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 DEFINE_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 tick_periodic(cpu); 97 next = ktime_add(next, tick_period); 98 } 99 } 100 101 /* 102 * Setup the device for a periodic tick 103 */ 104 void tick_setup_periodic(struct clock_event_device *dev, int broadcast) 105 { 106 tick_set_periodic_handler(dev, broadcast); 107 108 /* Broadcast setup ? */ 109 if (!tick_device_is_functional(dev)) 110 return; 111 112 if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) && 113 !tick_broadcast_oneshot_active()) { 114 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); 115 } else { 116 unsigned long seq; 117 ktime_t next; 118 119 do { 120 seq = read_seqbegin(&xtime_lock); 121 next = tick_next_period; 122 } while (read_seqretry(&xtime_lock, seq)); 123 124 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 125 126 for (;;) { 127 if (!clockevents_program_event(dev, next, ktime_get())) 128 return; 129 next = ktime_add(next, tick_period); 130 } 131 } 132 } 133 134 /* 135 * Setup the tick device 136 */ 137 static void tick_setup_device(struct tick_device *td, 138 struct clock_event_device *newdev, int cpu, 139 const cpumask_t *cpumask) 140 { 141 ktime_t next_event; 142 void (*handler)(struct clock_event_device *) = NULL; 143 144 /* 145 * First device setup ? 146 */ 147 if (!td->evtdev) { 148 /* 149 * If no cpu took the do_timer update, assign it to 150 * this cpu: 151 */ 152 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) { 153 tick_do_timer_cpu = cpu; 154 tick_next_period = ktime_get(); 155 tick_period = ktime_set(0, NSEC_PER_SEC / HZ); 156 } 157 158 /* 159 * Startup in periodic mode first. 160 */ 161 td->mode = TICKDEV_MODE_PERIODIC; 162 } else { 163 handler = td->evtdev->event_handler; 164 next_event = td->evtdev->next_event; 165 td->evtdev->event_handler = clockevents_handle_noop; 166 } 167 168 td->evtdev = newdev; 169 170 /* 171 * When the device is not per cpu, pin the interrupt to the 172 * current cpu: 173 */ 174 if (!cpus_equal(newdev->cpumask, *cpumask)) 175 irq_set_affinity(newdev->irq, *cpumask); 176 177 /* 178 * When global broadcasting is active, check if the current 179 * device is registered as a placeholder for broadcast mode. 180 * This allows us to handle this x86 misfeature in a generic 181 * way. 182 */ 183 if (tick_device_uses_broadcast(newdev, cpu)) 184 return; 185 186 if (td->mode == TICKDEV_MODE_PERIODIC) 187 tick_setup_periodic(newdev, 0); 188 else 189 tick_setup_oneshot(newdev, handler, next_event); 190 } 191 192 /* 193 * Check, if the new registered device should be used. 194 */ 195 static int tick_check_new_device(struct clock_event_device *newdev) 196 { 197 struct clock_event_device *curdev; 198 struct tick_device *td; 199 int cpu, ret = NOTIFY_OK; 200 unsigned long flags; 201 202 spin_lock_irqsave(&tick_device_lock, flags); 203 204 cpu = smp_processor_id(); 205 if (!cpu_isset(cpu, newdev->cpumask)) 206 goto out_bc; 207 208 td = &per_cpu(tick_cpu_device, cpu); 209 curdev = td->evtdev; 210 211 /* cpu local device ? */ 212 if (!cpus_equal(newdev->cpumask, cpumask_of_cpu(cpu))) { 213 214 /* 215 * If the cpu affinity of the device interrupt can not 216 * be set, ignore it. 217 */ 218 if (!irq_can_set_affinity(newdev->irq)) 219 goto out_bc; 220 221 /* 222 * If we have a cpu local device already, do not replace it 223 * by a non cpu local device 224 */ 225 if (curdev && cpus_equal(curdev->cpumask, cpumask_of_cpu(cpu))) 226 goto out_bc; 227 } 228 229 /* 230 * If we have an active device, then check the rating and the oneshot 231 * feature. 232 */ 233 if (curdev) { 234 /* 235 * Prefer one shot capable devices ! 236 */ 237 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && 238 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) 239 goto out_bc; 240 /* 241 * Check the rating 242 */ 243 if (curdev->rating >= newdev->rating) 244 goto out_bc; 245 } 246 247 /* 248 * Replace the eventually existing device by the new 249 * device. If the current device is the broadcast device, do 250 * not give it back to the clockevents layer ! 