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authorMark Brown <broonie@linaro.org>2013-07-17 18:34:04 +0100
committerMark Brown <broonie@linaro.org>2013-07-17 18:34:04 +0100
commit20ce13dacdefe4d429217e710bf5461a4c6d1cf9 (patch)
tree3fc24c16594a2329ad190438586ce709e6c94746 /arch/arm/common/bL_switcher.c
parent8bb495e3f02401ee6f76d1b1d77f3ac9f079e376 (diff)
parent8e3aa3f1462fc25b810e867059b292675f0d3a94 (diff)
downloadvexpress-lsk-topic/v3.10/iks.tar.gz
Merge branch 'iks' of git://git.linaro.org/people/nico/linux into lsk-v3.10-iksv3.10/topic/ikstopic/v3.10/iks
Diffstat (limited to 'arch/arm/common/bL_switcher.c')
-rw-r--r--arch/arm/common/bL_switcher.c860
1 files changed, 860 insertions, 0 deletions
diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
new file mode 100644
index 00000000000..1883c5b3e3f
--- /dev/null
+++ b/arch/arm/common/bL_switcher.c
@@ -0,0 +1,860 @@
+/*
+ * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
+ *
+ * Created by: Nicolas Pitre, March 2012
+ * Copyright: (C) 2012 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/atomic.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.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/cacheflush.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\tp15, 0, %0, c0, c0, 5" : "=r" (id));
+ return id & MPIDR_HWID_BITMASK;
+}
+
+/*
+ * Get a global nanosecond time stamp for tracing.
+ */
+static s64 get_ns(void)
+{
+ struct timespec ts;
+ getnstimeofday(&ts);
+ return timespec_to_ns(&ts);
+}
+
+/*
+ * 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;
+ struct tick_device *tdev;
+ enum clock_event_mode tdev_mode;
+ 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 sleep/schedule anymore.
+ */
+ local_irq_disable();
+ local_fiq_disable();
+ trace_cpu_migrate_begin(get_ns(), ob_mpidr);
+
+ /* redirect GIC's SGIs to our counterpart */
+ gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
+
+ tdev = tick_get_device(this_cpu);
+ if (tdev && !cpumask_equal(tdev->evtdev->cpumask, cpumask_of(this_cpu)))
+ tdev = NULL;
+ if (tdev) {
+ tdev_mode = tdev->evtdev->mode;
+ clockevents_set_mode(tdev->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
+ }
+
+ 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.
+ * This must be flushed to RAM as the resume code
+ * needs to access it while the caches are still disabled.
+ */
+ cpu_logical_map(this_cpu) = ib_mpidr;
+ cpu_logical_map(that_cpu) = ob_mpidr;
+ sync_cache_w(&cpu_logical_map(this_cpu));
+
+ /* 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();
+
+ if (tdev) {
+ clockevents_set_mode(tdev->evtdev, tdev_mode);
+ clockevents_program_event(tdev->evtdev,
+ tdev->evtdev->next_event, 1);
+ }
+
+ trace_cpu_migrate_finish(get_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;
+ struct sched_param param = { .sched_priority = 1 };
+ int cluster;
+ bL_switch_completion_handler completer;
+ void *completer_cookie;
+
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
+ 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);
+
+/*
+ * Detach an outstanding switch request.
+ *
+ * The switcher will continue with the switch request in the background,
+ * but the completer function will not be called.
+ *
+ * This may be necessary if the completer is in a kernel module which is
+ * about to be unloaded.
+ */
+void bL_switch_request_detach(unsigned int cpu,
+ bL_switch_completion_handler completer)
+{
+ struct bL_thread *t;
+
+ if (cpu >= ARRAY_SIZE(bL_threads)) {
+ pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
+ return;
+ }
+
+ t = &bL_threads[cpu];
+
+ if (IS_ERR(t->task) || !t->task)
+ return;
+
+ spin_lock(&t->lock);
+ if (t->completer == completer)
+ t->completer = NULL;
+ spin_unlock(&t->lock);
+}
+
+EXPORT_SYMBOL_GPL(bL_switch_request_detach);
+
+/*
+ * 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)
+ cpu_up(i);
+}
+
+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"
+ * pairing 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 = cpu_down(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(get_ns(), read_mpidr());
+}
+
+int bL_switcher_trace_trigger(void)
+{
+ int ret;
+
+ preempt_disable();
+
+ bL_switcher_trace_trigger_cpu(NULL);
+ ret = smp_call_function(bL_switcher_trace_trigger_cpu, NULL, true);
+
+ preempt_enable();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(bL_switcher_trace_trigger);
+
+static int bL_switcher_enable(void)
+{
+ int cpu, ret;
+
+ mutex_lock(&bL_switcher_activation_lock);
+ cpu_hotplug_driver_lock();
+ if (bL_switcher_active) {
+ cpu_hotplug_driver_unlock();
+ 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_warning("big.LITTLE switcher initialization failed\n");
+ bL_activation_notify(BL_NOTIFY_POST_DISABLE);
+
+out:
+ cpu_hotplug_driver_unlock();
+ 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);
+ cpu_hotplug_driver_lock();
+
+ 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:
+ cpu_hotplug_driver_unlock();
+ 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 while the switcher is active.
+ * We're just not ready to deal with that given the trickery involved.
+ */
+static int bL_switcher_hotplug_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_DOWN_PREPARE:
+ if (bL_switcher_active)
+ return NOTIFY_BAD;
+ }
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block bL_switcher_hotplug_notifier =
+ { &bL_switcher_hotplug_callback, NULL, 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 (MAX_NR_CLUSTERS != 2) {
+ pr_err("%s: only dual cluster systems are supported\n", __func__);
+ return -EINVAL;
+ }
+
+ register_cpu_notifier(&bL_switcher_hotplug_notifier);
+
+ 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);