tick-broadcast.c 15.6 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
/*
 * linux/kernel/time/tick-broadcast.c
 *
 * This file contains functions which emulate a local clock-event
 * device via a broadcast event source.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 *
 * This code is licenced under the GPL version 2. For details see
 * kernel-base/COPYING.
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
17
#include <linux/interrupt.h>
18 19 20 21 22 23 24 25 26 27 28
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>

#include "tick-internal.h"

/*
 * Broadcast support for broken x86 hardware, where the local apic
 * timer stops in C3 state.
 */

29
static struct tick_device tick_broadcast_device;
30 31 32
/* FIXME: Use cpumask_var_t. */
static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
static DECLARE_BITMAP(tmpmask, NR_CPUS);
33
static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
34
static int tick_broadcast_force;
35

36 37 38 39 40 41
#ifdef CONFIG_TICK_ONESHOT
static void tick_broadcast_clear_oneshot(int cpu);
#else
static inline void tick_broadcast_clear_oneshot(int cpu) { }
#endif

42 43 44 45 46 47 48 49
/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_broadcast_device(void)
{
	return &tick_broadcast_device;
}

50
struct cpumask *tick_get_broadcast_mask(void)
51
{
52
	return to_cpumask(tick_broadcast_mask);
53 54
}

55 56 57 58 59
/*
 * Start the device in periodic mode
 */
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
T
Thomas Gleixner 已提交
60
	if (bc)
61 62 63 64 65 66 67 68
		tick_setup_periodic(bc, 1);
}

/*
 * Check, if the device can be utilized as broadcast device:
 */
int tick_check_broadcast_device(struct clock_event_device *dev)
{
69 70 71
	if ((tick_broadcast_device.evtdev &&
	     tick_broadcast_device.evtdev->rating >= dev->rating) ||
	     (dev->features & CLOCK_EVT_FEAT_C3STOP))
72 73
		return 0;

74
	clockevents_exchange_device(tick_broadcast_device.evtdev, dev);
75
	tick_broadcast_device.evtdev = dev;
76
	if (!cpumask_empty(tick_get_broadcast_mask()))
77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
		tick_broadcast_start_periodic(dev);
	return 1;
}

/*
 * Check, if the device is the broadcast device
 */
int tick_is_broadcast_device(struct clock_event_device *dev)
{
	return (dev && tick_broadcast_device.evtdev == dev);
}

/*
 * Check, if the device is disfunctional and a place holder, which
 * needs to be handled by the broadcast device.
 */
int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
{
	unsigned long flags;
	int ret = 0;

98
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
99 100 101 102 103 104 105 106 107

	/*
	 * Devices might be registered with both periodic and oneshot
	 * mode disabled. This signals, that the device needs to be
	 * operated from the broadcast device and is a placeholder for
	 * the cpu local device.
	 */
	if (!tick_device_is_functional(dev)) {
		dev->event_handler = tick_handle_periodic;
108
		cpumask_set_cpu(cpu, tick_get_broadcast_mask());
109 110
		tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
		ret = 1;
111 112 113 114 115 116 117 118
	} else {
		/*
		 * When the new device is not affected by the stop
		 * feature and the cpu is marked in the broadcast mask
		 * then clear the broadcast bit.
		 */
		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
			int cpu = smp_processor_id();
119

120
			cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
121 122 123
			tick_broadcast_clear_oneshot(cpu);
		}
	}
124
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
125 126 127 128
	return ret;
}

/*
129
 * Broadcast the event to the cpus, which are set in the mask (mangled).
130
 */
131
static void tick_do_broadcast(struct cpumask *mask)
132
{
133
	int cpu = smp_processor_id();
134 135 136 137 138
	struct tick_device *td;

	/*
	 * Check, if the current cpu is in the mask
	 */
139 140
	if (cpumask_test_cpu(cpu, mask)) {
		cpumask_clear_cpu(cpu, mask);
141 142 143 144
		td = &per_cpu(tick_cpu_device, cpu);
		td->evtdev->event_handler(td->evtdev);
	}

