linux-kernel - Re: [PATCH v2 2/2] dt-bindings: iio: adc: devicetree bindings for texas instruments ads7142

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Date:   Sun, 16 May 2021 10:57:20 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Jozsef Horvath <info@...istro.hu>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Alexandru Ardelean <aardelean@...iqon.com>,
        Alexandru Ardelean <ardeleanalex@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Saravanan Sekar <sravanhome@...il.com>,
        Tomislav Denis <tomislav.denis@....com>,
        Gene Chen <gene_chen@...htek.com>,
        Alex Dewar <alex.dewar90@...il.com>,
        Lee Jones <lee.jones@...aro.org>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/2] dt-bindings: iio: adc: devicetree bindings for
 texas instruments ads7142

On Sun, 16 May 2021 07:31:05 +0000
Jozsef Horvath <info@...istro.hu> wrote:

> This is a device tree schema for iio driver for
>  Texas Instruments ADS7142 dual-channel, programmable sensor monitor.
> 
> Datasheet: https://www.ti.com/lit/ds/symlink/ads7142.pdf
> 
> Signed-off-by: Jozsef Horvath <info@...istro.hu>

Hi József,

A few comments inline.

thanks,

Jonathan
> ---
> 
> changes v1
>   - Redundant parameters (ti,threshold-rising, etc.)
>     are removed
>   - Supply name changed(vref -> avdd)
>   - Added dvdd supply
>   - All the properties are removed with prefix "ti,"
> changes v2
>   - "ti,prealert-count" parameter added, just for completeness.
> ---
>  .../bindings/iio/adc/ti,ads7142.yaml          | 110 ++++++++++++++++++
>  1 file changed, 110 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/ti,ads7142.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads7142.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads7142.yaml
> new file mode 100644
> index 000000000000..6e52079c68f7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/ti,ads7142.yaml
> @@ -0,0 +1,110 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/iio/adc/ti,ads7142.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Texas Instruments ADS7142 adc driver device tree bindings

ADC

> +
> +maintainers:
> +  - József Horváth <info@...istro.hu>
> +
> +description: |
> +  This document is for describing the required device tree parameters
> +   for ads7142 adc

ADC

> +  The required parameters for proper operation are described below.
> +
> +  Datasheet: https://www.ti.com/lit/ds/symlink/ads7142.pdf
> +
> +properties:
> +  compatible:
> +    const: ti,ads7142
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    description: |
> +      The BUSY/PDY pin is used as interrupt line

RDY ?

> +       in autonomous monitoring mode.
> +    maxItems: 1
> +
> +  avdd-supply:
> +    description: Regulator for the reference voltage
> +
> +  dvdd-supply: true
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +  "#io-channel-cells":
> +    const: 1
> +
> +  ti,prealert-count:
> +    description: |
> +      Sets the Pre-Alert Event Count for both,
> +       high and low comparators, for both the channels.

Interesting.  Why is this a device tree property rather than something
we want to configure from userspace?  Looks like it would map to _period
after scaling by the sampling frequency.

https://elixir.bootlin.com/linux/latest/source/Documentation/ABI/testing/sysfs-bus-iio#L1003


> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    maximum: 15
> +    minimum: 0
> +
> +patternProperties:
> +  "^channel@[0-1]$":
> +    $ref: "adc.yaml"
> +    type: object
> +    description: |
> +      Represents the external channels which are connected to the ADC.
> +    properties:
> +      reg:
> +        description: |
> +          The channel number.
> +        items:
> +          minimum: 0
> +          maximum: 1

enum: [0 1]
is a more compact way of putting this IIRC.
 
> +
> +    required:
> +      - reg
> +
> +    additionalProperties: false
> +
> +required:
> +  - compatible
> +  - "#io-channel-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +      adc@1f {
> +        compatible = "ti,ads7142";
> +        reg = <0x1f>;
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        #io-channel-cells = <1>;
> +
> +        avdd-supply = <&vdd_3v3_reg>;
> +        dvdd-supply = <&vdd_1v8_reg>;
> +
> +        interrupt-parent = <&gpio>;
> +        interrupts = <7 2>;
> +
> +        ti,prealert-count = <4>;
> +
> +        channel@0 {
> +          reg = <0>;
> +        };
> +
> +        channel@1 {
> +          reg = <1>;
> +        };
> +      };
> +    };
> +...
> +