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1/*
2 * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
3 *
4 * Created by: Nicolas Pitre, March 2012
5 * Copyright: (C) 2012-2013 Linaro Limited
6 *
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.
10 */
11
12#include <linux/atomic.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/sched.h>
17#include <linux/interrupt.h>
18#include <linux/cpu_pm.h>
19#include <linux/cpu.h>
20#include <linux/cpumask.h>
21#include <linux/kthread.h>
22#include <linux/wait.h>
23#include <linux/time.h>
24#include <linux/clockchips.h>
25#include <linux/hrtimer.h>
26#include <linux/tick.h>
27#include <linux/notifier.h>
28#include <linux/mm.h>
29#include <linux/mutex.h>
30#include <linux/smp.h>
31#include <linux/spinlock.h>
32#include <linux/string.h>
33#include <linux/sysfs.h>
34#include <linux/irqchip/arm-gic.h>
35#include <linux/moduleparam.h>
36
37#include <asm/smp_plat.h>
38#include <asm/cputype.h>
39#include <asm/suspend.h>
40#include <asm/mcpm.h>
41#include <asm/bL_switcher.h>
42
43#define CREATE_TRACE_POINTS
44#include <trace/events/power_cpu_migrate.h>
45
46
47/*
48 * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
49 * __attribute_const__ and we don't want the compiler to assume any
50 * constness here as the value _does_ change along some code paths.
51 */
52
53static int read_mpidr(void)
54{
55 unsigned int id;
56 asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
57 return id & MPIDR_HWID_BITMASK;
58}
59
60/*
61 * Get a global nanosecond time stamp for tracing.
62 */
63static s64 get_ns(void)
64{
65 struct timespec ts;
66 getnstimeofday(&ts);
67 return timespec_to_ns(&ts);
68}
69
70/*
71 * bL switcher core code.
72 */
73
74static void bL_do_switch(void *_arg)
75{
76 unsigned ib_mpidr, ib_cpu, ib_cluster;
77 long volatile handshake, **handshake_ptr = _arg;
78
79 pr_debug("%s\n", __func__);
80
81 ib_mpidr = cpu_logical_map(smp_processor_id());
82 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
83 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
84
85 /* Advertise our handshake location */
86 if (handshake_ptr) {
87 handshake = 0;
88 *handshake_ptr = &handshake;
89 } else
90 handshake = -1;
91
92 /*
93 * Our state has been saved at this point. Let's release our
94 * inbound CPU.
95 */
96 mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
97 sev();
98
99 /*
100 * From this point, we must assume that our counterpart CPU might
101 * have taken over in its parallel world already, as if execution
102 * just returned from cpu_suspend(). It is therefore important to
103 * be very careful not to make any change the other guy is not
104 * expecting. This is why we need stack isolation.
105 *
106 * Fancy under cover tasks could be performed here. For now
107 * we have none.
108 */
109
110 /*
111 * Let's wait until our inbound is alive.
112 */
113 while (!handshake) {
114 wfe();
115 smp_mb();
116 }
117
118 /* Let's put ourself down. */
119 mcpm_cpu_power_down();
120
121 /* should never get here */
122 BUG();
123}
124
125/*
126 * Stack isolation. To ensure 'current' remains valid, we just use another
127 * piece of our thread's stack space which should be fairly lightly used.
128 * The selected area starts just above the thread_info structure located
129 * at the very bottom of the stack, aligned to a cache line, and indexed
130 * with the cluster number.
131 */
132#define STACK_SIZE 512
133extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
134static int bL_switchpoint(unsigned long _arg)
135{
136 unsigned int mpidr = read_mpidr();
137 unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
138 void *stack = current_thread_info() + 1;
139 stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
140 stack += clusterid * STACK_SIZE + STACK_SIZE;
141 call_with_stack(bL_do_switch, (void *)_arg, stack);
142 BUG();
143}
144
145/*
146 * Generic switcher interface
147 */
148
149static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
150static int bL_switcher_cpu_pairing[NR_CPUS];
151
152/*
153 * bL_switch_to - Switch to a specific cluster for the current CPU
154 * @new_cluster_id: the ID of the cluster to switch to.
155 *
156 * This function must be called on the CPU to be switched.
157 * Returns 0 on success, else a negative status code.
158 */
159static int bL_switch_to(unsigned int new_cluster_id)
160{
161 unsigned int mpidr, this_cpu, that_cpu;
162 unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
163 struct completion inbound_alive;
164 struct tick_device *tdev;
165 enum clock_event_mode tdev_mode;
166 long volatile *handshake_ptr;
167 int ipi_nr, ret;
168
169 this_cpu = smp_processor_id();
170 ob_mpidr = read_mpidr();
171 ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
172 ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
173 BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
174
175 if (new_cluster_id == ob_cluster)
176 return 0;
177
178 that_cpu = bL_switcher_cpu_pairing[this_cpu];
179 ib_mpidr = cpu_logical_map(that_cpu);
180 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
181 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
182
183 pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
184 this_cpu, ob_mpidr, ib_mpidr);
185
186 this_cpu = smp_processor_id();
187
188 /* Close the gate for our entry vectors */
189 mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
190 mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
191
192 /* Install our "inbound alive" notifier. */
193 init_completion(&inbound_alive);
194 ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
195 ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
196 mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
197
198 /*
199 * Let's wake up the inbound CPU now in case it requires some delay
200 * to come online, but leave it gated in our entry vector code.
201 */
202 ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
203 if (ret) {
204 pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
205 return ret;
206 }
207
208 /*
209 * Raise a SGI on the inbound CPU to make sure it doesn't stall
210 * in a possible WFI, such as in bL_power_down().
211 */
212 gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
213
214 /*
215 * Wait for the inbound to come up. This allows for other
216 * tasks to be scheduled in the mean time.
