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 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 not affected by the powerstate ?
 221          */
 222         if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 223                 goto out;
 224
 225         if (!tick_device_is_functional(dev))
 226                 goto out;
 227
 228         switch (*reason) {
 229         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 230         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 231                 if (!cpu_isset(cpu, tick_broadcast_mask)) {
 232                         cpu_set(cpu, tick_broadcast_mask);
 233                         if (td->mode == TICKDEV_MODE_PERIODIC)
 234                                 clockevents_set_mode(dev,
 235                                                      CLOCK_EVT_MODE_SHUTDOWN);
 236                 }
 237                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 238                         dev->features |= CLOCK_EVT_FEAT_DUMMY;
 239                 break;
 240         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 241                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 242                         cpu_clear(cpu, tick_broadcast_mask);
 243                         if (td->mode == TICKDEV_MODE_PERIODIC)
 244                                 tick_setup_periodic(dev, 0);
 245                 }
 246                 break;
 247         }
 248
 249         if (cpus_empty(tick_broadcast_mask))
 250                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 251         else {
 252                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 253                         tick_broadcast_start_periodic(bc);
 254                 else
 255                         tick_broadcast_setup_oneshot(bc);
 256         }
 257 out:
 258         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 259 }
 260
 261 /*
 262  * Powerstate information: The system enters/leaves a state, where
 263  * affected devices might stop.
 264  */
 265 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 266 {
 267         if (!cpu_isset(*oncpu, cpu_online_map))
 268                 printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
 269                        "offline CPU #%d\n", *oncpu);
 270         else
 271                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 272                                          &reason, 1, 1);
 273 }
 274
 275 /*
 276  * Set the periodic handler depending on broadcast on/off
 277  */
 278 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 279 {
 280         if (!broadcast)
 281                 dev->event_handler = tick_handle_periodic;
 282         else
 283                 dev->event_handler = tick_handle_periodic_broadcast;
 284 }
 285
 286 /*
 287  * Remove a CPU from broadcasting
 288  */
 289 void tick_shutdown_broadcast(unsigned int *cpup)
 290 {
 291         struct clock_event_device *bc;
 292         unsigned long flags;
 293         unsigned int cpu = *cpup;
 294
 295         spin_lock_irqsave(&tick_broadcast_lock, flags);
 296
 297         bc = tick_broadcast_device.evtdev;
 298         cpu_clear(cpu, tick_broadcast_mask);
 299
 300         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 301                 if (bc && cpus_empty(tick_broadcast_mask))
 302                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 303         }
 304
 305         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 306 }
 307
 308 void tick_suspend_broadcast(void)
 309 {
 310         struct clock_event_device *bc;
 311         unsigned long flags;
 312
 313         spin_lock_irqsave(&tick_broadcast_lock, flags);
 314
 315         bc = tick_broadcast_device.evtdev;
 316         if (bc)
 317                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 318
 319         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 320 }
 321
 322 int tick_resume_broadcast(void)
 323 {
 324         struct clock_event_device *bc;
 325         unsigned long flags;
 326         int broadcast = 0;
 327
 328         spin_lock_irqsave(&tick_broadcast_lock, flags);
 329
 330         bc = tick_broadcast_device.evtdev;
 331
 332         if (bc) {
 333                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 334
 335                 switch (tick_broadcast_device.mode) {
 336                 case TICKDEV_MODE_PERIODIC:
 337                         if(!cpus_empty(tick_broadcast_mask))
 338                                 tick_broadcast_start_periodic(bc);
 339                         broadcast = cpu_isset(smp_processor_id(),
 340                                               tick_broadcast_mask);
 341                         break;
 342                 case TICKDEV_MODE_ONESHOT:
 343                         broadcast = tick_resume_broadcast_oneshot(bc);
 344                         break;
 345                 }
 346         }
 347         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 348
 349         return broadcast;
 350 }
 351
 352
 353 #ifdef CONFIG_TICK_ONESHOT
 354
 355 static cpumask_t tick_broadcast_oneshot_mask;
 356
 357 /*
 358  * Debugging: see timer_list.c
 359  */
 360 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 361 {
 362         return &tick_broadcast_oneshot_mask;
 363 }
 364
 365 static int tick_broadcast_set_event(ktime_t expires, int force)
 366 {
 367         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 368         ktime_t now = ktime_get();
 369         int res;
 370
 371         for(;;) {
 372                 res = clockevents_program_event(bc, expires, now);
 373                 if (!res || !force)
 374                         return res;
 375                 now = ktime_get();
 376                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 377         }
 378 }
 379
 380 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 381 {
 382         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 383         return 0;
 384 }
 385
 386 /*
 387  * Reprogram the broadcast device:
 388  *
 389  * Called with tick_broadcast_lock held and interrupts disabled.
