[PATCH 4.9 16/70] iio: adc: mcp3422: fix locking on error path

[Greg Kroah-Hartman]

From: Angelo Compagnucci <angelo.compagnucci@xxxxxxxxx>

[ Upstream commit a139ffa40f0c24b753838b8ef3dcf6ad10eb7854 ]

Reading from the chip should be unlocked on error path else the lock
could never being released.

Fixes: 07914c84ba30 ("iio: adc: Add driver for Microchip MCP3422/3/4 high resolution ADC")
Fixes: 3f1093d83d71 ("iio: adc: mcp3422: fix locking scope")
Acked-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
Signed-off-by: Angelo Compagnucci <angelo.compagnucci@xxxxxxxxx>
Link: https://lore.kernel.org/r/20200901093218.1500845-1-angelo.compagnucci@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iio/adc/mcp3422.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/iio/adc/mcp3422.c
+++ b/drivers/iio/adc/mcp3422.c
@@ -146,8 +146,10 @@ static int mcp3422_read_channel(struct m
 		config &= ~MCP3422_PGA_MASK;
 		config |= MCP3422_PGA_VALUE(adc->pga[req_channel]);
 		ret = mcp3422_update_config(adc, config);
-		if (ret < 0)
+		if (ret < 0) {
+			mutex_unlock(&adc->lock);
 			return ret;
+		}
 		msleep(mcp3422_read_times[MCP3422_SAMPLE_RATE(adc->config)]);
 	}