PM / devfreq: allow sysfs governor node to switch governor
This allows us to select governor runtime from the
default configuration without having to rebuild kernel
or the devfreq driver using the sysfs node:
/sys/class/devfreq/.../governor
cat of the governor will return valid governor
and an echo 'governor_name'>governor will switch
governor
Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index 40f98a9..66876de 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -11,7 +11,7 @@
Date: September 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
- The /sys/class/devfreq/.../governor shows the name of the
+ The /sys/class/devfreq/.../governor show or set the name of the
governor used by the corresponding devfreq object.
What: /sys/class/devfreq/.../cur_freq
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0d7be03..ff960f0 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -688,6 +688,49 @@
return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
}
+static ssize_t store_governor(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct devfreq *df = to_devfreq(dev);
+ int ret;
+ char str_governor[DEVFREQ_NAME_LEN + 1];
+ struct devfreq_governor *governor;
+
+ ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
+ if (ret != 1)
+ return -EINVAL;
+
+ mutex_lock(&devfreq_list_lock);
+ governor = find_devfreq_governor(str_governor);
+ if (IS_ERR(governor)) {
+ ret = PTR_ERR(governor);
+ goto out;
+ }
+ if (df->governor == governor)
+ goto out;
+
+ if (df->governor) {
+ ret = df->governor->event_handler(df, DEVFREQ_GOV_STOP, NULL);
+ if (ret) {
+ dev_warn(dev, "%s: Governor %s not stopped(%d)\n",
+ __func__, df->governor->name, ret);
+ goto out;
+ }
+ }
+ df->governor = governor;
+ strncpy(df->governor_name, governor->name, DEVFREQ_NAME_LEN);
+ ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
+ if (ret)
+ dev_warn(dev, "%s: Governor %s not started(%d)\n",
+ __func__, df->governor->name, ret);
+out:
+ mutex_unlock(&devfreq_list_lock);
+
+ if (!ret)
+ ret = count;
+ return ret;
+}
+
static ssize_t show_freq(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -873,7 +916,7 @@
}
static struct device_attribute devfreq_attrs[] = {
- __ATTR(governor, S_IRUGO, show_governor, NULL),
+ __ATTR(governor, S_IRUGO | S_IWUSR, show_governor, store_governor),
__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
__ATTR(available_frequencies, S_IRUGO, show_available_freqs, NULL),
__ATTR(target_freq, S_IRUGO, show_target_freq, NULL),