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