Re: [PATCH v2 4/5] dt-bindings: iio: adc: adi,ad7625: add LTC2387 and ADAQ2387x

[Conor Dooley]

On Wed, Nov 04, 2026 at 03:21:42PM +0200, Nicolae-Daniel Deaconescu wrote:
> From: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
> 
> Add the LTC2387-16, LTC2387-18, ADAQ23875, ADAQ23876 and ADAQ23878 to the
> binding. They are single channel differential ADCs like the AD762x and
> AD796x and are read the same way: CNV and CLK are driven by two PWMs and
> the LVDS data is captured by an AXI ADC. They differ in what is around the
> converter:
> 
> - Their output is double data rate on one or two lanes, selected by the
>   TWOLANES pin, described by adi,use-two-lanes.
> - They have no EN pins, and no clocks property, because the PWM provider
>   reports the clock its waveforms are derived from. The second PWM is named
>   clk, as that is the pin it drives, where the AD762x and AD796x name it
>   clk_gate.
> - The supplies are VDD, VDDL and OVDD on the LTC2387, and VDD, VIO, VS+ and
>   VS- on the ADAQ modules.
> - The ADAQ modules have a fully differential amplifier in front of the ADC.
>   Its gain is fixed on the ADAQ23875 and set by pin strapping on the
>   ADAQ23876 and ADAQ23878, described by adi,gain-milli.
> 
> The properties and supplies of the two groups of parts are made exclusive.
> The gain is described in the devicetree as the pin strapping can't be read
> from the part. There is no fallback compatible, as a driver for one of the
> existing parts would read these wrongly: their output is double data rate
> and has other timing limits.
> 
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
> Co-developed-by: Nicolae-Daniel Deaconescu <Nicolae-daniel.Deaconescu@xxxxxxxxxx>
> Signed-off-by: Nicolae-Daniel Deaconescu <Nicolae-daniel.Deaconescu@xxxxxxxxxx>
> ---
>  .../bindings/iio/adc/adi,ad7625.yaml          | 193 +++++++++++++++++-
>  1 file changed, 184 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7625.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7625.yaml
> index 8848562af28f..dbdded88236c 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7625.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7625.yaml
> @@ -4,7 +4,7 @@
>  $id: http://devicetree.org/schemas/iio/adc/adi,ad7625.yaml#
>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>  
> -title: Analog Devices Fast PulSAR Analog to Digital Converters
> +title: Analog Devices Fast PulSAR, LTC2387 and ADAQ2387x Analog to Digital Converters
>  
>  maintainers:
>    - Michael Hennerich <Michael.Hennerich@xxxxxxxxxx>
> @@ -17,6 +17,11 @@ description: |
>    * https://www.analog.com/en/products/ad7626.html
>    * https://www.analog.com/en/products/ad7960.html
>    * https://www.analog.com/en/products/ad7961.html
> +  * https://www.analog.com/en/products/ltc2387-16.html
> +  * https://www.analog.com/en/products/ltc2387-18.html
> +  * https://www.analog.com/en/products/adaq23875.html
> +  * https://www.analog.com/en/products/adaq23876.html
> +  * https://www.analog.com/en/products/adaq23878.html
>  
>  properties:
>    compatible:
> @@ -25,14 +30,37 @@ properties:
>        - adi,ad7626
>        - adi,ad7960
>        - adi,ad7961
> +      - adi,adaq23875
> +      - adi,adaq23876
> +      - adi,adaq23878
> +      - adi,ltc2387-16
> +      - adi,ltc2387-18
>  
>    vdd1-supply: true
>    vdd2-supply: true
>    vio-supply: true
>  
> +  vdd-supply:
> +    description: 5V analog power supply (VDD), LTC2387 and ADAQ parts only.
> +
> +  vddl-supply:
> +    description: 2.5V analog power supply (VDDL), LTC2387 parts only.
> +
> +  ovdd-supply:
> +    description: 2.5V output power supply (OVDD), LTC2387 parts only.
> +
> +  vs-p-supply:
> +    description: Amplifier positive supply (VS+), ADAQ parts only.
> +
> +  vs-n-supply:
> +    description:
> +      Amplifier negative supply (VS-), ADAQ parts only. Leave it out if VS-
> +      is tied to ground.
> +
>    ref-supply:
>      description:
> -      Voltage regulator for the external reference voltage (REF).
> +      Voltage regulator for the external reference voltage (REF, or REFBUF
> +      on the LTC2387 and ADAQ2387x).
>  
>    refin-supply:
>      description:
> @@ -40,18 +68,23 @@ properties:
>  
>    clocks:
>      description:
> -      The clock connected to the CLK pins, gated by the clk_gate PWM.
> +      The clock connected to the CLK pins, gated by the clk_gate PWM. Not
> +      described for the LTC2387 and ADAQ parts.
>      maxItems: 1
>  
>    pwms:
>      items:
>        - description: PWM connected to the CNV input on the ADC.
> -      - description: PWM that gates the clock connected to the ADC's CLK input.
> +      - description:
> +          PWM that gates the clock connected to the ADC's CLK input, so that
> +          it sees the burst of pulses for each conversion. It is named
> +          clk_gate for the AD762x and AD796x, and clk for the LTC2387 and
> +          ADAQ2387x.
>  
>    pwm-names:
>      items:
>        - const: cnv
> -      - const: clk_gate
> +      - enum: [clk_gate, clk]
>  
>    io-backends:
>      description:
> @@ -91,6 +124,23 @@ properties:
>        Indicates if EN3 is hard-wired to the high state. If neither this
>        nor en3-gpios are present, then EN3 is hard-wired low.
>  
> +  adi,use-two-lanes:
> +    $ref: /schemas/types.yaml#/definitions/flag
> +    description:
> +      Describes whether the TWOLANES pin of an LTC2387 or ADAQ part is set
> +      high, selecting two-lane LVDS output, or low, selecting one-lane
> +      output (the default).
> +
> +  adi,gain-milli:
> +    description:
> +      Gain of the fully-differential amplifier that the ADAQ modules
> +      integrate ahead of the LTC2387 die, expressed as gain * 1000. It is
> +      fixed on the ADAQ23875 and set by pin strapping on the ADAQ23876 and
> +      ADAQ23878, so it must match the board. Not allowed on the ADAQ23875,
> +      whose gain is fixed at 2.
> +    $ref: /schemas/types.yaml#/definitions/uint16
> +    enum: [370, 730, 870, 1380, 2250]
> +
>    en0-gpios:
>      description:
>        Configurable EN0 pin.
> @@ -109,10 +159,6 @@ properties:
>  
>  required:
>    - compatible
> -  - vdd1-supply
> -  - vdd2-supply
> -  - vio-supply
> -  - clocks
>    - pwms
>    - pwm-names
>    - io-backends
> @@ -157,6 +203,111 @@ allOf:
>          - required: [ref-supply]
>          - required: [refin-supply]
>  

> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - adi,ad7625
> +              - adi,ad7626
> +              - adi,ad7960
> +              - adi,ad7961
> +    then:
> +      properties:
> +        pwm-names:
> +          items:
> +            - const: cnv
> +            - const: clk_gate
> +        vdd-supply: false
> +        vddl-supply: false
> +        ovdd-supply: false
> +        vs-p-supply: false
> +        vs-n-supply: false
> +        adi,use-two-lanes: false
> +        adi,gain-milli: false
> +      required:
> +        - vdd1-supply
> +        - vdd2-supply
> +        - vio-supply
> +        - clocks
> +    else:
> +      # The LTC2387 and ADAQ parts have no EN pins and no clock to describe.
> +      properties:
> +        pwm-names:
> +          items:
> +            - const: cnv
> +            - const: clk
> +        vdd1-supply: false
> +        vdd2-supply: false
> +        clocks: false
> +        # REFIN is the bandgap output and the input of the reference buffer.
> +        # An external reference goes to REFBUF, through ref-supply.
> +        refin-supply: false
> +        en0-gpios: false
> +        en1-gpios: false
> +        en2-gpios: false
> +        en3-gpios: false
> +        adi,en0-always-on: false
> +        adi,en1-always-on: false
> +        adi,en2-always-on: false
> +        adi,en3-always-on: false
> +        adi,no-dco: false
> +      required:
> +        - vdd-supply

Honestly, when the devices are this different, I don't think having a
shared binding is worth it. Shared driver perhaps, but when so many
properties don't apply the things should be kept in different binding
files I think, this is just confusingly different IMO.

Thanks for sorting out the clocks thing though.

Conor.

> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - adi,ltc2387-16
> +              - adi,ltc2387-18
> +    then:
> +      properties:
> +        vio-supply: false
> +        vs-p-supply: false
> +        vs-n-supply: false
> +        adi,gain-milli: false
> +      required:
> +        - vddl-supply
> +        - ovdd-supply
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - adi,adaq23875
> +              - adi,adaq23876
> +              - adi,adaq23878
> +    then:
> +      properties:
> +        vddl-supply: false
> +        ovdd-supply: false
> +      required:
> +        - vio-supply
> +        - vs-p-supply
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: adi,adaq23875
> +    then:
> +      properties:
> +        adi,gain-milli: false
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - adi,adaq23876
> +              - adi,adaq23878
> +    then:
> +      required:
> +        - adi,gain-milli
> +
>  additionalProperties: false
>  
>  examples:
> @@ -174,3 +325,27 @@ examples:
>          en0-gpios = <&gpio0 86 GPIO_ACTIVE_HIGH>;
>          en1-gpios = <&gpio0 87 GPIO_ACTIVE_HIGH>;
>      };
> +  - |
> +    adc {
> +        compatible = "adi,ltc2387-16";
> +        io-backends = <&axi_adc>;
> +        ovdd-supply = <&supply_2_5V>;
> +        pwms = <&axi_pwm_gen 0 0 0>, <&axi_pwm_gen 1 0 0>;
> +        pwm-names = "cnv", "clk";
> +        ref-supply = <&supply_4_096V>;
> +        vdd-supply = <&supply_5V>;
> +        vddl-supply = <&supply_2_5V>;
> +    };
> +  - |
> +    adc {
> +        compatible = "adi,adaq23878";
> +        io-backends = <&axi_adc>;
> +        pwms = <&axi_pwm_gen 0 0 0>, <&axi_pwm_gen 1 0 0>;
> +        pwm-names = "cnv", "clk";
> +        vdd-supply = <&supply_5V>;
> +        vio-supply = <&supply_2_5V>;
> +        vs-n-supply = <&supply_0V>;
> +        vs-p-supply = <&supply_5V>;
> +        adi,gain-milli = /bits/ 16 <870>;
> +        adi,use-two-lanes;
> +    };
> -- 
> 2.34.1
>

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