145
	if (!cpumask_empty(mask)) {
146 147 148 149 150 151
		/*
		 * It might be necessary to actually check whether the devices
		 * have different broadcast functions. For now, just use the
		 * one of the first device. This works as long as we have this
		 * misfeature only on x86 (lapic)
		 */
152 153
		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
		td->evtdev->broadcast(mask);
154 155 156 157 158 159 160 161 162
	}
}

/*
 * Periodic broadcast:
 * - invoke the broadcast handlers
 */
static void tick_do_periodic_broadcast(void)
{
163
	raw_spin_lock(&tick_broadcast_lock);
164

165 166 167
	cpumask_and(to_cpumask(tmpmask),
		    cpu_online_mask, tick_get_broadcast_mask());
	tick_do_broadcast(to_cpumask(tmpmask));
168

169
	raw_spin_unlock(&tick_broadcast_lock);
170 171 172 173 174 175 176
}

/*
 * Event handler for periodic broadcast ticks
 */
static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
{
177 178
	ktime_t next;

179 180 181 182 183 184 185 186 187 188
	tick_do_periodic_broadcast();

	/*
	 * The device is in periodic mode. No reprogramming necessary:
	 */
	if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
		return;

	/*
	 * 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()
191 192
	 * sets dev->next_event only when the event is really
	 * programmed to the device.
193
	 */
194 195
	for (next = dev->next_event; ;) {
		next = ktime_add(next, tick_period);
196

197
		if (!clockevents_program_event(dev, next, false))
198 199 200 201 202 203 204 205 206
			return;
		tick_do_periodic_broadcast();
	}
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop
 */
207
static void tick_do_broadcast_on_off(unsigned long *reason)
208 209 210
{
	struct clock_event_device *bc, *dev;
	struct tick_device *td;
211
	unsigned long flags;
212
	int cpu, bc_stopped;
213

214
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
215 216 217 218 219 220 221

	cpu = smp_processor_id();
	td = &per_cpu(tick_cpu_device, cpu);
	dev = td->evtdev;
	bc = tick_broadcast_device.evtdev;

	/*
222
	 * Is the device not affected by the powerstate ?
223
	 */
224
	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
225 226
		goto out;

227 228
	if (!tick_device_is_functional(dev))
		goto out;
229

230
	bc_stopped = cpumask_empty(tick_get_broadcast_mask());
231

232 233 234
	switch (*reason) {
	case CLOCK_EVT_NOTIFY_BROADCAST_ON:
	case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
235 236
		if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
			cpumask_set_cpu(cpu, tick_get_broadcast_mask());
237 238
			if (tick_broadcast_device.mode ==
			    TICKDEV_MODE_PERIODIC)
239
				clockevents_shutdown(dev);
240
		}
241
		if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
242
			tick_broadcast_force = 1;
243 244
		break;
	case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
245
		if (!tick_broadcast_force &&
246 247
		    cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
			cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
248 249
			if (tick_broadcast_device.mode ==
			    TICKDEV_MODE_PERIODIC)
250 251
				tick_setup_periodic(dev, 0);
		}
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) {
259 260
		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
			tick_broadcast_start_periodic(bc);
261 262
		else
			tick_broadcast_setup_oneshot(bc);
263 264
	}
out:
265
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
266 267 268 269 270 271 272 273
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop.
 */
void tick_broadcast_on_off(unsigned long reason, int *oncpu)
{
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);
279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
}

/*
 * Set the periodic handler depending on broadcast on/off
 */
void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
{
	if (!broadcast)
		dev->event_handler = tick_handle_periodic;
	else
		dev->event_handler = tick_handle_periodic_broadcast;
}

/*
 * Remove a CPU from broadcasting
 */
void tick_shutdown_broadcast(unsigned int *cpup)
{
	struct clock_event_device *bc;
	unsigned long flags;
	unsigned int cpu = *cpup;

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

314 315 316 317 318
void tick_suspend_broadcast(void)
{
	struct clock_event_device *bc;
	unsigned long flags;

319
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
320 321

	bc = tick_broadcast_device.evtdev;
T
Thomas Gleixner 已提交
322
	if (bc)
323
		clockevents_shutdown(bc);
324

325
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
326 327 328 329 330 331 332 333
}

int tick_resume_broadcast(void)
{
	struct clock_event_device *bc;
	unsigned long flags;
	int broadcast = 0;

