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.

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>

1 files changed, 30 insertions, 12 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 329c5e3f3338..b5e7af60723c 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -324,11 +324,11 @@ 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 */
         }
@@ -1168,17 +1168,26 @@ 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;
@@ -1203,17 +1212,26 @@ 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;