Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / arch / arm / common / bL_switcher.c
blob57f3b751263616ebabea9142747d157ffec0f369
1 /*
2 * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
4 * Created by: Nicolas Pitre, March 2012
5 * Copyright: (C) 2012-2013 Linaro Limited
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
12 #include <linux/atomic.h>
13 #include <linux/init.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/sched/signal.h>
17 #include <uapi/linux/sched/types.h>
18 #include <linux/interrupt.h>
19 #include <linux/cpu_pm.h>
20 #include <linux/cpu.h>
21 #include <linux/cpumask.h>
22 #include <linux/kthread.h>
23 #include <linux/wait.h>
24 #include <linux/time.h>
25 #include <linux/clockchips.h>
26 #include <linux/hrtimer.h>
27 #include <linux/tick.h>
28 #include <linux/notifier.h>
29 #include <linux/mm.h>
30 #include <linux/mutex.h>
31 #include <linux/smp.h>
32 #include <linux/spinlock.h>
33 #include <linux/string.h>
34 #include <linux/sysfs.h>
35 #include <linux/irqchip/arm-gic.h>
36 #include <linux/moduleparam.h>
38 #include <asm/smp_plat.h>
39 #include <asm/cputype.h>
40 #include <asm/suspend.h>
41 #include <asm/mcpm.h>
42 #include <asm/bL_switcher.h>
44 #define CREATE_TRACE_POINTS
45 #include <trace/events/power_cpu_migrate.h>
49 * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
50 * __attribute_const__ and we don't want the compiler to assume any
51 * constness here as the value _does_ change along some code paths.
54 static int read_mpidr(void)
56 unsigned int id;
57 asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
58 return id & MPIDR_HWID_BITMASK;
62 * bL switcher core code.
65 static void bL_do_switch(void *_arg)
67 unsigned ib_mpidr, ib_cpu, ib_cluster;
68 long volatile handshake, **handshake_ptr = _arg;
70 pr_debug("%s\n", __func__);
72 ib_mpidr = cpu_logical_map(smp_processor_id());
73 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
74 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
76 /* Advertise our handshake location */
77 if (handshake_ptr) {
78 handshake = 0;
79 *handshake_ptr = &handshake;
80 } else
81 handshake = -1;
84 * Our state has been saved at this point. Let's release our
85 * inbound CPU.
87 mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
88 sev();
91 * From this point, we must assume that our counterpart CPU might
92 * have taken over in its parallel world already, as if execution
93 * just returned from cpu_suspend(). It is therefore important to
94 * be very careful not to make any change the other guy is not
95 * expecting. This is why we need stack isolation.
97 * Fancy under cover tasks could be performed here. For now
98 * we have none.
102 * Let's wait until our inbound is alive.
104 while (!handshake) {
105 wfe();
106 smp_mb();
109 /* Let's put ourself down. */
110 mcpm_cpu_power_down();
112 /* should never get here */
113 BUG();
117 * Stack isolation. To ensure 'current' remains valid, we just use another
118 * piece of our thread's stack space which should be fairly lightly used.
119 * The selected area starts just above the thread_info structure located
120 * at the very bottom of the stack, aligned to a cache line, and indexed
121 * with the cluster number.
123 #define STACK_SIZE 512
124 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
125 static int bL_switchpoint(unsigned long _arg)
127 unsigned int mpidr = read_mpidr();
128 unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
129 void *stack = current_thread_info() + 1;
130 stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
131 stack += clusterid * STACK_SIZE + STACK_SIZE;
132 call_with_stack(bL_do_switch, (void *)_arg, stack);
133 BUG();
137 * Generic switcher interface
140 static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
141 static int bL_switcher_cpu_pairing[NR_CPUS];
144 * bL_switch_to - Switch to a specific cluster for the current CPU
145 * @new_cluster_id: the ID of the cluster to switch to.
147 * This function must be called on the CPU to be switched.
148 * Returns 0 on success, else a negative status code.
