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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
  *
  * Created by:  Nicolas Pitre, March 2012
  * Copyright:   (C) 2012-2013  Linaro Limited
  */
 
 #include <linux/atomic.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/sched/signal.h>
 #include <uapi/linux/sched/types.h>
 #include <linux/interrupt.h>
 #include <linux/cpu_pm.h>
 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/kthread.h>
 #include <linux/wait.h>
 #include <linux/time.h>
 #include <linux/clockchips.h>
 #include <linux/hrtimer.h>
 #include <linux/tick.h>
 #include <linux/notifier.h>
 #include <linux/mm.h>
 #include <linux/mutex.h>
 #include <linux/smp.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/sysfs.h>
 #include <linux/irqchip/arm-gic.h>
 #include <linux/moduleparam.h>
 
 #include <asm/smp_plat.h>
 #include <asm/cputype.h>
 #include <asm/suspend.h>
 #include <asm/mcpm.h>
 #include <asm/bL_switcher.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/power_cpu_migrate.h>
 
 
 /*
  * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
  * __attribute_const__ and we don't want the compiler to assume any
  * constness here as the value _does_ change along some code paths.
  */
 
 static int read_mpidr(void)
 {
     unsigned int id;
     asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
     return id & MPIDR_HWID_BITMASK;
 }
 
 /*
  * bL switcher core code.
  */
 
 static void bL_do_switch(void *_arg)
 {
     unsigned ib_mpidr, ib_cpu, ib_cluster;
     long volatile handshake, **handshake_ptr = _arg;
 
     pr_debug("%s\n", __func__);
 
     ib_mpidr = cpu_logical_map(smp_processor_id());
     ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
     ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
 
     /* Advertise our handshake location */
     if (handshake_ptr) {
         handshake = 0;
         *handshake_ptr = &handshake;
     } else
         handshake = -1;
 
     /*
      * Our state has been saved at this point.  Let's release our
      * inbound CPU.
      */
     mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
     sev();
 
     /*
      * From this point, we must assume that our counterpart CPU might
      * have taken over in its parallel world already, as if execution
      * just returned from cpu_suspend().  It is therefore important to
      * be very careful not to make any change the other guy is not
      * expecting.  This is why we need stack isolation.
      *
      * Fancy under cover tasks could be performed here.  For now
      * we have none.
      */
 
     /*
      * Let's wait until our inbound is alive.
      */
     while (!handshake) {
         wfe();
         smp_mb();
     }
 
     /* Let's put ourself down. */
     mcpm_cpu_power_down();
 
     /* should never get here */
     BUG();
 }
 
 /*
  * Stack isolation.  To ensure 'current' remains valid, we just use another
  * piece of our thread's stack space which should be fairly lightly used.
  * The selected area starts just above the thread_info structure located
  * at the very bottom of the stack, aligned to a cache line, and indexed
  * with the cluster number.
  */
 #define STACK_SIZE 512
 extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
 static int bL_switchpoint(unsigned long _arg)
 {
     unsigned int mpidr = read_mpidr();
     unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
     void *stack = current_thread_info() + 1;
     stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
     stack += clusterid * STACK_SIZE + STACK_SIZE;
     call_with_stack(bL_do_switch, (void *)_arg, stack);
     BUG();
 }
 
 /*
  * Generic switcher interface
  */
 
 static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
 static int bL_switcher_cpu_pairing[NR_CPUS];
 
 /*
  * bL_switch_to - Switch to a specific cluster for the current CPU
  * @new_cluster_id: the ID of the cluster to switch to.
  *
  * This function must be called on the CPU to be switched.
  * Returns 0 on success, else a negative status code.
  */
 static int bL_switch_to(unsigned int new_cluster_id)
 {
     unsigned int mpidr, this_cpu, that_cpu;
     unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
     struct completion inbound_alive;
     long volatile *handshake_ptr;
     int ipi_nr, ret;
 
     this_cpu = smp_processor_id();
     ob_mpidr = read_mpidr();
     ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
     ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
     BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
 
     if (new_cluster_id == ob_cluster)
         return 0;
 
     that_cpu = bL_switcher_cpu_pairing[this_cpu];
     ib_mpidr = cpu_logical_map(that_cpu);
     ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
     ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
 
     pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
          this_cpu, ob_mpidr, ib_mpidr);
 
     this_cpu = smp_processor_id();
 