334
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
335 336 337

	bc = tick_broadcast_device.evtdev;

338
	if (bc) {
T
Thomas Gleixner 已提交
339 340
		clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);

341 342
		switch (tick_broadcast_device.mode) {
		case TICKDEV_MODE_PERIODIC:
343
			if (!cpumask_empty(tick_get_broadcast_mask()))
344
				tick_broadcast_start_periodic(bc);
345 346
			broadcast = cpumask_test_cpu(smp_processor_id(),
						     tick_get_broadcast_mask());
347 348 349 350 351
			break;
		case TICKDEV_MODE_ONESHOT:
			broadcast = tick_resume_broadcast_oneshot(bc);
			break;
		}
352
	}
353
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
354 355 356 357 358

	return broadcast;
}


359 360
#ifdef CONFIG_TICK_ONESHOT

361 362
/* FIXME: use cpumask_var_t. */
static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
363

364
/*
365
 * Exposed for debugging: see timer_list.c
366
 */
367
struct cpumask *tick_get_broadcast_oneshot_mask(void)
368
{
369
	return to_cpumask(tick_broadcast_oneshot_mask);
370 371
}

372 373 374
static int tick_broadcast_set_event(ktime_t expires, int force)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;
375

376
	return clockevents_program_event(bc, expires, force);
377 378
}

379 380 381
int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
	clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
382
	return 0;
383 384
}

385 386 387 388 389 390
/*
 * Called from irq_enter() when idle was interrupted to reenable the
 * per cpu device.
 */
void tick_check_oneshot_broadcast(int cpu)
{
391
	if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
392 393 394 395 396 397
		struct tick_device *td = &per_cpu(tick_cpu_device, cpu);

		clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
	}
}

398 399 400 401 402 403
/*
 * Handle oneshot mode broadcasting
 */
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
{
	struct tick_device *td;
404
	ktime_t now, next_event;
405 406
	int cpu;

407
	raw_spin_lock(&tick_broadcast_lock);
408 409
again:
	dev->next_event.tv64 = KTIME_MAX;
410
	next_event.tv64 = KTIME_MAX;
411
	cpumask_clear(to_cpumask(tmpmask));
412 413
	now = ktime_get();
	/* Find all expired events */
414
	for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
415 416
		td = &per_cpu(tick_cpu_device, cpu);
		if (td->evtdev->next_event.tv64 <= now.tv64)
417
			cpumask_set_cpu(cpu, to_cpumask(tmpmask));
418 419
		else if (td->evtdev->next_event.tv64 < next_event.tv64)
			next_event.tv64 = td->evtdev->next_event.tv64;
420 421 422
	}

	/*
423 424
	 * Wakeup the cpus which have an expired event.
	 */
425
	tick_do_broadcast(to_cpumask(tmpmask));
426 427 428 429 430 431 432 433 434 435

	/*
	 * Two reasons for reprogram:
	 *
	 * - The global event did not expire any CPU local
	 * events. This happens in dyntick mode, as the maximum PIT
	 * delta is quite small.
	 *
	 * - There are pending events on sleeping CPUs which were not
	 * in the event mask
436
	 */
437
	if (next_event.tv64 != KTIME_MAX) {
438
		/*
439 440
		 * Rearm the broadcast device. If event expired,
		 * repeat the above
441
		 */
442
		if (tick_broadcast_set_event(next_event, 0))
443 444
			goto again;
	}
445
	raw_spin_unlock(&tick_broadcast_lock);
446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop
 */
void tick_broadcast_oneshot_control(unsigned long reason)
{
	struct clock_event_device *bc, *dev;
	struct tick_device *td;
	unsigned long flags;
	int cpu;

	/*
	 * Periodic mode does not care about the enter/exit of power
	 * states
	 */
	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
464
		return;
465

466 467 468 469
	/*
	 * We are called with preemtion disabled from the depth of the
	 * idle code, so we can't be moved away.
	 */
470 471 472 473 474
	cpu = smp_processor_id();
	td = &per_cpu(tick_cpu_device, cpu);
	dev = td->evtdev;

