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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)) { | |
1ada5cba AK |
144 | /* Cycle through CPUs to check if the CPUs stay synchronized to |
145 | * each other. */ | |
146 | int next_cpu = next_cpu(raw_smp_processor_id(), cpu_online_map); | |
147 | if (next_cpu >= NR_CPUS) | |
148 | next_cpu = first_cpu(cpu_online_map); | |
149 | watchdog_timer.expires += WATCHDOG_INTERVAL; | |
150 | add_timer_on(&watchdog_timer, next_cpu); | |
5d8b34fd TG |
151 | } |
152 | spin_unlock(&watchdog_lock); | |
153 | } | |
b52f52a0 TG |
154 | static void clocksource_resume_watchdog(void) |
155 | { | |
8f89441b | 156 | set_bit(0, &watchdog_resumed); |
b52f52a0 TG |
157 | } |
158 | ||
5d8b34fd TG |
159 | static void clocksource_check_watchdog(struct clocksource *cs) |
160 | { | |
161 | struct clocksource *cse; | |
162 | unsigned long flags; | |
163 | ||
164 | spin_lock_irqsave(&watchdog_lock, flags); | |
165 | if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { | |
166 | int started = !list_empty(&watchdog_list); | |
167 | ||
168 | list_add(&cs->wd_list, &watchdog_list); | |
169 | if (!started && watchdog) { | |
170 | watchdog_last = watchdog->read(); | |
171 | watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; | |
1ada5cba | 172 | add_timer_on(&watchdog_timer, first_cpu(cpu_online_map)); |
5d8b34fd | 173 | } |
948ac6d7 TG |
174 | } else { |
175 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) | |
5d8b34fd TG |
176 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
177 | ||
178 | if (!watchdog || cs->rating > watchdog->rating) { | |
179 | if (watchdog) | |
180 | del_timer(&watchdog_timer); | |
181 | watchdog = cs; | |
1077f5a9 | 182 | init_timer_deferrable(&watchdog_timer); |
5d8b34fd TG |
183 | watchdog_timer.function = clocksource_watchdog; |
184 | ||
185 | /* Reset watchdog cycles */ | |
186 | list_for_each_entry(cse, &watchdog_list, wd_list) | |
187 | cse->flags &= ~CLOCK_SOURCE_WATCHDOG; | |
188 | /* Start if list is not empty */ | |
189 | if (!list_empty(&watchdog_list)) { | |
190 | watchdog_last = watchdog->read(); | |
191 | watchdog_timer.expires = | |
192 | jiffies + WATCHDOG_INTERVAL; | |
1ada5cba AK |
193 | add_timer_on(&watchdog_timer, |
194 | first_cpu(cpu_online_map)); | |
5d8b34fd TG |
195 | } |
196 | } | |
197 | } | |
198 | spin_unlock_irqrestore(&watchdog_lock, flags); | |
199 | } | |
200 | #else | |
201 | static void clocksource_check_watchdog(struct clocksource *cs) | |
202 | { | |
203 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) | |
204 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; | |
205 | } | |
b52f52a0 TG |
206 | |
207 | static inline void clocksource_resume_watchdog(void) { } | |
5d8b34fd TG |
208 | #endif |
209 | ||
b52f52a0 TG |
210 | /** |
211 | * clocksource_resume - resume the clocksource(s) | |
212 | */ | |
213 | void clocksource_resume(void) | |
214 | { | |
2e197586 | 215 | struct clocksource *cs; |
b52f52a0 TG |
216 | unsigned long flags; |
217 | ||
218 | spin_lock_irqsave(&clocksource_lock, flags); | |
219 | ||
2e197586 | 220 | list_for_each_entry(cs, &clocksource_list, list) { |
b52f52a0 TG |
221 | if (cs->resume) |
222 | cs->resume(); | |
223 | } | |
224 | ||
225 | clocksource_resume_watchdog(); | |
226 | ||
227 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
228 | } | |
229 | ||
734efb46 | 230 | /** |
a2752549 | 231 | * clocksource_get_next - Returns the selected clocksource |
734efb46 JS |
232 | * |
233 | */ | |
a2752549 | 234 | struct clocksource *clocksource_get_next(void) |
