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 static struct tick_device tick_broadcast_device;
  31 /* FIXME: Use cpumask_var_t. */
  32 static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
  33 static DECLARE_BITMAP(tmpmask, NR_CPUS);
  34 static DEFINE_SPINLOCK(tick_broadcast_lock);
  35 static int tick_broadcast_force;
  36
  37 #ifdef CONFIG_TICK_ONESHOT
  38 static void tick_broadcast_clear_oneshot(int cpu);
  39 #else
  40 static inline void tick_broadcast_clear_oneshot(int cpu) { }
  41 #endif
  42
  43 /*
  44  * Debugging: see timer_list.c
  45  */
  46 struct tick_device *tick_get_broadcast_device(void)
  47 {
  48         return &tick_broadcast_device;
  49 }
  50
  51 struct cpumask *tick_get_broadcast_mask(void)
  52 {
  53         return to_cpumask(tick_broadcast_mask);
  54 }
  55
  56 /*
  57  * Start the device in periodic mode
  58  */
  59 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  60 {
  61         if (bc)
  62                 tick_setup_periodic(bc, 1);
  63 }
  64
  65 /*
  66  * Check, if the device can be utilized as broadcast device:
  67  */
  68 int tick_check_broadcast_device(struct clock_event_device *dev)
  69 {
  70         if ((tick_broadcast_device.evtdev &&
  71              tick_broadcast_device.evtdev->rating >= dev->rating) ||
  72              (dev->features & CLOCK_EVT_FEAT_C3STOP))
  73                 return 0;
  74
  75         clockevents_exchange_device(NULL, dev);
  76         tick_broadcast_device.evtdev = dev;
  77         if (!cpumask_empty(tick_get_broadcast_mask()))
  78                 tick_broadcast_start_periodic(dev);
  79         return 1;
  80 }
  81
  82 /*
  83  * Check, if the device is the broadcast device
  84  */
  85 int tick_is_broadcast_device(struct clock_event_device *dev)
  86 {
  87         return (dev && tick_broadcast_device.evtdev == dev);
  88 }
  89
  90 /*
  91  * Check, if the device is disfunctional and a place holder, which
  92  * needs to be handled by the broadcast device.
  93  */
  94 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  95 {
  96         unsigned long flags;
  97         int ret = 0;
  98
  99         spin_lock_irqsave(&tick_broadcast_lock, flags);
 100
 101         /*
 102          * Devices might be registered with both periodic and oneshot
 103          * mode disabled. This signals, that the device needs to be
 104          * operated from the broadcast device and is a placeholder for
 105          * the cpu local device.
 106          */
 107         if (!tick_device_is_functional(dev)) {
 108                 dev->event_handler = tick_handle_periodic;
 109                 cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 110                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 111                 ret = 1;
 112         } else {
 113                 /*
 114                  * When the new device is not affected by the stop
 115                  * feature and the cpu is marked in the broadcast mask
 116                  * then clear the broadcast bit.
 117                  */
 118                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 119                         int cpu = smp_processor_id();
 120
 121                         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 122                         tick_broadcast_clear_oneshot(cpu);
 123                 }
 124         }
 125         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 126         return ret;
 127 }
 128
 129 /*
 130  * Broadcast the event to the cpus, which are set in the mask (mangled).
 131  */
 132 static void tick_do_broadcast(struct cpumask *mask)
 133 {
 134         int cpu = smp_processor_id();
 135         struct tick_device *td;
 136
 137         /*
 138          * Check, if the current cpu is in the mask
 139          */
 140         if (cpumask_test_cpu(cpu, mask)) {
 141                 cpumask_clear_cpu(cpu, mask);
 142                 td = &per_cpu(tick_cpu_device, cpu);
 143                 td->evtdev->event_handler(td->evtdev);
 144         }
 145
 146         if (!cpumask_empty(mask)) {
 147                 /*
 148                  * It might be necessary to actually check whether the devices
 149                  * have different broadcast functions. For now, just use the
 150                  * one of the first device. This works as long as we have this
 151                  * misfeature only on x86 (lapic)
 152                  */
 153                 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
 154                 td->evtdev->broadcast(mask);
 155         }
 156 }
 157
 158 /*
 159  * Periodic broadcast:
 160  * - invoke the broadcast handlers
 161  */
 162 static void tick_do_periodic_broadcast(void)
 163 {
 164         spin_lock(&tick_broadcast_lock);
 165
 166         cpumask_and(to_cpumask(tmpmask),
 167                     cpu_online_mask, tick_get_broadcast_mask());
 168         tick_do_broadcast(to_cpumask(tmpmask));
 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 = cpumask_empty(tick_get_broadcast_mask());
 232
 233         switch (*reason) {
 234         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 235         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 236                 if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 237                         cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 238                         if (tick_broadcast_device.mode ==
 239                             TICKDEV_MODE_PERIODIC)
 240                                 clockevents_shutdown(dev);
 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                     cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 248                         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 249                         if (tick_broadcast_device.mode ==
 250                             TICKDEV_MODE_PERIODIC)
 251                                 tick_setup_periodic(dev, 0);
 252                 }
 253                 break;
 254         }
 255
 256         if (cpumask_empty(tick_get_broadcast_mask())) {
 257                 if (!bc_stopped)
 258                         clockevents_shutdown(bc);
 259         } else if (bc_stopped) {
 260                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 261                         tick_broadcast_start_periodic(bc);
 262                 else
 263                         tick_broadcast_setup_oneshot(bc);
 264         }
 265 out:
 266         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 267 }
 268
 269 /*
 270  * Powerstate information: The system enters/leaves a state, where
 271  * affected devices might stop.
