[PATCH RESEND 3/4] PM / devfreq: Fix governor_store() failing when device has no current governor

[Yaxiong Tian]

Since devfreq_remove_governor() may clear the device's current governor
in certain situations, while governors actually exist independently
of the device, directly returning EINVAL in this case is inaccurate.

To fix this issue, remove this check and add relevant logic for when
df->governor is NULL.

Fixes: 483d557ee9a3 ("PM / devfreq: Clean up the devfreq instance name in sysfs attr")
Signed-off-by: Yaxiong Tian <tianyaxiong@xxxxxxxxxx>
---
 drivers/devfreq/devfreq.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0bf320123e3a..4a312f3c2421 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -1425,9 +1425,6 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 	char str_governor[DEVFREQ_NAME_LEN + 1];
 	const struct devfreq_governor *governor, *prev_governor;
 
-	if (!df->governor)
-		return -EINVAL;
-
 	ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor);
 	if (ret != 1)
 		return -EINVAL;
@@ -1438,6 +1435,18 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
 		ret = PTR_ERR(governor);
 		goto out;
 	}
+
+	if (!df->governor) {
+		df->governor = governor;
+		ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL);
+		if (ret) {
+			dev_warn(dev, "%s: Governor %s not started(%d)\n",
+				__func__, df->governor->name, ret);
+			df->governor = NULL;
+		}
+		goto out;
+	}
+
 	if (df->governor == governor) {
 		ret = 0;
 		goto out;
-- 
2.25.1