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Linux/arch/arm/common/bL_switcher.c

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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 
 53 static 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 
 64 static 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
123 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
124 static 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 
139 static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
140 static 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  */
149 static 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 
260 struct 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 
270 static struct bL_thread bL_threads[NR_CPUS];
271 
272 static 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, &param);
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 
309 static 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  */
345 int 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 }
375 EXPORT_SYMBOL_GPL(bL_switch_request_cb);
376 
377 /*
378  * Activation and configuration code.
379  */
380 
381 static DEFINE_MUTEX(bL_switcher_activation_lock);
382 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
383 static unsigned int bL_switcher_active;
384 static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
385 static cpumask_t bL_switcher_removed_logical_cpus;
386 
387 int bL_switcher_register_notifier(struct notifier_block *nb)
388 {
389         return blocking_notifier_chain_register(&bL_activation_notifier, nb);
390 }
391 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
392 
393 int bL_switcher_unregister_notifier(struct notifier_block *nb)
394 {
395         return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
396 }
397 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
398 
399 static 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 
410 static 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 
422 static 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. */
518 int 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 
537 static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
538 {
539         trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr());
540 }
541 
542 int 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 }
555 EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
556 
557 static 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 
595 error:
596         pr_warn("big.LITTLE switcher initialization failed\n");
597         bL_activation_notify(BL_NOTIFY_POST_DISABLE);
598 
599 out:
600         unlock_device_hotplug();
601         mutex_unlock(&bL_switcher_activation_lock);
602         return ret;
603 }
604 
605 #ifdef CONFIG_SYSFS
606 
607 static 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 
669 out:
670         unlock_device_hotplug();
671         mutex_unlock(&bL_switcher_activation_lock);
672 }
673 
674 static 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 
680 static 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 '':
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 
700 static 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 
708 static struct kobj_attribute bL_switcher_active_attr =
709         __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
710 
711 static struct kobj_attribute bL_switcher_trace_trigger_attr =
712         __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
713 
714 static struct attribute *bL_switcher_attrs[] = {
715         &bL_switcher_active_attr.attr,
716         &bL_switcher_trace_trigger_attr.attr,
717         NULL,
718 };
719 
720 static struct attribute_group bL_switcher_attr_group = {
721         .attrs = bL_switcher_attrs,
722 };
723 
724 static struct kobject *bL_switcher_kobj;
725 
726 static 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 
741 bool bL_switcher_get_enabled(void)
742 {
743         mutex_lock(&bL_switcher_activation_lock);
744 
745         return bL_switcher_active;
746 }
747 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
748 
749 void bL_switcher_put_enabled(void)
750 {
751         mutex_unlock(&bL_switcher_activation_lock);
752 }
753 EXPORT_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  */
760 static int bL_switcher_hotplug_callback(struct notifier_block *nfb,
761                                         unsigned long action, void *hcpu)
762 {
763         if (bL_switcher_active) {
764                 int pairing = bL_switcher_cpu_pairing[(unsigned long)hcpu];
765                 switch (action & 0xf) {
766                 case CPU_UP_PREPARE:
767                 case CPU_DOWN_PREPARE:
768                         if (pairing == -1)
769                                 return NOTIFY_BAD;
770                 }
771         }
772         return NOTIFY_DONE;
773 }
774 
775 static bool no_bL_switcher;
776 core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
777 
778 static int __init bL_switcher_init(void)
779 {
780         int ret;
781 
782         if (!mcpm_is_available())
783                 return -ENODEV;
784 
785         cpu_notifier(bL_switcher_hotplug_callback, 0);
786 
787         if (!no_bL_switcher) {
788                 ret = bL_switcher_enable();
789                 if (ret)
790                         return ret;
791         }
792 
793 #ifdef CONFIG_SYSFS
794         ret = bL_switcher_sysfs_init();
795         if (ret)
796                 pr_err("%s: unable to create sysfs entry\n", __func__);
797 #endif
798 
799         return 0;
800 }
801 
802 late_initcall(bL_switcher_init);
803 

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