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 30static struct tick_device tick_broadcast_device; 31static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS); 32static DECLARE_BITMAP(tmpmask, NR_CPUS); 33static DEFINE_RAW_SPINLOCK(tick_broadcast_lock); 34static int tick_broadcast_force; 35 36#ifdef CONFIG_TICK_ONESHOT 37static void tick_broadcast_clear_oneshot(int cpu); 38#else 39static inline void tick_broadcast_clear_oneshot(int cpu) { } 40#endif 41 42/* 43 * Debugging: see timer_list.c 44 */ 45struct tick_device *tick_get_broadcast_device(void) 46{ 47 return &tick_broadcast_device; 48} 49 50struct cpumask *tick_get_broadcast_mask(void) 51{ 52 return to_cpumask(tick_broadcast_mask); 53} 54 55/* 56 * Start the device in periodic mode 57 */ 58static void tick_broadcast_start_periodic(struct clock_event_device *bc) 59{ 60 if (bc) 61 tick_setup_periodic(bc, 1); 62} 63 64/* 65 * Check, if the device can be utilized as broadcast device: 66 */ 67int tick_check_broadcast_device(struct clock_event_device *dev) 68{ 69 if ((tick_broadcast_device.evtdev && 70 tick_broadcast_device.evtdev->rating >= dev->rating) || 71 (dev->features & CLOCK_EVT_FEAT_C3STOP)) 72 return 0; 73 74 clockevents_exchange_device(NULL, dev); 75 tick_broadcast_device.evtdev = dev; 76 if (!cpumask_empty(tick_get_broadcast_mask())) 77 tick_broadcast_start_periodic(dev); 78 return 1; 79} 80 81/* 82 * Check, if the device is the broadcast device 83 */ 84int tick_is_broadcast_device(struct clock_event_device *dev) 85{ 86 return (dev && tick_broadcast_device.evtdev == dev); 87} 88 89/* 90 * Check, if the device is disfunctional and a place holder, which 91 * needs to be handled by the broadcast device. 92 */ 93int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu) 94{ 95 unsigned long flags; 96 int ret = 0; 97 98 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 99 100 /* 101 * Devices might be registered with both periodic and oneshot 102 * mode disabled. This signals, that the device needs to be 103 * operated from the broadcast device and is a placeholder for 104 * the cpu local device. 105 */ 106 if (!tick_device_is_functional(dev)) { 107 dev->event_handler = tick_handle_periodic; 108 cpumask_set_cpu(cpu, tick_get_broadcast_mask()); 109 tick_broadcast_start_periodic(tick_broadcast_device.evtdev); 110 ret = 1; 111 } else { 112 /* 113 * When the new device is not affected by the stop 114 * feature and the cpu is marked in the broadcast mask 115 * then clear the broadcast bit. 116 */ 117 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) { 118 int cpu = smp_processor_id(); 119 120 cpumask_clear_cpu(cpu, tick_get_broadcast_mask()); 121 tick_broadcast_clear_oneshot(cpu); 122 } 123 } 124 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 125 return ret; 126} 127 128/* 129 * Broadcast the event to the cpus, which are set in the mask (mangled). 130 */ 131static void tick_do_broadcast(struct cpumask *mask) 132{ 133 int cpu = smp_processor_id(); 134 struct tick_device *td; 135 136 /* 137 * Check, if the current cpu is in the mask 138 */ 139 if (cpumask_test_cpu(cpu, mask)) { 140 cpumask_clear_cpu(cpu, mask); 141 td = &per_cpu(tick_cpu_device, cpu); 142 td->evtdev->event_handler(td->evtdev); 143 } 144 145 if (!cpumask_empty(mask)) { 146 /* 147 * It might be necessary to actually check whether the devices 148 * have different broadcast functions. For now, just use the 149 * one of the first device. This works as long as we have this 150 * misfeature only on x86 (lapic) 151 */ 152 td = &per_cpu(tick_cpu_device, cpumask_first(mask)); 153 td->evtdev->broadcast(mask); 154 } 155} 156 157/* 158 * Periodic broadcast: 159 * - invoke the broadcast handlers 160 */ 161static void tick_do_periodic_broadcast(void) 162{ 163 raw_spin_lock(&tick_broadcast_lock); 164 165 cpumask_and(to_cpumask(tmpmask), 166 cpu_online_mask, tick_get_broadcast_mask()); 167 tick_do_broadcast(to_cpumask(tmpmask)); 168 169 raw_spin_unlock(&tick_broadcast_lock); 