Re: [PATCH v7 3/4] dt-bindings: iio: adc: ad4080: add AD4880 support

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 21 Mar 2026 12:01:53 +0200
Antoniu Miclaus <antoniu.miclaus@analog.com> wrote:

> Add support for the AD4880, a dual-channel 20-bit 40MSPS SAR ADC
> with integrated fully differential amplifiers (FDA).
> 
> The AD4880 has two independent ADC channels, each with its own SPI
> configuration interface. This requires:
> - Two entries in reg property for primary and secondary channel
>   chip selects
> - Two io-backends entries for the two data channels
From the v6 discussion.  I'd just like to know a little more on this.
Are they really separate backends?

Given discussion about interleaved data, I was kind of assuming they
were different front end interfaces to a single backend IP.

The freedom this binding is giving is for those two backends to be
completely unrelated. I'm not sure if we want that.

Jonathan


> 
> Reviewed-by: David Lechner <dlechner@baylibre.com>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> Changes in v7:
>   - No changes
> 
>  .../bindings/iio/adc/adi,ad4080.yaml          | 53 ++++++++++++++++++-
>  1 file changed, 51 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> index ccd6a0ac1539..0cf86c6f9925 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> @@ -18,7 +18,11 @@ description: |
>    service a wide variety of precision, wide bandwidth data acquisition
>    applications.
>  
> +  The AD4880 is a dual-channel variant with two independent ADC channels,
> +  each with its own SPI configuration interface.
> +
>    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4080.pdf
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/ad4880.pdf
>  
>  $ref: /schemas/spi/spi-peripheral-props.yaml#
>  
> @@ -31,9 +35,15 @@ properties:
>        - adi,ad4084
>        - adi,ad4086
>        - adi,ad4087
> +      - adi,ad4880
>  
>    reg:
> -    maxItems: 1
> +    minItems: 1
> +    maxItems: 2
> +    description:
> +      SPI chip select(s). For single-channel devices, one chip select.
> +      For multi-channel devices like AD4880, two chip selects are required
> +      as each channel has its own SPI configuration interface.
>  
>    spi-max-frequency:
>      description: Configuration of the SPI bus.
> @@ -57,7 +67,10 @@ properties:
>    vrefin-supply: true
>  
>    io-backends:
> -    maxItems: 1
> +    minItems: 1
> +    items:
> +      - description: Backend for channel A (primary)
> +      - description: Backend for channel B (secondary)
>  
>    adi,lvds-cnv-enable:
>      description: Enable the LVDS signal type on the CNV pin. Default is CMOS.
> @@ -78,6 +91,25 @@ required:
>    - vdd33-supply
>    - vrefin-supply
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: adi,ad4880
> +    then:
> +      properties:
> +        reg:
> +          minItems: 2
> +        io-backends:
> +          minItems: 2
> +    else:
> +      properties:
> +        reg:
> +          maxItems: 1
> +        io-backends:
> +          maxItems: 1
> +
>  additionalProperties: false
>  
>  examples:
> @@ -98,4 +130,21 @@ examples:
>            io-backends = <&iio_backend>;
>          };
>      };
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@0 {
> +          compatible = "adi,ad4880";
> +          reg = <0>, <1>;
> +          spi-max-frequency = <10000000>;
> +          vdd33-supply = <&vdd33>;
> +          vddldo-supply = <&vddldo>;
> +          vrefin-supply = <&vrefin>;
> +          clocks = <&cnv>;
> +          clock-names = "cnv";
> +          io-backends = <&iio_backend_cha>, <&iio_backend_chb>;
> +        };
> +    };
>  ...