150 static int bL_switch_to(unsigned int new_cluster_id)
152 unsigned int mpidr, this_cpu, that_cpu;
153 unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
154 struct completion inbound_alive;
155 long volatile *handshake_ptr;
156 int ipi_nr, ret;
158 this_cpu = smp_processor_id();
159 ob_mpidr = read_mpidr();
160 ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
161 ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
162 BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
164 if (new_cluster_id == ob_cluster)
165 return 0;
167 that_cpu = bL_switcher_cpu_pairing[this_cpu];
168 ib_mpidr = cpu_logical_map(that_cpu);
169 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
170 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
172 pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
173 this_cpu, ob_mpidr, ib_mpidr);
175 this_cpu = smp_processor_id();
177 /* Close the gate for our entry vectors */
178 mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
179 mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
181 /* Install our "inbound alive" notifier. */
182 init_completion(&inbound_alive);
183 ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
184 ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
185 mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
188 * Let's wake up the inbound CPU now in case it requires some delay
189 * to come online, but leave it gated in our entry vector code.
191 ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
192 if (ret) {
193 pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
194 return ret;
198 * Raise a SGI on the inbound CPU to make sure it doesn't stall
199 * in a possible WFI, such as in bL_power_down().
201 gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
204 * Wait for the inbound to come up. This allows for other
205 * tasks to be scheduled in the mean time.
207 wait_for_completion(&inbound_alive);
208 mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
211 * From this point we are entering the switch critical zone
212 * and can't take any interrupts anymore.
214 local_irq_disable();
215 local_fiq_disable();
216 trace_cpu_migrate_begin(ktime_get_real_ns(), ob_mpidr);
218 /* redirect GIC's SGIs to our counterpart */
219 gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
221 tick_suspend_local();
223 ret = cpu_pm_enter();
225 /* we can not tolerate errors at this point */
226 if (ret)
227 panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
229 /* Swap the physical CPUs in the logical map for this logical CPU. */
230 cpu_logical_map(this_cpu) = ib_mpidr;
231 cpu_logical_map(that_cpu) = ob_mpidr;
233 /* Let's do the actual CPU switch. */
234 ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
235 if (ret > 0)
236 panic("%s: cpu_suspend() returned %d\n", __func__, ret);
238 /* We are executing on the inbound CPU at this point */
239 mpidr = read_mpidr();
240 pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
241 BUG_ON(mpidr != ib_mpidr);
243 mcpm_cpu_powered_up();
245 ret = cpu_pm_exit();
247 tick_resume_local();
249 trace_cpu_migrate_finish(ktime_get_real_ns(), ib_mpidr);
250 local_fiq_enable();
251 local_irq_enable();
253 *handshake_ptr = 1;
254 dsb_sev();
256 if (ret)
257 pr_err("%s exiting with error %d\n", __func__, ret);
258 return ret;
261 struct bL_thread {
262 spinlock_t lock;
263 struct task_struct *task;
264 wait_queue_head_t wq;
265 int wanted_cluster;
266 struct completion started;
267 bL_switch_completion_handler completer;
268 void *completer_cookie;
271 static struct bL_thread bL_threads[NR_CPUS];
273 static int bL_switcher_thread(void *arg)
275 struct bL_thread *t = arg;
276 struct sched_param param = { .sched_priority = 1 };
277 int cluster;
278 bL_switch_completion_handler completer;
279 void *completer_cookie;
281 sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
282 complete(&t->started);
284 do {
285 if (signal_pending(current))
286 flush_signals(current);
287 wait_event_interruptible(t->wq,
288 t->wanted_cluster != -1 ||
289 kthread_should_stop());
291 spin_lock(&t->lock);
292 cluster = t->wanted_cluster;
293 completer = t->completer;
294 completer_cookie = t->completer_cookie;
295 t->wanted_cluster = -1;
296 t->completer = NULL;
297 spin_unlock(&t->lock);
299 if (cluster != -1) {
300 bL_switch_to(cluster);
302 if (completer)
303 completer(completer_cookie);
305 } while (!kthread_should_stop());
307 return 0;
310 static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
312 struct task_struct *task;
314 task = kthread_create_on_node(bL_switcher_thread, arg,
315 cpu_to_node(cpu), "kswitcher_%d", cpu);
316 if (!IS_ERR(task)) {
317 kthread_bind(task, cpu);
318 wake_up_process(task);
319 } else
320 pr_err("%s failed for CPU %d\n", __func__, cpu);
321 return task;
325 * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
326 * with completion notification via a callback
328 * @cpu: the CPU to switch
329 * @new_cluster_id: the ID of the cluster to switch to.
