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Subject[PATCH v1 1/4] cpuidle: allow governor switch on cpuidle_register_driver()
Date

The recently introduced haltpoll driver is largely only useful with
haltpoll governor. To allow drivers to associate with a particular idle
behaviour, add a @governor property to 'struct cpuidle_driver' and thus
allow a cpuidle driver to switch to a *preferred* governor on idle driver
registration. We save the previous governor, and when an idle driver is
unregistered we switch back to that.

The @governor can be overridden by cpuidle.governor= boot param or
alternatively be ignored if the governor doesn't exist.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
drivers/cpuidle/cpuidle.h | 1 +
drivers/cpuidle/driver.c | 26 ++++++++++++++++++++++++++
drivers/cpuidle/governor.c | 6 +++---
include/linux/cpuidle.h | 3 +++
4 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
index d6613101af92..c046f49c1920 100644
--- a/drivers/cpuidle/cpuidle.h
+++ b/drivers/cpuidle/cpuidle.h
@@ -22,6 +22,7 @@ extern void cpuidle_install_idle_handler(void);
extern void cpuidle_uninstall_idle_handler(void);

/* governors */
+extern struct cpuidle_governor *cpuidle_find_governor(const char *str);
extern int cpuidle_switch_governor(struct cpuidle_governor *gov);

/* sysfs */
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index dc32f34e68d9..16a3f6c5ad69 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -87,6 +87,7 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
#else

static struct cpuidle_driver *cpuidle_curr_driver;
+static struct cpuidle_governor *cpuidle_prev_governor;

/**
* __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
@@ -254,12 +255,25 @@ static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
*/
int cpuidle_register_driver(struct cpuidle_driver *drv)
{
+ struct cpuidle_governor *gov;
int ret;

spin_lock(&cpuidle_driver_lock);
ret = __cpuidle_register_driver(drv);
spin_unlock(&cpuidle_driver_lock);

+ if (!ret && !strlen(param_governor) && drv->governor &&
+ (cpuidle_get_driver() == drv)) {
+ mutex_lock(&cpuidle_lock);
+ gov = cpuidle_find_governor(drv->governor);
+ if (gov) {
+ cpuidle_prev_governor = cpuidle_curr_governor;
+ if (cpuidle_switch_governor(gov) < 0)
+ cpuidle_prev_governor = NULL;
+ }
+ mutex_unlock(&cpuidle_lock);
+ }
+
return ret;
}
EXPORT_SYMBOL_GPL(cpuidle_register_driver);
@@ -274,9 +288,21 @@ EXPORT_SYMBOL_GPL(cpuidle_register_driver);
*/
void cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
+ bool enabled = (cpuidle_get_driver() == drv);
+
spin_lock(&cpuidle_driver_lock);
__cpuidle_unregister_driver(drv);
spin_unlock(&cpuidle_driver_lock);
+
+ if (!enabled)
+ return;
+
+ mutex_lock(&cpuidle_lock);
+ if (cpuidle_prev_governor) {
+ if (!cpuidle_switch_governor(cpuidle_prev_governor))
+ cpuidle_prev_governor = NULL;
+ }
+ mutex_unlock(&cpuidle_lock);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);

diff --git a/drivers/cpuidle/governor.c b/drivers/cpuidle/governor.c
index 2e3e14192bee..08707759469e 100644
--- a/drivers/cpuidle/governor.c
+++ b/drivers/cpuidle/governor.c
@@ -22,12 +22,12 @@ LIST_HEAD(cpuidle_governors);
struct cpuidle_governor *cpuidle_curr_governor;

/**
- * __cpuidle_find_governor - finds a governor of the specified name
+ * cpuidle_find_governor - finds a governor of the specified name
* @str: the name
*
* Must be called with cpuidle_lock acquired.
*/
-static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
+struct cpuidle_governor *cpuidle_find_governor(const char *str)
{
struct cpuidle_governor *gov;

@@ -87,7 +87,7 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
return -ENODEV;

mutex_lock(&cpuidle_lock);
- if (__cpuidle_find_governor(gov->name) == NULL) {
+ if (cpuidle_find_governor(gov->name) == NULL) {
ret = 0;
list_add_tail(&gov->governor_list, &cpuidle_governors);
if (!cpuidle_curr_governor ||
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 1a9f54eb3aa1..2dc4c6b19c25 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -121,6 +121,9 @@ struct cpuidle_driver {

/* the driver handles the cpus in cpumask */
struct cpumask *cpumask;
+
+ /* preferred governor to switch at register time */
+ const char *governor;
};

#ifdef CONFIG_CPU_IDLE
--
2.17.1
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