kernel/time/tick-broadcast.c

   1 /*
   2  * linux/kernel/time/tick-broadcast.c
   3  *
   4  * This file contains functions which emulate a local clock-event
   5  * device via a broadcast event source.
   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 "tick-internal.h"
  24
  25 /*
  26  * Broadcast support for broken x86 hardware, where the local apic
  27  * timer stops in C3 state.
  28  */
  29
  30 struct tick_device tick_broadcast_device;
  31 static cpumask_t tick_broadcast_mask;
  32 static DEFINE_SPINLOCK(tick_broadcast_lock);
  33 static int tick_broadcast_force;
  34
  35 #ifdef CONFIG_TICK_ONESHOT
  36 static void tick_broadcast_clear_oneshot(int cpu);
  37 #else
  38 static inline void tick_broadcast_clear_oneshot(int cpu) { }
  39 #endif
  40
  41 /*
  42  * Debugging: see timer_list.c
  43  */
  44 struct tick_device *tick_get_broadcast_device(void)
  45 {
  46         return &tick_broadcast_device;
  47 }
  48
  49 cpumask_t *tick_get_broadcast_mask(void)
  50 {
  51         return &tick_broadcast_mask;
  52 }
  53
  54 /*
  55  * Start the device in periodic mode
  56  */
  57 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  58 {
  59         if (bc)
  60                 tick_setup_periodic(bc, 1);
  61 }
  62
  63 /*
  64  * Check, if the device can be utilized as broadcast device:
  65  */
  66 int tick_check_broadcast_device(struct clock_event_device *dev)
  67 {
  68         if ((tick_broadcast_device.evtdev &&
  69              tick_broadcast_device.evtdev->rating >= dev->rating) ||
  70              (dev->features & CLOCK_EVT_FEAT_C3STOP))
  71                 return 0;
  72
  73         clockevents_exchange_device(NULL, dev);
  74         tick_broadcast_device.evtdev = dev;
  75         if (!cpus_empty(tick_broadcast_mask))
  76                 tick_broadcast_start_periodic(dev);
  77         return 1;
  78 }
  79
  80 /*
  81  * Check, if the device is the broadcast device
  82  */
  83 int tick_is_broadcast_device(struct clock_event_device *dev)
  84 {
  85         return (dev && tick_broadcast_device.evtdev == dev);
  86 }
  87
  88 /*
  89  * Check, if the device is disfunctional and a place holder, which
  90  * needs to be handled by the broadcast device.
  91  */
  92 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  93 {
  94         unsigned long flags;
  95         int ret = 0;
  96
  97         spin_lock_irqsave(&tick_broadcast_lock, flags);
  98
  99         /*
 100          * Devices might be registered with both periodic and oneshot
 101          * mode disabled. This signals, that the device needs to be
 102          * operated from the broadcast device and is a placeholder for
 103          * the cpu local device.
 104          */
 105         if (!tick_device_is_functional(dev)) {
 106                 dev->event_handler = tick_handle_periodic;
 107                 cpu_set(cpu, tick_broadcast_mask);
 108                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 109                 ret = 1;
 110         } else {
 111                 /*
 112                  * When the new device is not affected by the stop
 113                  * feature and the cpu is marked in the broadcast mask
 114                  * then clear the broadcast bit.
