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ARM: bL_switcher: Add synchronous enable/disable interface

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Some subsystems will need to know for sure whether the switcher is
enabled or disabled during certain critical regions.

This patch provides a simple mutex-based mechanism to discover
whether the switcher is enabled and temporarily lock out further
enable/disable:

  * bL_switcher_get_enabled() returns true iff the switcher is
    enabled and temporarily inhibits enable/disable.

  * bL_switcher_put_enabled() permits enable/disable of the switcher
    again after a previous call to bL_switcher_get_enabled().

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
This commit is contained in:
Dave Martin 2012-12-10 17:19:57 +00:00 committed by Nicolas Pitre
parent 7f63037c8f
commit c0f4375146
2 changed files with 28 additions and 2 deletions
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27
arch/arm/common/bL_switcher.c
View file

@ -23,6 +23,7 @@
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/irqchip/arm-gic.h>
@ -302,6 +303,7 @@ EXPORT_SYMBOL_GPL(bL_switch_request);
* Activation and configuration code.
*/
static DEFINE_MUTEX(bL_switcher_activation_lock);
static unsigned int bL_switcher_active;
static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
static cpumask_t bL_switcher_removed_logical_cpus;
@ -413,9 +415,11 @@ 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;
}
@ -424,6 +428,7 @@ static int bL_switcher_enable(void)
ret = bL_switcher_halve_cpus();
if (ret) {
cpu_hotplug_driver_unlock();
mutex_unlock(&bL_switcher_activation_lock);
return ret;
}
@ -436,9 +441,10 @@ static int bL_switcher_enable(void)
}
bL_switcher_active = 1;
cpu_hotplug_driver_unlock();
pr_info("big.LITTLE switcher initialized\n");
cpu_hotplug_driver_unlock();
mutex_unlock(&bL_switcher_activation_lock);
return 0;
}
@ -450,9 +456,11 @@ static void bL_switcher_disable(void)
struct bL_thread *t;
struct task_struct *task;
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;
}
bL_switcher_active = 0;
@ -497,6 +505,7 @@ static void bL_switcher_disable(void)
bL_switcher_restore_cpus();
cpu_hotplug_driver_unlock();
mutex_unlock(&bL_switcher_activation_lock);
}
static ssize_t bL_switcher_active_show(struct kobject *kobj,
@ -554,6 +563,20 @@ static int __init bL_switcher_sysfs_init(void)
#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.

3
arch/arm/include/asm/bL_switcher.h
View file

@ -14,4 +14,7 @@
int bL_switch_request(unsigned int cpu, unsigned int new_cluster_id);
bool bL_switcher_get_enabled(void);
void bL_switcher_put_enabled(void);
#endif