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