Re: [PATCH v2 1/2] dt-bindings: iio: addac: add AD74115

[Jonathan Cameron]

On Thu,  3 Nov 2022 11:44:35 +0200
Cosmin Tanislav <demonsingur@xxxxxxxxx> wrote:

> From: Cosmin Tanislav <cosmin.tanislav@xxxxxxxxxx>
> 
> The AD74115H is a single-channel, software-configurable, input and
> output device for industrial control applications. The AD74115H
> provides a wide range of use cases, integrated on a single chip.
> 
> These use cases include analog output, analog input, digital output,
> digital input, resistance temperature detector (RTD), and thermocouple
> measurement capability. The AD74115H also has an integrated HART modem.
> 
> A serial peripheral interface (SPI) is used to handle all communications
> to the device, including communications with the HART modem. The digital
> input and digital outputs can be accessed via the SPI or the
> general-purpose input and output (GPIO) pins to support higher
> speed data rates.
> 
> The device features a 16-bit, sigma-delta analog-to-digital converter
> (ADC) and a 14-bit digital-to-analog converter (DAC).
> The AD74115H contains a high accuracy 2.5 V on-chip reference that can
> be used as the DAC and ADC reference.
> 
> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@xxxxxxxxxx>

Hi Cosmin,

A few questions inline.  Complex device so I'll doubt we'll ever get this
binding to be as tidy as for simpler devices.  Hence most of the below are
suggestions rather than requirements from me.

Jonathan

> ---
>  .../bindings/iio/addac/adi,ad74115.yaml       | 370 ++++++++++++++++++
>  MAINTAINERS                                   |   7 +
>  2 files changed, 377 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml b/Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml
> new file mode 100644
> index 000000000000..621f11d5c1f3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/addac/adi,ad74115.yaml
> @@ -0,0 +1,370 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/addac/adi,ad74115.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices AD74115H device
> +
> +maintainers:
> +  - Cosmin Tanislav <cosmin.tanislav@xxxxxxxxxx>
> +
> +description: |
> +  The AD74115H is a single-channel software configurable input/output
> +  device for industrial control applications. It contains functionality for
> +  analog output, analog input, digital output, digital input, resistance
> +  temperature detector, and thermocouple measurements integrated into a single
> +  chip solution with an SPI interface. The device features a 16-bit ADC and a
> +  14-bit DAC.
> +
> +    https://www.analog.com/en/products/ad74115h.html
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,ad74115h
> +
> +  reg:
> +    maxItems: 1
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0

I'm not seeing any child nodes, so why do we need these two?

> +
> +  avdd-supply: true
> +  avcc-supply: true
> +  dvcc-supply: true
> +  aldo1v8-supply: true

aldo1v8 is an output pin. "1.8 V Analog LDO Output. Do not use ALDO1V8 externally."
The associated input is avcc.  Given we shouldn't connect anything to the pin,
we don't want it in the binding docs

> +  dovdd-supply: true
> +  refin-supply: true
> +

...

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      Conversion range for ADC conversion 2.
> +      0 - 0V to 12V
> +      1 - -12V to +12V
> +      2 - -2.5V to +2.5V
> +      3 - -2.5V to 0V
> +      4 - 0V to 2.5V
> +      5 - 0V to 0.625V
> +      6 - -104mV to +104mV
> +      7 - 0V to 12V

For a lot of similar cases we handle these numerically to give
a human readable dts.  Is there a strong reason not to do so here (in mv)


> +    minimum: 0
> +    maximum: 7
> +    default: 0
> +
> +  adi,sense-agnd-buffer-lp:
lp is a little ambiguous, given we have a habit of using it for low pass
in filters etc. Perhaps worth spelling these out?
     adi,sens-agnd-buffer-low-power etc?

> +    type: boolean
> +    description: |
> +      Whether to enable low-power buffered mode for the AGND sense pin.
> +
> +  adi,lf-buffer-lp:
> +    type: boolean
> +    description: |
> +      Whether to enable low-power buffered mode for the low-side filtered
> +      sense pin.
> +
> +  adi,hf-buffer-lp:
> +    type: boolean
> +    description: |
> +      Whether to enable low-power buffered mode for the high-side filtered
> +      sense pin.
> +
> +  adi,ext2-buffer-lp:
> +    type: boolean
> +    description: Whether to enable low-power buffered mode for the EXT2 pin.
> +
> +  adi,ext1-buffer-lp:
> +    type: boolean
> +    description: Whether to enable low-power buffered mode for the EXT1 pin.

> +
> +required:
> +  - compatible
> +  - reg
> +  - spi-cpol
> +  - avdd-supply
> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +  - if:
> +      properties:
> +        adi,digital-input-sink-range-high: true
> +    then:
> +      properties:
> +        adi,digital-input-sink-microamp:
> +          maximum: 7400
> +
> +additionalProperties: false

Does this need to be unevalutatedProperties to allow
for the extra ones in spi-periphera-props.yaml?

> +