217 */
218 wait_for_completion(&inbound_alive);
219 mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
220
221 /*
222 * From this point we are entering the switch critical zone
223 * and can't take any interrupts anymore.
224 */
225 local_irq_disable();
226 local_fiq_disable();
227 trace_cpu_migrate_begin(get_ns(), ob_mpidr);
228
229 /* redirect GIC's SGIs to our counterpart */
230 gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
231
232 tdev = tick_get_device(this_cpu);
233 if (tdev && !cpumask_equal(tdev->evtdev->cpumask, cpumask_of(this_cpu)))
234 tdev = NULL;
235 if (tdev) {
236 tdev_mode = tdev->evtdev->mode;
237 clockevents_set_mode(tdev->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
238 }
239
240 ret = cpu_pm_enter();
241
242 /* we can not tolerate errors at this point */
243 if (ret)
244 panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
245
246 /* Swap the physical CPUs in the logical map for this logical CPU. */
247 cpu_logical_map(this_cpu) = ib_mpidr;
248 cpu_logical_map(that_cpu) = ob_mpidr;
249
250 /* Let's do the actual CPU switch. */
251 ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
252 if (ret > 0)
253 panic("%s: cpu_suspend() returned %d\n", __func__, ret);
254
255 /* We are executing on the inbound CPU at this point */
256 mpidr = read_mpidr();
257 pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
258 BUG_ON(mpidr != ib_mpidr);
259
260 mcpm_cpu_powered_up();
261
262 ret = cpu_pm_exit();
263
264 if (tdev) {
265 clockevents_set_mode(tdev->evtdev, tdev_mode);
266 clockevents_program_event(tdev->evtdev,
267 tdev->evtdev->next_event, 1);
268 }
269
270 trace_cpu_migrate_finish(get_ns(), ib_mpidr);
271 local_fiq_enable();
272 local_irq_enable();
273
274 *handshake_ptr = 1;
275 dsb_sev();
276
277 if (ret)
278 pr_err("%s exiting with error %d\n", __func__, ret);
279 return ret;
280}
281
282struct bL_thread {
283 spinlock_t lock;
284 struct task_struct *task;
285 wait_queue_head_t wq;
286 int wanted_cluster;
287 struct completion started;
288 bL_switch_completion_handler completer;
289 void *completer_cookie;
290};
291
292static struct bL_thread bL_threads[NR_CPUS];
293
294static int bL_switcher_thread(void *arg)
295{
296 struct bL_thread *t = arg;
297 struct sched_param param = { .sched_priority = 1 };
298 int cluster;
299 bL_switch_completion_handler completer;
300 void *completer_cookie;
301
302 sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m);
303 complete(&t->started);
304
305 do {
306 if (signal_pending(current))
307 flush_signals(current);
308 wait_event_interruptible(t->wq,
309 t->wanted_cluster != -1 ||
310 kthread_should_stop());
311
312 spin_lock(&t->lock);
313 cluster = t->wanted_cluster;
314 completer = t->completer;
315 completer_cookie = t->completer_cookie;
316 t->wanted_cluster = -1;
317 t->completer = NULL;
318 spin_unlock(&t->lock);
319
320 if (cluster != -1) {
321 bL_switch_to(cluster);
322
323 if (completer)
324 completer(completer_cookie);
325 }
326 } while (!kthread_should_stop());
327
328 return 0;
329}
330
331static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
332{
333 struct task_struct *task;
334
335 task = kthread_create_on_node(bL_switcher_thread, arg,
336 cpu_to_node(cpu), "kswitcher_%d", cpu);
337 if (!IS_ERR(task)) {
338 kthread_bind(task, cpu);
339 wake_up_process(task);
340 } else
341 pr_err("%s failed for CPU %d\n", __func__, cpu);
342 return task;
343}
344
345/*
346 * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
347 * with completion notification via a callback
348 *
349 * @cpu: the CPU to switch
350 * @new_cluster_id: the ID of the cluster to switch to.
351 * @completer: switch completion callback. if non-NULL,
352 * @completer(@completer_cookie) will be called on completion of
353 * the switch, in non-atomic context.
354 * @completer_cookie: opaque context argument for @completer.
355 *
356 * This function causes a cluster switch on the given CPU by waking up
357 * the appropriate switcher thread. This function may or may not return
358 * before the switch has occurred.
359 *
360 * If a @completer callback function is supplied, it will be called when
361 * the switch is complete. This can be used to determine asynchronously
362 * when the switch is complete, regardless of when bL_switch_request()
363 * returns. When @completer is supplied, no new switch request is permitted
364 * for the affected CPU until after the switch is complete, and @completer
365 * has returned.
366 */
367int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
368 bL_switch_completion_handler completer,
369 void *completer_cookie)
370{
371 struct bL_thread *t;
372
373 if (cpu >= ARRAY_SIZE(bL_threads)) {
374 pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
375 return -EINVAL;
376 }
377
378 t = &bL_threads[cpu];
379
380 if (IS_ERR(t->task))
381 return PTR_ERR(t->task);
382 if (!t->task)
383 return -ESRCH;
384
385 spin_lock(&t->lock);
386 if (t->completer) {
387 spin_unlock(&t->lock);
388 return -EBUSY;
389 }
390 t->completer = completer;
391 t->completer_cookie = completer_cookie;
392 t->wanted_cluster = new_cluster_id;
393 spin_unlock(&t->lock);
394 wake_up(&t->wq);
395 return 0;
396}
397EXPORT_SYMBOL_GPL(bL_switch_request_cb);
398
399/*
400 * Activation and configuration code.
