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

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

drivers/staging/iio/adc/ad7793.c

+18 −11
Original line number Diff line number Diff line
@@ -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;