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@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/9879beec-05fc-4fc6-af62-d771e238954e@xxxxxxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
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;
--
2.43.0
