From: Angelo Compagnucci angelo.compagnucci@gmail.com
commit 3f1093d83d7164e4705e4232ccf76da54adfda85 upstream.
Locking should be held for the entire reading sequence involving setting the channel, waiting for the channel switch and reading from the channel. If not, reading from a channel can result mixing with the reading from another channel.
Fixes: 07914c84ba30 ("iio: adc: Add driver for Microchip MCP3422/3/4 high resolution ADC") Signed-off-by: Angelo Compagnucci angelo.compagnucci@gmail.com Link: https://lore.kernel.org/r/20200819075525.1395248-1-angelo.compagnucci@gmail.... Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iio/adc/mcp3422.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c index 819f26011500..fd1496c9c3fb 100644 --- a/drivers/iio/adc/mcp3422.c +++ b/drivers/iio/adc/mcp3422.c @@ -99,16 +99,12 @@ static int mcp3422_update_config(struct mcp3422 *adc, u8 newconfig) { int ret;
- mutex_lock(&adc->lock); - ret = i2c_master_send(adc->i2c, &newconfig, 1); if (ret > 0) { adc->config = newconfig; ret = 0; }
- mutex_unlock(&adc->lock); - return ret; }
@@ -141,6 +137,8 @@ static int mcp3422_read_channel(struct mcp3422 *adc, u8 config; u8 req_channel = channel->channel;
+ mutex_lock(&adc->lock); + if (req_channel != MCP3422_CHANNEL(adc->config)) { config = adc->config; config &= ~MCP3422_CHANNEL_MASK; @@ -153,7 +151,11 @@ static int mcp3422_read_channel(struct mcp3422 *adc, msleep(mcp3422_read_times[MCP3422_SAMPLE_RATE(adc->config)]); }
- return mcp3422_read(adc, value, &config); + ret = mcp3422_read(adc, value, &config); + + mutex_unlock(&adc->lock); + + return ret; }
static int mcp3422_read_raw(struct iio_dev *iio,