401 */
402
403static DEFINE_MUTEX(bL_switcher_activation_lock);
404static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
405static unsigned int bL_switcher_active;
406static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
407static cpumask_t bL_switcher_removed_logical_cpus;
408
409int bL_switcher_register_notifier(struct notifier_block *nb)
410{
411 return blocking_notifier_chain_register(&bL_activation_notifier, nb);
412}
413EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
414
415int bL_switcher_unregister_notifier(struct notifier_block *nb)
416{
417 return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
418}
419EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
420
421static int bL_activation_notify(unsigned long val)
422{
423 int ret;
424
425 ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
426 if (ret & NOTIFY_STOP_MASK)
427 pr_err("%s: notifier chain failed with status 0x%x\n",
428 __func__, ret);
429 return notifier_to_errno(ret);
430}
431
432static void bL_switcher_restore_cpus(void)
433{
434 int i;
435
436 for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
437 struct device *cpu_dev = get_cpu_device(i);
438 int ret = device_online(cpu_dev);
439 if (ret)
440 dev_err(cpu_dev, "switcher: unable to restore CPU\n");
441 }
442}
443
444static int bL_switcher_halve_cpus(void)
445{
446 int i, j, cluster_0, gic_id, ret;
447 unsigned int cpu, cluster, mask;
448 cpumask_t available_cpus;
449
450 /* First pass to validate what we have */
451 mask = 0;
452 for_each_online_cpu(i) {
453 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
454 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
455 if (cluster >= 2) {
456 pr_err("%s: only dual cluster systems are supported\n", __func__);
457 return -EINVAL;
458 }
459 if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
460 return -EINVAL;
461 mask |= (1 << cluster);
462 }
463 if (mask != 3) {
464 pr_err("%s: no CPU pairing possible\n", __func__);
465 return -EINVAL;
466 }
467
468 /*
469 * Now let's do the pairing. We match each CPU with another CPU
470 * from a different cluster. To get a uniform scheduling behavior
471 * without fiddling with CPU topology and compute capacity data,
472 * we'll use logical CPUs initially belonging to the same cluster.
473 */
474 memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
475 cpumask_copy(&available_cpus, cpu_online_mask);
476 cluster_0 = -1;
477 for_each_cpu(i, &available_cpus) {
478 int match = -1;
479 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
480 if (cluster_0 == -1)
481 cluster_0 = cluster;
482 if (cluster != cluster_0)
483 continue;
484 cpumask_clear_cpu(i, &available_cpus);
485 for_each_cpu(j, &available_cpus) {
486 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
487 /*
488 * Let's remember the last match to create "odd"
489 * pairings on purpose in order for other code not
490 * to assume any relation between physical and
491 * logical CPU numbers.
492 */
493 if (cluster != cluster_0)
494 match = j;
495 }
496 if (match != -1) {
497 bL_switcher_cpu_pairing[i] = match;
498 cpumask_clear_cpu(match, &available_cpus);
499 pr_info("CPU%d paired with CPU%d\n", i, match);
500 }
501 }
502
503 /*
504 * Now we disable the unwanted CPUs i.e. everything that has no
505 * pairing information (that includes the pairing counterparts).
506 */
507 cpumask_clear(&bL_switcher_removed_logical_cpus);
508 for_each_online_cpu(i) {
509 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
510 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
511
512 /* Let's take note of the GIC ID for this CPU */
513 gic_id = gic_get_cpu_id(i);
514 if (gic_id < 0) {
515 pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
516 bL_switcher_restore_cpus();
517 return -EINVAL;
518 }
519 bL_gic_id[cpu][cluster] = gic_id;
520 pr_info("GIC ID for CPU %u cluster %u is %u\n",
521 cpu, cluster, gic_id);
522
523 if (bL_switcher_cpu_pairing[i] != -1) {
524 bL_switcher_cpu_original_cluster[i] = cluster;
525 continue;
526 }
527
528 ret = device_offline(get_cpu_device(i));
529 if (ret) {
530 bL_switcher_restore_cpus();
531 return ret;
532 }
533 cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
534 }
535
536 return 0;
537}
538
539/* Determine the logical CPU a given physical CPU is grouped on. */
540int bL_switcher_get_logical_index(u32 mpidr)
541{
542 int cpu;
543
544 if (!bL_switcher_active)
545 return -EUNATCH;
546
547 mpidr &= MPIDR_HWID_BITMASK;
548 for_each_online_cpu(cpu) {
549 int pairing = bL_switcher_cpu_pairing[cpu];
550 if (pairing == -1)
551 continue;
552 if ((mpidr == cpu_logical_map(cpu)) ||
553 (mpidr == cpu_logical_map(pairing)))
554 return cpu;
555 }
556 return -EINVAL;
557}
558
559static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
560{
561 trace_cpu_migrate_current(get_ns(), read_mpidr());
562}
563
564int bL_switcher_trace_trigger(void)
565{
566 int ret;
567
568 preempt_disable();
569
570 bL_switcher_trace_trigger_cpu(NULL);
571 ret = smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
572
573 preempt_enable();
574
575 return ret;
576}
577EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
578
579static int bL_switcher_enable(void)
580{
581 int cpu, ret;
582
583 mutex_lock(&bL_switcher_activation_lock);
584 lock_device_hotplug();
585 if (bL_switcher_active) {
586 unlock_device_hotplug();
587 mutex_unlock(&bL_switcher_activation_lock);
588 return 0;
589 }
590
591 pr_info("big.LITTLE switcher initializing\n");
592
593 ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
594 if (ret)
595 goto error;
596
597 ret = bL_switcher_halve_cpus();
598 if (ret)
599 goto error;
600
601 bL_switcher_trace_trigger();
602
603 for_each_online_cpu(cpu) {
604 struct bL_thread *t = &bL_threads[cpu];
605 spin_lock_init(&t->lock);
606 init_waitqueue_head(&t->wq);
607 init_completion(&t->started);
608 t->wanted_cluster = -1;
609 t->task = bL_switcher_thread_create(cpu, t);
610 }
611
612 bL_switcher_active = 1;
613 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
614 pr_info("big.LITTLE switcher initialized\n");
615 goto out;
616
617error:
618 pr_warn("big.LITTLE switcher initialization failed\n");
619 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
620
621out:
622 unlock_device_hotplug();
623 mutex_unlock(&bL_switcher_activation_lock);
624 return ret;
625}
626
627#ifdef CONFIG_SYSFS
628
629static void bL_switcher_disable(void)
630{
631 unsigned int cpu, cluster;
632 struct bL_thread *t;
633 struct task_struct *task;
634
635 mutex_lock(&bL_switcher_activation_lock);
636 lock_device_hotplug();
637
638 if (!bL_switcher_active)
639 goto out;
640
641 if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
642 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
643 goto out;
644 }
645
646 bL_switcher_active = 0;
647
648 /*
649 * To deactivate the switcher, we must shut down the switcher
650 * threads to prevent any other requests from being accepted.
