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/irq.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
  34 #ifdef CONFIG_TICK_ONESHOT
  35 static void tick_broadcast_clear_oneshot(int cpu);
  36 #else
  37 static inline void tick_broadcast_clear_oneshot(int cpu) { }
  38 #endif
  39
  40 /*
  41  * Debugging: see timer_list.c
  42  */
  43 struct tick_device *tick_get_broadcast_device(void)
  44 {
  45         return &tick_broadcast_device;
  46 }
  47
  48 cpumask_t *tick_get_broadcast_mask(void)
  49 {
  50         return &tick_broadcast_mask;
  51 }
  52
  53 /*
  54  * Start the device in periodic mode
  55  */
  56 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  57 {
  58         if (bc)
  59                 tick_setup_periodic(bc, 1);
  60 }
  61
  62 /*
  63  * Check, if the device can be utilized as broadcast device:
  64  */
  65 int tick_check_broadcast_device(struct clock_event_device *dev)
  66 {
  67         if (tick_broadcast_device.evtdev ||
  68             (dev->features & CLOCK_EVT_FEAT_C3STOP))
  69                 return 0;
  70
  71         clockevents_exchange_device(NULL, dev);
  72         tick_broadcast_device.evtdev = dev;
  73         if (!cpus_empty(tick_broadcast_mask))
  74                 tick_broadcast_start_periodic(dev);
  75         return 1;
  76 }
  77
  78 /*
  79  * Check, if the device is the broadcast device
  80  */
  81 int tick_is_broadcast_device(struct clock_event_device *dev)
  82 {
  83         return (dev && tick_broadcast_device.evtdev == dev);
  84 }
  85
  86 /*
  87  * Check, if the device is disfunctional and a place holder, which
  88  * needs to be handled by the broadcast device.
  89  */
  90 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  91 {
  92         unsigned long flags;
  93         int ret = 0;
  94
  95         spin_lock_irqsave(&tick_broadcast_lock, flags);
  96
  97         /*
  98          * Devices might be registered with both periodic and oneshot
  99          * mode disabled. This signals, that the device needs to be
 100          * operated from the broadcast device and is a placeholder for
 101          * the cpu local device.
 102          */
 103         if (!tick_device_is_functional(dev)) {
 104                 dev->event_handler = tick_handle_periodic;
 105                 cpu_set(cpu, tick_broadcast_mask);
 106                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 107                 ret = 1;
 108         } else {
 109                 /*
 110                  * When the new device is not affected by the stop
 111                  * feature and the cpu is marked in the broadcast mask
 112                  * then clear the broadcast bit.
 113                  */
 114                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 115                         int cpu = smp_processor_id();
 116
 117                         cpu_clear(cpu, tick_broadcast_mask);
 118                         tick_broadcast_clear_oneshot(cpu);
 119                 }
 120         }
 121         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 122         return ret;
 123 }
 124
 125 /*
 126  * Broadcast the event to the cpus, which are set in the mask
 127  */
 128 int tick_do_broadcast(cpumask_t mask)
 129 {
 130         int ret = 0, cpu = smp_processor_id();
 131         struct tick_device *td;
 132
 133         /*
 134          * Check, if the current cpu is in the mask
 135          */
 136         if (cpu_isset(cpu, mask)) {
 137                 cpu_clear(cpu, mask);
 138                 td = &per_cpu(tick_cpu_device, cpu);
 139                 td->evtdev->event_handler(td->evtdev);
 140                 ret = 1;
 141         }
 142
 143         if (!cpus_empty(mask)) {
 144                 /*
 145                  * It might be necessary to actually check whether the devices
 146                  * have different broadcast functions. For now, just use the
 147                  * one of the first device. This works as long as we have this
 148                  * misfeature only on x86 (lapic)
 149                  */
 150                 cpu = first_cpu(mask);
 151                 td = &per_cpu(tick_cpu_device, cpu);
 152                 td->evtdev->broadcast(mask);
 153                 ret = 1;
 154         }
 155         return ret;
 156 }
 157
 158 /*
 159  * Periodic broadcast:
 160  * - invoke the broadcast handlers
 161  */
 162 static void tick_do_periodic_broadcast(void)
 163 {
 164         cpumask_t mask;
 165
 166         spin_lock(&tick_broadcast_lock);
 167
 168         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 169         tick_do_broadcast(mask);
 170
 171         spin_unlock(&tick_broadcast_lock);
 172 }
 173
 174 /*
 175  * Event handler for periodic broadcast ticks
 176  */
 177 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 178 {
 179         dev->next_event.tv64 = KTIME_MAX;
 180
 181         tick_do_periodic_broadcast();
 182
 183         /*
 184          * The device is in periodic mode. No reprogramming necessary:
 185          */
 186         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 187                 return;
 188
 189         /*
 190          * Setup the next period for devices, which do not have
 191          * periodic mode:
 192          */
 193         for (;;) {
 194                 ktime_t next = ktime_add(dev->next_event, tick_period);
 195
 196                 if (!clockevents_program_event(dev, next, ktime_get()))
 197                         return;
 198                 tick_do_periodic_broadcast();
 199         }
 200 }
 201
 202 /*
 203  * Powerstate information: The system enters/leaves a state, where
 204  * affected devices might stop
 205  */
 206 static void tick_do_broadcast_on_off(void *why)
 207 {
 208         struct clock_event_device *bc, *dev;
 209         struct tick_device *td;
 210         unsigned long flags, *reason = why;
 211         int cpu;
 212
 213         spin_lock_irqsave(&tick_broadcast_lock, flags);
 214
 215         cpu = smp_processor_id();
 216         td = &per_cpu(tick_cpu_device, cpu);
 217         dev = td->evtdev;
 218         bc = tick_broadcast_device.evtdev;
 219
 220         /*
 221          * Is the device in broadcast mode forever or is it not
 222          * affected by the powerstate ?
