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iio: adc: mcp3422: fix locking scope 

commit 3f1093d83d 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: 07914c84ba ("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>
5.4-rM2-2.2.x-imx-squashed
Angelo Compagnucci 2020-08-19 09:55:25 +02:00 committed by Greg Kroah-Hartman
parent f7db02316a
commit 5571056a58
1 changed files with 7 additions and 5 deletions
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12
drivers/iio/adc/mcp3422.c
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@ -95,16 +95,12 @@ 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;
}
@ -137,6 +133,8 @@ 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;
@ -151,7 +149,11 @@ 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,