 272  */
 273 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 274 {
 275         if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
 276                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 277                        "offline CPU #%d\n", *oncpu);
 278         else
 279                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 280                                          &reason, 1);
 281 }
 282
 283 /*
 284  * Set the periodic handler depending on broadcast on/off
 285  */
 286 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 287 {
 288         if (!broadcast)
 289                 dev->event_handler = tick_handle_periodic;
 290         else
 291                 dev->event_handler = tick_handle_periodic_broadcast;
 292 }
 293
 294 /*
 295  * Remove a CPU from broadcasting
 296  */
 297 void tick_shutdown_broadcast(unsigned int *cpup)
 298 {
 299         struct clock_event_device *bc;
 300         unsigned long flags;
 301         unsigned int cpu = *cpup;
 302
 303         spin_lock_irqsave(&tick_broadcast_lock, flags);
 304
 305         bc = tick_broadcast_device.evtdev;
 306         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 307
 308         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 309                 if (bc && cpumask_empty(tick_get_broadcast_mask()))
 310                         clockevents_shutdown(bc);
 311         }
 312
 313         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 314 }
 315
 316 void tick_suspend_broadcast(void)
 317 {
 318         struct clock_event_device *bc;
 319         unsigned long flags;
 320
 321         spin_lock_irqsave(&tick_broadcast_lock, flags);
 322
 323         bc = tick_broadcast_device.evtdev;
 324         if (bc)
 325                 clockevents_shutdown(bc);
 326
 327         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 328 }
 329
 330 int tick_resume_broadcast(void)
 331 {
 332         struct clock_event_device *bc;
 333         unsigned long flags;
 334         int broadcast = 0;
 335
 336         spin_lock_irqsave(&tick_broadcast_lock, flags);
 337
 338         bc = tick_broadcast_device.evtdev;
 339
 340         if (bc) {
 341                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 342
 343                 switch (tick_broadcast_device.mode) {
 344                 case TICKDEV_MODE_PERIODIC:
 345                         if (!cpumask_empty(tick_get_broadcast_mask()))
 346                                 tick_broadcast_start_periodic(bc);
 347                         broadcast = cpumask_test_cpu(smp_processor_id(),
 348                                                      tick_get_broadcast_mask());
 349                         break;
 350                 case TICKDEV_MODE_ONESHOT:
 351                         broadcast = tick_resume_broadcast_oneshot(bc);
 352                         break;
 353                 }
 354         }
 355         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 356
 357         return broadcast;
 358 }
 359
 360
 361 #ifdef CONFIG_TICK_ONESHOT
 362
 363 /* FIXME: use cpumask_var_t. */
 364 static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
 365
 366 /*
 367  * Exposed for debugging: see timer_list.c
 368  */
 369 struct cpumask *tick_get_broadcast_oneshot_mask(void)
 370 {
 371         return to_cpumask(tick_broadcast_oneshot_mask);
 372 }
 373
 374 static int tick_broadcast_set_event(ktime_t expires, int force)
 375 {
 376         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 377
 378         return tick_dev_program_event(bc, expires, force);
 379 }
 380
 381 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 382 {
 383         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 384         return 0;
 385 }
 386
 387 /*
 388  * Called from irq_enter() when idle was interrupted to reenable the
 389  * per cpu device.
 390  */
 391 void tick_check_oneshot_broadcast(int cpu)
 392 {
 393         if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
 394                 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
 395
 396                 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
 397         }
 398 }
 399
 400 /*
 401  * Handle oneshot mode broadcasting
 402  */
 403 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 404 {
 405         struct tick_device *td;
 406         ktime_t now, next_event;
 407         int cpu;
 408
 409         spin_lock(&tick_broadcast_lock);
 410 again:
 411         dev->next_event.tv64 = KTIME_MAX;
 412         next_event.tv64 = KTIME_MAX;
 413         cpumask_clear(to_cpumask(tmpmask));
 414         now = ktime_get();
 415         /* Find all expired events */
 416         for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
 417                 td = &per_cpu(tick_cpu_device, cpu);
 418                 if (td->evtdev->next_event.tv64 <= now.tv64)
 419                         cpumask_set_cpu(cpu, to_cpumask(tmpmask));
 420                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 421                         next_event.tv64 = td->evtdev->next_event.tv64;
 422         }
 423
 424         /*
 425          * Wakeup the cpus which have an expired event.
