ARM: bL_switcher: ability to enable and disable the switcher via sysfs
The /sys/kernel/bL_switcher/enable file allows to enable or disable the switcher by writing 1 or 0 to it respectively. It is still enabled by default on boot. Signed-off-by: Nicolas Pitre <nico@linaro.org>
This commit is contained in:
Nicolas Pitre
Родитель
ed96762e32
Коммит
6b7437aed1
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@ -24,6 +24,7 @@
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#include <linux/tick.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/sysfs.h>
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#include <linux/irqchip/arm-gic.h>
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#include <asm/smp_plat.h>
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@ -220,6 +221,7 @@ struct bL_thread {
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struct task_struct *task;
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wait_queue_head_t wq;
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int wanted_cluster;
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struct completion started;
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};
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static struct bL_thread bL_threads[NR_CPUS];
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@ -231,6 +233,7 @@ static int bL_switcher_thread(void *arg)
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int cluster;
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sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m);
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complete(&t->started);
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do {
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if (signal_pending(current))
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@ -246,7 +249,7 @@ static int bL_switcher_thread(void *arg)
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return 0;
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}
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static struct task_struct * __init bL_switcher_thread_create(int cpu, void *arg)
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static struct task_struct *bL_switcher_thread_create(int cpu, void *arg)
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{
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struct task_struct *task;
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@ -295,9 +298,11 @@ EXPORT_SYMBOL_GPL(bL_switch_request);
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* Activation and configuration code.
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*/
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static unsigned int bL_switcher_active;
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static unsigned int bL_switcher_cpu_original_cluster[MAX_CPUS_PER_CLUSTER];
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static cpumask_t bL_switcher_removed_logical_cpus;
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static void __init bL_switcher_restore_cpus(void)
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static void bL_switcher_restore_cpus(void)
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{
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int i;
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@ -305,7 +310,7 @@ static void __init bL_switcher_restore_cpus(void)
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cpu_up(i);
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}
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static int __init bL_switcher_halve_cpus(void)
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static int bL_switcher_halve_cpus(void)
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{
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int cpu, cluster, i, ret;
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cpumask_t cluster_mask[2], common_mask;
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@ -349,8 +354,10 @@ static int __init bL_switcher_halve_cpus(void)
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* is equal to their physical CPU number. This is
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* not perfect but good enough for now.
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*/
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if (cpu == i)
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if (cpu == i) {
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bL_switcher_cpu_original_cluster[cpu] = cluster;
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continue;
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}
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}
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ret = cpu_down(i);
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@ -364,18 +371,18 @@ static int __init bL_switcher_halve_cpus(void)
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return 0;
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}
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static int __init bL_switcher_init(void)
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static int bL_switcher_enable(void)
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{
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int cpu, ret;
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pr_info("big.LITTLE switcher initializing\n");
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if (MAX_NR_CLUSTERS != 2) {
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pr_err("%s: only dual cluster systems are supported\n", __func__);
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return -EINVAL;
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cpu_hotplug_driver_lock();
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if (bL_switcher_active) {
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cpu_hotplug_driver_unlock();
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return 0;
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}
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cpu_hotplug_driver_lock();
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pr_info("big.LITTLE switcher initializing\n");
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ret = bL_switcher_halve_cpus();
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if (ret) {
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cpu_hotplug_driver_unlock();
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@ -385,13 +392,155 @@ static int __init bL_switcher_init(void)
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for_each_online_cpu(cpu) {
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struct bL_thread *t = &bL_threads[cpu];
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init_waitqueue_head(&t->wq);
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init_completion(&t->started);
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t->wanted_cluster = -1;
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t->task = bL_switcher_thread_create(cpu, t);
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}
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bL_switcher_active = 1;
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cpu_hotplug_driver_unlock();
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pr_info("big.LITTLE switcher initialized\n");
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return 0;
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}
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#ifdef CONFIG_SYSFS
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static void bL_switcher_disable(void)
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{
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unsigned int cpu, cluster, i;
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struct bL_thread *t;
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struct task_struct *task;
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cpu_hotplug_driver_lock();
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if (!bL_switcher_active) {
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cpu_hotplug_driver_unlock();
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return;
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}
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bL_switcher_active = 0;
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/*
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* To deactivate the switcher, we must shut down the switcher
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* threads to prevent any other requests from being accepted.
