cpuidle: support multiple drivers

With the tegra3 and the big.LITTLE [1] new architectures, several cpus
with different characteristics (latencies and states) can co-exists on the
system.

The cpuidle framework has the limitation of handling only identical cpus.

This patch removes this limitation by introducing the multiple driver support
for cpuidle.

This option is configurable at compile time and should be enabled for the
architectures mentioned above. So there is no impact for the other platforms
if the option is disabled. The option defaults to 'n'. Note the multiple drivers
support is also compatible with the existing drivers, even if just one driver is
needed, all the cpu will be tied to this driver using an extra small chunk of
processor memory.

The multiple driver support use a per-cpu driver pointer instead of a global
variable and the accessor to this variable are done from a cpu context.

In order to keep the compatibility with the existing drivers, the function
'cpuidle_register_driver' and 'cpuidle_unregister_driver' will register
the specified driver for all the cpus.

The semantic for the output of /sys/devices/system/cpu/cpuidle/current_driver
remains the same except the driver name will be related to the current cpu.

The /sys/devices/system/cpu/cpu[0-9]/cpuidle/driver/name files are added
allowing to read the per cpu driver name.

[1] http://lwn.net/Articles/481055/

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 149 insertions, 17 deletions

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 8246662..3af841f 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -14,9 +14,11 @@
 
 #include "cpuidle.h"
 
-static struct cpuidle_driver *cpuidle_curr_driver;
 DEFINE_SPINLOCK(cpuidle_driver_lock);
 
+static void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu);
+static struct cpuidle_driver * __cpuidle_get_cpu_driver(int cpu);
+
 static void set_power_states(struct cpuidle_driver *drv)
 {
 	int i;
@@ -47,12 +49,7 @@ static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 		set_power_states(drv);
 }
 
-static void cpuidle_set_driver(struct cpuidle_driver *drv)
-{
-	cpuidle_curr_driver = drv;
-}
-
-static int __cpuidle_register_driver(struct cpuidle_driver *drv)
+static int __cpuidle_register_driver(struct cpuidle_driver *drv, int cpu)
 {
 	if (!drv || !drv->state_count)
 		return -EINVAL;
@@ -60,23 +57,84 @@ static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 	if (cpuidle_disabled())
 		return -ENODEV;
 
-	if (cpuidle_get_driver())
+	if (__cpuidle_get_cpu_driver(cpu))
 		return -EBUSY;
 
 	__cpuidle_driver_init(drv);
 
-	cpuidle_set_driver(drv);
+	__cpuidle_set_cpu_driver(drv, cpu);
 
 	return 0;
 }
 
-static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
+static void __cpuidle_unregister_driver(struct cpuidle_driver *drv, int cpu)
 {
-	if (drv != cpuidle_get_driver())
+	if (drv != __cpuidle_get_cpu_driver(cpu))
 		return;
 
 	if (!WARN_ON(drv->refcnt > 0))
-		cpuidle_set_driver(NULL);
+		__cpuidle_set_cpu_driver(NULL, cpu);
+}
+
+#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
+
+static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
+
+static void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu)
+{
+	per_cpu(cpuidle_drivers, cpu) = drv;
+}
+
+static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
+{
+	return per_cpu(cpuidle_drivers, cpu);
+}
+
+static void __cpuidle_unregister_all_cpu_driver(struct cpuidle_driver *drv)
+{
+	int cpu;
+	for_each_present_cpu(cpu)
+		__cpuidle_unregister_driver(drv, cpu);
+}
+
+static int __cpuidle_register_all_cpu_driver(struct cpuidle_driver *drv)
+{
+	int ret = 0;
+	int i, cpu;
+
+	for_each_present_cpu(cpu) {
+		ret = __cpuidle_register_driver(drv, cpu);
+		if (ret)
+			break;
+	}
+
+	if (ret)
+		for_each_present_cpu(i) {
+			if (i == cpu)
+				break;
+			__cpuidle_unregister_driver(drv, i);
+		}
+
+
+	return ret;
+}
+
+int cpuidle_register_cpu_driver(struct cpuidle_driver *drv, int cpu)
+{
+	int ret;
+
+	spin_lock(&cpuidle_driver_lock);
+	ret = __cpuidle_register_driver(drv, cpu);
+	spin_unlock(&cpuidle_driver_lock);
+
+	return ret;
+}
+
+void cpuidle_unregister_cpu_driver(struct cpuidle_driver *drv, int cpu)
+{
+	spin_lock(&cpuidle_driver_lock);
+	__cpuidle_unregister_driver(drv, cpu);
+	spin_unlock(&cpuidle_driver_lock);
 }
 
