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 = -1; 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 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC); 114 } else { 115 unsigned long seq; 116 ktime_t next; 117 118 do { 119 seq = read_seqbegin(&xtime_lock); 120 next = tick_next_period; 121 } while (read_seqretry(&xtime_lock, seq)); 122 123 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 124 125 for (;;) { 126 if (!clockevents_program_event(dev, next, ktime_get())) 127 return; 128 next = ktime_add(next, tick_period); 129 } 130 } 131 } 132 133 /* 134 * Setup the tick device 135 */ 136 static void tick_setup_device(struct tick_device *td, 137 struct clock_event_device *newdev, int cpu, 138 const cpumask_t *cpumask) 139 { 140 ktime_t next_event; 141 void (*handler)(struct clock_event_device *) = NULL; 142 143 /* 144 * First device setup ? 145 */ 146 if (!td->evtdev) { 147 /* 148 * If no cpu took the do_timer update, assign it to 149 * this cpu: 150 */ 151 if (tick_do_timer_cpu == -1) { 152 tick_do_timer_cpu = cpu; 153 tick_next_period = ktime_get(); 154 tick_period = ktime_set(0, NSEC_PER_SEC / HZ); 155 } 156 157 /* 158 * Startup in periodic mode first. 159 */ 160 td->mode = TICKDEV_MODE_PERIODIC; 161 } else { 162 handler = td->evtdev->event_handler; 163 next_event = td->evtdev->next_event; 164 td->evtdev->event_handler = clockevents_handle_noop; 165 } 166 167 td->evtdev = newdev; 168 169 /* 170 * When the device is not per cpu, pin the interrupt to the 171 * current cpu: 172 */ 173 if (!cpus_equal(newdev->cpumask, *cpumask)) 174 irq_set_affinity(newdev->irq, *cpumask); 175 176 /* 177 * When global broadcasting is active, check if the current 178 * device is registered as a placeholder for broadcast mode. 179 * This allows us to handle this x86 misfeature in a generic 180 * way. 181 */ 182 if (tick_device_uses_broadcast(newdev, cpu)) 183 return; 184 185 if (td->mode == TICKDEV_MODE_PERIODIC) 186 tick_setup_periodic(newdev, 0); 187 else 188 tick_setup_oneshot(newdev, handler, next_event); 189 } 190 191 /* 192 * Check, if the new registered device should be used. 193 */ 194 static int tick_check_new_device(struct clock_event_device *newdev) 195 { 196 struct clock_event_device *curdev; 197 struct tick_device *td; 198 int cpu, ret = NOTIFY_OK; 199 unsigned long flags; 200 201 spin_lock_irqsave(&tick_device_lock, flags); 202 203 cpu = smp_processor_id(); 204 if (!cpu_isset(cpu, newdev->cpumask)) 205 goto out_bc; 206 207 td = &per_cpu(tick_cpu_device, cpu); 208 curdev = td->evtdev; 209 210 /* cpu local device ? */ 211 if (!cpus_equal(newdev->cpumask, cpumask_of_cpu(cpu))) { 212 213 /* 214 * If the cpu affinity of the device interrupt can not 215 * be set, ignore it. 216 */ 217 if (!irq_can_set_affinity(newdev->irq)) 218 goto out_bc; 219 220 /* 221 * If we have a cpu local device already, do not replace it 222 * by a non cpu local device 223 */ 224 if (curdev && cpus_equal(curdev->cpumask, cpumask_of_cpu(cpu))) 225 goto out_bc; 226 } 227 228 /* 229 * If we have an active device, then check the rating and the oneshot 230 * feature. 231 */ 232 if (curdev) { 233 /* 234 * Prefer one shot capable devices ! 235 */ 236 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && 237 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) 238 goto out_bc; 239 /* 240 * Check the rating 241 */ 242 if (curdev->rating >= newdev->rating) 243 goto out_bc; 244 } 245 246 /* 247 * Replace the eventually existing device by the new 248 * device. If the current device is the broadcast device, do 249 * not give it back to the clockevents layer ! 