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;
 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         switch (*reason) {
 232         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 233         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 234                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 235                         cpu_set(cpu, tick_broadcast_mask);
 236                         if (td->mode == TICKDEV_MODE_PERIODIC)
 237                                 clockevents_set_mode(dev,
 238                                                      CLOCK_EVT_MODE_SHUTDOWN);
 239                 }
 240                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 241                         tick_broadcast_force = 1;
 242                 break;
 243         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 244                 if (!tick_broadcast_force &&
 245                     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                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 255         else {
 256                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 257                         tick_broadcast_start_periodic(bc);
 258                 else
 259                         tick_broadcast_setup_oneshot(bc);
 260         }
 261 out:
 262         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 263 }
 264
 265 /*
 266  * Powerstate information: The system enters/leaves a state, where
 267  * affected devices might stop.
 268  */
 269 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 270 {
 271         if (!cpu_isset(*oncpu, cpu_online_map))
 272                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 273                        "offline CPU #%d\n", *oncpu);
 274         else
 275                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 276                                          &reason, 1);
 277 }
 278
 279 /*
 280  * Set the periodic handler depending on broadcast on/off
 281  */
 282 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 283 {
 284         if (!broadcast)
 285                 dev->event_handler = tick_handle_periodic;
 286         else
 287                 dev->event_handler = tick_handle_periodic_broadcast;
 288 }
 289
 290 /*
 291  * Remove a CPU from broadcasting
 292  */
 293 void tick_shutdown_broadcast(unsigned int *cpup)
 294 {
 295         struct clock_event_device *bc;
 296         unsigned long flags;
 297         unsigned int cpu = *cpup;
 298
 299         spin_lock_irqsave(&tick_broadcast_lock, flags);
 300
 301         bc = tick_broadcast_device.evtdev;
 302         cpu_clear(cpu, tick_broadcast_mask);
 303
 304         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 305                 if (bc && cpus_empty(tick_broadcast_mask))
 306                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 307         }
 308
 309         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 310 }
 311
 312 void tick_suspend_broadcast(void)
 313 {
 314         struct clock_event_device *bc;
 315         unsigned long flags;
 316
 317         spin_lock_irqsave(&tick_broadcast_lock, flags);
 318
 319         bc = tick_broadcast_device.evtdev;
 320         if (bc)
 321                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 322
 323         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 324 }
 325
 326 int tick_resume_broadcast(void)
 327 {
 328         struct clock_event_device *bc;
 329         unsigned long flags;
 330         int broadcast = 0;
 331
 332         spin_lock_irqsave(&tick_broadcast_lock, flags);
 333
 334         bc = tick_broadcast_device.evtdev;
 335
 336         if (bc) {
 337                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 338
 339                 switch (tick_broadcast_device.mode) {
 340                 case TICKDEV_MODE_PERIODIC:
 341                         if(!cpus_empty(tick_broadcast_mask))
 342                                 tick_broadcast_start_periodic(bc);
 343                         broadcast = cpu_isset(smp_processor_id(),
 344                                               tick_broadcast_mask);
 345                         break;
 346                 case TICKDEV_MODE_ONESHOT:
 347                         broadcast = tick_resume_broadcast_oneshot(bc);
 348                         break;
 349                 }
 350         }
 351         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 352
 353         return broadcast;
 354 }
 355
 356
 357 #ifdef CONFIG_TICK_ONESHOT
 358
 359 static cpumask_t tick_broadcast_oneshot_mask;
 360
 361 /*
 362  * Debugging: see timer_list.c
 363  */
 364 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 365 {
 366         return &tick_broadcast_oneshot_mask;
 367 }
 368
 369 static int tick_broadcast_set_event(ktime_t expires, int force)
 370 {
 371         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 372         ktime_t now = ktime_get();
 373         int res;
 374
 375         for(;;) {
 376                 res = clockevents_program_event(bc, expires, now);
 377                 if (!res || !force)
 378                         return res;
 379                 now = ktime_get();
 380                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 381         }
 382 }
 383
 384 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 385 {
 386         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 387         return 0;
 388 }
 389
 390 /*
 391  * Handle oneshot mode broadcasting
 392  */
 393 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 394 {
 395         struct tick_device *td;
 396         cpumask_t mask;
 397         ktime_t now, next_event;
 398         int cpu;
 399
 400         spin_lock(&tick_broadcast_lock);
 401 again:
 402         dev->next_event.tv64 = KTIME_MAX;
 403         next_event.tv64 = KTIME_MAX;
 404         mask = CPU_MASK_NONE;
 405         now = ktime_get();
 406         /* Find all expired events */
 407         for_each_cpu_mask_nr(cpu, tick_broadcast_oneshot_mask) {
 408                 td = &per_cpu(tick_cpu_device, cpu);
 409                 if (td->evtdev->next_event.tv64 <= now.tv64)
 410                         cpu_set(cpu, mask);
 411                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 412                         next_event.tv64 = td->evtdev->next_event.tv64;
 413         }
 414
 415         /*
 416          * Wakeup the cpus which have an expired event.
