On Mon, 31 Aug 2020 14:59:47 +0200
Angelo Compagnucci <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>
> Signed-off-by: Angelo Compagnucci <angelo@xxxxxxxxxxxxxxxxxxxx>
> ---
Hi Angelo
Change log?
Given I've just sent a pull request including v2, we are probably now in a mess
if we actually need to use v3.
Jonathan
> drivers/iio/adc/mcp3422.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
> index d86c0b5d80a3..f96f0cecbcde 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;
> @@ -145,12 +143,18 @@ 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)]);
> }
>
> - 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,
