1 /* 2 * linux/kernel/time/clockevents.c 3 * 4 * This file contains functions which manage clock event devices. 5 * 6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> 7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar 8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner 9 * 10 * This code is licenced under the GPL version 2. For details see 11 * kernel-base/COPYING. 12 */ 13 14 #include <linux/clockchips.h> 15 #include <linux/hrtimer.h> 16 #include <linux/init.h> 17 #include <linux/module.h> 18 #include <linux/notifier.h> 19 #include <linux/smp.h> 20 #include <linux/sysdev.h> 21 22 #include "tick-internal.h" 23 24 /* The registered clock event devices */ 25 static LIST_HEAD(clockevent_devices); 26 static LIST_HEAD(clockevents_released); 27 28 /* Notification for clock events */ 29 static RAW_NOTIFIER_HEAD(clockevents_chain); 30 31 /* Protection for the above */ 32 static DEFINE_RAW_SPINLOCK(clockevents_lock); 33 34 /** 35 * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds 36 * @latch: value to convert 37 * @evt: pointer to clock event device descriptor 38 * 39 * Math helper, returns latch value converted to nanoseconds (bound checked) 40 */ 41 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt) 42 { 43 u64 clc = (u64) latch << evt->shift; 44 45 if (unlikely(!evt->mult)) { 46 evt->mult = 1; 47 WARN_ON(1); 48 } 49 50 do_div(clc, evt->mult); 51 if (clc < 1000) 52 clc = 1000; 53 if (clc > KTIME_MAX) 54 clc = KTIME_MAX; 55 56 return clc; 57 } 58 EXPORT_SYMBOL_GPL(clockevent_delta2ns); 59 60 /** 61 * clockevents_set_mode - set the operating mode of a clock event device 62 * @dev: device to modify 63 * @mode: new mode 64 * 65 * Must be called with interrupts disabled ! 66 */ 67 void clockevents_set_mode(struct clock_event_device *dev, 68 enum clock_event_mode mode) 69 { 70 if (dev->mode != mode) { 71 dev->set_mode(mode, dev); 72 dev->mode = mode; 73 74 /* 75 * A nsec2cyc multiplicator of 0 is invalid and we'd crash 76 * on it, so fix it up and emit a warning: 77 */ 78 if (mode == CLOCK_EVT_MODE_ONESHOT) { 79 if (unlikely(!dev->mult)) { 80 dev->mult = 1; 81 WARN_ON(1); 82 } 83 } 84 } 85 } 86 87 /** 88 * clockevents_shutdown - shutdown the device and clear next_event 89 * @dev: device to shutdown 90 */ 91 void clockevents_shutdown(struct clock_event_device *dev) 92 { 93 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); 94 dev->next_event.tv64 = KTIME_MAX; 95 } 96 97 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST 98 99 /* Limit min_delta to a jiffie */ 100 #define MIN_DELTA_LIMIT (NSEC_PER_SEC / HZ) 101 102 /** 103 * clockevents_increase_min_delta - raise minimum delta of a clock event device 104 * @dev: device to increase the minimum delta 105 * 106 * Returns 0 on success, -ETIME when the minimum delta reached the limit. 107 */ 108 static int clockevents_increase_min_delta(struct clock_event_device *dev) 109 { 110 /* Nothing to do if we already reached the limit */ 111 if (dev->min_delta_ns >= MIN_DELTA_LIMIT) { 112 printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n"); 113 dev->next_event.tv64 = KTIME_MAX; 114 return -ETIME; 115 } 116 117 if (dev->min_delta_ns < 5000) 118 dev->min_delta_ns = 5000; 119 else 120 dev->min_delta_ns += dev->min_delta_ns >> 1; 121 122 if (dev->min_delta_ns > MIN_DELTA_LIMIT) 123 dev->min_delta_ns = MIN_DELTA_LIMIT; 124 125 printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n", 126 dev->name ? dev->name : "?", 127 (unsigned long long) dev->min_delta_ns); 128 return 0; 129 } 130 131 /** 132 * clockevents_program_min_delta - Set clock event device to the minimum delay. 133 * @dev: device to program 134 * 135 * Returns 0 on success, -ETIME when the retry loop failed. 136 */ 137 static int clockevents_program_min_delta(struct clock_event_device *dev) 138 { 139 unsigned long long clc; 140 int64_t delta; 141 int i; 142 143 for (i = 0;;) { 144 delta = dev->min_delta_ns; 145 dev->next_event = ktime_add_ns(ktime_get(), delta); 146 147 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 148 return 0; 149 150 dev->retries++; 151 clc = ((unsigned long long) delta * dev->mult) >> dev->shift; 152 if (dev->set_next_event((unsigned long) clc, dev) == 0) 153 return 0; 154 155 if (++i > 2) { 156 /* 157 * We tried 3 times to program the device with the 158 * given min_delta_ns. Try to increase the minimum 159 * delta, if that fails as well get out of here. 160 */ 161 if (clockevents_increase_min_delta(dev)) 162 return -ETIME; 163 i = 0; 164 } 165 } 166 } 167 168 #else /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */ 169 170 /** 171 * clockevents_program_min_delta - Set clock event device to the minimum delay. 