 417          */
 418         tick_do_broadcast(mask);
 419
 420         /*
 421          * Two reasons for reprogram:
 422          *
 423          * - The global event did not expire any CPU local
 424          * events. This happens in dyntick mode, as the maximum PIT
 425          * delta is quite small.
 426          *
 427          * - There are pending events on sleeping CPUs which were not
 428          * in the event mask
 429          */
 430         if (next_event.tv64 != KTIME_MAX) {
 431                 /*
 432                  * Rearm the broadcast device. If event expired,
 433                  * repeat the above
 434                  */
 435                 if (tick_broadcast_set_event(next_event, 0))
 436                         goto again;
 437         }
 438         spin_unlock(&tick_broadcast_lock);
 439 }
 440
 441 /*
 442  * Powerstate information: The system enters/leaves a state, where
 443  * affected devices might stop
 444  */
 445 void tick_broadcast_oneshot_control(unsigned long reason)
 446 {
 447         struct clock_event_device *bc, *dev;
 448         struct tick_device *td;
 449         unsigned long flags;
 450         int cpu;
 451
 452         spin_lock_irqsave(&tick_broadcast_lock, flags);
 453
 454         /*
 455          * Periodic mode does not care about the enter/exit of power
 456          * states
 457          */
 458         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 459                 goto out;
 460
 461         bc = tick_broadcast_device.evtdev;
 462         cpu = smp_processor_id();
 463         td = &per_cpu(tick_cpu_device, cpu);
 464         dev = td->evtdev;
 465
 466         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 467                 goto out;
 468
 469         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 470                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 471                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 472                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 473                         if (dev->next_event.tv64 < bc->next_event.tv64)
 474                                 tick_broadcast_set_event(dev->next_event, 1);
 475                 }
 476         } else {
 477                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 478                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 479                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 480                         if (dev->next_event.tv64 != KTIME_MAX)
 481                                 tick_program_event(dev->next_event, 1);
 482                 }
 483         }
 484
 485 out:
 486         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 487 }
 488
 489 /*
 490  * Reset the one shot broadcast for a cpu
 491  *
 492  * Called with tick_broadcast_lock held
 493  */
 494 static void tick_broadcast_clear_oneshot(int cpu)
 495 {
 496         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 497 }
 498
 499 /**
 500  * tick_broadcast_setup_oneshot - setup the broadcast device
 501  */
 502 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 503 {
 504         bc->event_handler = tick_handle_oneshot_broadcast;
 505         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 506         bc->next_event.tv64 = KTIME_MAX;
 507 }
 508
 509 /*
 510  * Select oneshot operating mode for the broadcast device
 511  */
 512 void tick_broadcast_switch_to_oneshot(void)
 513 {
 514         struct clock_event_device *bc;
 515         unsigned long flags;
 516
 517         spin_lock_irqsave(&tick_broadcast_lock, flags);
 518
 519         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 520         bc = tick_broadcast_device.evtdev;
 521         if (bc)
 522                 tick_broadcast_setup_oneshot(bc);
 523         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 524 }
 525
 526
 527 /*
 528  * Remove a dead CPU from broadcasting
 529  */
 530 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 531 {
 532         unsigned long flags;
 533         unsigned int cpu = *cpup;
 534
 535         spin_lock_irqsave(&tick_broadcast_lock, flags);
 536
 537         /*
 538          * Clear the broadcast mask flag for the dead cpu, but do not
 539          * stop the broadcast device!
 540          */
 541         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 542
 543         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 544 }
 545
 546 #endif