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