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    Subject[PATCH 5.4 074/132] iio: adc: mcp3422: fix locking scope
    Date
    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.com
    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(-)

    --- a/drivers/iio/adc/mcp3422.c
    +++ b/drivers/iio/adc/mcp3422.c
    @@ -95,16 +95,12 @@ static int mcp3422_update_config(struct
    {
    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;
    }

    @@ -137,6 +133,8 @@ static int mcp3422_read_channel(struct m
    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;
    @@ -151,7 +149,11 @@ static int mcp3422_read_channel(struct m
    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,

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