4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Marc Ferland <marc.ferland@xxxxxxxxxxxx>
[ 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@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240501150554.1871390-1-marc.ferland@xxxxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/iio/dac/ad5592r-base.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iio/dac/ad5592r-base.c b/drivers/iio/dac/ad5592r-base.c
index 427946be41872..414134412a5f8 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);
--
2.43.0
