock_irqsave(&clocksource_lock, flags); | |
341 | list_del(&cs->list); | |
342 | if (clocksource_override == cs) | |
343 | clocksource_override = NULL; | |
344 | next_clocksource = select_clocksource(); | |
345 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
346 | } | |
347 | ||
2b013700 | 348 | #ifdef CONFIG_SYSFS |
734efb46 JS |
349 | /** |
350 | * sysfs_show_current_clocksources - sysfs interface for current clocksource | |
351 | * @dev: unused | |
352 | * @buf: char buffer to be filled with clocksource list | |
353 | * | |
354 | * Provides sysfs interface for listing current clocksource. | |
355 | */ | |
356 | static ssize_t | |
357 | sysfs_show_current_clocksources(struct sys_device *dev, char *buf) | |
358 | { | |
5e2cb101 | 359 | ssize_t count = 0; |
734efb46 JS |
360 | |
361 | spin_lock_irq(&clocksource_lock); | |
5e2cb101 | 362 | count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); |
734efb46 JS |
363 | spin_unlock_irq(&clocksource_lock); |
364 | ||
5e2cb101 | 365 | return count; |
734efb46 JS |
366 | } |
367 | ||
368 | /** | |
369 | * sysfs_override_clocksource - interface for manually overriding clocksource | |
370 | * @dev: unused | |
371 | * @buf: name of override clocksource | |
372 | * @count: length of buffer | |
373 | * | |
374 | * Takes input from sysfs interface for manually overriding the default | |
375 | * clocksource selction. | |
376 | */ | |
377 | static ssize_t sysfs_override_clocksource(struct sys_device *dev, | |
378 | const char *buf, size_t count) | |
379 | { | |
92c7e002 | 380 | struct clocksource *ovr = NULL; |
734efb46 | 381 | size_t ret = count; |
92c7e002 TG |
382 | int len; |
383 | ||
734efb46 JS |
384 | /* strings from sysfs write are not 0 terminated! */ |
385 | if (count >= sizeof(override_name)) | |
386 | return -EINVAL; | |
387 | ||
388 | /* strip of \n: */ | |
389 | if (buf[count-1] == '\n') | |
390 | count--; | |
734efb46 JS |
391 | |
392 | spin_lock_irq(&clocksource_lock); | |
393 | ||
92c7e002 TG |
394 | if (count > 0) |
395 | memcpy(override_name, buf, count); | |
734efb46 JS |
396 | override_name[count] = 0; |
397 | ||
92c7e002 TG |
398 | len = strlen(override_name); |
399 | if (len) { | |
2e197586 MK |
400 | struct clocksource *cs; |
401 | ||
92c7e002 TG |
402 | ovr = clocksource_override; |
403 | /* try to select it: */ | |
2e197586 | 404 | list_for_each_entry(cs, &clocksource_list, list) { |
92c7e002 TG |
405 | if (strlen(cs->name) == len && |
406 | !strcmp(cs->name, override_name)) | |
407 | ovr = cs; | |
408 | } | |
409 | } | |
410 | ||
411 | /* Reselect, when the override name has changed */ | |
412 | if (ovr != clocksource_override) { | |
413 | clocksource_override = ovr; | |
414 | next_clocksource = select_clocksource(); | |
415 | } | |
734efb46 JS |
416 | |
417 | spin_unlock_irq(&clocksource_lock); | |
418 | ||
419 | return ret; | |
420 | } | |
421 | ||
422 | /** | |
423 | * sysfs_show_available_clocksources - sysfs interface for listing clocksource | |
424 | * @dev: unused | |
425 | * @buf: char buffer to be filled with clocksource list | |
426 | * | |
427 | * Provides sysfs interface for listing registered clocksources | |
428 | */ | |
429 | static ssize_t | |
430 | sysfs_show_available_clocksources(struct sys_device *dev, char *buf) | |
431 | { | |
2e197586 | 432 | struct clocksource *src; |
