[PATCH] iio: dac: ad5592r: fix temperature scale

[PATCH] iio: dac: ad5592r: fix temperature scale

[marc.ferland]

From: Marc Ferland <marc.ferland@sonatest.com>

For temperature readings, the remainder is returned as nano Celsius
_but_ we mark it as IIO_VAL_INT_PLUS_MICRO. This results in incorrect
temperature reporting through hwmon for example. I have a board here
which reports the following when running 'sensors':

iio_hwmon-isa-0000
Adapter: ISA adapter
temp1:        +93.3°C

With the patch applied, it returns the correct temperature:

iio_hwmon-isa-0000
Adapter: ISA adapter
temp1:        +30.5°C

Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
---
 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 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);

base-commit: 98369dccd2f8e16bf4c6621053af7aa4821dcf8e
-- 
2.34.1

Re: [PATCH] iio: dac: ad5592r: fix temperature scale

[Jonathan Cameron]

On Tue, 30 Apr 2024 09:13:30 -0400
marc.ferland@gmail.com wrote:

> From: Marc Ferland <marc.ferland@sonatest.com>
> 
> For temperature readings, the remainder is returned as nano Celsius
> _but_ we mark it as IIO_VAL_INT_PLUS_MICRO. This results in incorrect
> temperature reporting through hwmon for example. I have a board here
> which reports the following when running 'sensors':
> 
> iio_hwmon-isa-0000
> Adapter: ISA adapter
> temp1:        +93.3°C
> 
> With the patch applied, it returns the correct temperature:
> 
> iio_hwmon-isa-0000
> Adapter: ISA adapter
> temp1:        +30.5°C
> 
> Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>

IIO temperature units are milli celcius, so I'm not following
the argument here.  The driver might be reporting in pico celcius
I suppose?  Call out that this is the scale factor though, so
it corresponds to 1LSB hence a small number is certainly plausible..

Reasonable to argue it's taking the integer and dividing by 10^9 hence
INT_PLUS_NANO is the right answer, but it isn't nano celsius.


Jonathan


> ---
>  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 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);
> 
> base-commit: 98369dccd2f8e16bf4c6621053af7aa4821dcf8e

Re: [PATCH] iio: dac: ad5592r: fix temperature scale

[Marc Ferland]

On Tue, Apr 30, 2024 at 9:59 AM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> On Tue, 30 Apr 2024 09:13:30 -0400
> marc.ferland@gmail.com wrote:
>
> > From: Marc Ferland <marc.ferland@sonatest.com>
> >
> > For temperature readings, the remainder is returned as nano Celsius
> > _but_ we mark it as IIO_VAL_INT_PLUS_MICRO. This results in incorrect
> > temperature reporting through hwmon for example. I have a board here
> > which reports the following when running 'sensors':
> >
> > iio_hwmon-isa-0000
> > Adapter: ISA adapter
> > temp1:        +93.3°C
> >
> > With the patch applied, it returns the correct temperature:
> >
> > iio_hwmon-isa-0000
> > Adapter: ISA adapter
> > temp1:        +30.5°C
> >
> > Signed-off-by: Marc Ferland <marc.ferland@sonatest.com>
>
> IIO temperature units are milli celcius, so I'm not following
> the argument here.  The driver might be reporting in pico celcius
> I suppose?  Call out that this is the scale factor though, so
> it corresponds to 1LSB hence a small number is certainly plausible..
>
> Reasonable to argue it's taking the integer and dividing by 10^9 hence
> INT_PLUS_NANO is the right answer, but it isn't nano celsius.
>

Oups! you're obviously right. I'll update my commit message and resend.
Marc