1 /* 2 * linux/kernel/time/tick-common.c 3 * 4 * This file contains the base functions to manage periodic tick 5 * related events. 6 * 7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> 8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar 9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner 10 * 11 * This code is licenced under the GPL version 2. For details see 12 * kernel-base/COPYING. 13 */ 14 #include <linux/cpu.h> 15 #include <linux/err.h> 16 #include <linux/hrtimer.h> 17 #include <linux/interrupt.h> 18 #include <linux/percpu.h> 19 #include <linux/profile.h> 20 #include <linux/sched.h> 21 #include <linux/tick.h> 22 23 #include <asm/irq_regs.h> 24 25 #include "tick-internal.h" 26 27 /* 28 * Tick devices 29 */ 30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device); 31 /* 32 * Tick next event: keeps track of the tick time 33 */ 34 ktime_t tick_next_period; 35 ktime_t tick_period; 36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT; 37 static DEFINE_RAW_SPINLOCK(tick_device_lock); 38 39 /* 40 * Debugging: see timer_list.c 41 */ 42 struct tick_device *tick_get_device(int cpu) 43 { 44 return &per_cpu(tick_cpu_device, cpu); 45 } 46 47 /** 48 * tick_is_oneshot_available - check for a oneshot capable event device 49 */ 50 int tick_is_oneshot_available(void) 51 { 52 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; 53 54 return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT); 55 } 56 57 /* 58 * Periodic tick 59 */ 60 static void tick_periodic(int cpu) 61 { 62 if (tick_do_timer_cpu == cpu) { 63 write_seqlock(&xtime_lock); 64 65 /* Keep track of the next tick event */ 66 tick_next_period = ktime_add(tick_next_period, tick_period); 67 68 do_timer(1); 69 write_sequnlock(&xtime_lock); 70 } 71 72 update_process_times(user_mode(get_irq_regs())); 73 profile_tick(CPU_PROFILING); 74 } 75 76 /* 77 * Event handler for periodic ticks 78 */ 79 void tick_handle_periodic(struct clock_event_device *dev) 80 { 81 int cpu = smp_processor_id(); 82 ktime_t next; 83 84 tick_periodic(cpu); 85 86 if (dev->mode != CLOCK_EVT_MODE_ONESHOT) 87 return; 88 /* 89 * Setup the next period for devices, which do not have 90 * periodic mode: 91 */ 92 next = ktime_add(dev->next_event, tick_period); 93 for (;;) { 94 if (!clockevents_program_event(dev, next, ktime_get())) 95 return; 96 /* 97 * Have to be careful here. If we're in oneshot mode, 98 * before we call tick_periodic() in a loop, we need 99 * to be sure we're using a real hardware clocksource. 100 * Otherwise we could get trapped in an infinite 101 * loop, as the tick_periodic() increments jiffies, 102 * when then will increment time, posibly causing 103 * the loop to trigger again and again. 104 */ 105 if (timekeeping_valid_for_hres()) 106 tick_periodic(cpu); 107 next = ktime_add(next, tick_period); 108 } 109 } 110 111 /* 112 * Setup the device for a periodic tick 113 */ 114 void tick_setup_periodic(struct clock_event_device *dev, int broadcast) 115 { 116 tick_set_periodic_handler(dev, broadcast); 117 118 /* Broadcast setup ? */ 119 if (!tick_device_is_functional(dev)) 120 return; 121 122 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && 123 !tick_broadcast_oneshot_active()) { 124 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); 125 } else { 126 unsigned long seq; 127 ktime_t next; 128 129 do { 130 seq = read_seqbegin(&xtime_lock); 131 next = tick_next_period; 132 } while (read_seqretry(&xtime_lock, seq)); 133 134 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 135 136 for (;;) { 137 if (!clockevents_program_event(dev, next, ktime_get())) 138 return; 139 next = ktime_add(next, tick_period); 140 } 141 } 142 } 143 144 /* 145 * Setup the tick device 146 */ 147 static void tick_setup_device(struct tick_device *td, 148 struct clock_event_device *newdev, int cpu, 149 const struct cpumask *cpumask) 150 { 151 ktime_t next_event; 152 void (*handler)(struct clock_event_device *) = NULL; 153 154 /* 155 * First device setup ? 