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 } 165 166 td->evtdev = newdev; 167 168 /* 169 * When the device is not per cpu, pin the interrupt to the 170 * current cpu: 171 */ 172 if (!cpus_equal(newdev->cpumask, *cpumask)) 173 irq_set_affinity(newdev->irq, *cpumask); 174 175 /* 176 * When global broadcasting is active, check if the current 177 * device is registered as a placeholder for broadcast mode. 178 * This allows us to handle this x86 misfeature in a generic 179 * way. 180 */ 181 if (tick_device_uses_broadcast(newdev, cpu)) 182 return; 183 184 if (td->mode == TICKDEV_MODE_PERIODIC) 185 tick_setup_periodic(newdev, 0); 186 else 187 tick_setup_oneshot(newdev, handler, next_event); 188 } 189 190 /* 191 * Check, if the new registered device should be used. 192 */ 193 static int tick_check_new_device(struct clock_event_device *newdev) 194 { 195 struct clock_event_device *curdev; 196 struct tick_device *td; 197 int cpu, ret = NOTIFY_OK; 198 unsigned long flags; 199 200 spin_lock_irqsave(&tick_device_lock, flags); 201 202 cpu = smp_processor_id(); 203 if (!cpu_isset(cpu, newdev->cpumask)) 204 goto out_bc; 205 206 td = &per_cpu(tick_cpu_device, cpu); 207 curdev = td->evtdev; 208 209 /* cpu local device ? */ 210 if (!cpus_equal(newdev->cpumask, cpumask_of_cpu(cpu))) { 211 212 /* 213 * If the cpu affinity of the device interrupt can not 214 * be set, ignore it. 215 */ 216 if (!irq_can_set_affinity(newdev->irq)) 217 goto out_bc; 218 219 /* 220 * If we have a cpu local device already, do not replace it 221 * by a non cpu local device 222 */ 223 if (curdev && cpus_equal(curdev->cpumask, cpumask_of_cpu(cpu))) 224 goto out_bc; 225 } 226 227 /* 228 * If we have an active device, then check the rating and the oneshot 229 * feature. 230 */ 231 if (curdev) { 232 /* 233 * Prefer one shot capable devices ! 234 */ 235 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) && 236 !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) 237 goto out_bc; 238 /* 239 * Check the rating 240 */ 241 if (curdev->rating >= newdev->rating) 242 goto out_bc; 243 } 244 245 /* 246 * Replace the eventually existing device by the new 247 * device. If the current device is the broadcast device, do 248 * not give it back to the clockevents layer ! 249 */ 250 if (tick_is_broadcast_device(curdev)) { 251 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN); 252 curdev = NULL; 253 } 254 clockevents_exchange_device(curdev, newdev); 255 tick_setup_device(td, newdev, cpu, &cpumask_of_cpu(cpu)); 256 if (newdev->features & CLOCK_EVT_FEAT_ONESHOT) 257 tick_oneshot_notify(); 258 259 spin_unlock_irqrestore(&tick_device_lock, flags); 260 return NOTIFY_STOP; 261 262 out_bc: 263 /* 264 * Can the new device be used as a broadcast device ? 265 */ 266 if (tick_check_broadcast_device(newdev)) 267 ret = NOTIFY_STOP; 268 269 spin_unlock_irqrestore(&tick_device_lock, flags); 270 271 return ret; 272 } 273 274 /* 275 * Shutdown an event device on a given cpu: 276 * 277 * This is called on a life CPU, when a CPU is dead. So we cannot 278 * access the hardware device itself. 279 * We just set the mode and remove it from the lists. 280 */ 281 static void tick_shutdown(unsigned int *cpup) 282 { 283 struct tick_device *td = &per_cpu(tick_cpu_device, *cpup); 284 struct clock_event_device *dev = td->evtdev; 285 unsigned long flags; 286 287 spin_lock_irqsave(&tick_device_lock, flags); 288 td->mode = TICKDEV_MODE_PERIODIC; 289 if (dev) { 290 /* 291 * Prevent that the clock events layer tries to call 292 * the set mode function! 293 */ 294 dev->mode = CLOCK_EVT_MODE_UNUSED; 295 clockevents_exchange_device(dev, NULL); 296 td->evtdev = NULL; 297 } 298 /* Transfer the do_timer job away from this cpu */ 299 if (*cpup == tick_do_timer_cpu) { 300 int cpu = first_cpu(cpu_online_map); 301 302 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1; 303 } 304 spin_unlock_irqrestore(&tick_device_lock, flags); 305 } 306 307 static void tick_suspend(void) 308 { 309 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 310 unsigned long flags; 311 312 spin_lock_irqsave(&tick_device_lock, flags); 313 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN); 314 spin_unlock_irqrestore(&tick_device_lock, flags); 315 } 316 317 static void tick_resume(void) 318 { 319 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 320 unsigned long flags; 321 int broadcast = tick_resume_broadcast(); 322 323 spin_lock_irqsave(&tick_device_lock, flags); 324 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME); 325 326 if (!broadcast) { 327 if (td->mode == TICKDEV_MODE_PERIODIC) 328 tick_setup_periodic(td->evtdev, 0); 329 else 330 tick_resume_oneshot(); 331 } 332 spin_unlock_irqrestore(&tick_device_lock, flags); 333 } 334 335 /* 336 * Notification about clock event devices 337 */ 338 static int tick_notify(struct notifier_block *nb, unsigned long reason, 339 void *dev) 340 { 341 switch (reason) { 342 343 case CLOCK_EVT_NOTIFY_ADD: 344 return tick_check_new_device(dev); 345 346 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 347 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 348 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: 349 tick_broadcast_on_off(reason, dev); 350 break; 351 352 case CLOCK_EVT_NOTIFY_BROADCAST_ENTER: 353 case CLOCK_EVT_NOTIFY_BROADCAST_EXIT: 354 tick_broadcast_oneshot_control(reason); 355 break; 356 357 case CLOCK_EVT_NOTIFY_CPU_DEAD: 358 tick_shutdown_broadcast_oneshot(dev); 359 tick_shutdown_broadcast(dev); 360 tick_shutdown(dev); 361 break; 362 363 case CLOCK_EVT_NOTIFY_SUSPEND: 364 tick_suspend(); 365 tick_suspend_broadcast(); 366 break; 367 368 case CLOCK_EVT_NOTIFY_RESUME: 369 tick_resume(); 370 break; 371 372 default: 373 break; 374 } 375 376 return NOTIFY_OK; 377 } 378 379 static struct notifier_block tick_notifier = { 380 .notifier_call = tick_notify, 381 }; 382 383 /** 384 * tick_init - initialize the tick control 385 * 386 * Register the notifier with the clockevents framework 387 */ 388 void __init tick_init(void) 389 { 390 clockevents_register_notifier(&tick_notifier); 391 } 392