 115                  */
 116                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 117                         int cpu = smp_processor_id();
 118
 119                         cpu_clear(cpu, tick_broadcast_mask);
 120                         tick_broadcast_clear_oneshot(cpu);
 121                 }
 122         }
 123         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 124         return ret;
 125 }
 126
 127 /*
 128  * Broadcast the event to the cpus, which are set in the mask
 129  */
 130 static void tick_do_broadcast(cpumask_t mask)
 131 {
 132         int cpu = smp_processor_id();
 133         struct tick_device *td;
 134
 135         /*
 136          * Check, if the current cpu is in the mask
 137          */
 138         if (cpu_isset(cpu, mask)) {
 139                 cpu_clear(cpu, mask);
 140                 td = &per_cpu(tick_cpu_device, cpu);
 141                 td->evtdev->event_handler(td->evtdev);
 142         }
 143
 144         if (!cpus_empty(mask)) {
 145                 /*
 146                  * It might be necessary to actually check whether the devices
 147                  * have different broadcast functions. For now, just use the
 148                  * one of the first device. This works as long as we have this
 149                  * misfeature only on x86 (lapic)
 150                  */
 151                 cpu = first_cpu(mask);
 152                 td = &per_cpu(tick_cpu_device, cpu);
 153                 td->evtdev->broadcast(mask);
 154         }
 155 }
 156
 157 /*
 158  * Periodic broadcast:
 159  * - invoke the broadcast handlers
 160  */
 161 static void tick_do_periodic_broadcast(void)
 162 {
 163         cpumask_t mask;
 164
 165         spin_lock(&tick_broadcast_lock);
 166
 167         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 168         tick_do_broadcast(mask);
 169
 170         spin_unlock(&tick_broadcast_lock);
 171 }
 172
 173 /*
 174  * Event handler for periodic broadcast ticks
 175  */
 176 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 177 {
 178         ktime_t next;
 179
 180         tick_do_periodic_broadcast();
 181
 182         /*
 183          * The device is in periodic mode. No reprogramming necessary:
 184          */
 185         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 186                 return;
 187
 188         /*
 189          * Setup the next period for devices, which do not have
 190          * periodic mode. We read dev->next_event first and add to it
 191          * when the event alrady expired. clockevents_program_event()
 192          * sets dev->next_event only when the event is really
 193          * programmed to the device.
 194          */
 195         for (next = dev->next_event; ;) {
 196                 next = ktime_add(next, tick_period);
 197
 198                 if (!clockevents_program_event(dev, next, ktime_get()))
 199                         return;
 200                 tick_do_periodic_broadcast();
 201         }
 202 }
 203
 204 /*
 205  * Powerstate information: The system enters/leaves a state, where
 206  * affected devices might stop
 207  */
 208 static void tick_do_broadcast_on_off(void *why)
 209 {
 210         struct clock_event_device *bc, *dev;
 211         struct tick_device *td;
 212         unsigned long flags, *reason = why;
 213         int cpu, bc_stopped;
 214
 215         spin_lock_irqsave(&tick_broadcast_lock, flags);
 216
 217         cpu = smp_processor_id();
 218         td = &per_cpu(tick_cpu_device, cpu);
 219         dev = td->evtdev;
 220         bc = tick_broadcast_device.evtdev;
 221
 222         /*
 223          * Is the device not affected by the powerstate ?
 224          */
 225         if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 226                 goto out;
 227
 228         if (!tick_device_is_functional(dev))
 229                 goto out;
 230
 231         bc_stopped = cpus_empty(tick_broadcast_mask);
 232
 233         switch (*reason) {
 234         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 235         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 236                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 237                         cpu_set(cpu, tick_broadcast_mask);
 238                         if (td->mode == TICKDEV_MODE_PERIODIC)
 239                                 clockevents_set_mode(dev,
 240                                                      CLOCK_EVT_MODE_SHUTDOWN);
 241                 }
 242                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 243                         tick_broadcast_force = 1;
 244                 break;
 245         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 246                 if (!tick_broadcast_force &&
 247                     cpu_isset(cpu, tick_broadcast_mask)) {
 248                         cpu_clear(cpu, tick_broadcast_mask);
 249                         if (td->mode == TICKDEV_MODE_PERIODIC)
 250                                 tick_setup_periodic(dev, 0);
 251                 }
 252                 break;
 253         }
 254
 255         if (cpus_empty(tick_broadcast_mask)) {
 256                 if (!bc_stopped)
 257                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 258         } else if (bc_stopped) {
 259                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 260                         tick_broadcast_start_periodic(bc);
 261                 else
 262                         tick_broadcast_setup_oneshot(bc);
 263         }
 264 out:
 265         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 266 }
 267
 268 /*
 269  * Powerstate information: The system enters/leaves a state, where
 270  * affected devices might stop.