170} 171 172/* 173 * Event handler for periodic broadcast ticks 174 */ 175static void tick_handle_periodic_broadcast(struct clock_event_device *dev) 176{ 177 ktime_t next; 178 179 tick_do_periodic_broadcast(); 180 181 /* 182 * The device is in periodic mode. No reprogramming necessary: 183 */ 184 if (dev->mode == CLOCK_EVT_MODE_PERIODIC) 185 return; 186 187 /* 188 * Setup the next period for devices, which do not have 189 * periodic mode. We read dev->next_event first and add to it 190 * when the event already expired. clockevents_program_event() 191 * sets dev->next_event only when the event is really 192 * programmed to the device. 193 */ 194 for (next = dev->next_event; ;) { 195 next = ktime_add(next, tick_period); 196 197 if (!clockevents_program_event(dev, next, ktime_get())) 198 return; 199 tick_do_periodic_broadcast(); 200 } 201} 202 203/* 204 * Powerstate information: The system enters/leaves a state, where 205 * affected devices might stop 206 */ 207static void tick_do_broadcast_on_off(unsigned long *reason) 208{ 209 struct clock_event_device *bc, *dev; 210 struct tick_device *td; 211 unsigned long flags; 212 int cpu, bc_stopped; 213 214 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 215 216 cpu = smp_processor_id(); 217 td = &per_cpu(tick_cpu_device, cpu); 218 dev = td->evtdev; 219 bc = tick_broadcast_device.evtdev; 220 221 /* 222 * Is the device not affected by the powerstate ? 223 */ 224 if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP)) 225 goto out; 226 227 if (!tick_device_is_functional(dev)) 228 goto out; 229 230 bc_stopped = cpumask_empty(tick_get_broadcast_mask()); 231 232 switch (*reason) { 233 case CLOCK_EVT_NOTIFY_BROADCAST_ON: 234 case CLOCK_EVT_NOTIFY_BROADCAST_FORCE: 235 if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) { 236 cpumask_set_cpu(cpu, tick_get_broadcast_mask()); 237 if (tick_broadcast_device.mode == 238 TICKDEV_MODE_PERIODIC) 239 clockevents_shutdown(dev); 240 } 241 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE) 242 tick_broadcast_force = 1; 243 break; 244 case CLOCK_EVT_NOTIFY_BROADCAST_OFF: 245 if (!tick_broadcast_force && 246 cpumask_test_cpu(cpu, tick_get_broadcast_mask())) { 247 cpumask_clear_cpu(cpu, tick_get_broadcast_mask()); 248 if (tick_broadcast_device.mode == 249 TICKDEV_MODE_PERIODIC) 250 tick_setup_periodic(dev, 0); 251 } 252 break; 253 } 254 255 if (cpumask_empty(tick_get_broadcast_mask())) { 256 if (!bc_stopped) 257 clockevents_shutdown(bc); 258 } else if (bc_stopped) { 259 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) 260 tick_broadcast_start_periodic(bc); 261 else 262 tick_broadcast_setup_oneshot(bc); 263 } 264out: 265 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 266} 267 268/* 269 * Powerstate information: The system enters/leaves a state, where 270 * affected devices might stop. 271 */ 272void tick_broadcast_on_off(unsigned long reason, int *oncpu) 273{ 274 if (!cpumask_test_cpu(*oncpu, cpu_online_mask)) 275 printk(KERN_ERR "tick-broadcast: ignoring broadcast for " 276 "offline CPU #%d\n", *oncpu); 277 else 278 tick_do_broadcast_on_off(&reason); 279} 280 281/* 282 * Set the periodic handler depending on broadcast on/off 283 */ 284void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast) 285{ 286 if (!broadcast) 287 dev->event_handler = tick_handle_periodic; 288 else 289 dev->event_handler = tick_handle_periodic_broadcast; 290} 291 292/* 293 * Remove a CPU from broadcasting 294 */ 295void tick_shutdown_broadcast(unsigned int *cpup) 296{ 297 struct clock_event_device *bc; 298 unsigned long flags; 299 unsigned int cpu = *cpup; 300 301 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 302 303 bc = tick_broadcast_device.evtdev; 304 cpumask_clear_cpu(cpu, tick_get_broadcast_mask()); 305 306 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) { 307 if (bc && cpumask_empty(tick_get_broadcast_mask())) 308 clockevents_shutdown(bc); 309 } 310 311 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 