From 279428df888319bf68f2686934897301a250bb84 Mon Sep 17 00:00:00 2001 From: Marc Ferland Date: Wed, 1 May 2024 11:05:54 -0400 Subject: iio: dac: ad5592r: fix temperature channel scaling value 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 Link: https://lore.kernel.org/r/20240501150554.1871390-1-marc.ferland@sonatest.com Cc: Signed-off-by: Jonathan Cameron --- drivers/iio/dac/ad5592r-base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/iio/dac') diff --git a/drivers/iio/dac/ad5592r-base.c b/drivers/iio/dac/ad5592r-base.c index 076bc9ecfb49..4763402dbcd6 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); -- cgit v1.2.3