PM / devfreq: Add current freq callback in device profile

Devfreq returns governor predicted frequency as current frequency
via sysfs interface. But device may not support all frequencies
that governor predicts. So add a callback in device profile to get
current freq from driver. Also add a new sysfs node to expose
governor predicted next target frequency.

Signed-off-by: Rajagopal Venkat <rajagopal.venkat@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/ABI/testing/sysfs-class-devfreq

@@ -19,7 +19,16 @@ Date:		September 2011
 Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
 Description:
 		The /sys/class/devfreq/.../cur_freq shows the current
-		frequency of the corresponding devfreq object.
+		frequency of the corresponding devfreq object. Same as
+		target_freq when get_cur_freq() is not implemented by
+		devfreq driver.
+
+What:		/sys/class/devfreq/.../target_freq
+Date:		September 2012
+Contact:	Rajagopal Venkat <rajagopal.venkat@linaro.org>
+Description:
+		The /sys/class/devfreq/.../target_freq shows the next governor
+		predicted target frequency of the corresponding devfreq object.
 
 What:		/sys/class/devfreq/.../polling_interval
 Date:		September 2011

drivers/devfreq/devfreq.c

@@ -463,6 +463,19 @@ static ssize_t show_governor(struct device *dev,
 
 static ssize_t show_freq(struct device *dev,
 			 struct device_attribute *attr, char *buf)
+{
+	unsigned long freq;
+	struct devfreq *devfreq = to_devfreq(dev);
+
+	if (devfreq->profile->get_cur_freq &&
+		!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
+			return sprintf(buf, "%lu\n", freq);
+
+	return sprintf(buf, "%lu\n", devfreq->previous_freq);
+}
+
+static ssize_t show_target_freq(struct device *dev,
+			struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
 }
@@ -563,6 +576,7 @@ static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
 static struct device_attribute devfreq_attrs[] = {
 	__ATTR(governor, S_IRUGO, show_governor, NULL),
 	__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
+	__ATTR(target_freq, S_IRUGO, show_target_freq, NULL),
 	__ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
 	       store_polling_interval),
 	__ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),

include/linux/devfreq.h

@@ -66,6 +66,8 @@ struct devfreq_dev_status {
  *			explained above with "DEVFREQ_FLAG_*" macros.
  * @get_dev_status	The device should provide the current performance
  *			status to devfreq, which is used by governors.
+ * @get_cur_freq	The device should provide the current frequency
+ *			at which it is operating.
  * @exit		An optional callback that is called when devfreq
  *			is removing the devfreq object due to error or
  *			from devfreq_remove_device() call. If the user
@@ -79,6 +81,7 @@ struct devfreq_dev_profile {
 	int (*target)(struct device *dev, unsigned long *freq, u32 flags);
 	int (*get_dev_status)(struct device *dev,
 			      struct devfreq_dev_status *stat);
+	int (*get_cur_freq)(struct device *dev, unsigned long *freq);
 	void (*exit)(struct device *dev);
 };