xref: /openbmc/linux/arch/arm/common/bL_switcher.c (revision 0030c1d4)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
4  *
5  * Created by:	Nicolas Pitre, March 2012
6  * Copyright:	(C) 2012-2013  Linaro Limited
7  */
8 
9 #include <linux/atomic.h>
10 #include <linux/init.h>
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/sched/signal.h>
14 #include <uapi/linux/sched/types.h>
15 #include <linux/interrupt.h>
16 #include <linux/cpu_pm.h>
17 #include <linux/cpu.h>
18 #include <linux/cpumask.h>
19 #include <linux/kthread.h>
20 #include <linux/wait.h>
21 #include <linux/time.h>
22 #include <linux/clockchips.h>
23 #include <linux/hrtimer.h>
24 #include <linux/tick.h>
25 #include <linux/notifier.h>
26 #include <linux/mm.h>
27 #include <linux/mutex.h>
28 #include <linux/smp.h>
29 #include <linux/spinlock.h>
30 #include <linux/string.h>
31 #include <linux/sysfs.h>
32 #include <linux/irqchip/arm-gic.h>
33 #include <linux/moduleparam.h>
34 
35 #include <asm/smp_plat.h>
36 #include <asm/cputype.h>
37 #include <asm/suspend.h>
38 #include <asm/mcpm.h>
39 #include <asm/bL_switcher.h>
40 
41 #define CREATE_TRACE_POINTS
42 #include <trace/events/power_cpu_migrate.h>
43 
44 
45 /*
46  * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
47  * __attribute_const__ and we don't want the compiler to assume any
48  * constness here as the value _does_ change along some code paths.
49  */
50 
read_mpidr(void)51 static int read_mpidr(void)
52 {
53 	unsigned int id;
54 	asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
55 	return id & MPIDR_HWID_BITMASK;
56 }
57 
58 /*
59  * bL switcher core code.
60  */
61 
bL_do_switch(void * _arg)62 static void bL_do_switch(void *_arg)
63 {
64 	unsigned ib_mpidr, ib_cpu, ib_cluster;
65 	long volatile handshake, **handshake_ptr = _arg;
66 
67 	pr_debug("%s\n", __func__);
68 
69 	ib_mpidr = cpu_logical_map(smp_processor_id());
70 	ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
71 	ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
72 
73 	/* Advertise our handshake location */
74 	if (handshake_ptr) {
75 		handshake = 0;
76 		*handshake_ptr = &handshake;
77 	} else
78 		handshake = -1;
79 
80 	/*
81 	 * Our state has been saved at this point.  Let's release our
82 	 * inbound CPU.
83 	 */
84 	mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
85 	sev();
86 
87 	/*
88 	 * From this point, we must assume that our counterpart CPU might
89 	 * have taken over in its parallel world already, as if execution
90 	 * just returned from cpu_suspend().  It is therefore important to
91 	 * be very careful not to make any change the other guy is not
92 	 * expecting.  This is why we need stack isolation.
93 	 *
94 	 * Fancy under cover tasks could be performed here.  For now
95 	 * we have none.
96 	 */
97 
98 	/*
99 	 * Let's wait until our inbound is alive.
100 	 */
101 	while (!handshake) {
102 		wfe();
103 		smp_mb();
104 	}
105 
106 	/* Let's put ourself down. */
107 	mcpm_cpu_power_down();
108 
109 	/* should never get here */
110 	BUG();
111 }
112 
113 /*
114  * Stack isolation.  To ensure 'current' remains valid, we just use another
115  * piece of our thread's stack space which should be fairly lightly used.
116  * The selected area starts just above the thread_info structure located
117  * at the very bottom of the stack, aligned to a cache line, and indexed
118  * with the cluster number.
119  */
120 #define STACK_SIZE 512
121 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
bL_switchpoint(unsigned long _arg)122 static int bL_switchpoint(unsigned long _arg)
123 {
124 	unsigned int mpidr = read_mpidr();
125 	unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
126 	void *stack = current_thread_info() + 1;
127 	stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
128 	stack += clusterid * STACK_SIZE + STACK_SIZE;
129 	call_with_stack(bL_do_switch, (void *)_arg, stack);
130 	BUG();
131 }
132 
133 /*
134  * Generic switcher interface
135  */
136 
137 static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
138 static int bL_switcher_cpu_pairing[NR_CPUS];
139 
140 /*
141  * bL_switch_to - Switch to a specific cluster for the current CPU
142  * @new_cluster_id: the ID of the cluster to switch to.
