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authorNicolas Pitre <nicolas.pitre@linaro.org>2012-11-22 00:05:07 -0500
committerNicolas Pitre <nicolas.pitre@linaro.org>2013-06-19 16:54:23 -0400
commit9b7beeac2a8f6f2629625e0766dbbd8582e43bd7 (patch)
tree0b7d988956a583b01c84289b53b35affc7cf7bdc /arch/arm/common/bL_switcher.c
parenteb3525e4e0279291d89546a1d8c240079943b8b2 (diff)
downloadvexpress-lsk-9b7beeac2a8f6f2629625e0766dbbd8582e43bd7.tar.gz
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>
Diffstat (limited to 'arch/arm/common/bL_switcher.c')
-rw-r--r--arch/arm/common/bL_switcher.c171
1 files changed, 160 insertions, 11 deletions
diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index 0d9ece547a1..31ca04c0ab4 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/arch/arm/common/bL_switcher.c
@@ -24,6 +24,7 @@
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/string.h>
+#include <linux/sysfs.h>
#include <linux/irqchip/arm-gic.h>
#include <asm/smp_plat.h>
@@ -227,6 +228,7 @@ struct bL_thread {
struct task_struct *task;
wait_queue_head_t wq;
int wanted_cluster;
+ struct completion started;
};
static struct bL_thread bL_threads[MAX_CPUS_PER_CLUSTER];
@@ -238,6 +240,7 @@ static int bL_switcher_thread(void *arg)
int cluster;
sched_setscheduler_nocheck(current, SCHED_FIFO, &param);
+ complete(&t->started);
do {
if (signal_pending(current))
@@ -253,7 +256,7 @@ static int bL_switcher_thread(void *arg)
return 0;
}
-static struct task_struct * __init bL_switcher_thread_create(int cpu, void *arg)
+static struct task_struct * bL_switcher_thread_create(int cpu, void *arg)
{
struct task_struct *task;
@@ -303,9 +306,11 @@ EXPORT_SYMBOL_GPL(bL_switch_request);
* Activation and configuration code.
*/
+static unsigned int bL_switcher_active;
+static unsigned int bL_switcher_cpu_original_cluster[MAX_CPUS_PER_CLUSTER];
static cpumask_t bL_switcher_removed_logical_cpus;
-static void __init bL_switcher_restore_cpus(void)
+static void bL_switcher_restore_cpus(void)
{
int i;
@@ -313,7 +318,7 @@ static void __init bL_switcher_restore_cpus(void)
cpu_up(i);
}
-static int __init bL_switcher_halve_cpus(void)
+static int bL_switcher_halve_cpus(void)
{
int cpu, cluster, i, ret;
cpumask_t cluster_mask[2], common_mask;
@@ -357,8 +362,10 @@ static int __init bL_switcher_halve_cpus(void)
* is equal to their physical CPU number. This is
* not perfect but good enough in most cases.
*/
- if (cpu == i)
+ if (cpu == i) {
+ bL_switcher_cpu_original_cluster[cpu] = cluster;
continue;
+ }
}
ret = cpu_down(i);
@@ -372,18 +379,18 @@ static int __init bL_switcher_halve_cpus(void)
return 0;
}
-static int __init bL_switcher_init(void)
+static int bL_switcher_enable(void)
{
int cpu, ret;
- pr_info("big.LITTLE switcher initializing\n");
-
- if (MAX_NR_CLUSTERS != 2) {
- pr_err("%s: only dual cluster systems are supported\n", __func__);
- return -EINVAL;
+ cpu_hotplug_driver_lock();
+ if (bL_switcher_active) {
+ cpu_hotplug_driver_unlock();
+ return 0;
}
- cpu_hotplug_driver_lock();
+ pr_info("big.LITTLE switcher initializing\n");
+
ret = bL_switcher_halve_cpus();
if (ret) {
cpu_hotplug_driver_unlock();
@@ -393,13 +400,155 @@ static int __init bL_switcher_init(void)
for_each_online_cpu(cpu) {
struct bL_thread *t = &bL_threads[cpu];
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;
cpu_hotplug_driver_unlock();
pr_info("big.LITTLE switcher initialized\n");
return 0;
}
+#ifdef CONFIG_SYSFS
+
+static void bL_switcher_disable(void)
+{
+ unsigned int cpu, cluster, i;
+ struct bL_thread *t;
+ struct task_struct *task;
+
+ cpu_hotplug_driver_lock();
+ if (!bL_switcher_active) {
+ cpu_hotplug_driver_unlock();
+ return;
+ }
+ 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) {
+ BUG_ON(cpu != (cpu_logical_map(cpu) & 0xff));
+ t = &bL_threads[cpu];
+ task = t->task;
+ t->task = NULL;
+ if (IS_ERR_OR_NULL(task))
+ continue;
+ kthread_stop(task);
+ /* no more switch may happen on this CPU at this point */
+ cluster = (cpu_logical_map(cpu) >> 8) & 0xff;
+ 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 = (cpu_logical_map(cpu) >> 8) & 0xff;
+ 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);
+ for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
+ if ((cpu_logical_map(i) & 0xff) != cpu)
+ continue;
+ pr_crit("%s: CPU %d can't be restored\n",
+ __func__, i);
+ cpumask_clear_cpu(i, &bL_switcher_removed_logical_cpus);
+ break;
+ }
+ }
+
+ bL_switcher_restore_cpus();
+ cpu_hotplug_driver_unlock();
+}
+
+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 struct kobj_attribute bL_switcher_active_attr =
+ __ATTR(active, 0644, bL_switcher_active_show, bL_switcher_active_store);
+
+static struct attribute *bL_switcher_attrs[] = {
+ &bL_switcher_active_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 */
+
+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;
+ }
+
+ 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);