linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: adc: Add TI ADS1018/ADS1118

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Message-ID: <09d8aa0c-8713-4673-8d70-ff5d59392c12@baylibre.com>
Date: Fri, 21 Nov 2025 16:32:52 -0600
From: David Lechner <dlechner@...libre.com>
To: Kurt Borja <kuurtb@...il.com>, Jonathan Cameron <jic23@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Tobias Sperling <tobias.sperling@...ting.com>
Cc: Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH 1/2] dt-bindings: iio: adc: Add TI ADS1018/ADS1118

On 11/21/25 11:16 AM, Kurt Borja wrote:
> Add documentation for Texas Instruments ADS1018 and ADS1118
> analog-to-digital converters.
> 
> Signed-off-by: Kurt Borja <kuurtb@...il.com>
> ---
>  .../devicetree/bindings/iio/adc/ti,ads1118.yaml    | 132 +++++++++++++++++++++
>  1 file changed, 132 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads1118.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads1118.yaml
> new file mode 100644
> index 000000000000..eb7228ed6ddb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/ti,ads1118.yaml

I like to make the file name match the lowest number. That way it matches
the first item in the compatible list.

> @@ -0,0 +1,132 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)

Better to be specific with GPL-2.0-only or GPL-2.0-or-later (your choice).

> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/ti,ads1118.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: TI ADS1018/ADS1118 SPI analog to digital converter
> +
> +maintainers:
> +  - Kurt Borja <kuurtb@...il.com>
> +
> +description: |
> +  The ADS1018/ADS1118 is a precision, low-power, 12-bit or 16-bit, noise-free,
> +  analog-to-digital converter (ADC). It integrates a programmable gain amplifier
> +  (PGA), voltage reference, oscillator and high-accuracy temperature sensor.
> +
> +  Datasheets:
> +    - ADS1018: https://www.ti.com/lit/ds/symlink/ads1018.pdf
> +    - ADS1118: https://www.ti.com/lit/ds/symlink/ads1118.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - ti,ads1018
> +      - ti,ads1118
> +
> +  reg:
> +    maxitems: 1

We know the max SCLK rate from the datasheet, so we can add:

spi-max-frequency:
  maximum: 4000000

And we need to explicitly mention this one (it isn't part of
spi-peripheral-props.yaml but rather comes from spi-controller.yaml):

spi-cpha: true

> +
> +  interrupts:
> +    description: DOUT/DRDY (Data Out/Data Ready) line.
> +    maxitems: 1
> +
> +  drdy-gpios:
> +    description:
> +      Extra GPIO line connected to DOUT/DRDY (Data Out/Data Ready). This allows
> +      distinguishing between latched and real DRDY IRQs.
> +    maxitems: 1
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +  '#io-channel-cells':
> +    const: 1
> +

All chips need power, so we should have:

vdd-supply: true

and make it required.

> +required:
> +  - compatible
> +  - reg
> +  - drdy-gpios

The chip can be used without needing the DRDY signal, so drdy-gpios and
interrupts should not be required.

> +  - '#address-cells'
> +  - '#size-cells'
> +
> +patternProperties:
> +  "^channel@[0-7]$":
> +    type: object
> +    $ref: /schemas/iio/adc/adc.yaml#
> +    description: Properties for a single ADC channel.
> +
> +    properties:
> +      reg:
> +        minimum: 0
> +        maximum: 7
> +        description: The channel index (0-7).
> +
> +      ti,gain:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        minimum: 0
> +        maximum: 5
> +        description:
> +          Programmable gain amplifier configuration, as described in the PGA
> +          Config Register Field description. If not present, the default is
> +          used.

The gain is programmable, so normally, we would set that by writing
to the in_voltageY_scale attribute rather than hard-coding it in the
devicetree.

> +
> +      ti,datarate:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        minimum: 0
> +        maximum: 7
> +        description:
> +          Data rate configuration, as described in the DR Config Register Field
> +          description. If not present, the default is used.

Likewise, the data rate should be set at runtime using a
sampling_frequency attribute rather than being hard-coded
in the devicetree.

> +
> +    required:
> +      - reg
> +
> +    additionalProperties: false
> +
So we shouldn't need explicit channel properties at this time.