143  *
144  * This function must be called on the CPU to be switched.
145  * Returns 0 on success, else a negative status code.
146  */
bL_switch_to(unsigned int new_cluster_id)147 static int bL_switch_to(unsigned int new_cluster_id)
148 {
149 	unsigned int mpidr, this_cpu, that_cpu;
150 	unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
151 	struct completion inbound_alive;
152 	long volatile *handshake_ptr;
153 	int ipi_nr, ret;
154 
155 	this_cpu = smp_processor_id();
156 	ob_mpidr = read_mpidr();
157 	ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
158 	ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
159 	BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
160 
161 	if (new_cluster_id == ob_cluster)
162 		return 0;
163 
164 	that_cpu = bL_switcher_cpu_pairing[this_cpu];
165 	ib_mpidr = cpu_logical_map(that_cpu);
166 	ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
167 	ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
168 
169 	pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
170 		 this_cpu, ob_mpidr, ib_mpidr);
171 
172 	this_cpu = smp_processor_id();
173 
174 	/* Close the gate for our entry vectors */
175 	mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
176 	mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
177 
178 	/* Install our "inbound alive" notifier. */
179 	init_completion(&inbound_alive);
180 	ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
181 	ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
182 	mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
183 
184 	/*
185 	 * Let's wake up the inbound CPU now in case it requires some delay
186 	 * to come online, but leave it gated in our entry vector code.
187 	 */
188 	ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
189 	if (ret) {
190 		pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
191 		return ret;
192 	}
193 
194 	/*
195 	 * Raise a SGI on the inbound CPU to make sure it doesn't stall
196 	 * in a possible WFI, such as in bL_power_down().
197 	 */
198 	gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
199 
200 	/*
201 	 * Wait for the inbound to come up.  This allows for other
202 	 * tasks to be scheduled in the mean time.
203 	 */
204 	wait_for_completion(&inbound_alive);
205 	mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
206 
207 	/*
208 	 * From this point we are entering the switch critical zone
209 	 * and can't take any interrupts anymore.
210 	 */
211 	local_irq_disable();
212 	local_fiq_disable();
213 	trace_cpu_migrate_begin(ktime_get_real_ns(), ob_mpidr);
214 
215 	/* redirect GIC's SGIs to our counterpart */
216 	gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
217 
218 	tick_suspend_local();
219 
220 	ret = cpu_pm_enter();
221 
222 	/* we can not tolerate errors at this point */
223 	if (ret)
224 		panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
225 
226 	/* Swap the physical CPUs in the logical map for this logical CPU. */
227 	cpu_logical_map(this_cpu) = ib_mpidr;
228 	cpu_logical_map(that_cpu) = ob_mpidr;
229 
230 	/* Let's do the actual CPU switch. */
231 	ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
232 	if (ret > 0)
233 		panic("%s: cpu_suspend() returned %d\n", __func__, ret);
234 
235 	/* We are executing on the inbound CPU at this point */
236 	mpidr = read_mpidr();
237 	pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
238 	BUG_ON(mpidr != ib_mpidr);
239 
240 	mcpm_cpu_powered_up();
241 
242 	ret = cpu_pm_exit();
243 
244 	tick_resume_local();
245 
246 	trace_cpu_migrate_finish(ktime_get_real_ns(), ib_mpidr);
247 	local_fiq_enable();
248 	local_irq_enable();
249 
250 	*handshake_ptr = 1;
251 	dsb_sev();
252 
253 	if (ret)
254 		pr_err("%s exiting with error %d\n", __func__, ret);