     /* Close the gate for our entry vectors */
     mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
     mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
 
     /* Install our "inbound alive" notifier. */
     init_completion(&inbound_alive);
     ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
     ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
     mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
 
     /*
      * Let's wake up the inbound CPU now in case it requires some delay
      * to come online, but leave it gated in our entry vector code.
      */
     ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
     if (ret) {
         pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
         return ret;
     }
 
     /*
      * Raise a SGI on the inbound CPU to make sure it doesn't stall
      * in a possible WFI, such as in bL_power_down().
      */
     gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
 
     /*
      * Wait for the inbound to come up.  This allows for other
      * tasks to be scheduled in the mean time.
      */
     wait_for_completion(&inbound_alive);
     mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
 
     /*
      * From this point we are entering the switch critical zone
      * and can't take any interrupts anymore.
      */
     local_irq_disable();
     local_fiq_disable();
     trace_cpu_migrate_begin(ktime_get_real_ns(), ob_mpidr);
 
     /* redirect GIC's SGIs to our counterpart */
     gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
 
     tick_suspend_local();
 
     ret = cpu_pm_enter();
 
     /* we can not tolerate errors at this point */
     if (ret)
         panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
 
     /* Swap the physical CPUs in the logical map for this logical CPU. */
     cpu_logical_map(this_cpu) = ib_mpidr;
     cpu_logical_map(that_cpu) = ob_mpidr;
 
     /* Let's do the actual CPU switch. */
     ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
     if (ret > 0)
         panic("%s: cpu_suspend() returned %d\n", __func__, ret);
 
     /* We are executing on the inbound CPU at this point */
     mpidr = read_mpidr();
     pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
     BUG_ON(mpidr != ib_mpidr);
 
     mcpm_cpu_powered_up();
 
     ret = cpu_pm_exit();
 
     tick_resume_local();
 
     trace_cpu_migrate_finish(ktime_get_real_ns(), ib_mpidr);
     local_fiq_enable();
     local_irq_enable();
 
     *handshake_ptr = 1;
     dsb_sev();
 
     if (ret)
         pr_err("%s exiting with error %d\n", __func__, ret);
     return ret;
 }
 
 struct bL_thread {
     spinlock_t lock;
     struct task_struct *task;
     wait_queue_head_t wq;
     int wanted_cluster;
     struct completion started;
     bL_switch_completion_handler completer;
     void *completer_cookie;
 };
 
 static struct bL_thread bL_threads[NR_CPUS];
 
 static int bL_switcher_thread(void *arg)
 {
     struct bL_thread *t = arg;
     int cluster;
     bL_switch_completion_handler completer;
     void *completer_cookie;
 
     sched_set_fifo_low(current);
     complete(&t->started);
 
     do {
         if (signal_pending(current))
             flush_signals(current);
         wait_event_interruptible(t->wq,
                 t->wanted_cluster != -1 ||
                 kthread_should_stop());
 
         spin_lock(&t->lock);
         cluster = t->wanted_cluster;
         completer = t->completer;
         completer_cookie = t->completer_cookie;
         t->wanted_cluster = -1;
         t->completer = NULL;
         spin_unlock(&t->lock);
 
         if (cluster != -1) {
             bL_switch_to(cluster);
 
             if (completer)
                 completer(completer_cookie);
         }
     } while (!kthread_should_stop());
 
     return 0;
 }
 
 static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
 {
     struct task_struct *task;
 
     task = kthread_create_on_node(bL_switcher_thread, arg,
                       cpu_to_node(cpu), "kswitcher_%d", cpu);
     if (!IS_ERR(task)) {
         kthread_bind(task, cpu);
         wake_up_process(task);
     } else
         pr_err("%s failed for CPU %d\n", __func__, cpu);
     return task;
 }
 