 223          */
 224         if (!dev || !tick_device_is_functional(dev) ||
 225             !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 226                 goto out;
 227
 228         if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
 229                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 230                         cpu_set(cpu, tick_broadcast_mask);
 231                         if (td->mode == TICKDEV_MODE_PERIODIC)
 232                                 clockevents_set_mode(dev,
 233                                                      CLOCK_EVT_MODE_SHUTDOWN);
 234                 }
 235         } else {
 236                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 237                         cpu_clear(cpu, tick_broadcast_mask);
 238                         if (td->mode == TICKDEV_MODE_PERIODIC)
 239                                 tick_setup_periodic(dev, 0);
 240                 }
 241         }
 242
 243         if (cpus_empty(tick_broadcast_mask))
 244                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 245         else {
 246                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 247                         tick_broadcast_start_periodic(bc);
 248                 else
 249                         tick_broadcast_setup_oneshot(bc);
 250         }
 251 out:
 252         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 253 }
 254
 255 /*
 256  * Powerstate information: The system enters/leaves a state, where
 257  * affected devices might stop.
 258  */
 259 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 260 {
 261         int cpu = get_cpu();
 262
 263         if (!cpu_isset(*oncpu, cpu_online_map)) {
 264                 printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
 265                        "offline CPU #%d\n", *oncpu);
 266         } else {
 267
 268                 if (cpu == *oncpu)
 269                         tick_do_broadcast_on_off(&reason);
 270                 else
 271                         smp_call_function_single(*oncpu,
 272                                                  tick_do_broadcast_on_off,
 273                                                  &reason, 1, 1);
 274         }
 275         put_cpu();
 276 }
 277
 278 /*
 279  * Set the periodic handler depending on broadcast on/off
 280  */
 281 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 282 {
 283         if (!broadcast)
 284                 dev->event_handler = tick_handle_periodic;
 285         else
 286                 dev->event_handler = tick_handle_periodic_broadcast;
 287 }
 288
 289 /*
 290  * Remove a CPU from broadcasting
 291  */
 292 void tick_shutdown_broadcast(unsigned int *cpup)
 293 {
 294         struct clock_event_device *bc;
 295         unsigned long flags;
 296         unsigned int cpu = *cpup;
 297
 298         spin_lock_irqsave(&tick_broadcast_lock, flags);
 299
 300         bc = tick_broadcast_device.evtdev;
 301         cpu_clear(cpu, tick_broadcast_mask);
 302
 303         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 304                 if (bc && cpus_empty(tick_broadcast_mask))
 305                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 306         }
 307
 308         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 309 }
 310
 311 void tick_suspend_broadcast(void)
 312 {
 313         struct clock_event_device *bc;
 314         unsigned long flags;
 315
 316         spin_lock_irqsave(&tick_broadcast_lock, flags);
 317
 318         bc = tick_broadcast_device.evtdev;
 319         if (bc)
 320                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 321
 322         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 323 }
 324
 325 int tick_resume_broadcast(void)
 326 {
 327         struct clock_event_device *bc;
 328         unsigned long flags;
 329         int broadcast = 0;
 330
 331         spin_lock_irqsave(&tick_broadcast_lock, flags);
 332
 333         bc = tick_broadcast_device.evtdev;
 334
 335         if (bc) {
 336                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 337
 338                 switch (tick_broadcast_device.mode) {
 339                 case TICKDEV_MODE_PERIODIC:
 340                         if(!cpus_empty(tick_broadcast_mask))
 341                                 tick_broadcast_start_periodic(bc);
 342                         broadcast = cpu_isset(smp_processor_id(),
 343                                               tick_broadcast_mask);
 344                         break;
 345                 case TICKDEV_MODE_ONESHOT:
 346                         broadcast = tick_resume_broadcast_oneshot(bc);
 347                         break;
 348                 }
 349         }
 350         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 351
 352         return broadcast;
 353 }
 354
 355
 356 #ifdef CONFIG_TICK_ONESHOT
 357
 358 static cpumask_t tick_broadcast_oneshot_mask;
 359
 360 /*
 361  * Debugging: see timer_list.c
 362  */
 363 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 364 {
 365         return &tick_broadcast_oneshot_mask;
 366 }
 367
 368 static int tick_broadcast_set_event(ktime_t expires, int force)
 369 {
 370         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 371         ktime_t now = ktime_get();
 372         int res;
 373
 374         for(;;) {
 375                 res = clockevents_program_event(bc, expires, now);
 376                 if (!res || !force)
 377                         return res;
 378                 now = ktime_get();
 379                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 380         }
 381 }
 382
 383 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 384 {
 385         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 386         return 0;
 387 }
 388
 389 /*
 390  * Reprogram the broadcast device:
 391  *
 392  * Called with tick_broadcast_lock held and interrupts disabled.
