iio: dac: ad5686: fix bit shift read register

BugLink: https://bugs.launchpad.net/bugs/1837477
commit 0e76df5c978338f3051e5126fc0c4245c57a307a upstream.

This patch solves the register readback issue with the bit shift. When the
dac resolution was lower than the register size (ex. 12 bits out of 16
bits) the readback value was not shifted with the difference in bits and
the value was higher. Also a mask is applied on the read value in order to
get the value relative to the actual bit size.

Fixes: 0357e488b8 ("iio:dac:ad5686: Refactor the driver")
Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
index 20254df7f9c7bf66a4d83dd608b589ec76cfd225..d9e951b39c7dca8db08ae8c995f167ba0ed44c4a 100644 (file)
--- a/drivers/iio/dac/ad5686.c
+++ b/drivers/iio/dac/ad5686.c
@@ -210,7 +210,8 @@ static int ad5686_read_raw(struct iio_dev *indio_dev,
                mutex_unlock(&indio_dev->mlock);
                if (ret < 0)
                        return ret;
-               *val = ret;
+               *val = (ret >> chan->scan_type.shift) &
+                       GENMASK(chan->scan_type.realbits - 1, 0);
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_SCALE:
                *val = st->vref_mv;