 /*
  * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
  *      with completion notification via a callback
  *
  * @cpu: the CPU to switch
  * @new_cluster_id: the ID of the cluster to switch to.
  * @completer: switch completion callback.  if non-NULL,
  *  @completer(@completer_cookie) will be called on completion of
  *  the switch, in non-atomic context.
  * @completer_cookie: opaque context argument for @completer.
  *
  * This function causes a cluster switch on the given CPU by waking up
  * the appropriate switcher thread.  This function may or may not return
  * before the switch has occurred.
  *
  * If a @completer callback function is supplied, it will be called when
  * the switch is complete.  This can be used to determine asynchronously
  * when the switch is complete, regardless of when bL_switch_request()
  * returns.  When @completer is supplied, no new switch request is permitted
  * for the affected CPU until after the switch is complete, and @completer
  * has returned.
  */
 int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
              bL_switch_completion_handler completer,
              void *completer_cookie)
 {
     struct bL_thread *t;
 
     if (cpu >= ARRAY_SIZE(bL_threads)) {
         pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
         return -EINVAL;
     }
 
     t = &bL_threads[cpu];
 
     if (IS_ERR(t->task))
         return PTR_ERR(t->task);
     if (!t->task)
         return -ESRCH;
 
     spin_lock(&t->lock);
     if (t->completer) {
         spin_unlock(&t->lock);
         return -EBUSY;
     }
     t->completer = completer;
     t->completer_cookie = completer_cookie;
     t->wanted_cluster = new_cluster_id;
     spin_unlock(&t->lock);
     wake_up(&t->wq);
     return 0;
 }
 EXPORT_SYMBOL_GPL(bL_switch_request_cb);
 
 /*
  * Activation and configuration code.
  */
 
 static DEFINE_MUTEX(bL_switcher_activation_lock);
 static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
 static unsigned int bL_switcher_active;
 static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
 static cpumask_t bL_switcher_removed_logical_cpus;
 
 int bL_switcher_register_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_register(&bL_activation_notifier, nb);
 }
 EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
 
 int bL_switcher_unregister_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
 }
 EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
 
 static int bL_activation_notify(unsigned long val)
 {
     int ret;
 
     ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
     if (ret & NOTIFY_STOP_MASK)
         pr_err("%s: notifier chain failed with status 0x%x\n",
             __func__, ret);
     return notifier_to_errno(ret);
 }
 
 static void bL_switcher_restore_cpus(void)
 {
     int i;
 
     for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
         struct device *cpu_dev = get_cpu_device(i);
         int ret = device_online(cpu_dev);
         if (ret)
             dev_err(cpu_dev, "switcher: unable to restore CPU\n");
     }
 }
 
 static int bL_switcher_halve_cpus(void)
 {
     int i, j, cluster_0, gic_id, ret;
     unsigned int cpu, cluster, mask;
     cpumask_t available_cpus;
 
     /* First pass to validate what we have */
     mask = 0;
     for_each_online_cpu(i) {
         cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
         cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
         if (cluster >= 2) {
             pr_err("%s: only dual cluster systems are supported\n", __func__);
             return -EINVAL;
         }
         if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
             return -EINVAL;
         mask |= (1 << cluster);
     }
     if (mask != 3) {
         pr_err("%s: no CPU pairing possible\n", __func__);
         return -EINVAL;
     }
 
     /*
      * Now let's do the pairing.  We match each CPU with another CPU
      * from a different cluster.  To get a uniform scheduling behavior
      * without fiddling with CPU topology and compute capacity data,
      * we'll use logical CPUs initially belonging to the same cluster.
      */
     memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
     cpumask_copy(&available_cpus, cpu_online_mask);
     cluster_0 = -1;
     for_each_cpu(i, &available_cpus) {
         int match = -1;
         cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
         if (cluster_0 == -1)
             cluster_0 = cluster;
         if (cluster != cluster_0)
             continue;
         cpumask_clear_cpu(i, &available_cpus);
         for_each_cpu(j, &available_cpus) {
             cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
             /*
              * Let's remember the last match to create "odd"
              * pairings on purpose in order for other code not
              * to assume any relation between physical and
              * logical CPU numbers.
              */
             if (cluster != cluster_0)
                 match = j;
         }
         if (match != -1) {
             bL_switcher_cpu_pairing[i] = match;
             cpumask_clear_cpu(match, &available_cpus);
             pr_info("CPU%d paired with CPU%d\n", i, match);
         }
     }
 
     /*
      * Now we disable the unwanted CPUs i.e. everything that has no
      * pairing information (that includes the pairing counterparts).
      */
     cpumask_clear(&bL_switcher_removed_logical_cpus);
     for_each_online_cpu(i) {
         cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
         cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
 
