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| author | Marc Ferland <marc.ferland@sonatest.com> | 2024-05-01 18:05:54 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-07-05 10:00:30 +0300 |
| commit | 9eaaefbae8f5ddbed0fce822042ad969f5f876c5 (patch) | |
| tree | ffef443028dda0e7fb321b48987bbcd7ff031ed1 /drivers | |
| parent | c101996c9dabd9d809c12f686547b7035c087f10 (diff) | |
| download | linux-9eaaefbae8f5ddbed0fce822042ad969f5f876c5.tar.xz | |
iio: dac: ad5592r: fix temperature channel scaling value
[ Upstream commit 279428df888319bf68f2686934897301a250bb84 ]
The scale value for the temperature channel is (assuming Vref=2.5 and
the datasheet):
376.7897513
When calculating both val and val2 for the temperature scale we
use (3767897513/25) and multiply it by Vref (here I assume 2500mV) to
obtain:
2500 * (3767897513/25) ==> 376789751300
Finally we divide with remainder by 10^9 to get:
val = 376
val2 = 789751300
However, we return IIO_VAL_INT_PLUS_MICRO (should have been NANO) as
the scale type. So when converting the raw temperature value to the
'processed' temperature value we will get (assuming raw=810,
offset=-753):
processed = (raw + offset) * scale_val
= (810 + -753) * 376
= 21432
processed += div((raw + offset) * scale_val2, 10^6)
+= div((810 + -753) * 789751300, 10^6)
+= 45015
==> 66447
==> 66.4 Celcius
instead of the expected 21.5 Celsius.
Fix this issue by changing IIO_VAL_INT_PLUS_MICRO to
IIO_VAL_INT_PLUS_NANO.
Fixes: 56ca9db862bf ("iio: dac: Add support for the AD5592R/AD5593R ADCs/DACs")
Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
Link: https://lore.kernel.org/r/20240501150554.1871390-1-marc.ferland@sonatest.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/iio/dac/ad5592r-base.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/iio/dac/ad5592r-base.c b/drivers/iio/dac/ad5592r-base.c index 427946be4187..414134412a5f 100644 --- a/drivers/iio/dac/ad5592r-base.c +++ b/drivers/iio/dac/ad5592r-base.c @@ -415,7 +415,7 @@ static int ad5592r_read_raw(struct iio_dev *iio_dev, s64 tmp = *val * (3767897513LL / 25LL); *val = div_s64_rem(tmp, 1000000000LL, val2); - return IIO_VAL_INT_PLUS_MICRO; + return IIO_VAL_INT_PLUS_NANO; } mutex_lock(&st->lock); |