156 */ 157 if (!td->evtdev) { 158 /* 159 * If no cpu took the do_timer update, assign it to 160 * this cpu: 161 */ 162 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { 163 tick_do_timer_cpu = cpu; 164 tick_next_period = ktime_get(); 165 tick_period = ktime_set(0, NSEC_PER_SEC / HZ); 166 } 167 168 /* 169 * Startup in periodic mode first. 170 */ 171 td->mode = TICKDEV_MODE_PERIODIC; 172 } else { 173 handler = td->evtdev->event_handler; 174 next_event = td->evtdev->next_event; 175 td->evtdev->event_handler = clockevents_handle_noop; 176 } 177 178 td->evtdev = newdev; 179 180 /* 181 * When the device is not per cpu, pin the interrupt to the 182 * current cpu: 183 */ 184 if (!cpumask_equal(newdev->cpumask, cpumask)) 185 irq_set_affinity(newdev->irq, cpumask); 186 187 /* 188 * When global broadcasting is active, check if the current 189 * device is registered as a placeholder for broadcast mode. 190 * This allows us to handle this x86 misfeature in a generic 191 * way. 192 */ 193 if (tick_device_uses_broadcast(newdev, cpu)) 194 return; 195 196 if (td->mode == TICKDEV_MODE_PERIODIC) 197 tick_setup_periodic(newdev, 0); 198 else 199 tick_setup_oneshot(newdev, handler, next_event); 200 } 201 202 /* 203 * Check, if the new registered device should be used. 204 */ 205 static int tick_check_new_device(struct clock_event_device *newdev) 206 { 207 struct clock_event_device *curdev; 208 struct tick_device *td; 209 int cpu, ret = NOTIFY_OK; 210 unsigned long flags; 211 212 raw_spin_lock_irqsave(&tick_device_lock, flags); 213 214 cpu = smp_processor_id(); 215 if (!cpumask_test_cpu(cpu, newdev->cpumask)) 216 goto out_bc; 217 218 td = &per_cpu(tick_cpu_device, cpu); 219 curdev = td->evtdev; 220 221 /* cpu local device ? */ 222 if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) { 223 224 /* 225 * If the cpu affinity of the device interrupt can not 226 * be set, ignore it. 227 */ 228 if (!irq_can_set_affinity(newdev->irq)) 229 goto out_bc; 230 231 /* 232 * If we have a cpu local device already, do not replace it 233 * by a non cpu local device 234 */ 235 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu))) 236 goto out_bc; 237 } 238 239 /* 240 * If we have an active device, then check the rating and the oneshot 241 * feature. 242 */ 243 if (curdev) { 244 /* 245 * Prefer one shot capable devices ! 246 */ 247 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && 248 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) 249 goto out_bc; 250 /* 251 * Check the rating 252 */ 253 if (curdev->rating >= newdev->rating) 254 goto out_bc; 255 } 256 257 /* 258 * Replace the eventually existing device by the new 259 * device. If the current device is the broadcast device, do 260 * not give it back to the clockevents layer ! 261 */ 262 if (tick_is_broadcast_device(curdev)) { 263 clockevents_shutdown(curdev); 264 curdev = NULL; 265 } 266 clockevents_exchange_device(curdev, newdev); 267 tick_setup_device(td, newdev, cpu, cpumask_of(cpu)); 268 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 269 tick_oneshot_notify(); 270 271 raw_spin_unlock_irqrestore(&tick_device_lock, flags); 272 return NOTIFY_STOP; 273 274 out_bc: 275 /* 276 * Can the new device be used as a broadcast device ? 