255 	return ret;
256 }
257 
258 struct bL_thread {
259 	spinlock_t lock;
260 	struct task_struct *task;
261 	wait_queue_head_t wq;
262 	int wanted_cluster;
263 	struct completion started;
264 	bL_switch_completion_handler completer;
265 	void *completer_cookie;
266 };
267 
268 static struct bL_thread bL_threads[NR_CPUS];
269 
bL_switcher_thread(void * arg)270 static int bL_switcher_thread(void *arg)
271 {
272 	struct bL_thread *t = arg;
273 	int cluster;
274 	bL_switch_completion_handler completer;
275 	void *completer_cookie;
276 
277 	sched_set_fifo_low(current);
278 	complete(&t->started);
279 
280 	do {
281 		if (signal_pending(current))
282 			flush_signals(current);
283 		wait_event_interruptible(t->wq,
284 				t->wanted_cluster != -1 ||
285 				kthread_should_stop());
286 
287 		spin_lock(&t->lock);
288 		cluster = t->wanted_cluster;
289 		completer = t->completer;
290 		completer_cookie = t->completer_cookie;
291 		t->wanted_cluster = -1;
292 		t->completer = NULL;
293 		spin_unlock(&t->lock);
294 
295 		if (cluster != -1) {
296 			bL_switch_to(cluster);
297 
298 			if (completer)
299 				completer(completer_cookie);
300 		}
301 	} while (!kthread_should_stop());
302 
303 	return 0;
304 }
305 
bL_switcher_thread_create(int cpu,void * arg)306 static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
307 {
308 	struct task_struct *task;
309 
310 	task = kthread_create_on_node(bL_switcher_thread, arg,
311 				      cpu_to_node(cpu), "kswitcher_%d", cpu);
312 	if (!IS_ERR(task)) {
313 		kthread_bind(task, cpu);
314 		wake_up_process(task);
315 	} else
316 		pr_err("%s failed for CPU %d\n", __func__, cpu);
317 	return task;
318 }
319 
320 /*
321  * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
322  *      with completion notification via a callback
323  *
324  * @cpu: the CPU to switch
325  * @new_cluster_id: the ID of the cluster to switch to.
326  * @completer: switch completion callback.  if non-NULL,
327  *	@completer(@completer_cookie) will be called on completion of
328  *	the switch, in non-atomic context.
329  * @completer_cookie: opaque context argument for @completer.
330  *
331  * This function causes a cluster switch on the given CPU by waking up
332  * the appropriate switcher thread.  This function may or may not return
333  * before the switch has occurred.
334  *
335  * If a @completer callback function is supplied, it will be called when
336  * the switch is complete.  This can be used to determine asynchronously
337  * when the switch is complete, regardless of when bL_switch_request()
338  * returns.  When @completer is supplied, no new switch request is permitted
339  * for the affected CPU until after the switch is complete, and @completer
340  * has returned.
341  */
bL_switch_request_cb(unsigned int cpu,unsigned int new_cluster_id,bL_switch_completion_handler completer,void * completer_cookie)342 int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
343 			 bL_switch_completion_handler completer,
344 			 void *completer_cookie)
345 {
346 	struct bL_thread *t;
347 
348 	if (cpu >= ARRAY_SIZE(bL_threads)) {
349 		pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
350 		return -EINVAL;
351 	}
352 
353 	t = &bL_threads[cpu];
354 
355 	if (IS_ERR(t->task))
356 		return PTR_ERR(t->task);
357 	if (!t->task)
358 		return -ESRCH;
359 
360 	spin_lock(&t->lock);
361 	if (t->completer) {
362 		spin_unlock(&t->lock);
363 		return -EBUSY;
364 	}
365 	t->completer = completer;
366 	t->completer_cookie = completer_cookie;
367 	t->wanted_cluster = new_cluster_id;
368 	spin_unlock(&t->lock);
369 	wake_up(&t->wq);
370 	return 0;
371 }
372 EXPORT_SYMBOL_GPL(bL_switch_request_cb);
373 
374 /*
375  * Activation and configuration code.
