PM / devfreq: add comments and Documentation

- Added missing ABI documents
- Added comments to clarify the objectives of functions

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Acked-by: Nishanth Menon <nm@ti.com>
Acked-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>

3 files changed, 32 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-devfreq b/Documentation/ABI/testing/sysfs-class-devfreq
index 0ba6ea2f89d9..ee39acacf6f8 100644
--- a/Documentation/ABI/testing/sysfs-class-devfreq
+++ b/Documentation/ABI/testing/sysfs-class-devfreq
@@ -78,3 +78,23 @@ Contact:	Nishanth Menon <nm@ti.com>
 Description:
                 The /sys/class/devfreq/.../available_governors shows
                 currently available governors in the system.
+
+What:           /sys/class/devfreq/.../min_freq
+Date:           January 2013
+Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+                The /sys/class/devfreq/.../min_freq shows and stores
+                the minimum frequency requested by users. It is 0 if
+                the user does not care. min_freq overrides the
+                frequency requested by governors.
+
+What:           /sys/class/devfreq/.../max_freq
+Date:           January 2013
+Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+                The /sys/class/devfreq/.../max_freq shows and stores
+                the maximum frequency requested by users. It is 0 if
+                the user does not care. max_freq overrides the
+                frequency requested by governors and min_freq.
+                The max_freq overrides min_freq because max_freq may be
+                used to throttle devices to avoid overheating.
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index abfa14dd8b4c..44c407986f64 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -527,6 +527,8 @@ EXPORT_SYMBOL(devfreq_add_device);
 /**
  * devfreq_remove_device() - Remove devfreq feature from a device.
  * @devfreq:    the devfreq instance to be removed
+ *
+ * The opposite of devfreq_add_device().
  */
 int devfreq_remove_device(struct devfreq *devfreq)
 {
@@ -542,6 +544,10 @@ EXPORT_SYMBOL(devfreq_remove_device);
 /**
  * devfreq_suspend_device() - Suspend devfreq of a device.
  * @devfreq: the devfreq instance to be suspended
+ *
+ * This function is intended to be called by the pm callbacks
+ * (e.g., runtime_suspend, suspend) of the device driver that
+ * holds the devfreq.
  */
 int devfreq_suspend_device(struct devfreq *devfreq)
 {
@@ -559,6 +565,10 @@ EXPORT_SYMBOL(devfreq_suspend_device);
 /**
  * devfreq_resume_device() - Resume devfreq of a device.
  * @devfreq: the devfreq instance to be resumed
+ *
+ * This function is intended to be called by the pm callbacks
+ * (e.g., runtime_resume, resume) of the device driver that
+ * holds the devfreq.
  */
 int devfreq_resume_device(struct devfreq *devfreq)
 {
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index fe8c4476f7e4..5f1ab92107e6 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -181,6 +181,8 @@ extern struct devfreq *devfreq_add_device(struct device *dev,
                                   const char *governor_name,
                                   void *data);
 extern int devfreq_remove_device(struct devfreq *devfreq);
+
+/* Supposed to be called by PM_SLEEP/PM_RUNTIME callbacks */
 extern int devfreq_suspend_device(struct devfreq *devfreq);
 extern int devfreq_resume_device(struct devfreq *devfreq);