734efb46 JS |
235 | { |
236 | unsigned long flags; | |
237 | ||
238 | spin_lock_irqsave(&clocksource_lock, flags); | |
239 | if (next_clocksource && finished_booting) { | |
240 | curr_clocksource = next_clocksource; | |
241 | next_clocksource = NULL; | |
242 | } | |
243 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
244 | ||
245 | return curr_clocksource; | |
246 | } | |
247 | ||
248 | /** | |
92c7e002 | 249 | * select_clocksource - Selects the best registered clocksource. |
734efb46 JS |
250 | * |
251 | * Private function. Must hold clocksource_lock when called. | |
252 | * | |
92c7e002 TG |
253 | * Select the clocksource with the best rating, or the clocksource, |
254 | * which is selected by userspace override. | |
734efb46 JS |
255 | */ |
256 | static struct clocksource *select_clocksource(void) | |
257 | { | |
5d8b34fd TG |
258 | struct clocksource *next; |
259 | ||
92c7e002 TG |
260 | if (list_empty(&clocksource_list)) |
261 | return NULL; | |
734efb46 | 262 | |
92c7e002 | 263 | if (clocksource_override) |
5d8b34fd TG |
264 | next = clocksource_override; |
265 | else | |
266 | next = list_entry(clocksource_list.next, struct clocksource, | |
267 | list); | |
734efb46 | 268 | |
5d8b34fd TG |
269 | if (next == curr_clocksource) |
270 | return NULL; | |
271 | ||
272 | return next; | |
734efb46 JS |
273 | } |
274 | ||
92c7e002 TG |
275 | /* |
276 | * Enqueue the clocksource sorted by rating | |
734efb46 | 277 | */ |
92c7e002 | 278 | static int clocksource_enqueue(struct clocksource *c) |
734efb46 | 279 | { |
92c7e002 | 280 | struct list_head *tmp, *entry = &clocksource_list; |
734efb46 JS |
281 | |
282 | list_for_each(tmp, &clocksource_list) { | |
92c7e002 TG |
283 | struct clocksource *cs; |
284 | ||
285 | cs = list_entry(tmp, struct clocksource, list); | |
286 | if (cs == c) | |
287 | return -EBUSY; | |
288 | /* Keep track of the place, where to insert */ | |
289 | if (cs->rating >= c->rating) | |
290 | entry = tmp; | |
734efb46 | 291 | } |
92c7e002 TG |
292 | list_add(&c->list, entry); |
293 | ||
294 | if (strlen(c->name) == strlen(override_name) && | |
295 | !strcmp(c->name, override_name)) | |
296 | clocksource_override = c; | |
734efb46 JS |
297 | |
298 | return 0; | |
299 | } | |
300 | ||
301 | /** | |
a2752549 | 302 | * clocksource_register - Used to install new clocksources |
734efb46 JS |
303 | * @t: clocksource to be registered |
304 | * | |
305 | * Returns -EBUSY if registration fails, zero otherwise. | |
306 | */ | |
a2752549 | 307 | int clocksource_register(struct clocksource *c) |
734efb46 | 308 | { |
734efb46 | 309 | unsigned long flags; |
5d8b34fd | 310 | int ret; |
734efb46 JS |
311 | |
312 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 TG |
313 | ret = clocksource_enqueue(c); |
314 | if (!ret) | |
734efb46 | 315 | next_clocksource = select_clocksource(); |
734efb46 | 316 | spin_unlock_irqrestore(&clocksource_lock, flags); |
5d8b34fd TG |
317 | if (!ret) |
318 | clocksource_check_watchdog(c); | |
734efb46 JS |
319 | return ret; |
320 | } | |
a2752549 | 321 | EXPORT_SYMBOL(clocksource_register); |
734efb46 JS |
322 | |
323 | /** | |
92c7e002 | 324 | * clocksource_change_rating - Change the rating of a registered clocksource |
734efb46 | 325 | * |
734efb46 | 326 | */ |
92c7e002 | 327 | void clocksource_change_rating(struct clocksource *cs, int rating) |
734efb46 JS |
328 | { |
329 | unsigned long flags; | |
330 | ||
331 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 | 332 | list_del(&cs->list); |
5d8b34fd | 333 | cs->rating = rating; |