312} 313 314void tick_suspend_broadcast(void) 315{ 316 struct clock_event_device *bc; 317 unsigned long flags; 318 319 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 320 321 bc = tick_broadcast_device.evtdev; 322 if (bc) 323 clockevents_shutdown(bc); 324 325 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 326} 327 328int tick_resume_broadcast(void) 329{ 330 struct clock_event_device *bc; 331 unsigned long flags; 332 int broadcast = 0; 333 334 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 335 336 bc = tick_broadcast_device.evtdev; 337 338 if (bc) { 339 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME); 340 341 switch (tick_broadcast_device.mode) { 342 case TICKDEV_MODE_PERIODIC: 343 if (!cpumask_empty(tick_get_broadcast_mask())) 344 tick_broadcast_start_periodic(bc); 345 broadcast = cpumask_test_cpu(smp_processor_id(), 346 tick_get_broadcast_mask()); 347 break; 348 case TICKDEV_MODE_ONESHOT: 349 broadcast = tick_resume_broadcast_oneshot(bc); 350 break; 351 } 352 } 353 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 354 355 return broadcast; 356} 357 358 359#ifdef CONFIG_TICK_ONESHOT 360 361static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS); 362 363/* 364 * Exposed for debugging: see timer_list.c 365 */ 366struct cpumask *tick_get_broadcast_oneshot_mask(void) 367{ 368 return to_cpumask(tick_broadcast_oneshot_mask); 369} 370 371static int tick_broadcast_set_event(ktime_t expires, int force) 372{ 373 struct clock_event_device *bc = tick_broadcast_device.evtdev; 374 375 return tick_dev_program_event(bc, expires, force); 376} 377 378int tick_resume_broadcast_oneshot(struct clock_event_device *bc) 379{ 380 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); 381 return 0; 382} 383 384/* 385 * Called from irq_enter() when idle was interrupted to reenable the 386 * per cpu device. 387 */ 388void tick_check_oneshot_broadcast(int cpu) 389{ 390 if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) { 391 struct tick_device *td = &per_cpu(tick_cpu_device, cpu); 392 393 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT); 394 } 395} 396 397/* 398 * Handle oneshot mode broadcasting 399 */ 400static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) 401{ 402 struct tick_device *td; 403 ktime_t now, next_event; 404 int cpu; 405 406 raw_spin_lock(&tick_broadcast_lock); 407again: 408 dev->next_event.tv64 = KTIME_MAX; 409 next_event.tv64 = KTIME_MAX; 410 cpumask_clear(to_cpumask(tmpmask)); 411 now = ktime_get(); 412 /* Find all expired events */ 413 for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) { 414 td = &per_cpu(tick_cpu_device, cpu); 415 if (td->evtdev->next_event.tv64 <= now.tv64) 416 cpumask_set_cpu(cpu, to_cpumask(tmpmask)); 417 else if (td->evtdev->next_event.tv64 < next_event.tv64) 418 next_event.tv64 = td->evtdev->next_event.tv64; 419 } 420 421 /* 422 * Wakeup the cpus which have an expired event. 423 */ 424 tick_do_broadcast(to_cpumask(tmpmask)); 425 426 /* 427 * Two reasons for reprogram: 428 * 429 * - The global event did not expire any CPU local 430 * events. This happens in dyntick mode, as the maximum PIT 431 * delta is quite small. 432 * 433 * - There are pending events on sleeping CPUs which were not 434 * in the event mask 435 */ 436 if (next_event.tv64 != KTIME_MAX) { 437 /* 438 * Rearm the broadcast device. If event expired, 439 * repeat the above 440 */ 441 if (tick_broadcast_set_event(next_event, 0)) 442 goto again; 443 } 444 raw_spin_unlock(&tick_broadcast_lock); 445} 446 447/* 448 * Powerstate information: The system enters/leaves a state, where 449 * affected devices might stop 450 */ 451void tick_broadcast_oneshot_control(unsigned long reason) 452{ 453 struct clock_event_device *bc, *dev; 454 struct tick_device *td; 455 unsigned long flags; 456 int cpu; 457 458 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 459 460 /* 461 * Periodic mode does not care about the enter/exit of power 462 * states 