Re: [PATCH v12 1/2] dt-bindings: adc: add AD7173

David Lechner <dlechner@xxxxxxxxxxxx> · Thu, 18 Jan 2024 16:42:47 -0600

On Thu, Jan 18, 2024 at 6:50 AM Dumitru Ceclan <mitrutzceclan@xxxxxxxxx> wrote:
>
> The AD7173 family offer a complete integrated Sigma-Delta ADC solution
> which can be used in high precision, low noise single channel applications
> or higher speed multiplexed applications. The Sigma-Delta ADC is intended
> primarily for measurement of signals close to DC but also delivers
> outstanding performance with input bandwidths out to ~10kHz.
>
> Signed-off-by: Dumitru Ceclan <mitrutzceclan@xxxxxxxxx>
> ---
>
> V11->V12
>  - Drop "binding", describe hardware in binding description
>  - Rename refin and refin2 to vref and vref2
>  - Add better description to external references to better show that the voltage
>     value that needs to be specified is the difference between the positive and
>     negative reference pins
>  - Add optional clocks properties
>  - Add optional adi,clock-select property
>  - Add option for second interrupt, error
>  - Add description to interrupts
> V10->V11
>  - Fix example warning: '#gpio-cells' is a dependency of 'gpio-controller'
>  - Add description to #gpio-cells property
> V9->V10
>  - Fix dt_binding_check type warning from adi,reference-select
> V8->v9
>  - Add gpio-controller and "#gpio-cells" properties
>  - Add missing avdd2 and iovdd supplies
>  - Add string type to reference-select
> V7->V8
>  - include missing fix from V6
> V6->V7 <no changes>
> V5->V6
>  - Moved global required property to proper placement
> V4 -> V5
>  - Use string enum instead of integers for "adi,reference-select"
>  - Fix conditional checking in regards to compatible
> V3 -> V4
>  - include supply attributes
>  - add channel attribute for selecting conversion reference
> V2 -> V3
>  - remove redundant descriptions
>  - use referenced 'bipolar' property
>  - remove newlines from example
> V1 -> V2 <no changes>
>
>  .../bindings/iio/adc/adi,ad7173.yaml          | 242 ++++++++++++++++++
>  1 file changed, 242 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
> new file mode 100644
> index 000000000000..4d0870cc014c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
> @@ -0,0 +1,242 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +# Copyright 2023 Analog Devices Inc.
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/adi,ad7173.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD7173 ADC
> +
> +maintainers:
> +  - Ceclan Dumitru <dumitru.ceclan@xxxxxxxxxx>
> +
> +description: |
> +  Analog Devices AD717x ADC's:
> +  The AD717x family offer a complete integrated Sigma-Delta ADC solution which
> +  can be used in high precision, low noise single channel applications
> +  (Life Science measurements) or higher speed multiplexed applications
> +  (Factory Automation PLC Input modules). The Sigma-Delta ADC is intended
> +  primarily for measurement of signals close to DC but also delivers
> +  outstanding performance with input bandwidths out to ~10kHz.
> +
> +  Datasheets for supported chips:
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7172-2.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7173-8.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7175-2.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7176-2.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,ad7172-2
> +      - adi,ad7173-8
> +      - adi,ad7175-2
> +      - adi,ad7176-2
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    minItems: 1
> +    description: |
> +      Ready interrupt: multiplexed with SPI data out. While SPI CS is low,
> +      can be used to indicate the completion of a conversion.
> +
> +      Error: The three error bits in the status register (ADC_ERROR, CRC_ERROR,
> +      and REG_ERROR) are OR'ed, inverted, and mapped to the ERROR pin. Therefore,
> +      the ERROR pin indicates that an error has occurred.
> +
> +  interrupt-names:
> +    minItems: 1
> +    items:
> +      - const: rdy
> +      - const: err
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +  spi-max-frequency:
> +    maximum: 20000000
> +
> +  gpio-controller:
> +    description: Marks the device node as a GPIO controller.
> +
> +  "#gpio-cells":
> +    const: 2
> +    description:
> +      The first cell is the GPIO number and the second cell specifies
> +      GPIO flags, as defined in <dt-bindings/gpio/gpio.h>.
> +
> +  vref-supply:
> +    description: |
> +      Differential external reference supply used for conversion. The reference
> +      voltage (Vref) specified here must be the voltage difference between the
> +      REF+ and REF- pins: Vref = (REF+) - (REF-).
> +
> +  vref2-supply:
> +    description: |
> +      Differential external reference supply used for conversion. The reference
> +      voltage (Vref2) specified here must be the voltage difference between the
> +      REF2+ and REF2- pins: Vref2 = (REF2+) - (REF2-).
> +
> +  avdd-supply:
> +    description: avdd supply, can be used as reference for conversion.