 271  */
 272 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 273 {
 274         if (!cpu_isset(*oncpu, cpu_online_map))
 275                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 276                        "offline CPU #%d\n", *oncpu);
 277         else
 278                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 279                                          &reason, 1);
 280 }
 281
 282 /*
 283  * Set the periodic handler depending on broadcast on/off
 284  */
 285 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 286 {
 287         if (!broadcast)
 288                 dev->event_handler = tick_handle_periodic;
 289         else
 290                 dev->event_handler = tick_handle_periodic_broadcast;
 291 }
 292
 293 /*
 294  * Remove a CPU from broadcasting
 295  */
 296 void tick_shutdown_broadcast(unsigned int *cpup)
 297 {
 298         struct clock_event_device *bc;
 299         unsigned long flags;
 300         unsigned int cpu = *cpup;
 301
 302         spin_lock_irqsave(&tick_broadcast_lock, flags);
 303
 304         bc = tick_broadcast_device.evtdev;
 305         cpu_clear(cpu, tick_broadcast_mask);
 306
 307         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 308                 if (bc && cpus_empty(tick_broadcast_mask))
 309                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 310         }
 311
 312         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 313 }
 314
 315 void tick_suspend_broadcast(void)
 316 {
 317         struct clock_event_device *bc;
 318         unsigned long flags;
 319
 320         spin_lock_irqsave(&tick_broadcast_lock, flags);
 321
 322         bc = tick_broadcast_device.evtdev;
 323         if (bc)
 324                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 325
 326         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 327 }
 328
 329 int tick_resume_broadcast(void)
 330 {
 331         struct clock_event_device *bc;
 332         unsigned long flags;
 333         int broadcast = 0;
 334
 335         spin_lock_irqsave(&tick_broadcast_lock, flags);
 336
 337         bc = tick_broadcast_device.evtdev;
 338
 339         if (bc) {
 340                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 341
 342                 switch (tick_broadcast_device.mode) {
 343                 case TICKDEV_MODE_PERIODIC:
 344                         if(!cpus_empty(tick_broadcast_mask))
 345                                 tick_broadcast_start_periodic(bc);
 346                         broadcast = cpu_isset(smp_processor_id(),
 347                                               tick_broadcast_mask);
 348                         break;
 349                 case TICKDEV_MODE_ONESHOT:
 350                         broadcast = tick_resume_broadcast_oneshot(bc);
 351                         break;
 352                 }
 353         }
 354         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 355
 356         return broadcast;
 357 }
 358
 359
 360 #ifdef CONFIG_TICK_ONESHOT
 361
 362 static cpumask_t tick_broadcast_oneshot_mask;
 363
 364 /*
 365  * Debugging: see timer_list.c
 366  */
 367 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 368 {
 369         return &tick_broadcast_oneshot_mask;
 370 }
 371
 372 static int tick_broadcast_set_event(ktime_t expires, int force)
 373 {
 374         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 375         ktime_t now = ktime_get();
 376         int res;
 377
 378         for(;;) {
 379                 res = clockevents_program_event(bc, expires, now);
 380                 if (!res || !force)
 381                         return res;
 382                 now = ktime_get();
 383                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 384         }
 385 }
 386
 387 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 388 {
 389         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 390         return 0;
 391 }
 392
 393 /*
 394  * Handle oneshot mode broadcasting
 395  */
 396 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 397 {
 398         struct tick_device *td;
 399         cpumask_t mask;
 400         ktime_t now, next_event;
 401         int cpu;
 402
 403         spin_lock(&tick_broadcast_lock);
 404 again:
 405         dev->next_event.tv64 = KTIME_MAX;
 406         next_event.tv64 = KTIME_MAX;
 407         mask = CPU_MASK_NONE;
 408         now = ktime_get();
 409         /* Find all expired events */
 410         for_each_cpu_mask_nr(cpu, tick_broadcast_oneshot_mask) {
 411                 td = &per_cpu(tick_cpu_device, cpu);
 412                 if (td->evtdev->next_event.tv64 <= now.tv64)
 413                         cpu_set(cpu, mask);
 414                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 415                         next_event.tv64 = td->evtdev->next_event.tv64;
 416         }
 417
 418         /*
 419          * Wakeup the cpus which have an expired event.
