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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> | |
31 | ||
32 | /* XXX - Would like a better way for initializing curr_clocksource */ | |
33 | extern struct clocksource clocksource_jiffies; | |
34 | ||
35 | /*[Clocksource internal variables]--------- | |
36 | * curr_clocksource: | |
37 | * currently selected clocksource. Initialized to clocksource_jiffies. | |
38 | * next_clocksource: | |
39 | * pending next selected clocksource. | |
40 | * clocksource_list: | |
41 | * linked list with the registered clocksources | |
42 | * clocksource_lock: | |
43 | * protects manipulations to curr_clocksource and next_clocksource | |
44 | * and the clocksource_list | |
45 | * override_name: | |
46 | * Name of the user-specified clocksource. | |
47 | */ | |
48 | static struct clocksource *curr_clocksource = &clocksource_jiffies; | |
49 | static struct clocksource *next_clocksource; | |
50 | static LIST_HEAD(clocksource_list); | |
51 | static DEFINE_SPINLOCK(clocksource_lock); | |
52 | static char override_name[32]; | |
53 | static int finished_booting; | |
54 | ||
55 | /* clocksource_done_booting - Called near the end of bootup | |
56 | * | |
57 | * Hack to avoid lots of clocksource churn at boot time | |
58 | */ | |
ad596171 | 59 | static int __init clocksource_done_booting(void) |
734efb46 JS |
60 | { |
61 | finished_booting = 1; | |
62 | return 0; | |
63 | } | |
64 | ||
65 | late_initcall(clocksource_done_booting); | |
66 | ||
67 | /** | |
a2752549 | 68 | * clocksource_get_next - Returns the selected clocksource |
734efb46 JS |
69 | * |
70 | */ | |
a2752549 | 71 | struct clocksource *clocksource_get_next(void) |
734efb46 JS |
72 | { |
73 | unsigned long flags; | |
74 | ||
75 | spin_lock_irqsave(&clocksource_lock, flags); | |
76 | if (next_clocksource && finished_booting) { | |
77 | curr_clocksource = next_clocksource; | |
78 | next_clocksource = NULL; | |
79 | } | |
80 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
81 | ||
82 | return curr_clocksource; | |
83 | } | |
84 | ||
85 | /** | |
86 | * select_clocksource - Finds the best registered clocksource. | |
87 | * | |
88 | * Private function. Must hold clocksource_lock when called. | |
89 | * | |
90 | * Looks through the list of registered clocksources, returning | |
91 | * the one with the highest rating value. If there is a clocksource | |
92 | * name that matches the override string, it returns that clocksource. | |
93 | */ | |
94 | static struct clocksource *select_clocksource(void) | |
95 | { | |
96 | struct clocksource *best = NULL; | |
97 | struct list_head *tmp; | |
98 | ||
99 | list_for_each(tmp, &clocksource_list) { | |
100 | struct clocksource *src; | |
101 | ||
102 | src = list_entry(tmp, struct clocksource, list); | |
103 | if (!best) | |
104 | best = src; | |
105 | ||
106 | /* check for override: */ | |
107 | if (strlen(src->name) == strlen(override_name) && | |
108 | !strcmp(src->name, override_name)) { | |
109 | best = src; | |
110 | break; | |
111 | } | |
112 | /* pick the highest rating: */ | |
113 | if (src->rating > best->rating) | |
114 | best = src; | |
115 | } | |
116 | ||
117 | return best; | |
118 | } | |
119 | ||
120 | /** | |
121 | * is_registered_source - Checks if clocksource is registered | |
122 | * @c: pointer to a clocksource | |
123 | * | |
124 | * Private helper function. Must hold clocksource_lock when called. | |
125 | * | |
126 | * Returns one if the clocksource is already registered, zero otherwise. | |
127 | */ | |
128 | static int is_registered_source(struct clocksource *c) | |
129 | { | |
130 | int len = strlen(c->name); | |
131 | struct list_head *tmp; | |
132 | ||
133 | list_for_each(tmp, &clocksource_list) { | |