651 * Then, if the final cluster for given logical CPU is not the
652 * same as the original one, we'll recreate a switcher thread
653 * just for the purpose of switching the CPU back without any
654 * possibility for interference from external requests.
655 */
656 for_each_online_cpu(cpu) {
657 t = &bL_threads[cpu];
658 task = t->task;
659 t->task = NULL;
660 if (!task || IS_ERR(task))
661 continue;
662 kthread_stop(task);
663 /* no more switch may happen on this CPU at this point */
664 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
665 if (cluster == bL_switcher_cpu_original_cluster[cpu])
666 continue;
667 init_completion(&t->started);
668 t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
669 task = bL_switcher_thread_create(cpu, t);
670 if (!IS_ERR(task)) {
671 wait_for_completion(&t->started);
672 kthread_stop(task);
673 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
674 if (cluster == bL_switcher_cpu_original_cluster[cpu])
675 continue;
676 }
677 /* If execution gets here, we're in trouble. */
678 pr_crit("%s: unable to restore original cluster for CPU %d\n",
679 __func__, cpu);
680 pr_crit("%s: CPU %d can't be restored\n",
681 __func__, bL_switcher_cpu_pairing[cpu]);
682 cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
683 &bL_switcher_removed_logical_cpus);
684 }
685
686 bL_switcher_restore_cpus();
687 bL_switcher_trace_trigger();
688
689 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
690
691out:
692 unlock_device_hotplug();
693 mutex_unlock(&bL_switcher_activation_lock);
694}
695
696static ssize_t bL_switcher_active_show(struct kobject *kobj,
697 struct kobj_attribute *attr, char *buf)
698{
699 return sprintf(buf, "%u\n", bL_switcher_active);
700}
701
702static ssize_t bL_switcher_active_store(struct kobject *kobj,
703 struct kobj_attribute *attr, const char *buf, size_t count)
704{
705 int ret;
706
707 switch (buf[0]) {
708 case '0':
709 bL_switcher_disable();
710 ret = 0;
711 break;
712 case '1':
713 ret = bL_switcher_enable();
714 break;
715 default:
716 ret = -EINVAL;
717 }
718
719 return (ret >= 0) ? count : ret;
720}
721
722static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj,
723 struct kobj_attribute *attr, const char *buf, size_t count)
724{
725 int ret = bL_switcher_trace_trigger();
726
727 return ret ? ret : count;
728}
729
730static struct kobj_attribute bL_switcher_active_attr =
731 __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
732
733static struct kobj_attribute bL_switcher_trace_trigger_attr =
734 __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
735
736static struct attribute *bL_switcher_attrs[] = {
737 &bL_switcher_active_attr.attr,
738 &bL_switcher_trace_trigger_attr.attr,
739 NULL,
740};
741
742static struct attribute_group bL_switcher_attr_group = {
743 .attrs = bL_switcher_attrs,
744};
745
746static struct kobject *bL_switcher_kobj;
747
748static int __init bL_switcher_sysfs_init(void)
749{
750 int ret;
751
752 bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
753 if (!bL_switcher_kobj)
754 return -ENOMEM;
755 ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
756 if (ret)
757 kobject_put(bL_switcher_kobj);
758 return ret;
759}
760
761#endif /* CONFIG_SYSFS */
762
763bool bL_switcher_get_enabled(void)
764{
765 mutex_lock(&bL_switcher_activation_lock);
766
767 return bL_switcher_active;
768}
769EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
770
771void bL_switcher_put_enabled(void)
772{
773 mutex_unlock(&bL_switcher_activation_lock);
774}
775EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
776
777/*
778 * Veto any CPU hotplug operation on those CPUs we've removed
779 * while the switcher is active.
780 * We're just not ready to deal with that given the trickery involved.
781 */
782static int bL_switcher_hotplug_callback(struct notifier_block *nfb,
783 unsigned long action, void *hcpu)
784{
785 if (bL_switcher_active) {
786 int pairing = bL_switcher_cpu_pairing[(unsigned long)hcpu];
787 switch (action & 0xf) {
788 case CPU_UP_PREPARE:
789 case CPU_DOWN_PREPARE:
790 if (pairing == -1)
791 return NOTIFY_BAD;
792 }
793 }
794 return NOTIFY_DONE;
795}
796
797static bool no_bL_switcher;
798core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
799
800static int __init bL_switcher_init(void)
801{
802 int ret;
803
804 if (!mcpm_is_available())
805 return -ENODEV;
806
807 cpu_notifier(bL_switcher_hotplug_callback, 0);
808
809 if (!no_bL_switcher) {
810 ret = bL_switcher_enable();
811 if (ret)
812 return ret;
813 }
814
815#ifdef CONFIG_SYSFS
816 ret = bL_switcher_sysfs_init();
817 if (ret)
818 pr_err("%s: unable to create sysfs entry\n", __func__);
819#endif
820
821 return 0;
822}
823
824late_initcall(bL_switcher_init);
1/*
2 * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
3 *
4 * Created by: Nicolas Pitre, March 2012
5 * Copyright: (C) 2012-2013 Linaro Limited
6 *
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.
