hwmon: (gpio-fan) Allow to stop FANs when CONFIG_PM is disabled

When CONFIG_PM is disabled, the GPIO controlled FANs can't be stopped by
using the sysfs attributes since commit 0d01110 ("hwmon: (gpio-fan)
Add regulator support").

Using either the 'pwm1' or the 'fan1_target' attribute fails the same way:

  $ echo 0 > /sys/class/hwmon/hwmon1/pwm1
  ash: write error: Function not implemented
  $ echo 0 > /sys/class/hwmon/hwmon1/fan1_target
  ash: write error: Function not implemented

Both commands were working flawlessly before the mentioned commit.

The issue happens because pm_runtime_put_sync() returns with -ENOSYS
when CONFIG_PM is disabled, and the set_fan_speed() function handles
this as an error.

In order to restore the previous behaviour, change the error check in
the set_fan_speed() function to ignore the -ENOSYS error code.

Cc: [email protected]
Fixes: 0d01110 ("hwmon: (gpio-fan) Add regulator support")
Signed-off-by: Gabor Juhos <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>

Author: juhosg

drivers/hwmon/gpio-fan.c

@@ -148,7 +148,7 @@ static int set_fan_speed(struct gpio_fan_data *fan_data, int speed_index)
 		int ret;
 
 		ret = pm_runtime_put_sync(fan_data->dev);
-		if (ret < 0)
+		if (ret < 0 && ret != -ENOSYS)
 			return ret;
 	}