92c7e002 | 334 | clocksource_enqueue(cs); |
734efb46 JS |
335 | next_clocksource = select_clocksource(); |
336 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
337 | } | |
338 | ||
4713e22c TG |
339 | /** |
340 | * clocksource_unregister - remove a registered clocksource | |
341 | */ | |
342 | void clocksource_unregister(struct clocksource *cs) | |
343 | { | |
344 | unsigned long flags; | |
345 | ||
346 | spin_lock_irqsave(&clocksource_lock, flags); | |
347 | list_del(&cs->list); | |
348 | if (clocksource_override == cs) | |
349 | clocksource_override = NULL; | |
350 | next_clocksource = select_clocksource(); | |
351 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
352 | } | |
353 | ||
2b013700 | 354 | #ifdef CONFIG_SYSFS |
734efb46 JS |
355 | /** |
356 | * sysfs_show_current_clocksources - sysfs interface for current clocksource | |
357 | * @dev: unused | |
358 | * @buf: char buffer to be filled with clocksource list | |
359 | * | |
360 | * Provides sysfs interface for listing current clocksource. | |
361 | */ | |
362 | static ssize_t | |
363 | sysfs_show_current_clocksources(struct sys_device *dev, char *buf) | |
364 | { | |
5e2cb101 | 365 | ssize_t count = 0; |
734efb46 JS |
366 | |
367 | spin_lock_irq(&clocksource_lock); | |
5e2cb101 | 368 | count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); |
734efb46 JS |
369 | spin_unlock_irq(&clocksource_lock); |
370 | ||
5e2cb101 | 371 | return count; |
734efb46 JS |
372 | } |
373 | ||
374 | /** | |
375 | * sysfs_override_clocksource - interface for manually overriding clocksource | |
376 | * @dev: unused | |
377 | * @buf: name of override clocksource | |
378 | * @count: length of buffer | |
379 | * | |
380 | * Takes input from sysfs interface for manually overriding the default | |
381 | * clocksource selction. | |
382 | */ | |
383 | static ssize_t sysfs_override_clocksource(struct sys_device *dev, | |
384 | const char *buf, size_t count) | |
385 | { | |
92c7e002 | 386 | struct clocksource *ovr = NULL; |
734efb46 | 387 | size_t ret = count; |
92c7e002 TG |
388 | int len; |
389 | ||
734efb46 JS |
390 | /* strings from sysfs write are not 0 terminated! */ |
391 | if (count >= sizeof(override_name)) | |
392 | return -EINVAL; | |
393 | ||
394 | /* strip of \n: */ | |
395 | if (buf[count-1] == '\n') | |
396 | count--; | |
734efb46 JS |
397 | |
398 | spin_lock_irq(&clocksource_lock); | |
399 | ||
92c7e002 TG |
400 | if (count > 0) |
401 | memcpy(override_name, buf, count); | |
734efb46 JS |
402 | override_name[count] = 0; |
403 | ||
92c7e002 TG |
404 | len = strlen(override_name); |
405 | if (len) { | |
2e197586 MK |
406 | struct clocksource *cs; |
407 | ||
92c7e002 TG |
408 | ovr = clocksource_override; |
409 | /* try to select it: */ | |
2e197586 | 410 | list_for_each_entry(cs, &clocksource_list, list) { |
92c7e002 TG |
411 | if (strlen(cs->name) == len && |
412 | !strcmp(cs->name, override_name)) | |
413 | ovr = cs; | |
414 | } | |
415 | } | |
416 | ||
417 | /* Reselect, when the override name has changed */ | |
418 | if (ovr != clocksource_override) { | |
419 | clocksource_override = ovr; | |
420 | next_clocksource = select_clocksource(); | |
421 | } | |
734efb46 JS |
422 | |
423 | spin_unlock_irq(&clocksource_lock); | |
424 | ||
425 | return ret; | |
426 | } | |
427 | ||
428 | /** | |
429 | * sysfs_show_available_clocksources - sysfs interface for listing clocksource | |
430 | * @dev: unused | |
431 | * @buf: char buffer to be filled with clocksource list | |
432 | * | |