10 */
11
12#include <linux/atomic.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/sched.h>
17#include <linux/interrupt.h>
18#include <linux/cpu_pm.h>
19#include <linux/cpu.h>
20#include <linux/cpumask.h>
21#include <linux/kthread.h>
22#include <linux/wait.h>
23#include <linux/time.h>
24#include <linux/clockchips.h>
25#include <linux/hrtimer.h>
26#include <linux/tick.h>
27#include <linux/notifier.h>
28#include <linux/mm.h>
29#include <linux/mutex.h>
30#include <linux/smp.h>
31#include <linux/spinlock.h>
32#include <linux/string.h>
33#include <linux/sysfs.h>
34#include <linux/irqchip/arm-gic.h>
35#include <linux/moduleparam.h>
36
37#include <asm/smp_plat.h>
38#include <asm/cputype.h>
39#include <asm/suspend.h>
40#include <asm/mcpm.h>
41#include <asm/bL_switcher.h>
42
43#define CREATE_TRACE_POINTS
44#include <trace/events/power_cpu_migrate.h>
45
46
47/*
48 * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
49 * __attribute_const__ and we don't want the compiler to assume any
50 * constness here as the value _does_ change along some code paths.
51 */
52
53static int read_mpidr(void)
54{
55 unsigned int id;
56 asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
57 return id & MPIDR_HWID_BITMASK;
58}
59
60/*
61 * bL switcher core code.
62 */
63
64static void bL_do_switch(void *_arg)
65{
66 unsigned ib_mpidr, ib_cpu, ib_cluster;
67 long volatile handshake, **handshake_ptr = _arg;
68
69 pr_debug("%s\n", __func__);
70
71 ib_mpidr = cpu_logical_map(smp_processor_id());
72 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
73 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
74
75 /* Advertise our handshake location */
76 if (handshake_ptr) {
77 handshake = 0;
78 *handshake_ptr = &handshake;
79 } else
80 handshake = -1;
81
82 /*
83 * Our state has been saved at this point. Let's release our
84 * inbound CPU.
85 */
86 mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
87 sev();
88
89 /*
90 * From this point, we must assume that our counterpart CPU might
91 * have taken over in its parallel world already, as if execution
92 * just returned from cpu_suspend(). It is therefore important to
93 * be very careful not to make any change the other guy is not
94 * expecting. This is why we need stack isolation.
95 *
96 * Fancy under cover tasks could be performed here. For now
97 * we have none.
98 */
99
100 /*
101 * Let's wait until our inbound is alive.
102 */
103 while (!handshake) {
104 wfe();
105 smp_mb();
106 }
107
108 /* Let's put ourself down. */
109 mcpm_cpu_power_down();
110
111 /* should never get here */
112 BUG();
113}
114
115/*
116 * Stack isolation. To ensure 'current' remains valid, we just use another
117 * piece of our thread's stack space which should be fairly lightly used.
118 * The selected area starts just above the thread_info structure located
119 * at the very bottom of the stack, aligned to a cache line, and indexed
120 * with the cluster number.
121 */
122#define STACK_SIZE 512
123extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
124static int bL_switchpoint(unsigned long _arg)
125{
126 unsigned int mpidr = read_mpidr();
127 unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
128 void *stack = current_thread_info() + 1;
129 stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
130 stack += clusterid * STACK_SIZE + STACK_SIZE;
131 call_with_stack(bL_do_switch, (void *)_arg, stack);
132 BUG();
133}
134
135/*
136 * Generic switcher interface
137 */
138
139static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
140static int bL_switcher_cpu_pairing[NR_CPUS];
141
142/*
143 * bL_switch_to - Switch to a specific cluster for the current CPU
144 * @new_cluster_id: the ID of the cluster to switch to.
145 *
146 * This function must be called on the CPU to be switched.
147 * Returns 0 on success, else a negative status code.
148 */
149static int bL_switch_to(unsigned int new_cluster_id)
150{
151 unsigned int mpidr, this_cpu, that_cpu;
152 unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
153 struct completion inbound_alive;
154 long volatile *handshake_ptr;
155 int ipi_nr, ret;
156
157 this_cpu = smp_processor_id();
158 ob_mpidr = read_mpidr();
159 ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
160 ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
161 BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
162
163 if (new_cluster_id == ob_cluster)
164 return 0;
165
166 that_cpu = bL_switcher_cpu_pairing[this_cpu];
167 ib_mpidr = cpu_logical_map(that_cpu);
168 ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
169 ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
170
171 pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
172 this_cpu, ob_mpidr, ib_mpidr);
173
174 this_cpu = smp_processor_id();
175
176 /* Close the gate for our entry vectors */
177 mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
178 mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
179
180 /* Install our "inbound alive" notifier. */
181 init_completion(&inbound_alive);
182 ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
183 ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
184 mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
185
186 /*
187 * Let's wake up the inbound CPU now in case it requires some delay
188 * to come online, but leave it gated in our entry vector code.
189 */
190 ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
191 if (ret) {
192 pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
193 return ret;
194 }
195
196 /*
197 * Raise a SGI on the inbound CPU to make sure it doesn't stall
198 * in a possible WFI, such as in bL_power_down().
199 */
200 gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
201
202 /*
203 * Wait for the inbound to come up. This allows for other
204 * tasks to be scheduled in the mean time.
