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Diffstat (limited to 'arch/arm/common/bL_switcher.c')
-rw-r--r--arch/arm/common/bL_switcher.c101
1 files changed, 78 insertions, 23 deletions
diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index c2d9c7da0a2..0a6d9737f0d 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/arch/arm/common/bL_switcher.c
@@ -15,8 +15,10 @@
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/cpu_pm.h>
+#include <linux/cpu.h>
#include <linux/cpumask.h>
-#include <linux/workqueue.h>
+#include <linux/kthread.h>
+#include <linux/wait.h>
#include <linux/clockchips.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
@@ -226,15 +228,48 @@ static int bL_switch_to(unsigned int new_cluster_id)
return ret;
}
-struct switch_args {
- unsigned int cluster;
- struct work_struct work;
+struct bL_thread {
+ struct task_struct *task;
+ wait_queue_head_t wq;
+ int wanted_cluster;
};
-static void __bL_switch_to(struct work_struct *work)
+static struct bL_thread bL_threads[MAX_CPUS_PER_CLUSTER];
+
+static int bL_switcher_thread(void *arg)
+{
+ struct bL_thread *t = arg;
+ struct sched_param param = { .sched_priority = 1 };
+ int cluster;
+
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
+
+ do {
+ if (signal_pending(current))
+ flush_signals(current);
+ wait_event_interruptible(t->wq,
+ t->wanted_cluster != -1 ||
+ kthread_should_stop());
+ cluster = xchg(&t->wanted_cluster, -1);
+ if (cluster != -1)
+ bL_switch_to(cluster);
+ } while (!kthread_should_stop());
+
+ return 0;
+}
+
+static struct task_struct * __init bL_switcher_thread_create(int cpu, void *arg)
{
- struct switch_args *args = container_of(work, struct switch_args, work);
- bL_switch_to(args->cluster);
+ 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;
}
/*
@@ -243,27 +278,47 @@ static void __bL_switch_to(struct work_struct *work)
* @cpu: the CPU to switch
* @new_cluster_id: the ID of the cluster to switch to.
*
- * This function causes a cluster switch on the given CPU. If the given
- * CPU is the same as the calling CPU then the switch happens right away.
- * Otherwise the request is put on a work queue to be scheduled on the
- * remote CPU.
+ * 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.
*/
-void bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
+int bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
{
- unsigned int this_cpu = get_cpu();
- struct switch_args args;
+ struct bL_thread *t;
- if (cpu == this_cpu) {
- bL_switch_to(new_cluster_id);
- put_cpu();
- return;
+ if (cpu >= MAX_CPUS_PER_CLUSTER) {
+ pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
+ return -EINVAL;
}
- put_cpu();
- args.cluster = new_cluster_id;
- INIT_WORK_ONSTACK(&args.work, __bL_switch_to);
- schedule_work_on(cpu, &args.work);
- flush_work(&args.work);
+ t = &bL_threads[cpu];
+ if (IS_ERR(t->task))
+ return PTR_ERR(t->task);
+ if (!t->task)
+ return -ESRCH;
+
+ t->wanted_cluster = new_cluster_id;
+ wake_up(&t->wq);
+ return 0;
}
EXPORT_SYMBOL_GPL(bL_switch_request);
+
+static int __init bL_switcher_init(void)
+{
+ int cpu;
+
+ pr_info("big.LITTLE switcher initializing\n");
+
+ for_each_online_cpu(cpu) {
+ struct bL_thread *t = &bL_threads[cpu];
+ init_waitqueue_head(&t->wq);
+ t->wanted_cluster = -1;
+ t->task = bL_switcher_thread_create(cpu, t);
+ }
+
+ pr_info("big.LITTLE switcher initialized\n");
+ return 0;
+}
+
+late_initcall(bL_switcher_init);