250 */ 251 if (tick_is_broadcast_device(curdev)) { 252 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN); 253 curdev = NULL; 254 } 255 clockevents_exchange_device(curdev, newdev); 256 tick_setup_device(td, newdev, cpu, &cpumask_of_cpu(cpu)); 257 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 258 tick_oneshot_notify(); 259 260 spin_unlock_irqrestore(&tick_device_lock, flags); 261 return NOTIFY_STOP; 262 263 out_bc: 264 /* 265 * Can the new device be used as a broadcast device ? 266 */ 267 if (tick_check_broadcast_device(newdev)) 268 ret = NOTIFY_STOP; 269 270 spin_unlock_irqrestore(&tick_device_lock, flags); 271 272 return ret; 273 } 274 275 /* 276 * Shutdown an event device on a given cpu: 277 * 278 * This is called on a life CPU, when a CPU is dead. So we cannot 279 * access the hardware device itself. 280 * We just set the mode and remove it from the lists. 281 */ 282 static void tick_shutdown(unsigned int *cpup) 283 { 284 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); 285 struct clock_event_device *dev = td->evtdev; 286 unsigned long flags; 287 288 spin_lock_irqsave(&tick_device_lock, flags); 289 td->mode = TICKDEV_MODE_PERIODIC; 290 if (dev) { 291 /* 292 * Prevent that the clock events layer tries to call 293 * the set mode function! 294 */ 295 dev->mode = CLOCK_EVT_MODE_UNUSED; 296 clockevents_exchange_device(dev, NULL); 297 td->evtdev = NULL; 298 } 299 /* Transfer the do_timer job away from this cpu */ 300 if (*cpup == tick_do_timer_cpu) { 301 int cpu = first_cpu(cpu_online_map); 302 303 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1; 304 } 305 spin_unlock_irqrestore(&tick_device_lock, flags); 306 } 307 308 static void tick_suspend(void) 309 { 310 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 311 unsigned long flags; 312 313 spin_lock_irqsave(&tick_device_lock, flags); 314 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN); 315 spin_unlock_irqrestore(&tick_device_lock, flags); 316 } 317 318 static void tick_resume(void) 319 { 320 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 321 unsigned long flags; 322 int broadcast = tick_resume_broadcast(); 323 324 spin_lock_irqsave(&tick_device_lock, flags); 325 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); 326 327 if (!broadcast) { 328 if (td->mode == TICKDEV_MODE_PERIODIC) 329 tick_setup_periodic(td->evtdev, 0); 330 else 331 tick_resume_oneshot(); 332 } 333 spin_unlock_irqrestore(&tick_device_lock, flags); 334 } 335 336 /* 337 * Notification about clock event devices 338 */ 339 static int tick_notify(struct notifier_block *nb, unsigned long reason, 340 void *dev) 341 { 342 switch (reason) { 343 344 case CLOCK_EVT_NOTIFY_ADD: 345 return tick_check_new_device(dev); 346 347 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 348 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 349 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: 350 tick_broadcast_on_off(reason, dev); 351 break; 352 353 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: 354 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: 355 tick_broadcast_oneshot_control(reason); 356 break; 357 358 case CLOCK_EVT_NOTIFY_CPU_DEAD: 359 tick_shutdown_broadcast_oneshot(dev); 360 tick_shutdown_broadcast(dev); 361 tick_shutdown(dev); 362 break; 363 364 case CLOCK_EVT_NOTIFY_SUSPEND: 365 tick_suspend(); 366 tick_suspend_broadcast(); 367 break; 368 369 case CLOCK_EVT_NOTIFY_RESUME: 370 tick_resume(); 371 break; 372 373 default: 374 break; 375 } 376 377 return NOTIFY_OK; 378 } 379 380 static struct notifier_block tick_notifier = { 381 .notifier_call = tick_notify, 382 }; 383 384 /** 385 * tick_init - initialize the tick control 386 * 387 * Register the notifier with the clockevents framework 388 */ 389 void __init tick_init(void) 390 { 391 clockevents_register_notifier(&tick_notifier); 392 } 393