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