6.9-stable review patch. If anyone has any objections, please let me know.
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From: Marc Ferland marc.ferland@sonatest.com
commit 279428df888319bf68f2686934897301a250bb84 upstream.
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: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iio/dac/ad5592r-base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- 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_d 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);