PM / devfreq: Fix available_governor sysfs

The devfreq using passive governor is not able to change the governor.
So, the user can not change the governor through 'available_governor' sysfs
entry. Also, the devfreq which don't use the passive governor is not able to
change to 'passive' governor on the fly.

Fixes: 996133119f57 ("PM / devfreq: Add new passive governor")
Cc: stable@vger.kernel.org
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

1 files changed, 27 insertions, 4 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 8e5938c9c7d6..ade279d29f1e 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -940,6 +940,9 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
         if (df->governor == governor) {
                 ret = 0;
                 goto out;
+        } else if (df->governor->immutable || governor->immutable) {
+                ret = -EINVAL;
+                goto out;
         }
 
         if (df->governor) {
@@ -969,13 +972,33 @@ static ssize_t available_governors_show(struct device *d,
                                         struct device_attribute *attr,
                                         char *buf)
 {
-        struct devfreq_governor *tmp_governor;
+        struct devfreq *df = to_devfreq(d);
         ssize_t count = 0;
 
         mutex_lock(&devfreq_list_lock);
-        list_for_each_entry(tmp_governor, &devfreq_governor_list, node)
-                count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
-                                   "%s ", tmp_governor->name);
+
+        /*
+         * The devfreq with immutable governor (e.g., passive) shows
+         * only own governor.
+         */
+        if (df->governor->immutable) {
+                count = scnprintf(&buf[count], DEVFREQ_NAME_LEN,
+                                   "%s ", df->governor_name);
+        /*
+         * The devfreq device shows the registered governor except for
+         * immutable governors such as passive governor .
+         */
+        } else {
+                struct devfreq_governor *governor;
+
+                list_for_each_entry(governor, &devfreq_governor_list, node) {
+                        if (governor->immutable)
+                                continue;
+                        count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
+                                           "%s ", governor->name);
+                }
+        }
+
         mutex_unlock(&devfreq_list_lock);
 
         /* Truncate the trailing space */