205 */
206 wait_for_completion(&inbound_alive);
207 mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
208
209 /*
210 * From this point we are entering the switch critical zone
211 * and can't take any interrupts anymore.
212 */
213 local_irq_disable();
214 local_fiq_disable();
215 trace_cpu_migrate_begin(ktime_get_real_ns(), ob_mpidr);
216
217 /* redirect GIC's SGIs to our counterpart */
218 gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
219
220 tick_suspend_local();
221
222 ret = cpu_pm_enter();
223
224 /* we can not tolerate errors at this point */
225 if (ret)
226 panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
227
228 /* Swap the physical CPUs in the logical map for this logical CPU. */
229 cpu_logical_map(this_cpu) = ib_mpidr;
230 cpu_logical_map(that_cpu) = ob_mpidr;
231
232 /* Let's do the actual CPU switch. */
233 ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
234 if (ret > 0)
235 panic("%s: cpu_suspend() returned %d\n", __func__, ret);
236
237 /* We are executing on the inbound CPU at this point */
238 mpidr = read_mpidr();
239 pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
240 BUG_ON(mpidr != ib_mpidr);
241
242 mcpm_cpu_powered_up();
243
244 ret = cpu_pm_exit();
245
246 tick_resume_local();
247
248 trace_cpu_migrate_finish(ktime_get_real_ns(), ib_mpidr);
249 local_fiq_enable();
250 local_irq_enable();
251
252 *handshake_ptr = 1;
253 dsb_sev();
254
255 if (ret)
256 pr_err("%s exiting with error %d\n", __func__, ret);
257 return ret;
258}
259
260struct bL_thread {
261 spinlock_t lock;
262 struct task_struct *task;
263 wait_queue_head_t wq;
264 int wanted_cluster;
265 struct completion started;
266 bL_switch_completion_handler completer;
267 void *completer_cookie;
268};
269
270static struct bL_thread bL_threads[NR_CPUS];
271
272static int bL_switcher_thread(void *arg)
273{
274 struct bL_thread *t = arg;
275 struct sched_param param = { .sched_priority = 1 };
276 int cluster;
277 bL_switch_completion_handler completer;
278 void *completer_cookie;
279
280 sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m);
281 complete(&t->started);
282
283 do {
284 if (signal_pending(current))
285 flush_signals(current);
286 wait_event_interruptible(t->wq,
287 t->wanted_cluster != -1 ||
288 kthread_should_stop());
289
290 spin_lock(&t->lock);
291 cluster = t->wanted_cluster;
292 completer = t->completer;
293 completer_cookie = t->completer_cookie;
294 t->wanted_cluster = -1;
295 t->completer = NULL;
296 spin_unlock(&t->lock);
297
298 if (cluster != -1) {
299 bL_switch_to(cluster);
300
301 if (completer)
302 completer(completer_cookie);
303 }
304 } while (!kthread_should_stop());
305
306 return 0;
307}
308
309static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
310{
311 struct task_struct *task;
312
313 task = kthread_create_on_node(bL_switcher_thread, arg,
314 cpu_to_node(cpu), "kswitcher_%d", cpu);
315 if (!IS_ERR(task)) {
316 kthread_bind(task, cpu);
317 wake_up_process(task);
318 } else
319 pr_err("%s failed for CPU %d\n", __func__, cpu);
320 return task;
321}
322
323/*
324 * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
325 * with completion notification via a callback
326 *
327 * @cpu: the CPU to switch
328 * @new_cluster_id: the ID of the cluster to switch to.
329 * @completer: switch completion callback. if non-NULL,
330 * @completer(@completer_cookie) will be called on completion of
331 * the switch, in non-atomic context.
332 * @completer_cookie: opaque context argument for @completer.
333 *
334 * This function causes a cluster switch on the given CPU by waking up
335 * the appropriate switcher thread. This function may or may not return
336 * before the switch has occurred.
337 *
338 * If a @completer callback function is supplied, it will be called when
339 * the switch is complete. This can be used to determine asynchronously
340 * when the switch is complete, regardless of when bL_switch_request()
341 * returns. When @completer is supplied, no new switch request is permitted
342 * for the affected CPU until after the switch is complete, and @completer
343 * has returned.
344 */
345int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
346 bL_switch_completion_handler completer,
347 void *completer_cookie)
348{
349 struct bL_thread *t;
350
351 if (cpu >= ARRAY_SIZE(bL_threads)) {
352 pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
353 return -EINVAL;
354 }
355
356 t = &bL_threads[cpu];
357
358 if (IS_ERR(t->task))
359 return PTR_ERR(t->task);
360 if (!t->task)
361 return -ESRCH;
362
363 spin_lock(&t->lock);
364 if (t->completer) {
365 spin_unlock(&t->lock);
366 return -EBUSY;
367 }
368 t->completer = completer;
369 t->completer_cookie = completer_cookie;
370 t->wanted_cluster = new_cluster_id;
371 spin_unlock(&t->lock);
372 wake_up(&t->wq);
373 return 0;
374}
375EXPORT_SYMBOL_GPL(bL_switch_request_cb);
376
377/*
378 * Activation and configuration code.
