[PATCH 4.9 044/207] power: supply: max17042_battery: Prevent int underflow in set_soc_threshold

From: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>

commit e660dbb68c6b3f7b9eb8b9775846a44f9798b719 upstream.

max17042_set_soc_threshold gets called with offset set to 1, which means
that minimum threshold value would underflow once SOC got down to 0,
causing invalid alerts from the gauge.

Fixes: e5f3872d2044 ("max17042: Add support for signalling change in SOC")
Cc: <redacted>
Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Reviewed-by: Krzysztof Kozlowski <redacted>
Signed-off-by: Sebastian Reichel <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/power/supply/max17042_battery.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/power/supply/max17042_battery.c
+++ b/drivers/power/supply/max17042_battery.c

@@ -752,7 +752,8 @@ static void max17042_set_soc_threshold(s
 	regmap_read(map, MAX17042_RepSOC, &soc);
 	soc >>= 8;
 	soc_tr = (soc + off) << 8;
-	soc_tr |= (soc - off);
+	if (off < soc)
+		soc_tr |= soc - off;
 	regmap_write(map, MAX17042_SALRT_Th, soc_tr);
 }