linux-kernel - Re: [PATCH 1/2] dt-bindings: adc: provide max34408/9 device tree binding document

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Message-ID: <20230924135359.6404a867@jic23-huawei>
Date:   Sun, 24 Sep 2023 13:53:59 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Ivan Mikhaylov <fr0st61te@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: adc: provide max34408/9 device tree
 binding document

On Mon, 18 Sep 2023 00:11:42 +0300
Ivan Mikhaylov <fr0st61te@...il.com> wrote:

> The i2c driver with Rsense option for current monitoring.
> 
> Signed-off-by: Ivan Mikhaylov <fr0st61te@...il.com>

Hi Ivan,

Welcome to IIO!

Looks good, but there are a few things I'd add to make this describe the device
a little more fully and flexibly.  Ideally we want a binding to fully describe
a device, even if the particular driver for Linux doesn't use all the features.
Some are easy though such as enabling regulators (that are probably turned on
already on your board)

Thanks,

Jonathan

> ---
>  .../bindings/iio/adc/maxim,max34408.yaml      | 63 +++++++++++++++++++
>  1 file changed, 63 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/maxim,max34408.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/maxim,max34408.yaml b/Documentation/devicetree/bindings/iio/adc/maxim,max34408.yaml
> new file mode 100644
> index 000000000000..ae7c6ddb13d8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/maxim,max34408.yaml
> @@ -0,0 +1,63 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/maxim,max34408.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Two- and four-channel current monitors with overcurrent control.
> +
> +maintainers:
> +  - Ivan Mikhaylov <fr0st61te@...il.com>
> +
> +description: |
> +  The MAX34408/MAX34409 are two- and four-channel current monitors that are
> +  configured and monitored with a standard I2C/SMBus serial interface. Each
> +  unidirectional current sensor offers precision high-side operation with a
> +  low full-scale sense voltage. The devices automatically sequence through
> +  two or four channels and collect the current-sense samples and average them
> +  to reduce the effect of impulse noise. The raw ADC samples are compared to
> +  user-programmable digital thresholds to indicate overcurrent conditions.
> +  Overcurrent conditions trigger a hardware output to provide an immediate
> +  indication to shut down any necessary external circuitry.
> +
> +  Specifications about the devices can be found at:
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/MAX34408-MAX34409.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - maxim,max34408
> +      - maxim,max34409
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  maxim,rsense-val-micro-ohms:
From the datasheet you link, it looks like this could be different for
the inputs?

> +    description:
> +      Adjust the Rsense value to monitor higher or lower current levels.
> +    enum: [250, 500, 1000, 5000, 10000, 50000, 100000, 200000, 500000]

These come from Table 18 which is example values I think?  Not sure there
is anything limiting us to those particular values given the equation given
just above that table should apply more generally.

> +    default: 1000

Please add regulator definitions.

supply-vdd: true
and add it to the required properties. It might be provided by a stub regulator
but we still list that as required.

Also good to add bindings for the other control pins that might be wired to be
in the binding from the start - no need for the driver to use them though.
Looks like we have SHTDN and ENA here that could be wired to GPIOs on the host.

> +
> +required:
> +  - compatible
> +  - reg
> +  - maxim,rsense-val-micro-ohms
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@1e {
> +              compatible = "maxim,max34409";
> +              reg = <0x1e>;
> +              maxim,rsense-val-micro-ohms = <1000>;
> +        };
> +    };