 420          */
 421         tick_do_broadcast(mask);
 422
 423         /*
 424          * Two reasons for reprogram:
 425          *
 426          * - The global event did not expire any CPU local
 427          * events. This happens in dyntick mode, as the maximum PIT
 428          * delta is quite small.
 429          *
 430          * - There are pending events on sleeping CPUs which were not
 431          * in the event mask
 432          */
 433         if (next_event.tv64 != KTIME_MAX) {
 434                 /*
 435                  * Rearm the broadcast device. If event expired,
 436                  * repeat the above
 437                  */
 438                 if (tick_broadcast_set_event(next_event, 0))
 439                         goto again;
 440         }
 441         spin_unlock(&tick_broadcast_lock);
 442 }
 443
 444 /*
 445  * Powerstate information: The system enters/leaves a state, where
 446  * affected devices might stop
 447  */
 448 void tick_broadcast_oneshot_control(unsigned long reason)
 449 {
 450         struct clock_event_device *bc, *dev;
 451         struct tick_device *td;
 452         unsigned long flags;
 453         int cpu;
 454
 455         spin_lock_irqsave(&tick_broadcast_lock, flags);
 456
 457         /*
 458          * Periodic mode does not care about the enter/exit of power
 459          * states
 460          */
 461         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 462                 goto out;
 463
 464         bc = tick_broadcast_device.evtdev;
 465         cpu = smp_processor_id();
 466         td = &per_cpu(tick_cpu_device, cpu);
 467         dev = td->evtdev;
 468
 469         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 470                 goto out;
 471
 472         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 473                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 474                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 475                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 476                         if (dev->next_event.tv64 < bc->next_event.tv64)
 477                                 tick_broadcast_set_event(dev->next_event, 1);
 478                 }
 479         } else {
 480                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 481                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 482                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 483                         if (dev->next_event.tv64 != KTIME_MAX)
 484                                 tick_program_event(dev->next_event, 1);
 485                 }
 486         }
 487
 488 out:
 489         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 490 }
 491
 492 /*
 493  * Reset the one shot broadcast for a cpu
 494  *
 495  * Called with tick_broadcast_lock held
 496  */
 497 static void tick_broadcast_clear_oneshot(int cpu)
 498 {
 499         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 500 }
 501
 502 /**
 503  * tick_broadcast_setup_oneshot - setup the broadcast device
 504  */
 505 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 506 {
 507         /* Set it up only once ! */
 508         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 509                 bc->event_handler = tick_handle_oneshot_broadcast;
 510                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 511                 bc->next_event.tv64 = KTIME_MAX;
 512         }
 513 }
 514
 515 /*
 516  * Select oneshot operating mode for the broadcast device
 517  */
 518 void tick_broadcast_switch_to_oneshot(void)
 519 {
 520         struct clock_event_device *bc;
 521         unsigned long flags;
 522
 523         spin_lock_irqsave(&tick_broadcast_lock, flags);
 524
 525         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 526         bc = tick_broadcast_device.evtdev;
 527         if (bc)
 528                 tick_broadcast_setup_oneshot(bc);
 529         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 530 }
 531
 532
 533 /*
 534  * Remove a dead CPU from broadcasting
 535  */
 536 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 537 {
 538         unsigned long flags;
 539         unsigned int cpu = *cpup;
 540
 541         spin_lock_irqsave(&tick_broadcast_lock, flags);
 542
 543         /*
 544          * Clear the broadcast mask flag for the dead cpu, but do not
 545          * stop the broadcast device!
 546          */
 547         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 548
 549         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 550 }
 551
 552 #endif