376  */
377 
378 static DEFINE_MUTEX(bL_switcher_activation_lock);
379 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
380 static unsigned int bL_switcher_active;
381 static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
382 static cpumask_t bL_switcher_removed_logical_cpus;
383 
bL_switcher_register_notifier(struct notifier_block * nb)384 int bL_switcher_register_notifier(struct notifier_block *nb)
385 {
386 	return blocking_notifier_chain_register(&bL_activation_notifier, nb);
387 }
388 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
389 
bL_switcher_unregister_notifier(struct notifier_block * nb)390 int bL_switcher_unregister_notifier(struct notifier_block *nb)
391 {
392 	return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
393 }
394 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
395 
bL_activation_notify(unsigned long val)396 static int bL_activation_notify(unsigned long val)
397 {
398 	int ret;
399 
400 	ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
401 	if (ret & NOTIFY_STOP_MASK)
402 		pr_err("%s: notifier chain failed with status 0x%x\n",
403 			__func__, ret);
404 	return notifier_to_errno(ret);
405 }
406 
bL_switcher_restore_cpus(void)407 static void bL_switcher_restore_cpus(void)
408 {
409 	int i;
410 
411 	for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
412 		struct device *cpu_dev = get_cpu_device(i);
413 		int ret = device_online(cpu_dev);
414 		if (ret)
415 			dev_err(cpu_dev, "switcher: unable to restore CPU\n");
416 	}
417 }
418 
bL_switcher_halve_cpus(void)419 static int bL_switcher_halve_cpus(void)
420 {
421 	int i, j, cluster_0, gic_id, ret;
422 	unsigned int cpu, cluster, mask;
423 	cpumask_t available_cpus;
424 
425 	/* First pass to validate what we have */
426 	mask = 0;
427 	for_each_online_cpu(i) {
428 		cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
429 		cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
430 		if (cluster >= 2) {
431 			pr_err("%s: only dual cluster systems are supported\n", __func__);
432 			return -EINVAL;
433 		}
434 		if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
435 			return -EINVAL;
436 		mask |= (1 << cluster);
437 	}
438 	if (mask != 3) {
439 		pr_err("%s: no CPU pairing possible\n", __func__);
440 		return -EINVAL;
441 	}
442 
443 	/*
444 	 * Now let's do the pairing.  We match each CPU with another CPU
445 	 * from a different cluster.  To get a uniform scheduling behavior
446 	 * without fiddling with CPU topology and compute capacity data,
447 	 * we'll use logical CPUs initially belonging to the same cluster.
448 	 */
449 	memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
450 	cpumask_copy(&available_cpus, cpu_online_mask);
451 	cluster_0 = -1;
452 	for_each_cpu(i, &available_cpus) {
453 		int match = -1;
454 		cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
455 		if (cluster_0 == -1)
456 			cluster_0 = cluster;
457 		if (cluster != cluster_0)
458 			continue;
459 		cpumask_clear_cpu(i, &available_cpus);
460 		for_each_cpu(j, &available_cpus) {
461 			cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
462 			/*
463 			 * Let's remember the last match to create "odd"
464 			 * pairings on purpose in order for other code not
465 			 * to assume any relation between physical and
466 			 * logical CPU numbers.
467 			 */
468 			if (cluster != cluster_0)
469 				match = j;
470 		}
471 		if (match != -1) {
472 			bL_switcher_cpu_pairing[i] = match;
473 			cpumask_clear_cpu(match, &available_cpus);
474 			pr_info("CPU%d paired with CPU%d\n", i, match);
475 		}
476 	}
477 
478 	/*
479 	 * Now we disable the unwanted CPUs i.e. everything that has no
480 	 * pairing information (that includes the pairing counterparts).
481 	 */
482 	cpumask_clear(&bL_switcher_removed_logical_cpus);
483 	for_each_online_cpu(i) {
484 		cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
485 		cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
486 
487 		/* Let's take note of the GIC ID for this CPU */
488 		gic_id = gic_get_cpu_id(i);
489 		if (gic_id < 0) {
490 			pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
491 			bL_switcher_restore_cpus();
492 			return -EINVAL;
493 		}
494 		bL_gic_id[cpu][cluster] = gic_id;
495 		pr_info("GIC ID for CPU %u cluster %u is %u\n",
496 			cpu, cluster, gic_id);
497 
498 		if (bL_switcher_cpu_pairing[i] != -1) {
