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             (dev->features & CLOCK_EVT_FEAT_C3STOP))
  69                 return 0;
  70
  71         clockevents_exchange_device(NULL, dev);
  72         tick_broadcast_device.evtdev = dev;
  73         if (!cpus_empty(tick_broadcast_mask))
  74                 tick_broadcast_start_periodic(dev);
  75         return 1;
  76 }
  77
  78 /*
  79  * Check, if the device is the broadcast device
  80  */
  81 int tick_is_broadcast_device(struct clock_event_device *dev)
  82 {
  83         return (dev && tick_broadcast_device.evtdev == dev);
  84 }
  85
  86 /*
  87  * Check, if the device is disfunctional and a place holder, which
  88  * needs to be handled by the broadcast device.
  89  */
  90 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  91 {
  92         unsigned long flags;
  93         int ret = 0;
  94
  95         spin_lock_irqsave(&tick_broadcast_lock, flags);
  96
  97         /*
  98          * Devices might be registered with both periodic and oneshot
  99          * mode disabled. This signals, that the device needs to be
 100          * operated from the broadcast device and is a placeholder for
 101          * the cpu local device.
 102          */
 103         if (!tick_device_is_functional(dev)) {
 104                 dev->event_handler = tick_handle_periodic;
 105                 cpu_set(cpu, tick_broadcast_mask);
 106                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 107                 ret = 1;
 108         } else {
 109                 /*
 110                  * When the new device is not affected by the stop
 111                  * feature and the cpu is marked in the broadcast mask
 112                  * then clear the broadcast bit.
 113                  */
 114                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 115                         int cpu = smp_processor_id();
 116
 117                         cpu_clear(cpu, tick_broadcast_mask);
 118                         tick_broadcast_clear_oneshot(cpu);
 119                 }
 120         }
 121         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 122         return ret;
 123 }
 124
 125 /*
 126  * Broadcast the event to the cpus, which are set in the mask
 127  */
 128 int tick_do_broadcast(cpumask_t mask)
 129 {
 130         int ret = 0, cpu = smp_processor_id();
 131         struct tick_device *td;
 132
 133         /*
 134          * Check, if the current cpu is in the mask
 135          */
 136         if (cpu_isset(cpu, mask)) {
 137                 cpu_clear(cpu, mask);
 138                 td = &per_cpu(tick_cpu_device, cpu);
 139                 td->evtdev->event_handler(td->evtdev);
 140                 ret = 1;
 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                 ret = 1;
 154         }
 155         return ret;
 156 }
 157
 158 /*
 159  * Periodic broadcast:
 160  * - invoke the broadcast handlers
 161  */
 162 static void tick_do_periodic_broadcast(void)
 163 {
 164         cpumask_t mask;
 165
 166         spin_lock(&tick_broadcast_lock);
 167
 168         cpus_and(mask, cpu_online_map, tick_broadcast_mask);
 169         tick_do_broadcast(mask);
 170
 171         spin_unlock(&tick_broadcast_lock);
 172 }
 173
 174 /*
 175  * Event handler for periodic broadcast ticks
 176  */
 177 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 178 {
 179         dev->next_event.tv64 = KTIME_MAX;
 180
 181         tick_do_periodic_broadcast();
 182
 183         /*
 184          * The device is in periodic mode. No reprogramming necessary:
 185          */
 186         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 187                 return;
 188
 189         /*
 190          * Setup the next period for devices, which do not have
 191          * periodic mode:
 192          */
 193         for (;;) {
 194                 ktime_t next = ktime_add(dev->next_event, tick_period);
 195
 196                 if (!clockevents_program_event(dev, next, ktime_get()))
 197                         return;
 198                 tick_do_periodic_broadcast();
 199         }
 200 }
 201
 202 /*
 203  * Powerstate information: The system enters/leaves a state, where
 204  * affected devices might stop
 205  */
 206 static void tick_do_broadcast_on_off(void *why)
 207 {
 208         struct clock_event_device *bc, *dev;
 209         struct tick_device *td;
 210         unsigned long flags, *reason = why;
 211         int cpu;
 212
 213         spin_lock_irqsave(&tick_broadcast_lock, flags);
 214
 215         cpu = smp_processor_id();
 216         td = &per_cpu(tick_cpu_device, cpu);
 217         dev = td->evtdev;
 218         bc = tick_broadcast_device.evtdev;
 219
 220         /*
 221          * Is the device in broadcast mode forever or is it not
 222          * affected by the powerstate ?
 223          */
 224         if (!dev || !tick_device_is_functional(dev) ||
 225             !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 226                 goto out;
 227
 228         if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
 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         } else {
 236                 if (cpu_isset(cpu, tick_broadcast_mask)) {
 237                         cpu_clear(cpu, tick_broadcast_mask);
 238                         if (td->mode == TICKDEV_MODE_PERIODIC)
 239                                 tick_setup_periodic(dev, 0);
 240                 }
 241         }
 242
 243         if (cpus_empty(tick_broadcast_mask))
 244                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 245         else {
 246                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 247                         tick_broadcast_start_periodic(bc);
 248                 else
 249                         tick_broadcast_setup_oneshot(bc);
 250         }
 251 out:
 252         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 253 }
 254
 255 /*
 256  * Powerstate information: The system enters/leaves a state, where
 257  * affected devices might stop.