I think it would be helpful to have a description similar to
vref-supply here. This is the voltage between AVDD and AVSS. So in
both cases AVDD=5V, AVSS=0V and AVDD=+2.5V, AVSS=-2.5V, this supply
should report 5V.

> +
> +  avdd2-supply:
> +    description: avdd2 supply, used as the input to the internal voltage regulator.

This supply is also referenced to AVSS.

> +
> +  iovdd-supply:
> +    description: iovdd supply, used for the chip digital interface.
> +
> +  clocks:
> +    maxItems: 1
> +    description: |
> +      Optional external clock source. Can include one clock source: external
> +      clock or external crystal.
> +
> +  clock-names:
> +    enum:
> +      - ext-clk
> +      - xtal
> +
> +  adi,clock-select:
> +    description: |
> +      Select the ADC clock source. Valid values are:
> +      int         : Internal oscillator
> +      int-out     : Internal oscillator with output on XTAL2 pin
> +      ext-clk     : External clock input on XTAL2 pin
> +      xtal        : External crystal on XTAL1 and XTAL2 pins
> +
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum:
> +      - int
> +      - int-out
> +      - ext-clk
> +      - xtal
> +    default: int
> +
> +patternProperties:
> +  "^channel@[0-9a-f]$":
> +    type: object
> +    $ref: adc.yaml
> +    unevaluatedProperties: false
> +
> +    properties:
> +      reg:
> +        minimum: 0
> +        maximum: 15
> +
> +      diff-channels:
> +        items:
> +          minimum: 0
> +          maximum: 31
> +
> +      adi,reference-select:
> +        description: |
> +          Select the reference source to use when converting on
> +          the specific channel. Valid values are:
> +          vref       : REF+  /REF−
> +          vref2      : REF2+ /REF2−
> +          refout-avss: REFOUT/AVSS (Internal reference)
> +          avdd       : AVDD

Could write this as AVDD/AVSS to be consistent with the other 3 options.

(Or if this is really AVDD to 0V, we may need to reconsider some of
our other decisions.)

> +
> +          External reference ref2 only available on ad7173-8.
> +          If not specified, internal reference used.
> +        $ref: /schemas/types.yaml#/definitions/string
> +        enum:
> +          - vref
> +          - vref2
> +          - refout-avss
> +          - avdd
> +        default: refout-avss
> +
> +    required:
> +      - reg
> +      - diff-channels
> +
> +required:
> +  - compatible
> +  - reg
> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +  - if:
> +      properties:
> +        compatible:
> +          not:
> +            contains:
> +              const: adi,ad7173-8
> +    then:
> +      properties:
> +        vref2-supply: false
> +      patternProperties:
> +        "^channel@[0-9a-f]$":
> +          properties:
> +            adi,reference-select:
> +              enum:
> +                - vref
> +                - refout-avss
> +                - avdd
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    spi {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      adc@0 {
> +        compatible = "adi,ad7173-8";
> +        reg = <0>;
> +
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
> +        interrupt-names = "rdy";
> +        interrupt-parent = <&gpio>;
> +        spi-max-frequency = <5000000>;
> +        gpio-controller;
> +        #gpio-cells = <2>;
> +
> +        vref-supply = <&dummy_regulator>;
> +
> +        channel@0 {
> +          reg = <0>;
> +          bipolar;
> +          diff-channels = <0 1>;
> +          adi,reference-select = "vref";
> +        };
> +
> +        channel@1 {
> +          reg = <1>;
> +          diff-channels = <2 3>;
> +        };
> +
> +        channel@2 {
> +          reg = <2>;
> +          bipolar;
> +          diff-channels = <4 5>;
> +        };
> +
> +        channel@3 {
> +          reg = <3>;
> +          bipolar;
> +          diff-channels = <6 7>;
> +        };
> +
> +        channel@4 {
> +          reg = <4>;
> +          diff-channels = <8 9>;
> +          adi,reference-select = "avdd";
> +        };
> +      };
> +    };
> --
> 2.42.0
>