         /* Let's take note of the GIC ID for this CPU */
         gic_id = gic_get_cpu_id(i);
         if (gic_id < 0) {
             pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
             bL_switcher_restore_cpus();
             return -EINVAL;
         }
         bL_gic_id[cpu][cluster] = gic_id;
         pr_info("GIC ID for CPU %u cluster %u is %u\n",
             cpu, cluster, gic_id);
 
         if (bL_switcher_cpu_pairing[i] != -1) {
             bL_switcher_cpu_original_cluster[i] = cluster;
             continue;
         }
 
         ret = device_offline(get_cpu_device(i));
         if (ret) {
             bL_switcher_restore_cpus();
             return ret;
         }
         cpumask_set_cpu(i, &bL_switcher_removed_logical_cpus);
     }
 
     return 0;
 }
 
 /* Determine the logical CPU a given physical CPU is grouped on. */
 int bL_switcher_get_logical_index(u32 mpidr)
 {
     int cpu;
 
     if (!bL_switcher_active)
         return -EUNATCH;
 
     mpidr &= MPIDR_HWID_BITMASK;
     for_each_online_cpu(cpu) {
         int pairing = bL_switcher_cpu_pairing[cpu];
         if (pairing == -1)
             continue;
         if ((mpidr == cpu_logical_map(cpu)) ||
             (mpidr == cpu_logical_map(pairing)))
             return cpu;
     }
     return -EINVAL;
 }
 
 static void bL_switcher_trace_trigger_cpu(void *__always_unused info)
 {
     trace_cpu_migrate_current(ktime_get_real_ns(), read_mpidr());
 }
 
 int bL_switcher_trace_trigger(void)
 {
     preempt_disable();
 
     bL_switcher_trace_trigger_cpu(NULL);
     smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
 
     preempt_enable();
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
 
 static int bL_switcher_enable(void)
 {
     int cpu, ret;
 
     mutex_lock(&bL_switcher_activation_lock);
     lock_device_hotplug();
     if (bL_switcher_active) {
         unlock_device_hotplug();
         mutex_unlock(&bL_switcher_activation_lock);
         return 0;
     }
 
     pr_info("big.LITTLE switcher initializing\n");
 
     ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
     if (ret)
         goto error;
 
     ret = bL_switcher_halve_cpus();
     if (ret)
         goto error;
 
     bL_switcher_trace_trigger();
 
     for_each_online_cpu(cpu) {
         struct bL_thread *t = &bL_threads[cpu];
         spin_lock_init(&t->lock);
         init_waitqueue_head(&t->wq);
         init_completion(&t->started);
         t->wanted_cluster = -1;
         t->task = bL_switcher_thread_create(cpu, t);
     }
 
     bL_switcher_active = 1;
     bL_activation_notify(BL_NOTIFY_POST_ENABLE);
     pr_info("big.LITTLE switcher initialized\n");
     goto out;
 
 error:
     pr_warn("big.LITTLE switcher initialization failed\n");
     bL_activation_notify(BL_NOTIFY_POST_DISABLE);
 
 out:
     unlock_device_hotplug();
     mutex_unlock(&bL_switcher_activation_lock);
     return ret;
 }
 
 #ifdef CONFIG_SYSFS
 
 static void bL_switcher_disable(void)
 {
     unsigned int cpu, cluster;
     struct bL_thread *t;
     struct task_struct *task;
 
     mutex_lock(&bL_switcher_activation_lock);
     lock_device_hotplug();
 
     if (!bL_switcher_active)
         goto out;
 
     if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
         bL_activation_notify(BL_NOTIFY_POST_ENABLE);
         goto out;
     }
 
     bL_switcher_active = 0;
 
     /*
      * To deactivate the switcher, we must shut down the switcher
      * threads to prevent any other requests from being accepted.
      * Then, if the final cluster for given logical CPU is not the
      * same as the original one, we'll recreate a switcher thread
      * just for the purpose of switching the CPU back without any
      * possibility for interference from external requests.
      */
     for_each_online_cpu(cpu) {
         t = &bL_threads[cpu];
         task = t->task;
         t->task = NULL;
         if (!task || IS_ERR(task))
             continue;
         kthread_stop(task);
         /* no more switch may happen on this CPU at this point */
         cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
         if (cluster == bL_switcher_cpu_original_cluster[cpu])
             continue;
         init_completion(&t->started);
         t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
         task = bL_switcher_thread_create(cpu, t);
         if (!IS_ERR(task)) {
             wait_for_completion(&t->started);
             kthread_stop(task);
             cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
             if (cluster == bL_switcher_cpu_original_cluster[cpu])
                 continue;
         }
         /* If execution gets here, we're in trouble. */
         pr_crit("%s: unable to restore original cluster for CPU %d\n",
             __func__, cpu);
         pr_crit("%s: CPU %d can't be restored\n",
             __func__, bL_switcher_cpu_pairing[cpu]);
         cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
                   &bL_switcher_removed_logical_cpus);
     }
 
