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