This is a note to let you know that I've just added the patch titled
iio: tmag5273: fix temperature offset
to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 3b8157ec4573e304a29b7bced627e144dbc3dfdb Mon Sep 17 00:00:00 2001 From: Javier Carrasco javier.carrasco@wolfvision.net Date: Tue, 21 Nov 2023 06:48:39 +0100 Subject: 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.ne... Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron Jonathan.Cameron@huawei.com --- 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;