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, 168 insertions, 6 deletions

diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
index 49b1f4bc..3409429 100644
--- a/drivers/cpuidle/sysfs.c
+++ b/drivers/cpuidle/sysfs.c
@@ -364,17 +364,17 @@ static inline void cpuidle_free_state_kobj(struct cpuidle_device *device, int i)
 }
 
 /**
- * cpuidle_add_driver_sysfs - adds driver-specific sysfs attributes
+ * cpuidle_add_state_sysfs - adds cpuidle states sysfs attributes
  * @device: the target device
  */
-int cpuidle_add_state_sysfs(struct cpuidle_device *device)
+static int cpuidle_add_state_sysfs(struct cpuidle_device *device)
 {
 	int i, ret = -ENOMEM;
 	struct cpuidle_state_kobj *kobj;
-	struct cpuidle_driver *drv = cpuidle_get_driver();
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(device);
 
 	/* state statistics */
-	for (i = 0; i < device->state_count; i++) {
+	for (i = 0; i < drv->state_count; i++) {
 		kobj = kzalloc(sizeof(struct cpuidle_state_kobj), GFP_KERNEL);
 		if (!kobj)
 			goto error_state;
@@ -401,10 +401,10 @@ error_state:
 }
 
 /**
- * cpuidle_remove_driver_sysfs - removes driver-specific sysfs attributes
+ * cpuidle_remove_driver_sysfs - removes the cpuidle states sysfs attributes
  * @device: the target device
  */
-void cpuidle_remove_state_sysfs(struct cpuidle_device *device)
+static void cpuidle_remove_state_sysfs(struct cpuidle_device *device)
 {
 	int i;
 
@@ -412,6 +412,168 @@ void cpuidle_remove_state_sysfs(struct cpuidle_device *device)
 		cpuidle_free_state_kobj(device, i);
 }
 
+#ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
+#define kobj_to_driver_kobj(k) container_of(k, struct cpuidle_driver_kobj, kobj)
+#define attr_to_driver_attr(a) container_of(a, struct cpuidle_driver_attr, attr)
+
+#define define_one_driver_ro(_name, show)                       \
+	static struct cpuidle_driver_attr attr_driver_##_name = \
+		__ATTR(_name, 0644, show, NULL)
+
+struct cpuidle_driver_kobj {
+	struct cpuidle_driver *drv;
+	struct completion kobj_unregister;
+	struct kobject kobj;
+};
+
+struct cpuidle_driver_attr {
+	struct attribute attr;
+	ssize_t (*show)(struct cpuidle_driver *, char *);
+	ssize_t (*store)(struct cpuidle_driver *, const char *, size_t);
+};
+
+static ssize_t show_driver_name(struct cpuidle_driver *drv, char *buf)
+{
+	ssize_t ret;
+
+	spin_lock(&cpuidle_driver_lock);
+	ret = sprintf(buf, "%s\n", drv ? drv->name : "none");
+	spin_unlock(&cpuidle_driver_lock);
+
+	return ret;
+}
+
+static void cpuidle_driver_sysfs_release(struct kobject *kobj)
+{
+	struct cpuidle_driver_kobj *driver_kobj = kobj_to_driver_kobj(kobj);
+	complete(&driver_kobj->kobj_unregister);
+}
+
+static ssize_t cpuidle_driver_show(struct kobject *kobj, struct attribute * attr,
+				   char * buf)
+{
+	int ret = -EIO;
+	struct cpuidle_driver_kobj *driver_kobj = kobj_to_driver_kobj(kobj);
+	struct cpuidle_driver_attr *dattr = attr_to_driver_attr(attr);
+
+	if (dattr->show)
+		ret = dattr->show(driver_kobj->drv, buf);
+
+	return ret;
+}
+
+static ssize_t cpuidle_driver_store(struct kobject *kobj, struct attribute *attr,
+				    const char *buf, size_t size)
+{
+	int ret = -EIO;
+	struct cpuidle_driver_kobj *driver_kobj = kobj_to_driver_kobj(kobj);
+	struct cpuidle_driver_attr *dattr = attr_to_driver_attr(attr);
+
+	if (dattr->store)
+		ret = dattr->store(driver_kobj->drv, buf, size);
+
+	return ret;
+}
+
+define_one_driver_ro(name, show_driver_name);
+
+static const struct sysfs_ops cpuidle_driver_sysfs_ops = {
+	.show = cpuidle_driver_show,
+	.store = cpuidle_driver_store,
+};
+
+static struct attribute *cpuidle_driver_default_attrs[] = {
+	&attr_driver_name.attr,
+	NULL
+};
+
+static struct kobj_type ktype_driver_cpuidle = {
+	.sysfs_ops = &cpuidle_driver_sysfs_ops,
+	.default_attrs = cpuidle_driver_default_attrs,
+	.release = cpuidle_driver_sysfs_release,
+};
+
+/**
+ * cpuidle_add_driver_sysfs - adds the driver name sysfs attribute
+ * @device: the target device
+ */
+static int cpuidle_add_driver_sysfs(struct cpuidle_device *dev)
+{
+	struct cpuidle_driver_kobj *kdrv;
+	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
+	int ret;
+
+	kdrv = kzalloc(sizeof(*kdrv), GFP_KERNEL);
+	if (!kdrv)
+		return -ENOMEM;
+
+	kdrv->drv = drv;
+	init_completion(&kdrv->kobj_unregister);
+
+	ret = kobject_init_and_add(&kdrv->kobj, &ktype_driver_cpuidle,
+				   &dev->kobj, "driver");
+	if (ret) {
+		kfree(kdrv);
+		return ret;
+	}
+
+	kobject_uevent(&kdrv->kobj, KOBJ_ADD);
+	dev->kobj_driver = kdrv;
+
+	return ret;
+}
+
+/**
+ * cpuidle_remove_driver_sysfs - removes the driver name sysfs attribute
+ * @device: the target device
+ */
+static void cpuidle_remove_driver_sysfs(struct cpuidle_device *dev)
+{
+	struct cpuidle_driver_kobj *kdrv = dev->kobj_driver;
+	kobject_put(&kdrv->kobj);
+	wait_for_completion(&kdrv->kobj_unregister);
+	kfree(kdrv);
+}
+#else
+static inline int cpuidle_add_driver_sysfs(struct cpuidle_device *dev)
+{
+	return 0;
+}
+
+static inline void cpuidle_remove_driver_sysfs(struct cpuidle_device *dev)
+{
+	;
+}
+#endif
+
+/**
+ * cpuidle_add_device_sysfs - adds device specific sysfs attributes
+ * @device: the target device
+ */
+int cpuidle_add_device_sysfs(struct cpuidle_device *device)
+{
+	int ret;
+
+	ret = cpuidle_add_state_sysfs(device);
+	if (ret)
+		return ret;
+
+	ret = cpuidle_add_driver_sysfs(device);
+	if (ret)
+		cpuidle_remove_state_sysfs(device);
+	return ret;
+}
+
+/**
+ * cpuidle_remove_device_sysfs : removes device specific sysfs attributes
+ * @device : the target device
+ */
+void cpuidle_remove_device_sysfs(struct cpuidle_device *device)
+{
+	cpuidle_remove_driver_sysfs(device);
+	cpuidle_remove_state_sysfs(device);
+}
+
 /**
  * cpuidle_add_sysfs - creates a sysfs instance for the target device
  * @dev: the target device