172 * @dev: device to program 173 * 174 * Returns 0 on success, -ETIME when the retry loop failed. 175 */ 176 static int clockevents_program_min_delta(struct clock_event_device *dev) 177 { 178 unsigned long long clc; 179 int64_t delta; 180 181 delta = dev->min_delta_ns; 182 dev->next_event = ktime_add_ns(ktime_get(), delta); 183 184 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 185 return 0; 186 187 dev->retries++; 188 clc = ((unsigned long long) delta * dev->mult) >> dev->shift; 189 return dev->set_next_event((unsigned long) clc, dev); 190 } 191 192 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */ 193 194 /** 195 * clockevents_program_event - Reprogram the clock event device. 196 * @dev: device to program 197 * @expires: absolute expiry time (monotonic clock) 198 * @force: program minimum delay if expires can not be set 199 * 200 * Returns 0 on success, -ETIME when the event is in the past. 201 */ 202 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 203 bool force) 204 { 205 unsigned long long clc; 206 int64_t delta; 207 int rc; 208 209 if (unlikely(expires.tv64 < 0)) { 210 WARN_ON_ONCE(1); 211 return -ETIME; 212 } 213 214 dev->next_event = expires; 215 216 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 217 return 0; 218 219 /* Shortcut for clockevent devices that can deal with ktime. */ 220 if (dev->features & CLOCK_EVT_FEAT_KTIME) 221 return dev->set_next_ktime(expires, dev); 222 223 delta = ktime_to_ns(ktime_sub(expires, ktime_get())); 224 if (delta <= 0) 225 return force ? clockevents_program_min_delta(dev) : -ETIME; 226 227 delta = min(delta, (int64_t) dev->max_delta_ns); 228 delta = max(delta, (int64_t) dev->min_delta_ns); 229 230 clc = ((unsigned long long) delta * dev->mult) >> dev->shift; 231 rc = dev->set_next_event((unsigned long) clc, dev); 232 233 return (rc && force) ? clockevents_program_min_delta(dev) : rc; 234 } 235 236 /** 237 * clockevents_register_notifier - register a clock events change listener 238 */ 239 int clockevents_register_notifier(struct notifier_block *nb) 240 { 241 unsigned long flags; 242 int ret; 243 244 raw_spin_lock_irqsave(&clockevents_lock, flags); 245 ret = raw_notifier_chain_register(&clockevents_chain, nb); 246 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 247 248 return ret; 249 } 250 251 /* 252 * Notify about a clock event change. Called with clockevents_lock 253 * held. 254 */ 255 static void clockevents_do_notify(unsigned long reason, void *dev) 256 { 257 raw_notifier_call_chain(&clockevents_chain, reason, dev); 258 } 259 260 /* 261 * Called after a notify add to make devices available which were 262 * released from the notifier call. 263 */ 264 static void clockevents_notify_released(void) 265 { 266 struct clock_event_device *dev; 267 268 while (!list_empty(&clockevents_released)) { 269 dev = list_entry(clockevents_released.next, 270 struct clock_event_device, list); 271 list_del(&dev->list); 272 list_add(&dev->list, &clockevent_devices); 273 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 274 } 275 } 276 277 /** 278 * clockevents_register_device - register a clock event device 279 * @dev: device to register 280 */ 281 void clockevents_register_device(struct clock_event_device *dev) 282 { 283 unsigned long flags; 284 285 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 286 if (!dev->cpumask) { 287 WARN_ON(num_possible_cpus() > 1); 288 dev->cpumask = cpumask_of(smp_processor_id()); 289 } 290 291 raw_spin_lock_irqsave(&clockevents_lock, flags); 292 293 list_add(&dev->list, &clockevent_devices); 294 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 295 clockevents_notify_released(); 296 297 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 298 } 299 EXPORT_SYMBOL_GPL(clockevents_register_device); 300 301 static void clockevents_config(struct clock_event_device *dev, 302 u32 freq) 303 { 304 u64 sec; 305 306 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT)) 307 return; 308 309 /* 310 * Calculate the maximum number of seconds we can sleep. Limit 311 * to 10 minutes for hardware which can program more than 312 * 32bit ticks so we still get reasonable conversion values. 