499 			bL_switcher_cpu_original_cluster[i] = cluster;
500 			continue;
501 		}
502 
503 		ret = device_offline(get_cpu_device(i));
504 		if (ret) {
505 			bL_switcher_restore_cpus();
506 			return ret;
507 		}
508 		cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
509 	}
510 
511 	return 0;
512 }
513 
514 /* Determine the logical CPU a given physical CPU is grouped on. */
bL_switcher_get_logical_index(u32 mpidr)515 int bL_switcher_get_logical_index(u32 mpidr)
516 {
517 	int cpu;
518 
519 	if (!bL_switcher_active)
520 		return -EUNATCH;
521 
522 	mpidr &= MPIDR_HWID_BITMASK;
523 	for_each_online_cpu(cpu) {
524 		int pairing = bL_switcher_cpu_pairing[cpu];
525 		if (pairing == -1)
526 			continue;
527 		if ((mpidr == cpu_logical_map(cpu)) ||
528 		    (mpidr == cpu_logical_map(pairing)))
529 			return cpu;
530 	}
531 	return -EINVAL;
532 }
533 
bL_switcher_trace_trigger_cpu(void * __always_unused info)534 static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
535 {
536 	trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr());
537 }
538 
bL_switcher_trace_trigger(void)539 int bL_switcher_trace_trigger(void)
540 {
541 	preempt_disable();
542 
543 	bL_switcher_trace_trigger_cpu(NULL);
544 	smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
545 
546 	preempt_enable();
547 
548 	return 0;
549 }
550 EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
551 
bL_switcher_enable(void)552 static int bL_switcher_enable(void)
553 {
554 	int cpu, ret;
555 
556 	mutex_lock(&bL_switcher_activation_lock);
557 	lock_device_hotplug();
558 	if (bL_switcher_active) {
559 		unlock_device_hotplug();
560 		mutex_unlock(&bL_switcher_activation_lock);
561 		return 0;
562 	}
563 
564 	pr_info("big.LITTLE switcher initializing\n");
565 
566 	ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
567 	if (ret)
568 		goto error;
569 
570 	ret = bL_switcher_halve_cpus();
571 	if (ret)
572 		goto error;
573 
574 	bL_switcher_trace_trigger();
575 
576 	for_each_online_cpu(cpu) {
577 		struct bL_thread *t = &bL_threads[cpu];
578 		spin_lock_init(&t->lock);
579 		init_waitqueue_head(&t->wq);
580 		init_completion(&t->started);
581 		t->wanted_cluster = -1;
582 		t->task = bL_switcher_thread_create(cpu, t);
583 	}
584 
585 	bL_switcher_active = 1;
586 	bL_activation_notify(BL_NOTIFY_POST_ENABLE);
587 	pr_info("big.LITTLE switcher initialized\n");
588 	goto out;
589 
590 error:
591 	pr_warn("big.LITTLE switcher initialization failed\n");
592 	bL_activation_notify(BL_NOTIFY_POST_DISABLE);
593 
594 out:
595 	unlock_device_hotplug();
596 	mutex_unlock(&bL_switcher_activation_lock);
597 	return ret;
598 }
599 
600 #ifdef CONFIG_SYSFS
601 
bL_switcher_disable(void)602 static void bL_switcher_disable(void)
603 {
604 	unsigned int cpu, cluster;
605 	struct bL_thread *t;
606 	struct task_struct *task;
607 
608 	mutex_lock(&bL_switcher_activation_lock);
609 	lock_device_hotplug();
610 
611 	if (!bL_switcher_active)
612 		goto out;
613 
614 	if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
615 		bL_activation_notify(BL_NOTIFY_POST_ENABLE);
616 		goto out;
617 	}
618 
619 	bL_switcher_active = 0;
620 
621 	/*
622 	 * To deactivate the switcher, we must shut down the switcher
623 	 * threads to prevent any other requests from being accepted.
624 	 * Then, if the final cluster for given logical CPU is not the
625 	 * same as the original one, we'll recreate a switcher thread
626 	 * just for the purpose of switching the CPU back without any
627 	 * possibility for interference from external requests.
628 	 */
629 	for_each_online_cpu(cpu) {
630 		t = &bL_threads[cpu];
631 		task = t->task;
632 		t->task = NULL;
633 		if (!task || IS_ERR(task))
634 			continue;
635 		kthread_stop(task);
636 		/* no more switch may happen on this CPU at this point */
637 		cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
638 		if (cluster == bL_switcher_cpu_original_cluster[cpu])
639 			continue;
640 		init_completion(&t->started);
641 		t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
642 		task = bL_switcher_thread_create(cpu, t);
643 		if (!IS_ERR(task)) {
644 			wait_for_completion(&t->started);
645 			kthread_stop(task);
646 			cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
647 			if (cluster == bL_switcher_cpu_original_cluster[cpu])
648 				continue;
649 		}
650 		/* If execution gets here, we're in trouble. */