 258  */
 259 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 260 {
 261         int cpu = get_cpu();
 262
 263         if (!cpu_isset(*oncpu, cpu_online_map)) {
 264                 printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
 265                        "offline CPU #%d\n", *oncpu);
 266         } else {
 267
 268                 if (cpu == *oncpu)
 269                         tick_do_broadcast_on_off(&reason);
 270                 else
 271                         smp_call_function_single(*oncpu,
 272                                                  tick_do_broadcast_on_off,
 273                                                  &reason, 1, 1);
 274         }
 275         put_cpu();
 276 }
 277
 278 /*
 279  * Set the periodic handler depending on broadcast on/off
 280  */
 281 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 282 {
 283         if (!broadcast)
 284                 dev->event_handler = tick_handle_periodic;
 285         else
 286                 dev->event_handler = tick_handle_periodic_broadcast;
 287 }
 288
 289 /*
 290  * Remove a CPU from broadcasting
 291  */
 292 void tick_shutdown_broadcast(unsigned int *cpup)
 293 {
 294         struct clock_event_device *bc;
 295         unsigned long flags;
 296         unsigned int cpu = *cpup;
 297
 298         spin_lock_irqsave(&tick_broadcast_lock, flags);
 299
 300         bc = tick_broadcast_device.evtdev;
 301         cpu_clear(cpu, tick_broadcast_mask);
 302
 303         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 304                 if (bc && cpus_empty(tick_broadcast_mask))
 305                         clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 306         }
 307
 308         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 309 }
 310
 311 void tick_suspend_broadcast(void)
 312 {
 313         struct clock_event_device *bc;
 314         unsigned long flags;
 315
 316         spin_lock_irqsave(&tick_broadcast_lock, flags);
 317
 318         bc = tick_broadcast_device.evtdev;
 319         if (bc)
 320                 clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
 321
 322         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 323 }
 324
 325 int tick_resume_broadcast(void)
 326 {
 327         struct clock_event_device *bc;
 328         unsigned long flags;
 329         int broadcast = 0;
 330
 331         spin_lock_irqsave(&tick_broadcast_lock, flags);
 332
 333         bc = tick_broadcast_device.evtdev;
 334
 335         if (bc) {
 336                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 337
 338                 switch (tick_broadcast_device.mode) {
 339                 case TICKDEV_MODE_PERIODIC:
 340                         if(!cpus_empty(tick_broadcast_mask))
 341                                 tick_broadcast_start_periodic(bc);
 342                         broadcast = cpu_isset(smp_processor_id(),
 343                                               tick_broadcast_mask);
 344                         break;
 345                 case TICKDEV_MODE_ONESHOT:
 346                         broadcast = tick_resume_broadcast_oneshot(bc);
 347                         break;
 348                 }
 349         }
 350         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 351
 352         return broadcast;
 353 }
 354
 355
 356 #ifdef CONFIG_TICK_ONESHOT
 357
 358 static cpumask_t tick_broadcast_oneshot_mask;
 359
 360 /*
 361  * Debugging: see timer_list.c
 362  */
 363 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 364 {
 365         return &tick_broadcast_oneshot_mask;
 366 }
 367
 368 static int tick_broadcast_set_event(ktime_t expires, int force)
 369 {
 370         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 371         ktime_t now = ktime_get();
 372         int res;
 373
 374         for(;;) {
 375                 res = clockevents_program_event(bc, expires, now);
 376                 if (!res || !force)
 377                         return res;
 378                 now = ktime_get();
 379                 expires = ktime_add(now, ktime_set(0, bc->min_delta_ns));
 380         }
 381 }
 382
 383 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 384 {
 385         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 386         return 0;
 387 }
 388
 389 /*
 390  * Handle oneshot mode broadcasting
 391  */
 392 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 393 {
 394         struct tick_device *td;
 395         cpumask_t mask;
 396         ktime_t now, next_event;
 397         int cpu;
 398
 399         spin_lock(&tick_broadcast_lock);
 400 again:
 401         dev->next_event.tv64 = KTIME_MAX;
 402         next_event.tv64 = KTIME_MAX;
 403         mask = CPU_MASK_NONE;
 404         now = ktime_get();
 405         /* Find all expired events */
 406         for (cpu = first_cpu(tick_broadcast_oneshot_mask); cpu != NR_CPUS;
 407              cpu = next_cpu(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_highres - setup the broadcast device for highres
 501  */
 502 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 503 {
 504         if (bc->mode != CLOCK_EVT_MODE_ONESHOT) {
 505                 bc->event_handler = tick_handle_oneshot_broadcast;
 506                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 507                 bc->next_event.tv64 = KTIME_MAX;
 508         }
 509 }
 510
 511 /*
 512  * Select oneshot operating mode for the broadcast device
 513  */
 514 void tick_broadcast_switch_to_oneshot(void)
 515 {
 516         struct clock_event_device *bc;
 517         unsigned long flags;
 518
 519         spin_lock_irqsave(&tick_broadcast_lock, flags);
 520
 521         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 522         bc = tick_broadcast_device.evtdev;
 523         if (bc)
 524                 tick_broadcast_setup_oneshot(bc);
 525         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 526 }
 527
 528
 529 /*
 530  * Remove a dead CPU from broadcasting
 531  */
 532 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 533 {
 534         unsigned long flags;
 535         unsigned int cpu = *cpup;
 536
 537         spin_lock_irqsave(&tick_broadcast_lock, flags);
 538
 539         /*
 540          * Clear the broadcast mask flag for the dead cpu, but do not
 541          * stop the broadcast device!
 542          */
 543         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 544
 545         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 546 }
 547
 548 #endif