On Wed, 19 Aug 2020 09:55:25 +0200
angelo.compagnucci@xxxxxxxxx wrote:
> From: Angelo Compagnucci <angelo.compagnucci@xxxxxxxxx>
>
> 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@xxxxxxxxx>
Applied to the fixes-togreg branch of iio.git and marked for stable.
Thanks,
Jonathan
> ---
> 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 d86c0b5d80a3..02a60fb164cd 100644
> --- a/drivers/iio/adc/mcp3422.c
> +++ b/drivers/iio/adc/mcp3422.c
> @@ -96,16 +96,12 @@ 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;
> }
>
> @@ -138,6 +134,8 @@ 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;
> @@ -150,7 +148,11 @@ 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,
