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 /** 98 * clockevents_program_event - Reprogram the clock event device. 99 * @expires: absolute expiry time (monotonic clock) 100 * 101 * Returns 0 on success, -ETIME when the event is in the past. 102 */ 103 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires, 104 ktime_t now) 105 { 106 unsigned long long clc; 107 int64_t delta; 108 109 if (unlikely(expires.tv64 < 0)) { 110 WARN_ON_ONCE(1); 111 return -ETIME; 112 } 113 114 delta = ktime_to_ns(ktime_sub(expires, now)); 115 116 if (delta <= 0) 117 return -ETIME; 118 119 dev->next_event = expires; 120 121 if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN) 122 return 0; 123 124 if (delta > dev->max_delta_ns) 125 delta = dev->max_delta_ns; 126 if (delta < dev->min_delta_ns) 127 delta = dev->min_delta_ns; 128 129 clc = delta * dev->mult; 130 clc >>= dev->shift; 131 132 return dev->set_next_event((unsigned long) clc, dev); 133 } 134 135 /** 136 * clockevents_register_notifier - register a clock events change listener 137 */ 138 int clockevents_register_notifier(struct notifier_block *nb) 139 { 140 unsigned long flags; 141 int ret; 142 143 raw_spin_lock_irqsave(&clockevents_lock, flags); 144 ret = raw_notifier_chain_register(&clockevents_chain, nb); 145 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 146 147 return ret; 148 } 149 150 /* 151 * Notify about a clock event change. Called with clockevents_lock 152 * held. 153 */ 154 static void clockevents_do_notify(unsigned long reason, void *dev) 155 { 156 raw_notifier_call_chain(&clockevents_chain, reason, dev); 157 } 158 159 /* 160 * Called after a notify add to make devices available which were 161 * released from the notifier call. 162 */ 163 static void clockevents_notify_released(void) 164 { 165 struct clock_event_device *dev; 166 167 while (!list_empty(&clockevents_released)) { 168 dev = list_entry(clockevents_released.next, 169 struct clock_event_device, list); 170 list_del(&dev->list); 171 list_add(&dev->list, &clockevent_devices); 172 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 173 } 174 } 175 176 /** 177 * clockevents_register_device - register a clock event device 178 * @dev: device to register 179 */ 180 void clockevents_register_device(struct clock_event_device *dev) 181 { 182 unsigned long flags; 183 184 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 185 if (!dev->cpumask) { 186 WARN_ON(num_possible_cpus() > 1); 187 dev->cpumask = cpumask_of(smp_processor_id()); 188 } 189 190 raw_spin_lock_irqsave(&clockevents_lock, flags); 191 192 list_add(&dev->list, &clockevent_devices); 193 clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev); 194 clockevents_notify_released(); 195 196 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 197 } 198 EXPORT_SYMBOL_GPL(clockevents_register_device); 199 200 static void clockevents_config(struct clock_event_device *dev, 201 u32 freq) 202 { 203 u64 sec; 204 205 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT)) 206 return; 207 208 /* 209 * Calculate the maximum number of seconds we can sleep. Limit 210 * to 10 minutes for hardware which can program more than 211 * 32bit ticks so we still get reasonable conversion values. 212 */ 213 sec = dev->max_delta_ticks; 214 do_div(sec, freq); 215 if (!sec) 216 sec = 1; 217 else if (sec > 600 && dev->max_delta_ticks > UINT_MAX) 218 sec = 600; 219 220 clockevents_calc_mult_shift(dev, freq, sec); 221 dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev); 222 dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev); 223 } 224 225 /** 226 * clockevents_config_and_register - Configure and register a clock event device 227 * @dev: device to register 228 * @freq: The clock frequency 229 * @min_delta: The minimum clock ticks to program in oneshot mode 230 * @max_delta: The maximum clock ticks to program in oneshot mode 231 * 232 * min/max_delta can be 0 for devices which do not support oneshot mode. 233 */ 234 void clockevents_config_and_register(struct clock_event_device *dev, 235 u32 freq, unsigned long min_delta, 236 unsigned long max_delta) 237 { 238 dev->min_delta_ticks = min_delta; 239 dev->max_delta_ticks = max_delta; 240 clockevents_config(dev, freq); 241 clockevents_register_device(dev); 242 } 243 244 /** 245 * clockevents_update_freq - Update frequency and reprogram a clock event device. 246 * @dev: device to modify 247 * @freq: new device frequency 248 * 249 * Reconfigure and reprogram a clock event device in oneshot 250 * mode. Must be called on the cpu for which the device delivers per 251 * cpu timer events with interrupts disabled! Returns 0 on success, 252 * -ETIME when the event is in the past. 253 */ 254 int clockevents_update_freq(struct clock_event_device *dev, u32 freq) 255 { 256 clockevents_config(dev, freq); 257 258 if (dev->mode != CLOCK_EVT_MODE_ONESHOT) 259 return 0; 260 261 return clockevents_program_event(dev, dev->next_event, ktime_get()); 262 } 263 264 /* 265 * Noop handler when we shut down an event device 266 */ 267 void clockevents_handle_noop(struct clock_event_device *dev) 268 { 269 } 270 271 /** 272 * clockevents_exchange_device - release and request clock devices 273 * @old: device to release (can be NULL) 274 * @new: device to request (can be NULL) 275 * 276 * Called from the notifier chain. clockevents_lock is held already 277 */ 278 void clockevents_exchange_device(struct clock_event_device *old, 279 struct clock_event_device *new) 280 { 281 unsigned long flags; 282 283 local_irq_save(flags); 284 /* 285 * Caller releases a clock event device. We queue it into the 286 * released list and do a notify add later. 287 */ 288 if (old) { 289 clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED); 290 list_del(&old->list); 291 list_add(&old->list, &clockevents_released); 292 } 293 294 if (new) { 295 BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED); 296 clockevents_shutdown(new); 297 } 298 local_irq_restore(flags); 299 } 300 301 #ifdef CONFIG_GENERIC_CLOCKEVENTS 302 /** 303 * clockevents_notify - notification about relevant events 304 */ 305 void clockevents_notify(unsigned long reason, void *arg) 306 { 307 struct clock_event_device *dev, *tmp; 308 unsigned long flags; 309 int cpu; 310 311 raw_spin_lock_irqsave(&clockevents_lock, flags); 312 clockevents_do_notify(reason, arg); 313 314 switch (reason) { 315 case CLOCK_EVT_NOTIFY_CPU_DEAD: 316 /* 317 * Unregister the clock event devices which were 318 * released from the users in the notify chain. 319 */ 320 list_for_each_entry_safe(dev, tmp, &clockevents_released, list) 321 list_del(&dev->list); 322 /* 323 * Now check whether the CPU has left unused per cpu devices 324 */ 325 cpu = *((int *)arg); 326 list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) { 327 if (cpumask_test_cpu(cpu, dev->cpumask) && 328 cpumask_weight(dev->cpumask) == 1 && 329 !tick_is_broadcast_device(dev)) { 330 BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED); 331 list_del(&dev->list); 332 } 333 } 334 break; 335 default: 336 break; 337 } 338 raw_spin_unlock_irqrestore(&clockevents_lock, flags); 339 } 340 EXPORT_SYMBOL_GPL(clockevents_notify); 341 #endif 342