330 * @completer: switch completion callback. if non-NULL,
331 * @completer(@completer_cookie) will be called on completion of
332 * the switch, in non-atomic context.
333 * @completer_cookie: opaque context argument for @completer.
335 * This function causes a cluster switch on the given CPU by waking up
336 * the appropriate switcher thread. This function may or may not return
337 * before the switch has occurred.
339 * If a @completer callback function is supplied, it will be called when
340 * the switch is complete. This can be used to determine asynchronously
341 * when the switch is complete, regardless of when bL_switch_request()
342 * returns. When @completer is supplied, no new switch request is permitted
343 * for the affected CPU until after the switch is complete, and @completer
344 * has returned.
346 int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
347 bL_switch_completion_handler completer,
348 void *completer_cookie)
350 struct bL_thread *t;
352 if (cpu >= ARRAY_SIZE(bL_threads)) {
353 pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
354 return -EINVAL;
357 t = &bL_threads[cpu];
359 if (IS_ERR(t->task))
360 return PTR_ERR(t->task);
361 if (!t->task)
362 return -ESRCH;
364 spin_lock(&t->lock);
365 if (t->completer) {
366 spin_unlock(&t->lock);
367 return -EBUSY;
369 t->completer = completer;
370 t->completer_cookie = completer_cookie;
371 t->wanted_cluster = new_cluster_id;
372 spin_unlock(&t->lock);
373 wake_up(&t->wq);
374 return 0;
376 EXPORT_SYMBOL_GPL(bL_switch_request_cb);
379 * Activation and configuration code.
382 static DEFINE_MUTEX(bL_switcher_activation_lock);
383 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
384 static unsigned int bL_switcher_active;
385 static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
386 static cpumask_t bL_switcher_removed_logical_cpus;
388 int bL_switcher_register_notifier(struct notifier_block *nb)
390 return blocking_notifier_chain_register(&bL_activation_notifier, nb);
392 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
394 int bL_switcher_unregister_notifier(struct notifier_block *nb)
396 return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
398 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
400 static int bL_activation_notify(unsigned long val)
402 int ret;
404 ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
405 if (ret & NOTIFY_STOP_MASK)
406 pr_err("%s: notifier chain failed with status 0x%x\n",
407 __func__, ret);
408 return notifier_to_errno(ret);
411 static void bL_switcher_restore_cpus(void)
413 int i;
415 for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
416 struct device *cpu_dev = get_cpu_device(i);
417 int ret = device_online(cpu_dev);
418 if (ret)
419 dev_err(cpu_dev, "switcher: unable to restore CPU\n");
423 static int bL_switcher_halve_cpus(void)
425 int i, j, cluster_0, gic_id, ret;
426 unsigned int cpu, cluster, mask;
427 cpumask_t available_cpus;
429 /* First pass to validate what we have */
430 mask = 0;
431 for_each_online_cpu(i) {
432 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
433 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
434 if (cluster >= 2) {
435 pr_err("%s: only dual cluster systems are supported\n", __func__);
436 return -EINVAL;
438 if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
439 return -EINVAL;
440 mask |= (1 << cluster);
442 if (mask != 3) {
443 pr_err("%s: no CPU pairing possible\n", __func__);
444 return -EINVAL;
448 * Now let's do the pairing. We match each CPU with another CPU
449 * from a different cluster. To get a uniform scheduling behavior
450 * without fiddling with CPU topology and compute capacity data,
451 * we'll use logical CPUs initially belonging to the same cluster.
453 memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
454 cpumask_copy(&available_cpus, cpu_online_mask);
455 cluster_0 = -1;
456 for_each_cpu(i, &available_cpus) {
457 int match = -1;
458 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
459 if (cluster_0 == -1)
460 cluster_0 = cluster;
461 if (cluster != cluster_0)
462 continue;
463 cpumask_clear_cpu(i, &available_cpus);
464 for_each_cpu(j, &available_cpus) {
465 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
467 * Let's remember the last match to create "odd"
468 * pairings on purpose in order for other code not
469 * to assume any relation between physical and
470 * logical CPU numbers.