134 | struct clocksource *src; | |
135 | ||
136 | src = list_entry(tmp, struct clocksource, list); | |
137 | if (strlen(src->name) == len && !strcmp(src->name, c->name)) | |
138 | return 1; | |
139 | } | |
140 | ||
141 | return 0; | |
142 | } | |
143 | ||
144 | /** | |
a2752549 | 145 | * clocksource_register - Used to install new clocksources |
734efb46 JS |
146 | * @t: clocksource to be registered |
147 | * | |
148 | * Returns -EBUSY if registration fails, zero otherwise. | |
149 | */ | |
a2752549 | 150 | int clocksource_register(struct clocksource *c) |
734efb46 JS |
151 | { |
152 | int ret = 0; | |
153 | unsigned long flags; | |
154 | ||
155 | spin_lock_irqsave(&clocksource_lock, flags); | |
156 | /* check if clocksource is already registered */ | |
157 | if (is_registered_source(c)) { | |
158 | printk("register_clocksource: Cannot register %s. " | |
159 | "Already registered!", c->name); | |
160 | ret = -EBUSY; | |
161 | } else { | |
162 | /* register it */ | |
163 | list_add(&c->list, &clocksource_list); | |
164 | /* scan the registered clocksources, and pick the best one */ | |
165 | next_clocksource = select_clocksource(); | |
166 | } | |
167 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
168 | return ret; | |
169 | } | |
a2752549 | 170 | EXPORT_SYMBOL(clocksource_register); |
734efb46 JS |
171 | |
172 | /** | |
a2752549 | 173 | * clocksource_reselect - Rescan list for next clocksource |
734efb46 JS |
174 | * |
175 | * A quick helper function to be used if a clocksource changes its | |
5d0cf410 | 176 | * rating. Forces the clocksource list to be re-scanned for the best |
734efb46 JS |
177 | * clocksource. |
178 | */ | |
a2752549 | 179 | void clocksource_reselect(void) |
734efb46 JS |
180 | { |
181 | unsigned long flags; | |
182 | ||
183 | spin_lock_irqsave(&clocksource_lock, flags); | |
184 | next_clocksource = select_clocksource(); | |
185 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
186 | } | |
a2752549 | 187 | EXPORT_SYMBOL(clocksource_reselect); |
734efb46 | 188 | |
2b013700 | 189 | #ifdef CONFIG_SYSFS |
734efb46 JS |
190 | /** |
191 | * sysfs_show_current_clocksources - sysfs interface for current clocksource | |
192 | * @dev: unused | |
193 | * @buf: char buffer to be filled with clocksource list | |
194 | * | |
195 | * Provides sysfs interface for listing current clocksource. | |
196 | */ | |
197 | static ssize_t | |
198 | sysfs_show_current_clocksources(struct sys_device *dev, char *buf) | |
199 | { | |
200 | char *curr = buf; | |
201 | ||
202 | spin_lock_irq(&clocksource_lock); | |
203 | curr += sprintf(curr, "%s ", curr_clocksource->name); | |
204 | spin_unlock_irq(&clocksource_lock); | |
205 | ||
206 | curr += sprintf(curr, "\n"); | |
207 | ||
208 | return curr - buf; | |
209 | } | |
210 | ||
211 | /** | |
212 | * sysfs_override_clocksource - interface for manually overriding clocksource | |
213 | * @dev: unused | |
214 | * @buf: name of override clocksource | |
215 | * @count: length of buffer | |
216 | * | |
217 | * Takes input from sysfs interface for manually overriding the default | |
218 | * clocksource selction. | |
219 | */ | |
220 | static ssize_t sysfs_override_clocksource(struct sys_device *dev, | |
221 | const char *buf, size_t count) | |
222 | { | |
223 | size_t ret = count; | |
224 | /* strings from sysfs write are not 0 terminated! */ | |
225 | if (count >= sizeof(override_name)) | |
226 | return -EINVAL; | |
227 | ||
228 | /* strip of \n: */ | |
229 | if (buf[count-1] == '\n') | |
230 | count--; | |
231 | if (count < 1) | |
232 | return -EINVAL; | |
233 | ||
234 | spin_lock_irq(&clocksource_lock); | |
235 | ||
236 | /* copy the name given: */ | |
237 | memcpy(override_name, buf, count); | |
238 | override_name[count] = 0; | |
239 | ||