379 */
380
381static DEFINE_MUTEX(bL_switcher_activation_lock);
382static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
383static unsigned int bL_switcher_active;
384static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
385static cpumask_t bL_switcher_removed_logical_cpus;
386
387int bL_switcher_register_notifier(struct notifier_block *nb)
388{
389 return blocking_notifier_chain_register(&bL_activation_notifier, nb);
390}
391EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
392
393int bL_switcher_unregister_notifier(struct notifier_block *nb)
394{
395 return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
396}
397EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
398
399static int bL_activation_notify(unsigned long val)
400{
401 int ret;
402
403 ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
404 if (ret & NOTIFY_STOP_MASK)
405 pr_err("%s: notifier chain failed with status 0x%x\n",
406 __func__, ret);
407 return notifier_to_errno(ret);
408}
409
410static void bL_switcher_restore_cpus(void)
411{
412 int i;
413
414 for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
415 struct device *cpu_dev = get_cpu_device(i);
416 int ret = device_online(cpu_dev);
417 if (ret)
418 dev_err(cpu_dev, "switcher: unable to restore CPU\n");
419 }
420}
421
422static int bL_switcher_halve_cpus(void)
423{
424 int i, j, cluster_0, gic_id, ret;
425 unsigned int cpu, cluster, mask;
426 cpumask_t available_cpus;
427
428 /* First pass to validate what we have */
429 mask = 0;
430 for_each_online_cpu(i) {
431 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
432 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
433 if (cluster >= 2) {
434 pr_err("%s: only dual cluster systems are supported\n", __func__);
435 return -EINVAL;
436 }
437 if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
438 return -EINVAL;
439 mask |= (1 << cluster);
440 }
441 if (mask != 3) {
442 pr_err("%s: no CPU pairing possible\n", __func__);
443 return -EINVAL;
444 }
445
446 /*
447 * Now let's do the pairing. We match each CPU with another CPU
448 * from a different cluster. To get a uniform scheduling behavior
449 * without fiddling with CPU topology and compute capacity data,
450 * we'll use logical CPUs initially belonging to the same cluster.
451 */
452 memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
453 cpumask_copy(&available_cpus, cpu_online_mask);
454 cluster_0 = -1;
455 for_each_cpu(i, &available_cpus) {
456 int match = -1;
457 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
458 if (cluster_0 == -1)
459 cluster_0 = cluster;
460 if (cluster != cluster_0)
461 continue;
462 cpumask_clear_cpu(i, &available_cpus);
463 for_each_cpu(j, &available_cpus) {
464 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
465 /*
466 * Let's remember the last match to create "odd"
467 * pairings on purpose in order for other code not
468 * to assume any relation between physical and
469 * logical CPU numbers.
470 */
471 if (cluster != cluster_0)
472 match = j;
473 }
474 if (match != -1) {
475 bL_switcher_cpu_pairing[i] = match;
476 cpumask_clear_cpu(match, &available_cpus);
477 pr_info("CPU%d paired with CPU%d\n", i, match);
478 }
479 }
480
481 /*
482 * Now we disable the unwanted CPUs i.e. everything that has no
483 * pairing information (that includes the pairing counterparts).
484 */
485 cpumask_clear(&bL_switcher_removed_logical_cpus);
486 for_each_online_cpu(i) {
487 cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
488 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
489
490 /* Let's take note of the GIC ID for this CPU */
491 gic_id = gic_get_cpu_id(i);
492 if (gic_id < 0) {
493 pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
494 bL_switcher_restore_cpus();
495 return -EINVAL;
496 }
497 bL_gic_id[cpu][cluster] = gic_id;
498 pr_info("GIC ID for CPU %u cluster %u is %u\n",
499 cpu, cluster, gic_id);
500
501 if (bL_switcher_cpu_pairing[i] != -1) {
502 bL_switcher_cpu_original_cluster[i] = cluster;
503 continue;
504 }
505
506 ret = device_offline(get_cpu_device(i));
507 if (ret) {
508 bL_switcher_restore_cpus();
509 return ret;
510 }
511 cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
512 }
513
514 return 0;
515}
516
517/* Determine the logical CPU a given physical CPU is grouped on. */
518int bL_switcher_get_logical_index(u32 mpidr)
519{
520 int cpu;
521
522 if (!bL_switcher_active)
523 return -EUNATCH;
524
525 mpidr &= MPIDR_HWID_BITMASK;
526 for_each_online_cpu(cpu) {
527 int pairing = bL_switcher_cpu_pairing[cpu];
528 if (pairing == -1)
529 continue;
530 if ((mpidr == cpu_logical_map(cpu)) ||
531 (mpidr == cpu_logical_map(pairing)))
532 return cpu;
533 }
534 return -EINVAL;
535}
536
537static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
538{
539 trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr());
540}
541
542int bL_switcher_trace_trigger(void)
543{
544 int ret;
545
546 preempt_disable();
547
548 bL_switcher_trace_trigger_cpu(NULL);
549 ret = smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
550
551 preempt_enable();
552
553 return ret;
554}
555EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
556
557static int bL_switcher_enable(void)
558{
559 int cpu, ret;
560
561 mutex_lock(&bL_switcher_activation_lock);
562 lock_device_hotplug();
563 if (bL_switcher_active) {
564 unlock_device_hotplug();
565 mutex_unlock(&bL_switcher_activation_lock);
566 return 0;
567 }
568
569 pr_info("big.LITTLE switcher initializing\n");
570
571 ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
572 if (ret)
573 goto error;
574
575 ret = bL_switcher_halve_cpus();
576 if (ret)
577 goto error;
578
579 bL_switcher_trace_trigger();
580
581 for_each_online_cpu(cpu) {
582 struct bL_thread *t = &bL_threads[cpu];
583 spin_lock_init(&t->lock);
584 init_waitqueue_head(&t->wq);
585 init_completion(&t->started);
586 t->wanted_cluster = -1;
587 t->task = bL_switcher_thread_create(cpu, t);
588 }
589
590 bL_switcher_active = 1;
591 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
592 pr_info("big.LITTLE switcher initialized\n");
593 goto out;
594
595error:
596 pr_warn("big.LITTLE switcher initialization failed\n");
597 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
598
599out:
600 unlock_device_hotplug();
601 mutex_unlock(&bL_switcher_activation_lock);
602 return ret;
603}
604
605#ifdef CONFIG_SYSFS
606
607static void bL_switcher_disable(void)
608{
609 unsigned int cpu, cluster;
610 struct bL_thread *t;
611 struct task_struct *task;
612
613 mutex_lock(&bL_switcher_activation_lock);
614 lock_device_hotplug();
615
616 if (!bL_switcher_active)
617 goto out;
618
619 if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
620 bL_activation_notify(BL_NOTIFY_POST_ENABLE);
621 goto out;
622 }
623
624 bL_switcher_active = 0;
625
626 /*
627 * To deactivate the switcher, we must shut down the switcher
628 * threads to prevent any other requests from being accepted.
