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 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; 52 static struct clocksource *clocksource_override; 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 core bootup 59 * 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. 63 */ 64 static int __init clocksource_done_booting(void) 65 { 66 finished_booting = 1; 67 return 0; 68 } 69 fs_initcall(clocksource_done_booting); 70 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; 77 static unsigned long watchdog_resumed; 78 79 /* 80 * Interval: 0.5sec Threshold: 0.0625s 81 */ 82 #define WATCHDOG_INTERVAL (HZ >> 1) 83 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) 84 85 static void clocksource_ratewd(struct clocksource *cs, int64_t delta) 86 { 87 if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD) 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); 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; 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 /* 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); 151 } 152 spin_unlock(&watchdog_lock); 153 } 154 static void clocksource_resume_watchdog(void) 155 { 156 set_bit(0, &watchdog_resumed); 157 } 158 159 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; 172 add_timer_on(&watchdog_timer, first_cpu(cpu_online_map)); 173 } 174 } else { 175 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) 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; 182 init_timer_deferrable(&watchdog_timer); 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; 193 add_timer_on(&watchdog_timer, 194 first_cpu(cpu_online_map)); 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 } 206 207 static inline void clocksource_resume_watchdog(void) { } 208 #endif 209 210 /** 211 * clocksource_resume - resume the clocksource(s) 212 */ 213 void clocksource_resume(void) 214 { 215 struct clocksource *cs; 216 unsigned long flags; 217 218 spin_lock_irqsave(&clocksource_lock, flags); 219 220 list_for_each_entry(cs, &clocksource_list, list) { 221 if (cs->resume) 222 cs->resume(); 223 } 224 225 clocksource_resume_watchdog(); 226 227 spin_unlock_irqrestore(&clocksource_lock, flags); 228 } 229 230 /** 231 * clocksource_get_next - Returns the selected clocksource 232 * 233 */ 234 struct clocksource *clocksource_get_next(void) 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 /** 249 * select_clocksource - Selects the best registered clocksource. 250 * 251 * Private function. Must hold clocksource_lock when called. 252 * 253 * Select the clocksource with the best rating, or the clocksource, 254 * which is selected by userspace override. 255 */ 256 static struct clocksource *select_clocksource(void) 257 { 258 struct clocksource *next; 259 260 if (list_empty(&clocksource_list)) 261 return NULL; 262 263 if (clocksource_override) 264 next = clocksource_override; 265 else 266 next = list_entry(clocksource_list.next, struct clocksource, 267 list); 268 269 if (next == curr_clocksource) 270 return NULL; 271 272 return next; 273 } 274 275 /* 276 * Enqueue the clocksource sorted by rating 277 */ 278 static int clocksource_enqueue(struct clocksource *c) 279 { 280 struct list_head *tmp, *entry = &clocksource_list; 281 282 list_for_each(tmp, &clocksource_list) { 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; 291 } 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; 297 298 return 0; 299 } 300 301 /** 302 * clocksource_register - Used to install new clocksources 303 * @t: clocksource to be registered 304 * 305 * Returns -EBUSY if registration fails, zero otherwise. 306 */ 307 int clocksource_register(struct clocksource *c) 308 { 309 unsigned long flags; 310 int ret; 311 312 spin_lock_irqsave(&clocksource_lock, flags); 313 ret = clocksource_enqueue(c); 314 if (!ret) 315 next_clocksource = select_clocksource(); 316 spin_unlock_irqrestore(&clocksource_lock, flags); 317 if (!ret) 318 clocksource_check_watchdog(c); 319 return ret; 320 } 321 EXPORT_SYMBOL(clocksource_register); 322 323 /** 324 * clocksource_change_rating - Change the rating of a registered clocksource 325 * 326 */ 327 void clocksource_change_rating(struct clocksource *cs, int rating) 328 { 329 unsigned long flags; 330 331 spin_lock_irqsave(&clocksource_lock, flags); 332 list_del(&cs->list); 333 cs->rating = rating; 334 clocksource_enqueue(cs); 335 next_clocksource = select_clocksource(); 336 spin_unlock_irqrestore(&clocksource_lock, flags); 337 } 338 339 /** 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 } 353 354 #ifdef CONFIG_SYSFS 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 { 365 ssize_t count = 0; 366 367 spin_lock_irq(&clocksource_lock); 368 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); 369 spin_unlock_irq(&clocksource_lock); 370 371 return count; 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 { 386 struct clocksource *ovr = NULL; 387 size_t ret = count; 388 int len; 389 390 /* 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--; 397 398 spin_lock_irq(&clocksource_lock); 399 400 if (count > 0) 401 memcpy(override_name, buf, count); 402 override_name[count] = 0; 403 404 len = strlen(override_name); 405 if (len) { 406 struct clocksource *cs; 407 408 ovr = clocksource_override; 409 /* try to select it: */ 410 list_for_each_entry(cs, &clocksource_list, list) { 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 } 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 { 438 struct clocksource *src; 439 ssize_t count = 0; 440 441 spin_lock_irq(&clocksource_lock); 442 list_for_each_entry(src, &clocksource_list, list) { 443 count += snprintf(buf + count, 444 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), 445 "%s ", src->name); 446 } 447 spin_unlock_irq(&clocksource_lock); 448 449 count += snprintf(buf + count, 450 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); 451 452 return count; 453 } 454 455 /* 456 * Sysfs setup bits: 457 */ 458 static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources, 459 sysfs_override_clocksource); 460 461 static SYSDEV_ATTR(available_clocksource, 0600, 462 sysfs_show_available_clocksources, NULL); 463 464 static struct sysdev_class clocksource_sysclass = { 465 .name = "clocksource", 466 }; 467 468 static struct sys_device device_clocksource = { 469 .id = 0, 470 .cls = &clocksource_sysclass, 471 }; 472 473 static int __init init_clocksource_sysfs(void) 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); 491 #endif /* CONFIG_SYSFS */ 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 { 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"); 528 return boot_override_clocksource(str); 529 } 530 531 __setup("clock=", boot_override_clock); 532