	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
475 476 477
		return;

	bc = tick_broadcast_device.evtdev;
478

479
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
480
	if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
481 482
		if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
			cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
483 484 485 486 487
			clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
			if (dev->next_event.tv64 < bc->next_event.tv64)
				tick_broadcast_set_event(dev->next_event, 1);
		}
	} else {
488 489 490
		if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
			cpumask_clear_cpu(cpu,
					  tick_get_broadcast_oneshot_mask());
491 492 493 494 495
			clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
			if (dev->next_event.tv64 != KTIME_MAX)
				tick_program_event(dev->next_event, 1);
		}
	}
496
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
497 498
}

499 500 501 502 503 504 505
/*
 * Reset the one shot broadcast for a cpu
 *
 * Called with tick_broadcast_lock held
 */
static void tick_broadcast_clear_oneshot(int cpu)
{
506
	cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
507 508
}

509 510
static void tick_broadcast_init_next_event(struct cpumask *mask,
					   ktime_t expires)
511 512 513 514
{
	struct tick_device *td;
	int cpu;

515
	for_each_cpu(cpu, mask) {
516 517 518 519 520 521
		td = &per_cpu(tick_cpu_device, cpu);
		if (td->evtdev)
			td->evtdev->next_event = expires;
	}
}

522
/**
523
 * tick_broadcast_setup_oneshot - setup the broadcast device
524 525 526
 */
void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
527 528
	int cpu = smp_processor_id();

529 530
	/* Set it up only once ! */
	if (bc->event_handler != tick_handle_oneshot_broadcast) {
531 532
		int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;

533 534
		bc->event_handler = tick_handle_oneshot_broadcast;
		clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
535 536 537 538 539 540 541 542 543 544

		/* Take the do_timer update */
		tick_do_timer_cpu = cpu;

		/*
		 * We must be careful here. There might be other CPUs
		 * waiting for periodic broadcast. We need to set the
		 * oneshot_mask bits for those and program the
		 * broadcast device to fire.
		 */
545 546 547 548 549 550 551 552 553
		cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
		cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
		cpumask_or(tick_get_broadcast_oneshot_mask(),
			   tick_get_broadcast_oneshot_mask(),
			   to_cpumask(tmpmask));

		if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
			tick_broadcast_init_next_event(to_cpumask(tmpmask),
						       tick_next_period);
554 555 556
			tick_broadcast_set_event(tick_next_period, 1);
		} else
			bc->next_event.tv64 = KTIME_MAX;
557 558 559 560 561 562 563 564 565
	} else {
		/*
		 * The first cpu which switches to oneshot mode sets
		 * the bit for all other cpus which are in the general
		 * (periodic) broadcast mask. So the bit is set and
		 * would prevent the first broadcast enter after this
		 * to program the bc device.
		 */
		tick_broadcast_clear_oneshot(cpu);
566
	}
567 568 569 570 571 572 573 574 575 576
}

/*
 * Select oneshot operating mode for the broadcast device
 */
void tick_broadcast_switch_to_oneshot(void)
{
	struct clock_event_device *bc;
	unsigned long flags;

577
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
578 579
	if (cpumask_empty(tick_get_broadcast_mask()))
		goto end;
580 581 582 583 584

	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
	bc = tick_broadcast_device.evtdev;
	if (bc)
		tick_broadcast_setup_oneshot(bc);
585 586

end:
587
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
588 589 590 591 592 593 594 595 596 597 598
}


/*
 * Remove a dead CPU from broadcasting
 */
void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
{
	unsigned long flags;
	unsigned int cpu = *cpup;

599
	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
600

601 602 603 604
	/*
	 * Clear the broadcast mask flag for the dead cpu, but do not
	 * stop the broadcast device!
	 */
605
	cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
606

607
	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
608 609
}

610 611 612 613 614 615 616 617
/*
 * Check, whether the broadcast device is in one shot mode
 */
int tick_broadcast_oneshot_active(void)
{
	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
}

618 619 620 621 622 623 624 625 626 627
/*
 * Check whether the broadcast device supports oneshot.
 */
bool tick_broadcast_oneshot_available(void)
{
	struct clock_event_device *bc = tick_broadcast_device.evtdev;

	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
}

628
#endif