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