The current offset has the scale already applied to it. The ABI documentation defines the offset parameter as "offset to be added to <type>[Y]_raw prior to scaling by <type>[Y]_scale in order to obtain value in the <type> units as specified in <type>[Y]_raw documentation" The right value is obtained at 0 degrees Celsius by the formula provided in the datasheet: T = Tsens_t0 + (Tadc_t - Tadc_t0) / Tadc_res where: T = 0 degrees Celsius Tsens_t0 (reference temperature) = 25 degrees Celsius Tadc_t0 (16-bit format for Tsens_t0) = 17508 Tadc_res = 60.1 LSB/degree Celsius The resulting offset is 16005.5, which has been truncated to 16005 to provide an integer value with a precision loss smaller than the 1-LSB measurement precision. Fix the offset to apply its value prior to scaling. Signed-off-by: Javier Carrasco <javier.carrasco@xxxxxxxxxxxxxx> --- Changes in v2: - Fixed typo in the offset value (16005 instead of 16605) (Jonathan Cameron) - Link to v1: https://lore.kernel.org/r/20231023-topic-tmag5273x1_temp_offset-v1-1-983dca43292c@xxxxxxxxxxxxxx --- drivers/iio/magnetometer/tmag5273.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iio/magnetometer/tmag5273.c b/drivers/iio/magnetometer/tmag5273.c index c5e5c4ad681e..e8c4ca142d21 100644 --- a/drivers/iio/magnetometer/tmag5273.c +++ b/drivers/iio/magnetometer/tmag5273.c @@ -356,7 +356,7 @@ static int tmag5273_read_raw(struct iio_dev *indio_dev, case IIO_CHAN_INFO_OFFSET: switch (chan->type) { case IIO_TEMP: - *val = -266314; + *val = -16005; return IIO_VAL_INT; default: return -EINVAL; --- base-commit: 05d3ef8bba77c1b5f98d941d8b2d4aeab8118ef1 change-id: 20231023-topic-tmag5273x1_temp_offset-17774cbce961 Best regards, -- Javier Carrasco <javier.carrasco@xxxxxxxxxxxxxx>