     bL_switcher_restore_cpus();
     bL_switcher_trace_trigger();
 
     bL_activation_notify(BL_NOTIFY_POST_DISABLE);
 
 out:
     unlock_device_hotplug();
     mutex_unlock(&bL_switcher_activation_lock);
 }
 
 static ssize_t bL_switcher_active_show(struct kobject *kobj,
         struct kobj_attribute *attr, char *buf)
 {
     return sprintf(buf, "%u\n", bL_switcher_active);
 }
 
 static ssize_t bL_switcher_active_store(struct kobject *kobj,
         struct kobj_attribute *attr, const char *buf, size_t count)
 {
     int ret;
 
     switch (buf[0]) {
     case '0':
         bL_switcher_disable();
         ret = 0;
         break;
     case '1':
         ret = bL_switcher_enable();
         break;
     default:
         ret = -EINVAL;
     }
 
     return (ret >= 0) ? count : ret;
 }
 
 static ssize_t bL_switcher_trace_trigger_store(struct kobject *kobj,
         struct kobj_attribute *attr, const char *buf, size_t count)
 {
     int ret = bL_switcher_trace_trigger();
 
     return ret ? ret : count;
 }
 
 static struct kobj_attribute bL_switcher_active_attr =
     __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
 
 static struct kobj_attribute bL_switcher_trace_trigger_attr =
     __ATTR(trace_trigger, 0200, NULL, bL_switcher_trace_trigger_store);
 
 static struct attribute *bL_switcher_attrs[] = {
     &bL_switcher_active_attr.attr,
     &bL_switcher_trace_trigger_attr.attr,
     NULL,
 };
 
 static struct attribute_group bL_switcher_attr_group = {
     .attrs = bL_switcher_attrs,
 };
 
 static struct kobject *bL_switcher_kobj;
 
 static int __init bL_switcher_sysfs_init(void)
 {
     int ret;
 
     bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
     if (!bL_switcher_kobj)
         return -ENOMEM;
     ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
     if (ret)
         kobject_put(bL_switcher_kobj);
     return ret;
 }
 
 #endif  /* CONFIG_SYSFS */
 
 bool bL_switcher_get_enabled(void)
 {
     mutex_lock(&bL_switcher_activation_lock);
 
     return bL_switcher_active;
 }
 EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
 
 void bL_switcher_put_enabled(void)
 {
     mutex_unlock(&bL_switcher_activation_lock);
 }
 EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
 
 /*
  * Veto any CPU hotplug operation on those CPUs we've removed
  * while the switcher is active.
  * We're just not ready to deal with that given the trickery involved.
  */
 static int bL_switcher_cpu_pre(unsigned int cpu)
 {
     int pairing;
 
     if (!bL_switcher_active)
         return 0;
 
     pairing = bL_switcher_cpu_pairing[cpu];
 
     if (pairing == -1)
         return -EINVAL;
     return 0;
 }
 
 static bool no_bL_switcher;
 core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
 
 static int __init bL_switcher_init(void)
 {
     int ret;
 
     if (!mcpm_is_available())
         return -ENODEV;
 
     cpuhp_setup_state_nocalls(CPUHP_ARM_BL_PREPARE, "arm/bl:prepare",
                   bL_switcher_cpu_pre, NULL);
     ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "arm/bl:predown",
                     NULL, bL_switcher_cpu_pre);
     if (ret < 0) {
         cpuhp_remove_state_nocalls(CPUHP_ARM_BL_PREPARE);
         pr_err("bL_switcher: Failed to allocate a hotplug state\n");
         return ret;
     }
     if (!no_bL_switcher) {
         ret = bL_switcher_enable();
         if (ret)
             return ret;
     }
 
 #ifdef CONFIG_SYSFS
     ret = bL_switcher_sysfs_init();
     if (ret)
         pr_err("%s: unable to create sysfs entry\n", __func__);
 #endif
 
     return 0;
 }
 
 late_initcall(bL_switcher_init);

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