power/supply: ingenic-battery: Don't change scale if there's only one

The ADC in the JZ4740 can work either in high-precision mode with a 2.5V
range, or in low-precision mode with a 7.5V range. The code in place in
this driver will select the proper scale according to the maximum
voltage of the battery.

The JZ4770 however only has one mode, with a 6.6V range. If only one
scale is available, there's no need to change it (and nothing to change
it to), and trying to do so will fail with -EINVAL.

Fixes: fb24ccfbe1e0 ("power: supply: add Ingenic JZ47xx battery driver.")
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Acked-by: Artur Rojek <contact@artur-rojek.eu>
Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/drivers/power/supply/ingenic-battery.c b/drivers/power/supply/ingenic-battery.c
index 35816d4b301201cb1b195488cf2a529ff2fb8708..2748715c4c756ee412563b6894eb6aad78c53da5 100644 (file)
--- a/drivers/power/supply/ingenic-battery.c
+++ b/drivers/power/supply/ingenic-battery.c
@@ -100,10 +100,17 @@ static int ingenic_battery_set_scale(struct ingenic_battery *bat)
                return -EINVAL;
        }
 
-       return iio_write_channel_attribute(bat->channel,
-                                          scale_raw[best_idx],
-                                          scale_raw[best_idx + 1],
-                                          IIO_CHAN_INFO_SCALE);
+       /* Only set scale if there is more than one (fractional) entry */
+       if (scale_len > 2) {
+               ret = iio_write_channel_attribute(bat->channel,
+                                                 scale_raw[best_idx],
+                                                 scale_raw[best_idx + 1],
+                                                 IIO_CHAN_INFO_SCALE);
+               if (ret)
+                       return ret;
+       }
+
+       return 0;
 }
 
 static enum power_supply_property ingenic_battery_properties[] = {