 390  */
 391 static int tick_broadcast_reprogram(void)
 392 {
 393         ktime_t expires = { .tv64 = KTIME_MAX };
 394         struct tick_device *td;
 395         int cpu;
 396
 397         /*
 398          * Find the event which expires next:
 399          */
 400         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 401              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 402                 td = &per_cpu(tick_cpu_device, cpu);
 403                 if (td->evtdev->next_event.tv64 < expires.tv64)
 404                         expires = td->evtdev->next_event;
 405         }
 406
 407         if (expires.tv64 == KTIME_MAX)
 408                 return 0;
 409
 410         return tick_broadcast_set_event(expires, 0);
 411 }
 412
 413 /*
 414  * Handle oneshot mode broadcasting
 415  */
 416 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 417 {
 418         struct tick_device *td;
 419         cpumask_t mask;
 420         ktime_t now;
 421         int cpu;
 422
 423         spin_lock(&tick_broadcast_lock);
 424 again:
 425         dev->next_event.tv64 = KTIME_MAX;
 426         mask = CPU_MASK_NONE;
 427         now = ktime_get();
 428         /* Find all expired events */
 429         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 430              cpu = next_cpu(cpu, tick_broadcast_oneshot_mask)) {
 431                 td = &per_cpu(tick_cpu_device, cpu);
 432                 if (td->evtdev->next_event.tv64 <= now.tv64)
 433                         cpu_set(cpu, mask);
 434         }
 435
 436         /*
 437          * Wakeup the cpus which have an expired event. The broadcast
 438          * device is reprogrammed in the return from idle code.
 439          */
 440         if (!tick_do_broadcast(mask)) {
 441                 /*
 442                  * The global event did not expire any CPU local
 443                  * events. This happens in dyntick mode, as the
 444                  * maximum PIT delta is quite small.
 445                  */
 446                 if (tick_broadcast_reprogram())
 447                         goto again;
 448         }
 449         spin_unlock(&tick_broadcast_lock);
 450 }
 451
 452 /*
 453  * Powerstate information: The system enters/leaves a state, where
 454  * affected devices might stop
 455  */
 456 void tick_broadcast_oneshot_control(unsigned long reason)
 457 {
 458         struct clock_event_device *bc, *dev;
 459         struct tick_device *td;
 460         unsigned long flags;
 461         int cpu;
 462
 463         spin_lock_irqsave(&tick_broadcast_lock, flags);
 464
 465         /*
 466          * Periodic mode does not care about the enter/exit of power
 467          * states
 468          */
 469         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 470                 goto out;
 471
 472         bc = tick_broadcast_device.evtdev;
 473         cpu = smp_processor_id();
 474         td = &per_cpu(tick_cpu_device, cpu);
 475         dev = td->evtdev;
 476
 477         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 478                 goto out;
 479
 480         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 481                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 482                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 483                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 484                         if (dev->next_event.tv64 < bc->next_event.tv64)
 485                                 tick_broadcast_set_event(dev->next_event, 1);
 486                 }
 487         } else {
 488                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 489                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 490                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 491                         if (dev->next_event.tv64 != KTIME_MAX)
 492                                 tick_program_event(dev->next_event, 1);
 493                 }
 494         }
 495
 496 out:
 497         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 498 }
 499
 500 /*
 501  * Reset the one shot broadcast for a cpu
 502  *
 503  * Called with tick_broadcast_lock held
 504  */
 505 static void tick_broadcast_clear_oneshot(int cpu)
 506 {
 507         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 508 }
 509
 510 /**
 511  * tick_broadcast_setup_oneshot - setup the broadcast device
 512  */
 513 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 514 {
 515         bc->event_handler = tick_handle_oneshot_broadcast;
 516         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 517         bc->next_event.tv64 = KTIME_MAX;
 518 }
 519
 520 /*
 521  * Select oneshot operating mode for the broadcast device
 522  */
 523 void tick_broadcast_switch_to_oneshot(void)
 524 {
 525         struct clock_event_device *bc;
 526         unsigned long flags;
 527
 528         spin_lock_irqsave(&tick_broadcast_lock, flags);
 529
 530         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 531         bc = tick_broadcast_device.evtdev;
 532         if (bc)
 533                 tick_broadcast_setup_oneshot(bc);
 534         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 535 }
 536
 537
 538 /*
 539  * Remove a dead CPU from broadcasting
 540  */
 541 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 542 {
 543         unsigned long flags;
 544         unsigned int cpu = *cpup;
 545
 546         spin_lock_irqsave(&tick_broadcast_lock, flags);
 547
 548         /*
 549          * Clear the broadcast mask flag for the dead cpu, but do not
 550          * stop the broadcast device!
 551          */
 552         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 553
 554         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 555 }
 556
 557 #endif