 393  */
 394 static int tick_broadcast_reprogram(void)
 395 {
 396         ktime_t expires = { .tv64 = KTIME_MAX };
 397         struct tick_device *td;
 398         int cpu;
 399
 400         /*
 401          * Find the event which expires next:
 402          */
 403         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 404              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 405                 td = &per_cpu(tick_cpu_device, cpu);
 406                 if (td->evtdev->next_event.tv64 < expires.tv64)
 407                         expires = td->evtdev->next_event;
 408         }
 409
 410         if (expires.tv64 == KTIME_MAX)
 411                 return 0;
 412
 413         return tick_broadcast_set_event(expires, 0);
 414 }
 415
 416 /*
 417  * Handle oneshot mode broadcasting
 418  */
 419 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 420 {
 421         struct tick_device *td;
 422         cpumask_t mask;
 423         ktime_t now;
 424         int cpu;
 425
 426         spin_lock(&tick_broadcast_lock);
 427 again:
 428         dev->next_event.tv64 = KTIME_MAX;
 429         mask = CPU_MASK_NONE;
 430         now = ktime_get();
 431         /* Find all expired events */
 432         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 433              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 434                 td = &per_cpu(tick_cpu_device, cpu);
 435                 if (td->evtdev->next_event.tv64 <= now.tv64)
 436                         cpu_set(cpu, mask);
 437         }
 438
 439         /*
 440          * Wakeup the cpus which have an expired event. The broadcast
 441          * device is reprogrammed in the return from idle code.
 442          */
 443         if (!tick_do_broadcast(mask)) {
 444                 /*
 445                  * The global event did not expire any CPU local
 446                  * events. This happens in dyntick mode, as the
 447                  * maximum PIT delta is quite small.
 448                  */
 449                 if (tick_broadcast_reprogram())
 450                         goto again;
 451         }
 452         spin_unlock(&tick_broadcast_lock);
 453 }
 454
 455 /*
 456  * Powerstate information: The system enters/leaves a state, where
 457  * affected devices might stop
 458  */
 459 void tick_broadcast_oneshot_control(unsigned long reason)
 460 {
 461         struct clock_event_device *bc, *dev;
 462         struct tick_device *td;
 463         unsigned long flags;
 464         int cpu;
 465
 466         spin_lock_irqsave(&tick_broadcast_lock, flags);
 467
 468         /*
 469          * Periodic mode does not care about the enter/exit of power
 470          * states
 471          */
 472         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 473                 goto out;
 474
 475         bc = tick_broadcast_device.evtdev;
 476         cpu = smp_processor_id();
 477         td = &per_cpu(tick_cpu_device, cpu);
 478         dev = td->evtdev;
 479
 480         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 481                 goto out;
 482
 483         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 484                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 485                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 486                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 487                         if (dev->next_event.tv64 < bc->next_event.tv64)
 488                                 tick_broadcast_set_event(dev->next_event, 1);
 489                 }
 490         } else {
 491                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 492                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 493                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 494                         if (dev->next_event.tv64 != KTIME_MAX)
 495                                 tick_program_event(dev->next_event, 1);
 496                 }
 497         }
 498
 499 out:
 500         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 501 }
 502
 503 /*
 504  * Reset the one shot broadcast for a cpu
 505  *
 506  * Called with tick_broadcast_lock held
 507  */
 508 static void tick_broadcast_clear_oneshot(int cpu)
 509 {
 510         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 511 }
 512
 513 /**
 514  * tick_broadcast_setup_highres - setup the broadcast device for highres
 515  */
 516 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 517 {
 518         if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
 519                 bc->event_handler = tick_handle_oneshot_broadcast;
 520                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 521                 bc->next_event.tv64 = KTIME_MAX;
 522         }
 523 }
 524
 525 /*
 526  * Select oneshot operating mode for the broadcast device
 527  */
 528 void tick_broadcast_switch_to_oneshot(void)
 529 {
 530         struct clock_event_device *bc;
 531         unsigned long flags;
 532
 533         spin_lock_irqsave(&tick_broadcast_lock, flags);
 534
 535         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 536         bc = tick_broadcast_device.evtdev;
 537         if (bc)
 538                 tick_broadcast_setup_oneshot(bc);
 539         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 540 }
 541
 542
 543 /*
 544  * Remove a dead CPU from broadcasting
 545  */
 546 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 547 {
 548         unsigned long flags;
 549         unsigned int cpu = *cpup;
 550
 551         spin_lock_irqsave(&tick_broadcast_lock, flags);
 552
 553         /*
 554          * Clear the broadcast mask flag for the dead cpu, but do not
 555          * stop the broadcast device!
 556          */
 557         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 558
 559         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 560 }
 561
 562 #endif