472 if (cluster != cluster_0)
473 match = j;
475 if (match != -1) {
476 bL_switcher_cpu_pairing[i] = match;
477 cpumask_clear_cpu(match, &available_cpus);
478 pr_info("CPU%d paired with CPU%d\n", i, match);
483 * Now we disable the unwanted CPUs i.e. everything that has no
484 * pairing information (that includes the pairing counterparts).
486 cpumask_clear(&bL_switcher_removed_logical_cpus);
487 for_each_online_cpu(i) {
488 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
489 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
491 /* Let's take note of the GIC ID for this CPU */
492 gic_id = gic_get_cpu_id(i);
493 if (gic_id < 0) {
494 pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
495 bL_switcher_restore_cpus();
496 return -EINVAL;
498 bL_gic_id[cpu][cluster] = gic_id;
499 pr_info("GIC ID for CPU %u cluster %u is %u\n",
500 cpu, cluster, gic_id);
502 if (bL_switcher_cpu_pairing[i] != -1) {
503 bL_switcher_cpu_original_cluster[i] = cluster;
504 continue;
507 ret = device_offline(get_cpu_device(i));
508 if (ret) {
509 bL_switcher_restore_cpus();
510 return ret;
512 cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
515 return 0;
518 /* Determine the logical CPU a given physical CPU is grouped on. */
519 int bL_switcher_get_logical_index(u32 mpidr)
521 int cpu;
523 if (!bL_switcher_active)
524 return -EUNATCH;
526 mpidr &= MPIDR_HWID_BITMASK;
527 for_each_online_cpu(cpu) {
528 int pairing = bL_switcher_cpu_pairing[cpu];
529 if (pairing == -1)
530 continue;
531 if ((mpidr == cpu_logical_map(cpu)) ||
532 (mpidr == cpu_logical_map(pairing)))
533 return cpu;
535 return -EINVAL;
538 static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
540 trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr());
543 int bL_switcher_trace_trigger(void)
545 int ret;
547 preempt_disable();
549 bL_switcher_trace_trigger_cpu(NULL);
550 ret = smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
552 preempt_enable();
554 return ret;
556 EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
558 static int bL_switcher_enable(void)
560 int cpu, ret;
562 mutex_lock(&bL_switcher_activation_lock);
563 lock_device_hotplug();
564 if (bL_switcher_active) {
565 unlock_device_hotplug();
566 mutex_unlock(&bL_switcher_activation_lock);
567 return 0;
570 pr_info("big.LITTLE switcher initializing\n");
572 ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
573 if (ret)
574 goto error;
576 ret = bL_switcher_halve_cpus();
577 if (ret)
578 goto error;
580 bL_switcher_trace_trigger();
582 for_each_online_cpu(cpu) {
583 struct bL_thread *t = &bL_threads[cpu];
584 spin_lock_init(&t->lock);
585 init_waitqueue_head(&t->wq);
586 init_completion(&t->started);
587 t->wanted_cluster = -1;
588 t->task = bL_switcher_thread_create(cpu, t);
591 bL_switcher_active = 1;
592 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
593 pr_info("big.LITTLE switcher initialized\n");
594 goto out;
596 error:
597 pr_warn("big.LITTLE switcher initialization failed\n");
598 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
600 out:
601 unlock_device_hotplug();
602 mutex_unlock(&bL_switcher_activation_lock);
603 return ret;
606 #ifdef CONFIG_SYSFS
608 static void bL_switcher_disable(void)
610 unsigned int cpu, cluster;
611 struct bL_thread *t;
612 struct task_struct *task;
614 mutex_lock(&bL_switcher_activation_lock);
615 lock_device_hotplug();
617 if (!bL_switcher_active)
618 goto out;
620 if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
621 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
622 goto out;
625 bL_switcher_active = 0;
628 * To deactivate the switcher, we must shut down the switcher
629 * threads to prevent any other requests from being accepted.
630 * Then, if the final cluster for given logical CPU is not the
631 * same as the original one, we'll recreate a switcher thread
632 * just for the purpose of switching the CPU back without any
633 * possibility for interference from external requests.