651 		pr_crit("%s: unable to restore original cluster for CPU %d\n",
652 			__func__, cpu);
653 		pr_crit("%s: CPU %d can't be restored\n",
654 			__func__, bL_switcher_cpu_pairing[cpu]);
655 		cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
656 				  &bL_switcher_removed_logical_cpus);
657 	}
658 
659 	bL_switcher_restore_cpus();
660 	bL_switcher_trace_trigger();
661 
662 	bL_activation_notify(BL_NOTIFY_POST_DISABLE);
663 
664 out:
665 	unlock_device_hotplug();
666 	mutex_unlock(&bL_switcher_activation_lock);
667 }
668 
bL_switcher_active_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)669 static ssize_t bL_switcher_active_show(struct kobject *kobj,
670 		struct kobj_attribute *attr, char *buf)
671 {
672 	return sprintf(buf, "%u\n", bL_switcher_active);
673 }
674 
bL_switcher_active_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)675 static ssize_t bL_switcher_active_store(struct kobject *kobj,
676 		struct kobj_attribute *attr, const char *buf, size_t count)
677 {
678 	int ret;
679 
680 	switch (buf[0]) {
681 	case '0':
682 		bL_switcher_disable();
683 		ret = 0;
684 		break;
685 	case '1':
686 		ret = bL_switcher_enable();
687 		break;
688 	default:
689 		ret = -EINVAL;
690 	}
691 
692 	return (ret >= 0) ? count : ret;
693 }
694 
bL_switcher_trace_trigger_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)695 static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj,
696 		struct kobj_attribute *attr, const char *buf, size_t count)
697 {
698 	int ret = bL_switcher_trace_trigger();
699 
700 	return ret ? ret : count;
701 }
702 
703 static struct kobj_attribute bL_switcher_active_attr =
704 	__ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
705 
706 static struct kobj_attribute bL_switcher_trace_trigger_attr =
707 	__ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
708 
709 static struct attribute *bL_switcher_attrs[] = {
710 	&bL_switcher_active_attr.attr,
711 	&bL_switcher_trace_trigger_attr.attr,
712 	NULL,
713 };
714 
715 static struct attribute_group bL_switcher_attr_group = {
716 	.attrs = bL_switcher_attrs,
717 };
718 
719 static struct kobject *bL_switcher_kobj;
720 
bL_switcher_sysfs_init(void)721 static int __init bL_switcher_sysfs_init(void)
722 {
723 	int ret;
724 
725 	bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
726 	if (!bL_switcher_kobj)
727 		return -ENOMEM;
728 	ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
729 	if (ret)
730 		kobject_put(bL_switcher_kobj);
731 	return ret;
732 }
733 
734 #endif  /* CONFIG_SYSFS */
735 
bL_switcher_get_enabled(void)736 bool bL_switcher_get_enabled(void)
737 {
738 	mutex_lock(&bL_switcher_activation_lock);
739 
740 	return bL_switcher_active;
741 }
742 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
743 
bL_switcher_put_enabled(void)744 void bL_switcher_put_enabled(void)
745 {
746 	mutex_unlock(&bL_switcher_activation_lock);
747 }
748 EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
749 
750 /*
751  * Veto any CPU hotplug operation on those CPUs we've removed
752  * while the switcher is active.
753  * We're just not ready to deal with that given the trickery involved.
754  */
bL_switcher_cpu_pre(unsigned int cpu)755 static int bL_switcher_cpu_pre(unsigned int cpu)
756 {
757 	int pairing;
758 
759 	if (!bL_switcher_active)
760 		return 0;
761 
762 	pairing = bL_switcher_cpu_pairing[cpu];
763 
764 	if (pairing == -1)
765 		return -EINVAL;
766 	return 0;
767 }
768 
769 static bool no_bL_switcher;
770 core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
771 
bL_switcher_init(void)772 static int __init bL_switcher_init(void)
773 {
774 	int ret;
775 
776 	if (!mcpm_is_available())
777 		return -ENODEV;
778 
779 	cpuhp_setup_state_nocalls(CPUHP_ARM_BL_PREPARE, "arm/bl:prepare",
780 				  bL_switcher_cpu_pre, NULL);
781 	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "arm/bl:predown",
782 					NULL, bL_switcher_cpu_pre);
783 	if (ret < 0) {
784 		cpuhp_remove_state_nocalls(CPUHP_ARM_BL_PREPARE);
785 		pr_err("bL_switcher: Failed to allocate a hotplug state\n");
786 		return ret;
787 	}
788 	if (!no_bL_switcher) {
789 		ret = bL_switcher_enable();
790 		if (ret)
791 			return ret;
792 	}
793 
794 #ifdef CONFIG_SYSFS
795 	ret = bL_switcher_sysfs_init();
796 	if (ret)
797 		pr_err("%s: unable to create sysfs entry\n", __func__);
798 #endif
799 
800 	return 0;
801 }
802 
803 late_initcall(bL_switcher_init);
804