463 */ 464 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) 465 goto out; 466 467 bc = tick_broadcast_device.evtdev; 468 cpu = smp_processor_id(); 469 td = &per_cpu(tick_cpu_device, cpu); 470 dev = td->evtdev; 471 472 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) 473 goto out; 474 475 if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) { 476 if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) { 477 cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask()); 478 clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); 479 if (dev->next_event.tv64 < bc->next_event.tv64) 480 tick_broadcast_set_event(dev->next_event, 1); 481 } 482 } else { 483 if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) { 484 cpumask_clear_cpu(cpu, 485 tick_get_broadcast_oneshot_mask()); 486 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 487 if (dev->next_event.tv64 != KTIME_MAX) 488 tick_program_event(dev->next_event, 1); 489 } 490 } 491 492out: 493 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 494} 495 496/* 497 * Reset the one shot broadcast for a cpu 498 * 499 * Called with tick_broadcast_lock held 500 */ 501static void tick_broadcast_clear_oneshot(int cpu) 502{ 503 cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask()); 504} 505 506static void tick_broadcast_init_next_event(struct cpumask *mask, 507 ktime_t expires) 508{ 509 struct tick_device *td; 510 int cpu; 511 512 for_each_cpu(cpu, mask) { 513 td = &per_cpu(tick_cpu_device, cpu); 514 if (td->evtdev) 515 td->evtdev->next_event = expires; 516 } 517} 518 519/** 520 * tick_broadcast_setup_oneshot - setup the broadcast device 521 */ 522void tick_broadcast_setup_oneshot(struct clock_event_device *bc) 523{ 524 /* Set it up only once ! */ 525 if (bc->event_handler != tick_handle_oneshot_broadcast) { 526 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC; 527 int cpu = smp_processor_id(); 528 529 bc->event_handler = tick_handle_oneshot_broadcast; 530 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); 531 532 /* Take the do_timer update */ 533 tick_do_timer_cpu = cpu; 534 535 /* 536 * We must be careful here. There might be other CPUs 537 * waiting for periodic broadcast. We need to set the 538 * oneshot_mask bits for those and program the 539 * broadcast device to fire. 540 */ 541 cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask()); 542 cpumask_clear_cpu(cpu, to_cpumask(tmpmask)); 543 cpumask_or(tick_get_broadcast_oneshot_mask(), 544 tick_get_broadcast_oneshot_mask(), 545 to_cpumask(tmpmask)); 546 547 if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) { 548 tick_broadcast_init_next_event(to_cpumask(tmpmask), 549 tick_next_period); 550 tick_broadcast_set_event(tick_next_period, 1); 551 } else 552 bc->next_event.tv64 = KTIME_MAX; 553 } 554} 555 556/* 557 * Select oneshot operating mode for the broadcast device 558 */ 559void tick_broadcast_switch_to_oneshot(void) 560{ 561 struct clock_event_device *bc; 562 unsigned long flags; 563 564 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 565 566 tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; 567 bc = tick_broadcast_device.evtdev; 568 if (bc) 569 tick_broadcast_setup_oneshot(bc); 570 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 571} 572 573 574/* 575 * Remove a dead CPU from broadcasting 576 */ 577void tick_shutdown_broadcast_oneshot(unsigned int *cpup) 578{ 579 unsigned long flags; 580 unsigned int cpu = *cpup; 581 582 raw_spin_lock_irqsave(&tick_broadcast_lock, flags); 583 584 /* 585 * Clear the broadcast mask flag for the dead cpu, but do not 586 * stop the broadcast device! 587 */ 588 cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask()); 589 590 raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); 591} 592 593/* 594 * Check, whether the broadcast device is in one shot mode 595 */ 596int tick_broadcast_oneshot_active(void) 597{ 598 return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT; 599} 600 601#endif 602