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              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 static void tick_do_broadcast(cpumask_t mask)
 130 {
 131         int 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         }
 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         }
 154 }
 155
 156 /*
 157  * Periodic broadcast:
 158  * - invoke the broadcast handlers
 159  */
 160 static void tick_do_periodic_broadcast(void)
 161 {
 162         cpumask_t mask;
 163
 164         spin_lock(&tick_broadcast_lock);
 165
 166         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 167         tick_do_broadcast(mask);
 168
 169         spin_unlock(&tick_broadcast_lock);
 170 }
 171
 172 /*
 173  * Event handler for periodic broadcast ticks
 174  */
 175 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 176 {
 177         ktime_t next;
 178
 179         tick_do_periodic_broadcast();
 180
 181         /*
 182          * The device is in periodic mode. No reprogramming necessary:
 183          */
 184         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 185                 return;
 186
 187         /*
 188          * Setup the next period for devices, which do not have
 189          * periodic mode. We read dev->next_event first and add to it
 190          * when the event alrady expired. clockevents_program_event()
 191          * sets dev->next_event only when the event is really
 192          * programmed to the device.
 193          */
 194         for (next = dev->next_event; ;) {
 195                 next = ktime_add(next, tick_period);
 196
 197                 if (!clockevents_program_event(dev, next, ktime_get()))
 198                         return;
 199                 tick_do_periodic_broadcast();
 200         }
 201 }
 202
 203 /*
 204  * Powerstate information: The system enters/leaves a state, where
 205  * affected devices might stop
 206  */
 207 static void tick_do_broadcast_on_off(void *why)
 208 {
 209         struct clock_event_device *bc, *dev;
 210         struct tick_device *td;
 211         unsigned long flags, *reason = why;
 212         int cpu, bc_stopped;
 213
 214         spin_lock_irqsave(&tick_broadcast_lock, flags);
 215
 216         cpu = smp_processor_id();
 217         td = &per_cpu(tick_cpu_device, cpu);
 218         dev = td->evtdev;
 219         bc = tick_broadcast_device.evtdev;
 220
 221         /*
 222          * Is the device not affected by the powerstate ?
 223          */
 224         if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 225                 goto out;
 226
 227         if (!tick_device_is_functional(dev))
 228                 goto out;
 229
 230         bc_stopped = cpus_empty(tick_broadcast_mask);
 231
 232         switch (*reason) {
 233         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 234         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 235                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 236                         cpu_set(cpu, tick_broadcast_mask);
 237                         if (td->mode == TICKDEV_MODE_PERIODIC)
 238                                 clockevents_set_mode(dev,
 239                                                      CLOCK_EVT_MODE_SHUTDOWN);
 240                 }
 241                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 242                         dev->features |= CLOCK_EVT_FEAT_DUMMY;
 243                 break;
 244         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 245                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 246                         cpu_clear(cpu, tick_broadcast_mask);
 247                         if (td->mode == TICKDEV_MODE_PERIODIC)
 248                                 tick_setup_periodic(dev, 0);
 249                 }
 250                 break;
 251         }
 252
 253         if (cpus_empty(tick_broadcast_mask)) {
 254                 if (!bc_stopped)
 255                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 256         } else if (bc_stopped) {
 257                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 258                         tick_broadcast_start_periodic(bc);
 259                 else
 260                         tick_broadcast_setup_oneshot(bc);
 261         }
 262 out:
 263         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 264 }
 265
 266 /*
 267  * Powerstate information: The system enters/leaves a state, where
 268  * affected devices might stop.
 269  */
 270 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 271 {
 272         if (!cpu_isset(*oncpu, cpu_online_map))
 273                 printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
 274                        "offline CPU #%d\n", *oncpu);
 275         else
 276                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 277                                          &reason, 1, 1);
 278 }
 279
 280 /*
 281  * Set the periodic handler depending on broadcast on/off
 282  */
 283 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 284 {
 285         if (!broadcast)
 286                 dev->event_handler = tick_handle_periodic;
 287         else
 288                 dev->event_handler = tick_handle_periodic_broadcast;
 289 }
 290
 291 /*
 292  * Remove a CPU from broadcasting
 293  */
 294 void tick_shutdown_broadcast(unsigned int *cpup)
 295 {
 296         struct clock_event_device *bc;
 297         unsigned long flags;
 298         unsigned int cpu = *cpup;
 299
 300         spin_lock_irqsave(&tick_broadcast_lock, flags);
 301
 302         bc = tick_broadcast_device.evtdev;
 303         cpu_clear(cpu, tick_broadcast_mask);
 304
 305         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 306                 if (bc && cpus_empty(tick_broadcast_mask))
 307                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 308         }
 309
 310         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 311 }
 312
 313 void tick_suspend_broadcast(void)
 314 {
 315         struct clock_event_device *bc;
 316         unsigned long flags;
 317
 318         spin_lock_irqsave(&tick_broadcast_lock, flags);
 319
 320         bc = tick_broadcast_device.evtdev;
 321         if (bc)
 322                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 323
 324         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 325 }
 326
 327 int tick_resume_broadcast(void)
 328 {
 329         struct clock_event_device *bc;
 330         unsigned long flags;
 331         int broadcast = 0;
 332
 333         spin_lock_irqsave(&tick_broadcast_lock, flags);
 334
 335         bc = tick_broadcast_device.evtdev;
 336
 337         if (bc) {
 338                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 339
 340                 switch (tick_broadcast_device.mode) {
 341                 case TICKDEV_MODE_PERIODIC:
 342                         if(!cpus_empty(tick_broadcast_mask))
 343                                 tick_broadcast_start_periodic(bc);
 344                         broadcast = cpu_isset(smp_processor_id(),