5e2cb101 | 433 | ssize_t count = 0; |
734efb46 JS |
434 | |
435 | spin_lock_irq(&clocksource_lock); | |
2e197586 | 436 | list_for_each_entry(src, &clocksource_list, list) { |
5e2cb101 MX |
437 | count += snprintf(buf + count, |
438 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), | |
439 | "%s ", src->name); | |
734efb46 JS |
440 | } |
441 | spin_unlock_irq(&clocksource_lock); | |
442 | ||
5e2cb101 MX |
443 | count += snprintf(buf + count, |
444 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); | |
734efb46 | 445 | |
5e2cb101 | 446 | return count; |
734efb46 JS |
447 | } |
448 | ||
449 | /* | |
450 | * Sysfs setup bits: | |
451 | */ | |
452 | static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources, | |
f5f1a24a | 453 | sysfs_override_clocksource); |
734efb46 JS |
454 | |
455 | static SYSDEV_ATTR(available_clocksource, 0600, | |
f5f1a24a | 456 | sysfs_show_available_clocksources, NULL); |
734efb46 JS |
457 | |
458 | static struct sysdev_class clocksource_sysclass = { | |
af5ca3f4 | 459 | .name = "clocksource", |
734efb46 JS |
460 | }; |
461 | ||
462 | static struct sys_device device_clocksource = { | |
463 | .id = 0, | |
464 | .cls = &clocksource_sysclass, | |
465 | }; | |
466 | ||
ad596171 | 467 | static int __init init_clocksource_sysfs(void) |
734efb46 JS |
468 | { |
469 | int error = sysdev_class_register(&clocksource_sysclass); | |
470 | ||
471 | if (!error) | |
472 | error = sysdev_register(&device_clocksource); | |
473 | if (!error) | |
474 | error = sysdev_create_file( | |
475 | &device_clocksource, | |
476 | &attr_current_clocksource); | |
477 | if (!error) | |
478 | error = sysdev_create_file( | |
479 | &device_clocksource, | |
480 | &attr_available_clocksource); | |
481 | return error; | |
482 | } | |
483 | ||
484 | device_initcall(init_clocksource_sysfs); | |
2b013700 | 485 | #endif /* CONFIG_SYSFS */ |
734efb46 JS |
486 | |
487 | /** | |
488 | * boot_override_clocksource - boot clock override | |
489 | * @str: override name | |
490 | * | |
491 | * Takes a clocksource= boot argument and uses it | |
492 | * as the clocksource override name. | |
493 | */ | |
494 | static int __init boot_override_clocksource(char* str) | |
495 | { | |
496 | unsigned long flags; | |
497 | spin_lock_irqsave(&clocksource_lock, flags); | |
498 | if (str) | |
499 | strlcpy(override_name, str, sizeof(override_name)); | |
500 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
501 | return 1; | |
502 | } | |
503 | ||
504 | __setup("clocksource=", boot_override_clocksource); | |
505 | ||
506 | /** | |
507 | * boot_override_clock - Compatibility layer for deprecated boot option | |
508 | * @str: override name | |
509 | * | |
510 | * DEPRECATED! Takes a clock= boot argument and uses it | |
511 | * as the clocksource override name | |
512 | */ | |
513 | static int __init boot_override_clock(char* str) | |
514 | { | |
5d0cf410 JS |
515 | if (!strcmp(str, "pmtmr")) { |
516 | printk("Warning: clock=pmtmr is deprecated. " | |
517 | "Use clocksource=acpi_pm.\n"); | |
518 | return boot_override_clocksource("acpi_pm"); | |
519 | } | |
520 | printk("Warning! clock= boot option is deprecated. " | |
521 | "Use clocksource=xyz\n"); | |
734efb46 JS |
522 | return boot_override_clocksource(str); |
523 | } | |
524 | ||
525 | __setup("clock=", boot_override_clock); |