iio: adc: mcp3422: fix locking on error path

BugLink: https://bugs.launchpad.net/bugs/1896824
[ 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@huawei.com>
Signed-off-by: Angelo Compagnucci <angelo.compagnucci@gmail.com>
Link: https://lore.kernel.org/r/20200901093218.1500845-1-angelo.compagnucci@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: William Breathitt Gray <william.gray@canonical.com>

diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
index ea24d7c58b12707fab8d2726e37ff2bef5c32ede..4d03b1f265d9cf9eb2137bdb00af2b6a761b5a00 100644 (file)
--- a/drivers/iio/adc/mcp3422.c
+++ b/drivers/iio/adc/mcp3422.c
@@ -144,8 +144,10 @@ static int mcp3422_read_channel(struct mcp3422 *adc,
                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)]);
        }