Date: Wed, 19 Jun 2024 08:13:41 -0500
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, broonie@...nel.org,
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 nuno.sa@...log.com, marcelo.schmitt1@...il.com
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 5/6] dt-bindings: iio: adc: Add AD4000

On 6/18/24 6:12 PM, Marcelo Schmitt wrote:
> Add device tree documentation for AD4000 series of ADC devices.
> 
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4000-4004-4008.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4001-4005.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4002-4006-4010.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4003-4007-4011.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4020-4021-4022.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4001.pdf
> Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4003.pdf

Datasheets URLs are listed in the patch, so probably don't need them
in the commit message too.

> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  .../bindings/iio/adc/adi,ad4000.yaml          | 231 ++++++++++++++++++
>  MAINTAINERS                                   |   7 +
>  2 files changed, 238 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml
> new file mode 100644
> index 000000000000..ba50f9e0784b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml
> @@ -0,0 +1,231 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/adi,ad4000.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD4000 and similar Analog to Digital Converters
> +
> +maintainers:
> +  - Marcelo Schmitt <marcelo.schmitt@...log.com>
> +
> +description: |
> +  Analog Devices AD4000 family of Analog to Digital Converters with SPI support.
> +  Specifications can be found at:
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4000-4004-4008.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4001-4005.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4002-4006-4010.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4003-4007-4011.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/ad4020-4021-4022.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4001.pdf
> +    https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4003.pdf
> +
> +$ref: /schemas/spi/spi-peripheral-props.yaml#
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - const: adi,ad4000
> +      - items:
> +          - enum:
> +              - adi,ad4004
> +              - adi,ad4008
> +          - const: adi,ad4000
> +      - const: adi,ad4001
> +      - items:
> +          - enum:
> +              - adi,ad4005
> +          - const: adi,ad4001
> +      - const: adi,ad4002
> +      - items:
> +          - enum:
> +              - adi,ad4006
> +              - adi,ad4010
> +          - const: adi,ad4002
> +      - const: adi,ad4003
> +      - items:
> +          - enum:
> +              - adi,ad4007
> +              - adi,ad4011
> +          - const: adi,ad4003
> +      - const: adi,ad4020
> +      - items:
> +          - enum:
> +              - adi,ad4021
> +              - adi,ad4022
> +          - const: adi,ad4020
> +

There are data sheets listed for adaq400x but no compatibles.

> +  reg:
> +    maxItems: 1
> +
> +  spi-max-frequency:
> +    maximum: 102040816 # for VIO > 2.7 V, 81300813 for VIO > 1.7 V
> +
> +  adi,spi-mode:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [ single, chain ]
> +    description: |
> +      This property indicates the SPI wiring configuration.
> +
> +      When this property is omitted, it is assumed that the device is using what
> +      the datasheet calls "4-wire mode". This is the conventional SPI mode used
> +      when there are multiple devices on the same bus. In this mode, the CNV
> +      line is used to initiate the conversion and the SDI line is connected to
> +      CS on the SPI controller.
> +
> +      When this property is present, it indicates that the device is using one
> +      of the following alternative wiring configurations:
> +
> +      * single: The datasheet calls this "3-wire mode". (NOTE: The datasheet's
> +        definition of 3-wire mode is NOT at all related to the standard
> +        spi-3wire property!) This mode is often used when the ADC is the only
> +        device on the bus. In this mode, SDI is connected to MOSI or to VIO, and
> +        the CNV line can be connected to the CS line of the SPI controller or to
> +        a GPIO, in which case the CS line of the controller is unused.
> +      * chain: The datasheet calls this "chain mode". This mode is used to save
> +        on wiring when multiple ADCs are used. In this mode, the SDI line of
> +        one chip is tied to the SDO of the next chip in the chain and the SDI of
> +        the last chip in the chain is tied to GND. Only the first chip in the
> +        chain is connected to the SPI bus. The CNV line of all chips are tied
> +        together. The CS line of the SPI controller can be used as the CNV line
> +        only if it is active high.
> +
> +  '#daisy-chained-devices': true
> +
> +  vdd-supply:
> +    description: A 1.8V supply that powers the chip (VDD).
> +
> +  vio-supply:
> +    description:
> +      A 1.8V to 5.5V supply for the digital inputs and outputs (VIO).
> +
> +  ref-supply:
> +    description:
> +      A 2.5 to 5V supply for the external reference voltage (REF).
> +
> +  cnv-gpios:
> +    description:
> +      The Convert Input (CNV). This input has multiple functions. It initiates
> +      the conversions and selects the SPI mode of the device (chain or CS). In
> +      'single' mode, this property is omitted if the CNV pin is connected to the
> +      CS line of the SPI controller.
> +    maxItems: 1
> +
> +  adi,high-z-input:
> +    type: boolean
> +    description:
> +      High-Z mode allows the amplifier and RC filter in front of the ADC to be
> +      chosen based on the signal bandwidth of interest, rather than the settling
> +      requirements of the switched capacitor SAR ADC inputs.
> +
> +  adi,gain-milli:
> +    description: |
> +      The hardware gain applied to the ADC input (in milli units).
> +      The gain provided by the ADC input scaler is defined by the hardware
> +      connections between chip pins OUT+, R1K-, R1K1-, R1K+, R1K1+, and OUT-.
> +      If not present, default to 1000 (no actual gain applied).
> +    $ref: /schemas/types.yaml#/definitions/uint16