313 */ 314 sec = dev->max_delta_ticks; 315 do_div(sec, freq); 316 if (!sec) 317 sec = 1; 318 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX) 319 sec = 600; 320 321 clockevents_calc_mult_shift(dev, freq, sec); 322 dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev); 323 dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev); 324 } 325 326 /** 327 * clockevents_config_and_register - Configure and register a clock event device 328 * @dev: device to register 329 * @freq: The clock frequency 330 * @min_delta: The minimum clock ticks to program in oneshot mode 331 * @max_delta: The maximum clock ticks to program in oneshot mode 332 * 333 * min/max_delta can be 0 for devices which do not support oneshot mode. 334 */ 335 void clockevents_config_and_register(struct clock_event_device *dev, 336 u32 freq, unsigned long min_delta, 337 unsigned long max_delta) 338 { 339 dev->min_delta_ticks = min_delta; 340 dev->max_delta_ticks = max_delta; 341 clockevents_config(dev, freq); 342 clockevents_register_device(dev); 343 } 344 345 /** 346 * clockevents_update_freq - Update frequency and reprogram a clock event device. 347 * @dev: device to modify 348 * @freq: new device frequency 349 * 350 * Reconfigure and reprogram a clock event device in oneshot 351 * mode. Must be called on the cpu for which the device delivers per 352 * cpu timer events with interrupts disabled! Returns 0 on success, 353 * -ETIME when the event is in the past. 354 */ 355 int clockevents_update_freq(struct clock_event_device *dev, u32 freq) 356 { 357 clockevents_config(dev, freq); 358 359 if (dev->mode != CLOCK_EVT_MODE_ONESHOT) 360 return 0; 361 362 return clockevents_program_event(dev, dev->next_event, false); 363 } 364 365 /* 366 * Noop handler when we shut down an event device 367 */ 368 void clockevents_handle_noop(struct clock_event_device *dev) 369 { 370 } 371 372 /** 373 * clockevents_exchange_device - release and request clock devices 374 * @old: device to release (can be NULL) 375 * @new: device to request (can be NULL) 376 * 377 * Called from the notifier chain. clockevents_lock is held already 378 */ 379 void clockevents_exchange_device(struct clock_event_device *old, 380 struct clock_event_device *new) 381 { 382 unsigned long flags; 383 384 local_irq_save(flags); 385 /* 386 * Caller releases a clock event device. We queue it into the 387 * released list and do a notify add later. 388 */ 389 if (old) { 390 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); 391 list_del(&old->list); 392 list_add(&old->list, &clockevents_released); 393 } 394 395 if (new) { 396 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); 397 clockevents_shutdown(new); 398 } 399 local_irq_restore(flags); 400 } 401 402 #ifdef CONFIG_GENERIC_CLOCKEVENTS 403 /** 404 * clockevents_notify - notification about relevant events 405 */ 406 void clockevents_notify(unsigned long reason, void *arg) 407 { 408 struct clock_event_device *dev, *tmp; 409 unsigned long flags; 410 int cpu; 411 412 raw_spin_lock_irqsave(&clockevents_lock, flags); 413 clockevents_do_notify(reason, arg); 414 415 switch (reason) { 416 case CLOCK_EVT_NOTIFY_CPU_DEAD: 417 /* 418 * Unregister the clock event devices which were 419 * released from the users in the notify chain. 420 */ 421 list_for_each_entry_safe(dev, tmp, &clockevents_released, list) 422 list_del(&dev->list); 423 /* 424 * Now check whether the CPU has left unused per cpu devices 425 */ 426 cpu = *((int *)arg); 427 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) { 428 if (cpumask_test_cpu(cpu, dev->cpumask) && 429 cpumask_weight(dev->cpumask) == 1 && 430 !tick_is_broadcast_device(dev)) { 431 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 432 list_del(&dev->list); 433 } 434 } 435 break; 436 default: 437 break; 438 } 439 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 440 } 441 EXPORT_SYMBOL_GPL(clockevents_notify); 442 #endif 443