240 | /* try to select it: */ | |
241 | next_clocksource = select_clocksource(); | |
242 | ||
243 | spin_unlock_irq(&clocksource_lock); | |
244 | ||
245 | return ret; | |
246 | } | |
247 | ||
248 | /** | |
249 | * sysfs_show_available_clocksources - sysfs interface for listing clocksource | |
250 | * @dev: unused | |
251 | * @buf: char buffer to be filled with clocksource list | |
252 | * | |
253 | * Provides sysfs interface for listing registered clocksources | |
254 | */ | |
255 | static ssize_t | |
256 | sysfs_show_available_clocksources(struct sys_device *dev, char *buf) | |
257 | { | |
258 | struct list_head *tmp; | |
259 | char *curr = buf; | |
260 | ||
261 | spin_lock_irq(&clocksource_lock); | |
262 | list_for_each(tmp, &clocksource_list) { | |
263 | struct clocksource *src; | |
264 | ||
265 | src = list_entry(tmp, struct clocksource, list); | |
266 | curr += sprintf(curr, "%s ", src->name); | |
267 | } | |
268 | spin_unlock_irq(&clocksource_lock); | |
269 | ||
270 | curr += sprintf(curr, "\n"); | |
271 | ||
272 | return curr - buf; | |
273 | } | |
274 | ||
275 | /* | |
276 | * Sysfs setup bits: | |
277 | */ | |
278 | static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources, | |
279 | sysfs_override_clocksource); | |
280 | ||
281 | static SYSDEV_ATTR(available_clocksource, 0600, | |
282 | sysfs_show_available_clocksources, NULL); | |
283 | ||
284 | static struct sysdev_class clocksource_sysclass = { | |
285 | set_kset_name("clocksource"), | |
286 | }; | |
287 | ||
288 | static struct sys_device device_clocksource = { | |
289 | .id = 0, | |
290 | .cls = &clocksource_sysclass, | |
291 | }; | |
292 | ||
ad596171 | 293 | static int __init init_clocksource_sysfs(void) |
734efb46 JS |
294 | { |
295 | int error = sysdev_class_register(&clocksource_sysclass); | |
296 | ||
297 | if (!error) | |
298 | error = sysdev_register(&device_clocksource); | |
299 | if (!error) | |
300 | error = sysdev_create_file( | |
301 | &device_clocksource, | |
302 | &attr_current_clocksource); | |
303 | if (!error) | |
304 | error = sysdev_create_file( | |
305 | &device_clocksource, | |
306 | &attr_available_clocksource); | |
307 | return error; | |
308 | } | |
309 | ||
310 | device_initcall(init_clocksource_sysfs); | |
2b013700 | 311 | #endif /* CONFIG_SYSFS */ |
734efb46 JS |
312 | |
313 | /** | |
314 | * boot_override_clocksource - boot clock override | |
315 | * @str: override name | |
316 | * | |
317 | * Takes a clocksource= boot argument and uses it | |
318 | * as the clocksource override name. | |
319 | */ | |
320 | static int __init boot_override_clocksource(char* str) | |
321 | { | |
322 | unsigned long flags; | |
323 | spin_lock_irqsave(&clocksource_lock, flags); | |
324 | if (str) | |
325 | strlcpy(override_name, str, sizeof(override_name)); | |
326 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
327 | return 1; | |
328 | } | |
329 | ||
330 | __setup("clocksource=", boot_override_clocksource); | |
331 | ||
332 | /** | |
333 | * boot_override_clock - Compatibility layer for deprecated boot option | |
334 | * @str: override name | |
335 | * | |
336 | * DEPRECATED! Takes a clock= boot argument and uses it | |
337 | * as the clocksource override name | |
338 | */ | |
339 | static int __init boot_override_clock(char* str) | |
340 | { | |
5d0cf410 JS |
341 | if (!strcmp(str, "pmtmr")) { |
342 | printk("Warning: clock=pmtmr is deprecated. " | |
343 | "Use clocksource=acpi_pm.\n"); | |
344 | return boot_override_clocksource("acpi_pm"); | |
345 | } | |
346 | printk("Warning! clock= boot option is deprecated. " | |
347 | "Use clocksource=xyz\n"); | |
734efb46 JS |
348 | return boot_override_clocksource(str); |
349 | } | |
350 | ||
351 | __setup("clock=", boot_override_clock); |