Commit 2a9e0662 authored by Lars-Peter Clausen's avatar Lars-Peter Clausen Committed by Jonathan Cameron

staging:iio:ad7793: Fix temperature scale and offset

The temperature channel uses the internal 1.17V reference with 0.81 mv/C. The
reported temperature is in Kevlin, so we need to add the Kelvin to Celcius
offset when reporting the offset for the temperature channel.
Signed-off-by: default avatarLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: default avatarJonathan Cameron <jic23@kernel.org>
parent 680f8ea0
......@@ -617,30 +617,37 @@ static int ad7793_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT_PLUS_NANO;
} else {
/* 1170mV / 2^23 * 6 */
scale_uv = (1170ULL * 100000000ULL * 6ULL)
>> (chan->scan_type.realbits -
(unipolar ? 0 : 1));
scale_uv = (1170ULL * 100000000ULL * 6ULL);
}
break;
case IIO_TEMP:
/* Always uses unity gain and internal ref */
scale_uv = (2500ULL * 100000000ULL)
>> (chan->scan_type.realbits -
(unipolar ? 0 : 1));
/* 1170mV / 0.81 mV/C / 2^23 */
scale_uv = 1444444444444ULL;
break;
default:
return -EINVAL;
}
*val2 = do_div(scale_uv, 100000000) * 10;
*val = scale_uv;
scale_uv >>= (chan->scan_type.realbits - (unipolar ? 0 : 1));
*val = 0;
*val2 = scale_uv;
return IIO_VAL_INT_PLUS_NANO;
case IIO_CHAN_INFO_OFFSET:
if (!unipolar)
*val -= (1 << (chan->scan_type.realbits - 1));
*val = -(1 << (chan->scan_type.realbits - 1));
else
*val = 0;
/* Kelvin to Celsius */
if (chan->type == IIO_TEMP) {
unsigned long long offset;
unsigned int shift;
shift = chan->scan_type.realbits - (unipolar ? 0 : 1);
offset = 273ULL << shift;
do_div(offset, 1444);
*val -= offset;
}
return IIO_VAL_INT;
}
return -EINVAL;
......
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