 345                                               tick_broadcast_mask);
 346                         break;
 347                 case TICKDEV_MODE_ONESHOT:
 348                         broadcast = tick_resume_broadcast_oneshot(bc);
 349                         break;
 350                 }
 351         }
 352         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 353
 354         return broadcast;
 355 }
 356
 357
 358 #ifdef CONFIG_TICK_ONESHOT
 359
 360 static cpumask_t tick_broadcast_oneshot_mask;
 361
 362 /*
 363  * Debugging: see timer_list.c
 364  */
 365 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 366 {
 367         return &tick_broadcast_oneshot_mask;
 368 }
 369
 370 static int tick_broadcast_set_event(ktime_t expires, int force)
 371 {
 372         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 373         ktime_t now = ktime_get();
 374         int res;
 375
 376         for(;;) {
 377                 res = clockevents_program_event(bc, expires, now);
 378                 if (!res || !force)
 379                         return res;
 380                 now = ktime_get();
 381                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 382         }
 383 }
 384
 385 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 386 {
 387         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 388         return 0;
 389 }
 390
 391 /*
 392  * Handle oneshot mode broadcasting
 393  */
 394 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 395 {
 396         struct tick_device *td;
 397         cpumask_t mask;
 398         ktime_t now, next_event;
 399         int cpu;
 400
 401         spin_lock(&tick_broadcast_lock);
 402 again:
 403         dev->next_event.tv64 = KTIME_MAX;
 404         next_event.tv64 = KTIME_MAX;
 405         mask = CPU_MASK_NONE;
 406         now = ktime_get();
 407         /* Find all expired events */
 408         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 409              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 410                 td = &per_cpu(tick_cpu_device, cpu);
 411                 if (td->evtdev->next_event.tv64 <= now.tv64)
 412                         cpu_set(cpu, mask);
 413                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 414                         next_event.tv64 = td->evtdev->next_event.tv64;
 415         }
 416
 417         /*
 418          * Wakeup the cpus which have an expired event.
 419          */
 420         tick_do_broadcast(mask);
 421
 422         /*
 423          * Two reasons for reprogram:
 424          *
 425          * - The global event did not expire any CPU local
 426          * events. This happens in dyntick mode, as the maximum PIT
 427          * delta is quite small.
 428          *
 429          * - There are pending events on sleeping CPUs which were not
 430          * in the event mask
 431          */
 432         if (next_event.tv64 != KTIME_MAX) {
 433                 /*
 434                  * Rearm the broadcast device. If event expired,
 435                  * repeat the above
 436                  */
 437                 if (tick_broadcast_set_event(next_event, 0))
 438                         goto again;
 439         }
 440         spin_unlock(&tick_broadcast_lock);
 441 }
 442
 443 /*
 444  * Powerstate information: The system enters/leaves a state, where
 445  * affected devices might stop
 446  */
 447 void tick_broadcast_oneshot_control(unsigned long reason)
 448 {
 449         struct clock_event_device *bc, *dev;
 450         struct tick_device *td;
 451         unsigned long flags;
 452         int cpu;
 453
 454         spin_lock_irqsave(&tick_broadcast_lock, flags);
 455
 456         /*
 457          * Periodic mode does not care about the enter/exit of power
 458          * states
 459          */
 460         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 461                 goto out;
 462
 463         bc = tick_broadcast_device.evtdev;
 464         cpu = smp_processor_id();
 465         td = &per_cpu(tick_cpu_device, cpu);
 466         dev = td->evtdev;
 467
 468         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 469                 goto out;
 470
 471         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 472                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 473                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 474                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 475                         if (dev->next_event.tv64 < bc->next_event.tv64)
 476                                 tick_broadcast_set_event(dev->next_event, 1);
 477                 }
 478         } else {
 479                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 480                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 481                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 482                         if (dev->next_event.tv64 != KTIME_MAX)
 483                                 tick_program_event(dev->next_event, 1);
 484                 }
 485         }
 486
 487 out:
 488         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 489 }
 490
 491 /*
 492  * Reset the one shot broadcast for a cpu
 493  *
 494  * Called with tick_broadcast_lock held
 495  */
 496 static void tick_broadcast_clear_oneshot(int cpu)
 497 {
 498         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 499 }
 500
 501 /**
 502  * tick_broadcast_setup_oneshot - setup the broadcast device
 503  */
 504 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 505 {
 506         /* Set it up only once ! */
 507         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 508                 bc->event_handler = tick_handle_oneshot_broadcast;
 509                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 510                 bc->next_event.tv64 = KTIME_MAX;
 511         }
 512 }
 513
 514 /*
 515  * Select oneshot operating mode for the broadcast device
 516  */
 517 void tick_broadcast_switch_to_oneshot(void)
 518 {
 519         struct clock_event_device *bc;
 520         unsigned long flags;
 521
 522         spin_lock_irqsave(&tick_broadcast_lock, flags);
 523
 524         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 525         bc = tick_broadcast_device.evtdev;
 526         if (bc)
 527                 tick_broadcast_setup_oneshot(bc);
 528         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 529 }
 530
 531
 532 /*
 533  * Remove a dead CPU from broadcasting
 534  */
 535 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 536 {
 537         unsigned long flags;
 538         unsigned int cpu = *cpup;
 539
 540         spin_lock_irqsave(&tick_broadcast_lock, flags);
 541
 542         /*
 543          * Clear the broadcast mask flag for the dead cpu, but do not
 544          * stop the broadcast device!
 545          */
 546         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 547
 548         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 549 }
 550
 551 #endif