PM / devfreq: Fix handling of min/max_freq == 0

Commit ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when adding the
devfreq device") initializes df->min/max_freq with the min/max OPP when
the device is added. Later commit f1d981eaecf8 ("PM / devfreq: Use the
available min/max frequency") adds df->scaling_min/max_freq and the
following to the frequency adjustment code:

  max_freq = MIN(devfreq->scaling_max_freq, devfreq->max_freq);

With the current handling of min/max_freq this is incorrect:

Even though df->max_freq is now initialized to a value != 0 user space
can still set it to 0, in this case max_freq would be 0 instead of
df->scaling_max_freq as intended. In consequence the frequency adjustment
is not performed:

  if (max_freq && freq > max_freq) {
	freq = max_freq;

To fix this set df->min/max freq to the min/max OPP in max/max_freq_store,
when the user passes a value of 0. This also prevents df->max_freq from
being set below the min OPP when df->min_freq is 0, and similar for
min_freq. Since it is now guaranteed that df->min/max_freq can't be 0 the
checks for this case can be removed.

Change-Id: I4092597dd0d81fd3937bf3a97a9e2639d542d030
Fixes: f1d981eaecf8 ("PM / devfreq: Use the available min/max frequency")
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
[cw00.choi: Backported from mainline kernel]
Signed-off--by: Chanwoo Choi <cw00.choi@samsung.com>

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index dbf971a..5db7249 100644 (file)
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -361,11 +361,11 @@ int update_devfreq(struct devfreq *devfreq)
        max_freq = min(devfreq->scaling_max_freq, devfreq->max_freq);
        min_freq = max(devfreq->scaling_min_freq, devfreq->min_freq);
 
-       if (min_freq && freq < min_freq) {
+       if (freq < min_freq) {
                freq = min_freq;
                flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
        }
-       if (max_freq && freq > max_freq) {
+       if (freq > max_freq) {
                freq = max_freq;
                flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
        }
@@ -1254,17 +1254,26 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
        struct devfreq *df = to_devfreq(dev);
        unsigned long value;
        int ret;
-       unsigned long max;
 
        ret = sscanf(buf, "%lu", &value);
        if (ret != 1)
                return -EINVAL;
 
        mutex_lock(&df->lock);
-       max = df->max_freq;
-       if (value && max && value > max) {
-               ret = -EINVAL;
-               goto unlock;
+
+       if (value) {
+               if (value > df->max_freq) {
+                       ret = -EINVAL;
+                       goto unlock;
+               }
+       } else {
+               unsigned long *freq_table = df->profile->freq_table;
+
+               /* Get minimum frequency according to sorting order */
+               if (freq_table[0] < freq_table[df->profile->max_state - 1])
+                       value = freq_table[0];
+               else
+                       value = freq_table[df->profile->max_state - 1];
        }
 
        df->min_freq = value;
@@ -1289,17 +1298,26 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
        struct devfreq *df = to_devfreq(dev);
        unsigned long value;
        int ret;
-       unsigned long min;
 
        ret = sscanf(buf, "%lu", &value);
        if (ret != 1)
                return -EINVAL;
 
        mutex_lock(&df->lock);
-       min = df->min_freq;
-       if (value && min && value < min) {
-               ret = -EINVAL;
-               goto unlock;
+
+       if (value) {
+               if (value < df->min_freq) {
+                       ret = -EINVAL;
+                       goto unlock;
+               }
+       } else {
+               unsigned long *freq_table = df->profile->freq_table;
+
+               /* Get maximum frequency according to sorting order */
+               if (freq_table[0] < freq_table[df->profile->max_state - 1])
+                       value = freq_table[df->profile->max_state - 1];
+               else
+                       value = freq_table[0];
        }
 
        df->max_freq = value;