635 for_each_online_cpu(cpu) {
636 t = &bL_threads[cpu];
637 task = t->task;
638 t->task = NULL;
639 if (!task || IS_ERR(task))
640 continue;
641 kthread_stop(task);
642 /* no more switch may happen on this CPU at this point */
643 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
644 if (cluster == bL_switcher_cpu_original_cluster[cpu])
645 continue;
646 init_completion(&t->started);
647 t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
648 task = bL_switcher_thread_create(cpu, t);
649 if (!IS_ERR(task)) {
650 wait_for_completion(&t->started);
651 kthread_stop(task);
652 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
653 if (cluster == bL_switcher_cpu_original_cluster[cpu])
654 continue;
656 /* If execution gets here, we're in trouble. */
657 pr_crit("%s: unable to restore original cluster for CPU %d\n",
658 __func__, cpu);
659 pr_crit("%s: CPU %d can't be restored\n",
660 __func__, bL_switcher_cpu_pairing[cpu]);
661 cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
662 &bL_switcher_removed_logical_cpus);
665 bL_switcher_restore_cpus();
666 bL_switcher_trace_trigger();
668 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
670 out:
671 unlock_device_hotplug();
672 mutex_unlock(&bL_switcher_activation_lock);
675 static ssize_t bL_switcher_active_show(struct kobject *kobj,
676 struct kobj_attribute *attr, char *buf)
678 return sprintf(buf, "%u\n", bL_switcher_active);
681 static ssize_t bL_switcher_active_store(struct kobject *kobj,
682 struct kobj_attribute *attr, const char *buf, size_t count)
684 int ret;
686 switch (buf[0]) {
687 case '0':
688 bL_switcher_disable();
689 ret = 0;
690 break;
691 case '1':
692 ret = bL_switcher_enable();
693 break;
694 default:
695 ret = -EINVAL;
698 return (ret >= 0) ? count : ret;
701 static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj,
702 struct kobj_attribute *attr, const char *buf, size_t count)
704 int ret = bL_switcher_trace_trigger();
706 return ret ? ret : count;
709 static struct kobj_attribute bL_switcher_active_attr =
710 __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
712 static struct kobj_attribute bL_switcher_trace_trigger_attr =
713 __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
715 static struct attribute *bL_switcher_attrs[] = {
716 &bL_switcher_active_attr.attr,
717 &bL_switcher_trace_trigger_attr.attr,
718 NULL,
721 static struct attribute_group bL_switcher_attr_group = {
722 .attrs = bL_switcher_attrs,
725 static struct kobject *bL_switcher_kobj;
727 static int __init bL_switcher_sysfs_init(void)
729 int ret;
731 bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
732 if (!bL_switcher_kobj)
733 return -ENOMEM;
734 ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
735 if (ret)
736 kobject_put(bL_switcher_kobj);
737 return ret;
740 #endif /* CONFIG_SYSFS */
742 bool bL_switcher_get_enabled(void)
744 mutex_lock(&bL_switcher_activation_lock);
746 return bL_switcher_active;
748 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
750 void bL_switcher_put_enabled(void)
752 mutex_unlock(&bL_switcher_activation_lock);
754 EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
757 * Veto any CPU hotplug operation on those CPUs we've removed
758 * while the switcher is active.
759 * We're just not ready to deal with that given the trickery involved.
761 static int bL_switcher_cpu_pre(unsigned int cpu)
763 int pairing;
765 if (!bL_switcher_active)
766 return 0;
768 pairing = bL_switcher_cpu_pairing[cpu];
770 if (pairing == -1)
771 return -EINVAL;
772 return 0;
775 static bool no_bL_switcher;
776 core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
778 static int __init bL_switcher_init(void)
780 int ret;
782 if (!mcpm_is_available())
783 return -ENODEV;
785 cpuhp_setup_state_nocalls(CPUHP_ARM_BL_PREPARE, "arm/bl:prepare",
786 bL_switcher_cpu_pre, NULL);
787 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "arm/bl:predown",
788 NULL, bL_switcher_cpu_pre);
789 if (ret < 0) {
790 cpuhp_remove_state_nocalls(CPUHP_ARM_BL_PREPARE);
791 pr_err("bL_switcher: Failed to allocate a hotplug state\n");
792 return ret;
794 if (!no_bL_switcher) {
795 ret = bL_switcher_enable();
796 if (ret)
797 return ret;
800 #ifdef CONFIG_SYSFS
801 ret = bL_switcher_sysfs_init();
802 if (ret)
803 pr_err("%s: unable to create sysfs entry\n", __func__);
804 #endif
806 return 0;
809 late_initcall(bL_switcher_init);