linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: adc: ad4080: add AD4880 support

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Message-ID: <5d2e85cd-caa2-43a6-a451-3b822bd0ef01@baylibre.com>
Date: Thu, 29 Jan 2026 10:20:27 -0600
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>,
 Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: adc: ad4080: add AD4880 support

On 1/29/26 9:27 AM, Antoniu Miclaus wrote:
> Add AD4880 dual-channel ADC to the AD4080 bindings. The AD4880 is a
> dual-channel variant with two independent ADC channels, each with its
> own SPI configuration interface.
> 
> For AD4880, the binding requires:
> - adi,aux-spi-cs property for secondary channel chip select
> - Two io-backends entries for each channel's data interface
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
>  .../bindings/iio/adc/adi,ad4080.yaml          | 49 ++++++++++++++++++-
>  1 file changed, 48 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> index ccd6a0ac1539..3909e3095507 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4080.yaml
> @@ -18,6 +18,9 @@ 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

Can we get a datasheet link?

>  
>  $ref: /schemas/spi/spi-peripheral-props.yaml#
> @@ -31,10 +34,18 @@ properties:
>        - adi,ad4084
>        - adi,ad4086
>        - adi,ad4087
> +      - adi,ad4880
>  
>    reg:
>      maxItems: 1
>  
> +  adi,aux-spi-cs:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Chip select for the auxiliary SPI interface used by multi-channel
> +      devices like AD4880. Each additional channel beyond the first requires
> +      its own SPI configuration interface on a separate chip select.
> +
>    spi-max-frequency:
>      description: Configuration of the SPI bus.
>      maximum: 50000000
> @@ -57,7 +68,8 @@ properties:
>    vrefin-supply: true
>  
>    io-backends:
> -    maxItems: 1
> +    minItems: 1
> +    maxItems: 2
>  
>    adi,lvds-cnv-enable:
>      description: Enable the LVDS signal type on the CNV pin. Default is CMOS.
> @@ -78,6 +90,23 @@ required:
>    - vdd33-supply
>    - vrefin-supply
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: adi,ad4880
> +    then:
> +      properties:
> +        io-backends:
> +          minItems: 2
> +      required:
> +        - adi,aux-spi-cs
> +    else:
> +      properties:
> +        io-backends:
> +          maxItems: 1
> +
>  additionalProperties: false
>  
>  examples:
> @@ -98,4 +127,22 @@ examples:
>            io-backends = <&iio_backend>;
>          };
>      };
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@0 {
> +          compatible = "adi,ad4880";
> +          reg = <0>;
> +          adi,aux-spi-cs = <1>;

We can already have multiple reg for a multiple CS device.

             reg = <0>, <1>;

So we shouldn't need a new adi,aux-spi-cs property for that.

> +          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>;
> +        };
> +    };
>  ...