629 * Then, if the final cluster for given logical CPU is not the
630 * same as the original one, we'll recreate a switcher thread
631 * just for the purpose of switching the CPU back without any
632 * possibility for interference from external requests.
633 */
634 for_each_online_cpu(cpu) {
635 t = &bL_threads[cpu];
636 task = t->task;
637 t->task = NULL;
638 if (!task || IS_ERR(task))
639 continue;
640 kthread_stop(task);
641 /* no more switch may happen on this CPU at this point */
642 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
643 if (cluster == bL_switcher_cpu_original_cluster[cpu])
644 continue;
645 init_completion(&t->started);
646 t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
647 task = bL_switcher_thread_create(cpu, t);
648 if (!IS_ERR(task)) {
649 wait_for_completion(&t->started);
650 kthread_stop(task);
651 cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
652 if (cluster == bL_switcher_cpu_original_cluster[cpu])
653 continue;
654 }
655 /* If execution gets here, we're in trouble. */
656 pr_crit("%s: unable to restore original cluster for CPU %d\n",
657 __func__, cpu);
658 pr_crit("%s: CPU %d can't be restored\n",
659 __func__, bL_switcher_cpu_pairing[cpu]);
660 cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
661 &bL_switcher_removed_logical_cpus);
662 }
663
664 bL_switcher_restore_cpus();
665 bL_switcher_trace_trigger();
666
667 bL_activation_notify(BL_NOTIFY_POST_DISABLE);
668
669out:
670 unlock_device_hotplug();
671 mutex_unlock(&bL_switcher_activation_lock);
672}
673
674static ssize_t bL_switcher_active_show(struct kobject *kobj,
675 struct kobj_attribute *attr, char *buf)
676{
677 return sprintf(buf, "%u\n", bL_switcher_active);
678}
679
680static ssize_t bL_switcher_active_store(struct kobject *kobj,
681 struct kobj_attribute *attr, const char *buf, size_t count)
682{
683 int ret;
684
685 switch (buf[0]) {
686 case '0':
687 bL_switcher_disable();
688 ret = 0;
689 break;
690 case '1':
691 ret = bL_switcher_enable();
692 break;
693 default:
694 ret = -EINVAL;
695 }
696
697 return (ret >= 0) ? count : ret;
698}
699
700static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj,
701 struct kobj_attribute *attr, const char *buf, size_t count)
702{
703 int ret = bL_switcher_trace_trigger();
704
705 return ret ? ret : count;
706}
707
708static struct kobj_attribute bL_switcher_active_attr =
709 __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
710
711static struct kobj_attribute bL_switcher_trace_trigger_attr =
712 __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
713
714static struct attribute *bL_switcher_attrs[] = {
715 &bL_switcher_active_attr.attr,
716 &bL_switcher_trace_trigger_attr.attr,
717 NULL,
718};
719
720static struct attribute_group bL_switcher_attr_group = {
721 .attrs = bL_switcher_attrs,
722};
723
724static struct kobject *bL_switcher_kobj;
725
726static int __init bL_switcher_sysfs_init(void)
727{
728 int ret;
729
730 bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
731 if (!bL_switcher_kobj)
732 return -ENOMEM;
733 ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
734 if (ret)
735 kobject_put(bL_switcher_kobj);
736 return ret;
737}
738
739#endif /* CONFIG_SYSFS */
740
741bool bL_switcher_get_enabled(void)
742{
743 mutex_lock(&bL_switcher_activation_lock);
744
745 return bL_switcher_active;
746}
747EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
748
749void bL_switcher_put_enabled(void)
750{
751 mutex_unlock(&bL_switcher_activation_lock);
752}
753EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
754
755/*
756 * Veto any CPU hotplug operation on those CPUs we've removed
757 * while the switcher is active.
758 * We're just not ready to deal with that given the trickery involved.
759 */
760static int bL_switcher_cpu_pre(unsigned int cpu)
761{
762 int pairing;
763
764 if (!bL_switcher_active)
765 return 0;
766
767 pairing = bL_switcher_cpu_pairing[cpu];
768
769 if (pairing == -1)
770 return -EINVAL;
771 return 0;
772}
773
774static bool no_bL_switcher;
775core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
776
777static int __init bL_switcher_init(void)
778{
779 int ret;
780
781 if (!mcpm_is_available())
782 return -ENODEV;
783
784 cpuhp_setup_state_nocalls(CPUHP_ARM_BL_PREPARE, "arm/bl:prepare",
785 bL_switcher_cpu_pre, NULL);
786 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "arm/bl:predown",
787 NULL, bL_switcher_cpu_pre);
788 if (ret < 0) {
789 cpuhp_remove_state_nocalls(CPUHP_ARM_BL_PREPARE);
790 pr_err("bL_switcher: Failed to allocate a hotplug state\n");
791 return ret;
792 }
793 if (!no_bL_switcher) {
794 ret = bL_switcher_enable();
795 if (ret)
796 return ret;
797 }
798
799#ifdef CONFIG_SYSFS
800 ret = bL_switcher_sysfs_init();
801 if (ret)
802 pr_err("%s: unable to create sysfs entry\n", __func__);
803#endif
804
805 return 0;
806}
807
808late_initcall(bL_switcher_init);