251 */ 252 if (tick_is_broadcast_device(curdev)) { 253 clockevents_shutdown(curdev); 254 curdev = NULL; 255 } 256 clockevents_exchange_device(curdev, newdev); 257 tick_setup_device(td, newdev, cpu, &cpumask_of_cpu(cpu)); 258 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 259 tick_oneshot_notify(); 260 261 spin_unlock_irqrestore(&tick_device_lock, flags); 262 return NOTIFY_STOP; 263 264 out_bc: 265 /* 266 * Can the new device be used as a broadcast device ? 267 */ 268 if (tick_check_broadcast_device(newdev)) 269 ret = NOTIFY_STOP; 270 271 spin_unlock_irqrestore(&tick_device_lock, flags); 272 273 return ret; 274 } 275 276 /* 277 * Shutdown an event device on a given cpu: 278 * 279 * This is called on a life CPU, when a CPU is dead. So we cannot 280 * access the hardware device itself. 281 * We just set the mode and remove it from the lists. 282 */ 283 static void tick_shutdown(unsigned int *cpup) 284 { 285 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); 286 struct clock_event_device *dev = td->evtdev; 287 unsigned long flags; 288 289 spin_lock_irqsave(&tick_device_lock, flags); 290 td->mode = TICKDEV_MODE_PERIODIC; 291 if (dev) { 292 /* 293 * Prevent that the clock events layer tries to call 294 * the set mode function! 295 */ 296 dev->mode = CLOCK_EVT_MODE_UNUSED; 297 clockevents_exchange_device(dev, NULL); 298 td->evtdev = NULL; 299 } 300 /* Transfer the do_timer job away from this cpu */ 301 if (*cpup == tick_do_timer_cpu) { 302 int cpu = first_cpu(cpu_online_map); 303 304 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : 305 TICK_DO_TIMER_NONE; 306 } 307 spin_unlock_irqrestore(&tick_device_lock, flags); 308 } 309 310 static void tick_suspend(void) 311 { 312 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 313 unsigned long flags; 314 315 spin_lock_irqsave(&tick_device_lock, flags); 316 clockevents_shutdown(td->evtdev); 317 spin_unlock_irqrestore(&tick_device_lock, flags); 318 } 319 320 static void tick_resume(void) 321 { 322 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 323 unsigned long flags; 324 int broadcast = tick_resume_broadcast(); 325 326 spin_lock_irqsave(&tick_device_lock, flags); 327 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); 328 329 if (!broadcast) { 330 if (td->mode == TICKDEV_MODE_PERIODIC) 331 tick_setup_periodic(td->evtdev, 0); 332 else 333 tick_resume_oneshot(); 334 } 335 spin_unlock_irqrestore(&tick_device_lock, flags); 336 } 337 338 /* 339 * Notification about clock event devices 340 */ 341 static int tick_notify(struct notifier_block *nb, unsigned long reason, 342 void *dev) 343 { 344 switch (reason) { 345 346 case CLOCK_EVT_NOTIFY_ADD: 347 return tick_check_new_device(dev); 348 349 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 350 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 351 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: 352 tick_broadcast_on_off(reason, dev); 353 break; 354 355 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: 356 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: 357 tick_broadcast_oneshot_control(reason); 358 break; 359 360 case CLOCK_EVT_NOTIFY_CPU_DEAD: 361 tick_shutdown_broadcast_oneshot(dev); 362 tick_shutdown_broadcast(dev); 363 tick_shutdown(dev); 364 break; 365 366 case CLOCK_EVT_NOTIFY_SUSPEND: 367 tick_suspend(); 368 tick_suspend_broadcast(); 369 break; 370 371 case CLOCK_EVT_NOTIFY_RESUME: 372 tick_resume(); 373 break; 374 375 default: 376 break; 377 } 378 379 return NOTIFY_OK; 380 } 381 382 static struct notifier_block tick_notifier = { 383 .notifier_call = tick_notify, 384 }; 385 386 /** 387 * tick_init - initialize the tick control 388 * 389 * Register the notifier with the clockevents framework 390 */ 391 void __init tick_init(void) 392 { 393 clockevents_register_notifier(&tick_notifier); 394 } 395