Re: [PATCH v3 4/8] dt-bindings: iio: adc: add input-chopping property

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 10 Jul 2026 17:50:37 -0500
"David Lechner (TI)" <dlechner@baylibre.com> wrote:

> Add a generic input-chopping property to adc.yaml. This is a feature
> seen frequently in ADCs that are designed to measure resistive loads,
> such as RTDs and strain gauges. Enabling this can reduce offset errors
> by swapping the positive and negative input channels on every other
> conversion. This can have side-effects in timing and filter response, so
> it is not always desirable to enable this feature in some applications.
> Therefore, it is best to make this a property that can be enabled or
> disabled in the device tree.
> 
> Signed-off-by: David Lechner (TI) <dlechner@baylibre.com>
> ---
> v3 changes:
> * Renamed property to input-chopping to reflect more common terminology.
> * Removed "allowed" from the description.
> * Extended description to explain when it should not be used.
> 
> v2 changes:
> * New patch.
> ---
>  Documentation/devicetree/bindings/iio/adc/adc.yaml | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adc.yaml b/Documentation/devicetree/bindings/iio/adc/adc.yaml
> index 308857f11220..c408feebd46d 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adc.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adc.yaml
> @@ -80,6 +80,14 @@ properties:
>        ADCs usually allow choosing between internal reference sources or a pair
>        of external pins.
>  
> +  input-chopping:
> +    type: boolean
> +    description:
> +      If set, the positive and negative input channels are swapped on every
> +      other conversion to reduce offset error. This generally comes at the
> +      expense of added settling time between conversions, so should be omitted
> +      on systems with high-frequency signals or high data rate requirements.

I'm lazy so I didn't check back, but in my mental model of this, the DT is simply
saying that the analog circuitry is suitable for doing chopping.  Driver decision
on whether to do it.  Perhaps we can reword it for that?
> +
>    excitation-channels:
>      $ref: /schemas/types.yaml#/definitions/uint32-array
>      description:
>