277 */ 278 if (tick_check_broadcast_device(newdev)) 279 ret = NOTIFY_STOP; 280 281 raw_spin_unlock_irqrestore(&tick_device_lock, flags); 282 283 return ret; 284 } 285 286 /* 287 * Transfer the do_timer job away from a dying cpu. 288 * 289 * Called with interrupts disabled. 290 */ 291 static void tick_handover_do_timer(int *cpup) 292 { 293 if (*cpup == tick_do_timer_cpu) { 294 int cpu = cpumask_first(cpu_online_mask); 295 296 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu : 297 TICK_DO_TIMER_NONE; 298 } 299 } 300 301 /* 302 * Shutdown an event device on a given cpu: 303 * 304 * This is called on a life CPU, when a CPU is dead. So we cannot 305 * access the hardware device itself. 306 * We just set the mode and remove it from the lists. 307 */ 308 static void tick_shutdown(unsigned int *cpup) 309 { 310 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); 311 struct clock_event_device *dev = td->evtdev; 312 unsigned long flags; 313 314 raw_spin_lock_irqsave(&tick_device_lock, flags); 315 td->mode = TICKDEV_MODE_PERIODIC; 316 if (dev) { 317 /* 318 * Prevent that the clock events layer tries to call 319 * the set mode function! 320 */ 321 dev->mode = CLOCK_EVT_MODE_UNUSED; 322 clockevents_exchange_device(dev, NULL); 323 td->evtdev = NULL; 324 } 325 raw_spin_unlock_irqrestore(&tick_device_lock, flags); 326 } 327 328 static void tick_suspend(void) 329 { 330 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 331 unsigned long flags; 332 333 raw_spin_lock_irqsave(&tick_device_lock, flags); 334 clockevents_shutdown(td->evtdev); 335 raw_spin_unlock_irqrestore(&tick_device_lock, flags); 336 } 337 338 static void tick_resume(void) 339 { 340 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 341 unsigned long flags; 342 int broadcast = tick_resume_broadcast(); 343 344 raw_spin_lock_irqsave(&tick_device_lock, flags); 345 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); 346 347 if (!broadcast) { 348 if (td->mode == TICKDEV_MODE_PERIODIC) 349 tick_setup_periodic(td->evtdev, 0); 350 else 351 tick_resume_oneshot(); 352 } 353 raw_spin_unlock_irqrestore(&tick_device_lock, flags); 354 } 355 356 /* 357 * Notification about clock event devices 358 */ 359 static int tick_notify(struct notifier_block *nb, unsigned long reason, 360 void *dev) 361 { 362 switch (reason) { 363 364 case CLOCK_EVT_NOTIFY_ADD: 365 return tick_check_new_device(dev); 366 367 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 368 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 369 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: 370 tick_broadcast_on_off(reason, dev); 371 break; 372 373 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: 374 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: 375 tick_broadcast_oneshot_control(reason); 376 break; 377 378 case CLOCK_EVT_NOTIFY_CPU_DYING: 379 tick_handover_do_timer(dev); 380 break; 381 382 case CLOCK_EVT_NOTIFY_CPU_DEAD: 383 tick_shutdown_broadcast_oneshot(dev); 384 tick_shutdown_broadcast(dev); 385 tick_shutdown(dev); 386 break; 387 388 case CLOCK_EVT_NOTIFY_SUSPEND: 389 tick_suspend(); 390 tick_suspend_broadcast(); 391 break; 392 393 case CLOCK_EVT_NOTIFY_RESUME: 394 tick_resume(); 395 break; 396 397 default: 398 break; 399 } 400 401 return NOTIFY_OK; 402 } 403 404 static struct notifier_block tick_notifier = { 405 .notifier_call = tick_notify, 406 }; 407 408 /** 409 * tick_init - initialize the tick control 410 * 411 * Register the notifier with the clockevents framework 412 */ 413 void __init tick_init(void) 414 { 415 clockevents_register_notifier(&tick_notifier); 416 } 417