 /**
@@ -88,7 +146,7 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
 	int ret;
 
 	spin_lock(&cpuidle_driver_lock);
-	ret = __cpuidle_register_driver(drv);
+	ret = __cpuidle_register_all_cpu_driver(drv);
 	spin_unlock(&cpuidle_driver_lock);
 
 	return ret;
@@ -96,13 +154,48 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 
 /**
- * cpuidle_get_driver - return the current driver
+ * cpuidle_unregister_driver - unregisters a driver
+ * @drv: the driver
  */
-struct cpuidle_driver *cpuidle_get_driver(void)
+void cpuidle_unregister_driver(struct cpuidle_driver *drv)
+{
+	spin_lock(&cpuidle_driver_lock);
+	__cpuidle_unregister_all_cpu_driver(drv);
+	spin_unlock(&cpuidle_driver_lock);
+}
+EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
+
+#else
+
+static struct cpuidle_driver *cpuidle_curr_driver;
+
+static inline void __cpuidle_set_cpu_driver(struct cpuidle_driver *drv, int cpu)
+{
+	cpuidle_curr_driver = drv;
+}
+
+static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
 {
 	return cpuidle_curr_driver;
 }
-EXPORT_SYMBOL_GPL(cpuidle_get_driver);
+
+/**
+ * cpuidle_register_driver - registers a driver
+ * @drv: the driver
+ */
+int cpuidle_register_driver(struct cpuidle_driver *drv)
+{
+	int ret, cpu;
+
+	cpu = get_cpu();
+	spin_lock(&cpuidle_driver_lock);
+	ret = __cpuidle_register_driver(drv, cpu);
+	spin_unlock(&cpuidle_driver_lock);
+	put_cpu();
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 
 /**
  * cpuidle_unregister_driver - unregisters a driver
@@ -110,11 +203,50 @@ EXPORT_SYMBOL_GPL(cpuidle_get_driver);
  */
 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 {
+	int cpu;
+
+	cpu = get_cpu();
 	spin_lock(&cpuidle_driver_lock);
-	__cpuidle_unregister_driver(drv);
+	__cpuidle_unregister_driver(drv, cpu);
 	spin_unlock(&cpuidle_driver_lock);
+	put_cpu();
 }
 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
+#endif
+
+/**
+ * cpuidle_get_driver - return the current driver
+ */
+struct cpuidle_driver *cpuidle_get_driver(void)
+{
+	struct cpuidle_driver *drv;
+	int cpu;
+
+	cpu = get_cpu();
+	drv = __cpuidle_get_cpu_driver(cpu);
+	put_cpu();
+
+	return drv;
+}
+EXPORT_SYMBOL_GPL(cpuidle_get_driver);
+
+/**
+ * cpuidle_get_cpu_driver - return the driver tied with a cpu
+ */
+struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
+{
+	struct cpuidle_driver *drv;
+
+	if (!dev)
+		return NULL;
+
+	spin_lock(&cpuidle_driver_lock);
+	drv = __cpuidle_get_cpu_driver(dev->cpu);
+	spin_unlock(&cpuidle_driver_lock);
+
+	return drv;
+}
+EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 
 struct cpuidle_driver *cpuidle_driver_ref(void)
 {