 426          */
 427         tick_do_broadcast(to_cpumask(tmpmask));
 428
 429         /*
 430          * Two reasons for reprogram:
 431          *
 432          * - The global event did not expire any CPU local
 433          * events. This happens in dyntick mode, as the maximum PIT
 434          * delta is quite small.
 435          *
 436          * - There are pending events on sleeping CPUs which were not
 437          * in the event mask
 438          */
 439         if (next_event.tv64 != KTIME_MAX) {
 440                 /*
 441                  * Rearm the broadcast device. If event expired,
 442                  * repeat the above
 443                  */
 444                 if (tick_broadcast_set_event(next_event, 0))
 445                         goto again;
 446         }
 447         spin_unlock(&tick_broadcast_lock);
 448 }
 449
 450 /*
 451  * Powerstate information: The system enters/leaves a state, where
 452  * affected devices might stop
 453  */
 454 void tick_broadcast_oneshot_control(unsigned long reason)
 455 {
 456         struct clock_event_device *bc, *dev;
 457         struct tick_device *td;
 458         unsigned long flags;
 459         int cpu;
 460
 461         spin_lock_irqsave(&tick_broadcast_lock, flags);
 462
 463         /*
 464          * Periodic mode does not care about the enter/exit of power
 465          * states
 466          */
 467         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 468                 goto out;
 469
 470         bc = tick_broadcast_device.evtdev;
 471         cpu = smp_processor_id();
 472         td = &per_cpu(tick_cpu_device, cpu);
 473         dev = td->evtdev;
 474
 475         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 476                 goto out;
 477
 478         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 479                 if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 480                         cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
 481                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 482                         if (dev->next_event.tv64 < bc->next_event.tv64)
 483                                 tick_broadcast_set_event(dev->next_event, 1);
 484                 }
 485         } else {
 486                 if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 487                         cpumask_clear_cpu(cpu,
 488                                           tick_get_broadcast_oneshot_mask());
 489                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 490                         if (dev->next_event.tv64 != KTIME_MAX)
 491                                 tick_program_event(dev->next_event, 1);
 492                 }
 493         }
 494
 495 out:
 496         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 497 }
 498
 499 /*
 500  * Reset the one shot broadcast for a cpu
 501  *
 502  * Called with tick_broadcast_lock held
 503  */
 504 static void tick_broadcast_clear_oneshot(int cpu)
 505 {
 506         cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 507 }
 508
 509 static void tick_broadcast_init_next_event(struct cpumask *mask,
 510                                            ktime_t expires)
 511 {
 512         struct tick_device *td;
 513         int cpu;
 514
 515         for_each_cpu(cpu, mask) {
 516                 td = &per_cpu(tick_cpu_device, cpu);
 517                 if (td->evtdev)
 518                         td->evtdev->next_event = expires;
 519         }
 520 }
 521
 522 /**
 523  * tick_broadcast_setup_oneshot - setup the broadcast device
 524  */
 525 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 526 {
 527         /* Set it up only once ! */
 528         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 529                 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
 530                 int cpu = smp_processor_id();
 531
 532                 bc->event_handler = tick_handle_oneshot_broadcast;
 533                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 534
 535                 /* Take the do_timer update */
 536                 tick_do_timer_cpu = cpu;
 537
 538                 /*
 539                  * We must be careful here. There might be other CPUs
 540                  * waiting for periodic broadcast. We need to set the
 541                  * oneshot_mask bits for those and program the
 542                  * broadcast device to fire.
 543                  */
 544                 cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
 545                 cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
 546                 cpumask_or(tick_get_broadcast_oneshot_mask(),
 547                            tick_get_broadcast_oneshot_mask(),
 548                            to_cpumask(tmpmask));
 549
 550                 if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
 551                         tick_broadcast_init_next_event(to_cpumask(tmpmask),
 552                                                        tick_next_period);
 553                         tick_broadcast_set_event(tick_next_period, 1);
 554                 } else
 555                         bc->next_event.tv64 = KTIME_MAX;
 556         }
 557 }
 558
 559 /*
 560  * Select oneshot operating mode for the broadcast device
 561  */
 562 void tick_broadcast_switch_to_oneshot(void)
 563 {
 564         struct clock_event_device *bc;
 565         unsigned long flags;
 566
 567         spin_lock_irqsave(&tick_broadcast_lock, flags);
 568
 569         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 570         bc = tick_broadcast_device.evtdev;
 571         if (bc)
 572                 tick_broadcast_setup_oneshot(bc);
 573         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 574 }
 575
 576
 577 /*
 578  * Remove a dead CPU from broadcasting
 579  */
 580 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 581 {
 582         unsigned long flags;
 583         unsigned int cpu = *cpup;
 584
 585         spin_lock_irqsave(&tick_broadcast_lock, flags);
 586
 587         /*
 588          * Clear the broadcast mask flag for the dead cpu, but do not
 589          * stop the broadcast device!
 590          */
 591         cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 592
 593         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 594 }
 595
 596 /*
 597  * Check, whether the broadcast device is in one shot mode
 598  */
 599 int tick_broadcast_oneshot_active(void)
 600 {
 601         return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 602 }
 603
 604 #endif