linux-kernel - Re: [PATCH v2 1/2] dt-bindings: adc: provide max34408/9 device tree binding document

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Date:   Mon, 2 Oct 2023 10:21:55 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Ivan Mikhaylov <fr0st61te@...il.com>
CC:     Conor Dooley <conor@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        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 v2 1/2] dt-bindings: adc: provide max34408/9 device tree
 binding document

On Sat, 30 Sep 2023 22:38:58 +0300
Ivan Mikhaylov <fr0st61te@...il.com> wrote:

> On Sat, 2023-09-30 at 10:37 +0100, Conor Dooley wrote:
> > Hey,
> > 
> > On Fri, Sep 29, 2023 at 11:08:43PM +0300, Ivan Mikhaylov wrote:  
> > > The hardware binding for i2c current monitoring device with
> > > overcurrent
> > > control.
> > > 
> > > Signed-off-by: Ivan Mikhaylov <fr0st61te@...il.com>
> > > ---
> > >  .../bindings/iio/adc/maxim,max34408.yaml      | 101
> > > ++++++++++++++++++
> > >  1 file changed, 101 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..cdf89fa4c80e
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/adc/maxim,max34408.yaml
> > > @@ -0,0 +1,101 @@
> > > +# 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,input1-rsense-val-micro-ohms:
> > > +    description:
> > > +      Adjust the Rsense value to monitor higher or lower current
> > > levels for
> > > +      input 1.
> > > +    enum: [250, 500, 1000, 5000, 10000, 50000, 100000, 200000,
> > > 500000]
> > > +    default: 1000
> > > +
> > > +  maxim,input2-rsense-val-micro-ohms:
> > > +    description:
> > > +      Adjust the Rsense value to monitor higher or lower current
> > > levels for
> > > +      input 2.
> > > +    enum: [250, 500, 1000, 5000, 10000, 50000, 100000, 200000,
> > > 500000]
> > > +    default: 1000
> > > +
> > > +  maxim,input3-rsense-val-micro-ohms:
> > > +    description:
> > > +      Adjust the Rsense value to monitor higher or lower current
> > > levels for
> > > +      input 3.
> > > +    enum: [250, 500, 1000, 5000, 10000, 50000, 100000, 200000,
> > > 500000]
> > > +    default: 1000
> > > +
> > > +  maxim,input4-rsense-val-micro-ohms:
> > > +    description:
> > > +      Adjust the Rsense value to monitor higher or lower current
> > > levels for
> > > +      input 4.
> > > +    enum: [250, 500, 1000, 5000, 10000, 50000, 100000, 200000,
> > > 500000]
> > > +    default: 1000  
> > 
> > Having 4 almost identical properties makes it seem like this should
> > have
> > some channel nodes, each containing an rsense-micro-ohms type
> > property.  
> 
> Conor, I'll look through.
> 
> >   
> > > +
> > > +  maxim,shtdn:
> > > +    description:
> > > +      Shutdown Output. Open-drain output. This output transitions
> > > to high impedance
> > > +      when any of the digital comparator thresholds are exceeded
> > > as long as the ENA
> > > +      pin is high.
> > > +    type: boolean  
> > 
> > I don't understand what this property is used for. The description
> > here,
> > and below for "ena", read like they are the descriptions in the
> > datasheet for the pin, rather than how to use the property.
> > 
> > The drivers don't appear to contain users either - what is the point
> > of
> > these properties?  
> 
> ena and shtdn physical pins of hardware, in the previous version
> Jonathan asked about adding them into yaml even if it's not used in
> code. should I do it in some other way?

Yes, use the gpio bindings.

enable-gpios, isshutdown-gpios 
perhaps - though try and find a similar example for the naming.

The shutdown one is a bit unusual in that it indicates the device
has shutdown for one of several possible reasons (IIRC)

Jonathan

> 
> >   
> > > +
> > > +  maxim,ena:
> > > +    description:
> > > +      SHTDN Enable Input. CMOS digital input. Connect to GND to
> > > clear the latch and
> > > +      unconditionally deassert (force low) the SHTDN output and
> > > reset the shutdown
> > > +      delay. Connect to VDD to enable normal latch operation of
> > > the SHTDN output.
> > > +    type: boolean
> > > +
> > > +  supply-vdd: true  
> > 
> > As pointed out by the bot, this is not correct. You need to use a
> > -supply affix, not a supply-prefix.  
> 
> Oops.
> 
> Thanks.
> 
>