433 | * Provides sysfs interface for listing registered clocksources | |
434 | */ | |
435 | static ssize_t | |
436 | sysfs_show_available_clocksources(struct sys_device *dev, char *buf) | |
437 | { | |
2e197586 | 438 | struct clocksource *src; |
5e2cb101 | 439 | ssize_t count = 0; |
734efb46 JS |
440 | |
441 | spin_lock_irq(&clocksource_lock); | |
2e197586 | 442 | list_for_each_entry(src, &clocksource_list, list) { |
5e2cb101 MX |
443 | count += snprintf(buf + count, |
444 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), | |
445 | "%s ", src->name); | |
734efb46 JS |
446 | } |
447 | spin_unlock_irq(&clocksource_lock); | |
448 | ||
5e2cb101 MX |
449 | count += snprintf(buf + count, |
450 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); | |
734efb46 | 451 | |
5e2cb101 | 452 | return count; |
734efb46 JS |
453 | } |
454 | ||
455 | /* | |
456 | * Sysfs setup bits: | |
457 | */ | |
458 | static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources, | |
f5f1a24a | 459 | sysfs_override_clocksource); |
734efb46 JS |
460 | |
461 | static SYSDEV_ATTR(available_clocksource, 0600, | |
f5f1a24a | 462 | sysfs_show_available_clocksources, NULL); |
734efb46 JS |
463 | |
464 | static struct sysdev_class clocksource_sysclass = { | |
af5ca3f4 | 465 | .name = "clocksource", |
734efb46 JS |
466 | }; |
467 | ||
468 | static struct sys_device device_clocksource = { | |
469 | .id = 0, | |
470 | .cls = &clocksource_sysclass, | |
471 | }; | |
472 | ||
ad596171 | 473 | static int __init init_clocksource_sysfs(void) |
734efb46 JS |
474 | { |
475 | int error = sysdev_class_register(&clocksource_sysclass); | |
476 | ||
477 | if (!error) | |
478 | error = sysdev_register(&device_clocksource); | |
479 | if (!error) | |
480 | error = sysdev_create_file( | |
481 | &device_clocksource, | |
482 | &attr_current_clocksource); | |
483 | if (!error) | |
484 | error = sysdev_create_file( | |
485 | &device_clocksource, | |
486 | &attr_available_clocksource); | |
487 | return error; | |
488 | } | |
489 | ||
490 | device_initcall(init_clocksource_sysfs); | |
2b013700 | 491 | #endif /* CONFIG_SYSFS */ |
734efb46 JS |
492 | |
493 | /** | |
494 | * boot_override_clocksource - boot clock override | |
495 | * @str: override name | |
496 | * | |
497 | * Takes a clocksource= boot argument and uses it | |
498 | * as the clocksource override name. | |
499 | */ | |
500 | static int __init boot_override_clocksource(char* str) | |
501 | { | |
502 | unsigned long flags; | |
503 | spin_lock_irqsave(&clocksource_lock, flags); | |
504 | if (str) | |
505 | strlcpy(override_name, str, sizeof(override_name)); | |
506 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
507 | return 1; | |
508 | } | |
509 | ||
510 | __setup("clocksource=", boot_override_clocksource); | |
511 | ||
512 | /** | |
513 | * boot_override_clock - Compatibility layer for deprecated boot option | |
514 | * @str: override name | |
515 | * | |
516 | * DEPRECATED! Takes a clock= boot argument and uses it | |
517 | * as the clocksource override name | |
518 | */ | |
519 | static int __init boot_override_clock(char* str) | |
520 | { | |
5d0cf410 JS |
521 | if (!strcmp(str, "pmtmr")) { |
522 | printk("Warning: clock=pmtmr is deprecated. " | |
523 | "Use clocksource=acpi_pm.\n"); | |
524 | return boot_override_clocksource("acpi_pm"); | |
525 | } | |
526 | printk("Warning! clock= boot option is deprecated. " | |
527 | "Use clocksource=xyz\n"); | |
734efb46 JS |
528 | return boot_override_clocksource(str); |
529 | } | |
530 | ||
531 | __setup("clock=", boot_override_clock); |