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| author | Javier Carrasco <javier.carrasco@wolfvision.net> | 2023-11-21 06:48:39 +0100 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2023-11-25 15:13:18 +0000 |
| commit | 3b8157ec4573e304a29b7bced627e144dbc3dfdb (patch) | |
| tree | 4f6865a2bb83e44f07ba371b13240ed3663ab3b7 /drivers/iio/magnetometer | |
| parent | 54cf39ec16335dadbe1ba008d8e5e98dae3e26f8 (diff) | |
| download | lwn-3b8157ec4573e304a29b7bced627e144dbc3dfdb.tar.gz lwn-3b8157ec4573e304a29b7bced627e144dbc3dfdb.zip | |
iio: tmag5273: fix temperature offset
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@wolfvision.net>
Link: https://lore.kernel.org/r/9879beec-05fc-4fc6-af62-d771e238954e@wolfvision.net
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/iio/magnetometer')
| -rw-r--r-- | drivers/iio/magnetometer/tmag5273.c | 2 |
1 files changed, 1 insertions, 1 deletions
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; |