cpuidle: allow governor switch on cpuidle_register_driver()

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>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpuidle/cpuidle.h b/drivers/cpuidle/cpuidle.h
index d6613101af9246ee112df42c36a5abd2d63ceb56..9f336af17fa6038abe7b939b6c4718fd6965c540 100644 (file)
--- a/drivers/cpuidle/cpuidle.h
+++ b/drivers/cpuidle/cpuidle.h
@@ -9,6 +9,7 @@
 /* For internal use only */
 extern char param_governor[];
 extern struct cpuidle_governor *cpuidle_curr_governor;
+extern struct cpuidle_governor *cpuidle_prev_governor;
 extern struct list_head cpuidle_governors;
 extern struct list_head cpuidle_detected_devices;
 extern struct mutex cpuidle_lock;
@@ -22,6 +23,7 @@ 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 dc32f34e68d9379dceee6f04795fe81473a8f9ca..80c1a830d99178c8906e66e044dbe445798b9ab6 100644 (file)
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -254,12 +254,25 @@ 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 +287,21 @@ 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 2e3e14192beee760b1341261b4b3da6ed1ff0d98..e9801f26c73270c6665a117a60b1e45d32186217 100644 (file)
--- a/drivers/cpuidle/governor.c
+++ b/drivers/cpuidle/governor.c
@@ -20,14 +20,15 @@ char param_governor[CPUIDLE_NAME_LEN];
 
 LIST_HEAD(cpuidle_governors);
 struct cpuidle_governor *cpuidle_curr_governor;
+struct cpuidle_governor *cpuidle_prev_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 +88,7 @@ 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 1a9f54eb3aa1e01221c92279b58a2a22374679c9..2dc4c6b19c253c860d29cc6913cb1f6f85bd448a 100644 (file)
--- 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