Il giorno sab 1 ago 2020 alle ore 18:46 Jonathan Cameron
<jic23@xxxxxxxxxxxxxxxxxxxxx> ha scritto:
>
> On Sat, 1 Aug 2020 15:55:11 +0200
> Angelo Compagnucci <angelo.compagnucci@xxxxxxxxx> wrote:
>
> > 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.
> >
> > Signed-off-by: Angelo Compagnucci <angelo.compagnucci@xxxxxxxxx>
>
> Looks like we should be backporting this. Fixes tag please.
I don't know what it fixes, there is no signalled bug for this, I
simply discovered it doing some testing.
>
> 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,
>
--
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