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* Then, if the final cluster for given logical CPU is not the
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* same as the original one, we'll recreate a switcher thread
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* just for the purpose of switching the CPU back without any
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* possibility for interference from external requests.
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*/
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for_each_online_cpu(cpu) {
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BUG_ON(cpu != (cpu_logical_map(cpu) & 0xff));
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t = &bL_threads[cpu];
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task = t->task;
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t->task = NULL;
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if (!task || IS_ERR(task))
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continue;
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kthread_stop(task);
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/* no more switch may happen on this CPU at this point */
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cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
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if (cluster == bL_switcher_cpu_original_cluster[cpu])
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continue;
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init_completion(&t->started);
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t->wanted_cluster = bL_switcher_cpu_original_cluster[cpu];
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task = bL_switcher_thread_create(cpu, t);
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if (!IS_ERR(task)) {
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wait_for_completion(&t->started);
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kthread_stop(task);
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cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
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if (cluster == bL_switcher_cpu_original_cluster[cpu])
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continue;
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}
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/* If execution gets here, we're in trouble. */
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pr_crit("%s: unable to restore original cluster for CPU %d\n",
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__func__, cpu);
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for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
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if ((cpu_logical_map(i) & 0xff) != cpu)
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continue;
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pr_crit("%s: CPU %d can't be restored\n",
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__func__, i);
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cpumask_clear_cpu(i, &bL_switcher_removed_logical_cpus);
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break;
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}
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}
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bL_switcher_restore_cpus();
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cpu_hotplug_driver_unlock();
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}
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static ssize_t bL_switcher_active_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
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{
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return sprintf(buf, "%u\n", bL_switcher_active);
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}
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static ssize_t bL_switcher_active_store(struct kobject *kobj,
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struct kobj_attribute *attr, const char *buf, size_t count)
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{
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int ret;
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switch (buf[0]) {
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case '0':
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bL_switcher_disable();
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ret = 0;
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break;
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case '1':
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ret = bL_switcher_enable();
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break;
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default:
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ret = -EINVAL;
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}
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return (ret >= 0) ? count : ret;
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}
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static struct kobj_attribute bL_switcher_active_attr =
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__ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
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static struct attribute *bL_switcher_attrs[] = {
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&bL_switcher_active_attr.attr,
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NULL,
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};
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static struct attribute_group bL_switcher_attr_group = {
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.attrs = bL_switcher_attrs,
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};
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static struct kobject *bL_switcher_kobj;
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static int __init bL_switcher_sysfs_init(void)
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{
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int ret;
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bL_switcher_kobj = kobject_create_and_add("bL_switcher", kernel_kobj);
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if (!bL_switcher_kobj)
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return -ENOMEM;
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ret = sysfs_create_group(bL_switcher_kobj, &bL_switcher_attr_group);
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if (ret)
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kobject_put(bL_switcher_kobj);
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return ret;
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}
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#endif /* CONFIG_SYSFS */
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static int __init bL_switcher_init(void)
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{
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int ret;
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if (MAX_NR_CLUSTERS != 2) {
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pr_err("%s: only dual cluster systems are supported\n", __func__);
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return -EINVAL;
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}
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ret = bL_switcher_enable();
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if (ret)
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return ret;
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#ifdef CONFIG_SYSFS
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ret = bL_switcher_sysfs_init();
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if (ret)
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pr_err("%s: unable to create sysfs entry\n", __func__);
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#endif
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return 0;
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}
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late_initcall(bL_switcher_init);
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