From 86b9182df8bb12610d4d6feac45a69f3ed57bfd2 Mon Sep 17 00:00:00 2001
From: Paul Cercueil <paul@crapouillou.net>
Date: Sat, 16 Nov 2019 14:56:19 +0100
Subject: [PATCH] power/supply: ingenic-battery: Don't change scale if there's only one
Git-commit: 86b9182df8bb12610d4d6feac45a69f3ed57bfd2
Patch-mainline: v5.6-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/power/supply/ingenic-battery.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/power/supply/ingenic-battery.c b/drivers/power/supply/ingenic-battery.c
index 35816d4b3012..2748715c4c75 100644
--- 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[] = {
-- 
2.16.4