PM / devfreq: add min/max_freq limit requested by users.

The frequency requested to devfreq device driver from devfreq governors
is restricted by min_freq and max_freq input.
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

drivers/devfreq/devfreq.c

@@ -501,12 +501,82 @@ static ssize_t show_central_polling(struct device *dev,
 		       !to_devfreq(dev)->governor->no_central_polling);
 }
 
+static ssize_t store_min_freq(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long value;
+	int ret;
+	unsigned long max;
+
+	ret = sscanf(buf, "%lu", &value);
+	if (ret != 1)
+		goto out;
+
+	mutex_lock(&df->lock);
+	max = df->max_freq;
+	if (value && max && value > max) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	df->min_freq = value;
+	update_devfreq(df);
+	ret = count;
+unlock:
+	mutex_unlock(&df->lock);
+out:
+	return ret;
+}
+
+static ssize_t show_min_freq(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	return sprintf(buf, "%lu\n", to_devfreq(dev)->min_freq);
+}
+
+static ssize_t store_max_freq(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct devfreq *df = to_devfreq(dev);
+	unsigned long value;
+	int ret;
+	unsigned long min;
+
+	ret = sscanf(buf, "%lu", &value);
+	if (ret != 1)
+		goto out;
+
+	mutex_lock(&df->lock);
+	min = df->min_freq;
+	if (value && min && value < min) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	df->max_freq = value;
+	update_devfreq(df);
+	ret = count;
+unlock:
+	mutex_unlock(&df->lock);
+out:
+	return ret;
+}
+
+static ssize_t show_max_freq(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	return sprintf(buf, "%lu\n", to_devfreq(dev)->max_freq);
+}
+
 static struct device_attribute devfreq_attrs[] = {
 	__ATTR(governor, S_IRUGO, show_governor, NULL),
 	__ATTR(cur_freq, S_IRUGO, show_freq, NULL),
 	__ATTR(central_polling, S_IRUGO, show_central_polling, 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),
+	__ATTR(max_freq, S_IRUGO | S_IWUSR, show_max_freq, store_max_freq),
 	{ },
 };
 

drivers/devfreq/governor_performance.c

@@ -18,7 +18,10 @@ static int devfreq_performance_func(struct devfreq *df,
 	 * target callback should be able to get floor value as
 	 * said in devfreq.h
 	 */
+	if (!df->max_freq)
 		*freq = UINT_MAX;
+	else
+		*freq = df->max_freq;
 	return 0;
 }
 

drivers/devfreq/governor_powersave.c

@@ -18,7 +18,7 @@ static int devfreq_powersave_func(struct devfreq *df,
 	 * target callback should be able to get ceiling value as
 	 * said in devfreq.h
 	 */
-	*freq = 0;
+	*freq = df->min_freq;
 	return 0;
 }
 

drivers/devfreq/governor_simpleondemand.c

@@ -25,6 +25,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
 	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
 	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
 	struct devfreq_simple_ondemand_data *data = df->data;
+	unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
 
 	if (err)
 		return err;
@@ -41,7 +42,7 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
 
 	/* Assume MAX if it is going to be divided by zero */
 	if (stat.total_time == 0) {
-		*freq = UINT_MAX;
+		*freq = max;
 		return 0;
 	}
 
@@ -54,13 +55,13 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
 	/* Set MAX if it's busy enough */
 	if (stat.busy_time * 100 >
 	    stat.total_time * dfso_upthreshold) {
-		*freq = UINT_MAX;
+		*freq = max;
 		return 0;
 	}
 
 	/* Set MAX if we do not know the initial frequency */
 	if (stat.current_frequency == 0) {
-		*freq = UINT_MAX;
+		*freq = max;
 		return 0;
 	}
 
@@ -79,6 +80,11 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
 	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
 	*freq = (unsigned long) b;
 
+	if (df->min_freq && *freq < df->min_freq)
+		*freq = df->min_freq;
+	if (df->max_freq && *freq > df->max_freq)
+		*freq = df->max_freq;
+
 	return 0;
 }
 

drivers/devfreq/governor_userspace.c

@@ -25,10 +25,19 @@ static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
 {
 	struct userspace_data *data = df->data;
 
-	if (!data->valid)
+	if (data->valid) {
+		unsigned long adjusted_freq = data->user_frequency;
+
+		if (df->max_freq && adjusted_freq > df->max_freq)
+			adjusted_freq = df->max_freq;
+
+		if (df->min_freq && adjusted_freq < df->min_freq)
+			adjusted_freq = df->min_freq;
+
+		*freq = adjusted_freq;
+	} else {
 		*freq = df->previous_freq; /* No user freq specified yet */
-	else
-		*freq = data->user_frequency;
+	}
 	return 0;
 }
 

include/linux/devfreq.h

@@ -124,6 +124,8 @@ struct devfreq_governor {
  *		touch this.
  * @being_removed	a flag to mark that this object is being removed in
  *			order to prevent trying to remove the object multiple times.
+ * @min_freq	Limit minimum frequency requested by user (0: none)
+ * @max_freq	Limit maximum frequency requested by user (0: none)
  *
  * This structure stores the devfreq information for a give device.
  *
@@ -149,6 +151,9 @@ struct devfreq {
 	void *data; /* private data for governors */
 
 	bool being_removed;
+
+	unsigned long min_freq;
+	unsigned long max_freq;
 };
 
 #if defined(CONFIG_PM_DEVFREQ)