Any particular reason why this needs to be uint16 instead of the more
common uint32?

> +    enum: [454, 909, 1000, 1900]
> +    default: 1000
> +
> +  interrupts:
> +    description:
> +      The SDO pin can also function as a busy indicator. This node should be
> +      connected to an interrupt that is triggered when the SDO line goes low
> +      while the SDI line is high and the CNV line is low ('single' mode) or the
> +      SDI line is low and the CNV line is high ('multi' mode); or when the SDO
> +      line goes high while the SDI and CNV lines are high (chain mode),
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - vdd-supply
> +  - vio-supply
> +  - ref-supply
> +
> +allOf:
> +  # in '4-wire' mode, cnv-gpios is required, for other modes it is optional
> +  - if:
> +      not:
> +        required:
> +          - adi,spi-mode
> +    then:
> +      required:
> +        - cnv-gpios
> +  # The configuration register can only be accessed in '3-wire' mode
> +  - if:
> +      not:
> +        properties:
> +          adi,spi-mode:
> +            contains:
> +              enum:
> +                - single

adi,spi-mode is not an array and we are only checking for one value,
so this could be simplified to:

  properties:
    adi,spi-mode:
      const: single

> +    then:
> +      properties:
> +        adi,high-z-input: false
> +  # chain mode has lower SCLK max rate
> +  - if:
> +      required:
> +        - adi,spi-mode
> +      properties:
> +        adi,spi-mode:
> +          const: chain
> +    then:
> +      properties:
> +        spi-max-frequency:
> +          maximum: 50000000 # for VIO > 2.7 V, 40000000 for VIO > 1.7 V
> +      required:
> +        - '#daisy-chained-devices'
> +    else:
> +      properties:
> +        '#daisy-chained-devices': false
> +  # Gain property only applies to ADAQ devices
> +  - if:
> +      properties:
> +        compatible:
> +          not:
> +            contains:
> +              enum:
> +                - adi,adaq4001
> +                - adi,adaq4003
> +    then:
> +      properties:
> +        adi,gain-milli: false
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        /* Example for a AD devices */

Comments are a bit redundant since it says "examples:" above and
the type of the chip in the compatible string.

> +        adc@0 {
> +            compatible = "adi,ad4020";
> +            reg = <0>;
> +            spi-max-frequency = <71000000>;
> +            vdd-supply = <&supply_1_8V>;
> +            vio-supply = <&supply_1_8V>;
> +            ref-supply = <&supply_5V>;
> +            cnv-gpios = <&gpio0 88 GPIO_ACTIVE_HIGH>;
> +        };
> +    };
> +  - |
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +        /* Example for a ADAQ devices */
> +        adc@0 {
> +            compatible = "adi,adaq4003";
> +            reg = <0>;
> +            spi-max-frequency = <80000000>;
> +            vdd-supply = <&supply_1_8V>;
> +            vio-supply = <&supply_1_8V>;
> +            ref-supply = <&supply_5V>;
> +            adi,high-z-input;
> +            adi,gain-milli = /bits/ 16 <454>;
> +            adi,spi-mode = "single";
> +        };
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bff979a507ba..1f052b9cd912 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1200,6 +1200,13 @@ W:	https://ez.analog.com/linux-software-drivers
>  F:	Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
>  F:	drivers/iio/dac/ad3552r.c
>  
> +ANALOG DEVICES INC AD4000 DRIVER
> +M:	Marcelo Schmitt <marcelo.schmitt@...log.com>
> +L:	linux-iio@...r.kernel.org
> +S:	Supported
> +W:	https://ez.analog.com/linux-software-drivers
> +F:	Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml
> +
>  ANALOG DEVICES INC AD4130 DRIVER
>  M:	Cosmin Tanislav <cosmin.tanislav@...log.com>
>  L:	linux-iio@...r.kernel.org

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