[v3,10/13] dt-bindings: iio: Add AD7091R-8

Add device tree documentation for AD7091R-8.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
 .../bindings/iio/adc/adi,ad7091r8.yaml        | 99 +++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad7091r8.yaml

Hi David, thank you for your suggestions.
Comments inline.

On 12/07, David Lechner wrote:
> On Thu, Dec 7, 2023 at 12:42 PM Marcelo Schmitt
> <marcelo.schmitt@analog.com> wrote:
> >
> > Add device tree documentation for AD7091R-8.
> >
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> >  .../bindings/iio/adc/adi,ad7091r8.yaml        | 99 +++++++++++++++++++
> >  1 file changed, 99 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad7091r8.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7091r8.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7091r8.yaml
> > new file mode 100644
> > index 000000000000..02320778f225
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7091r8.yaml
> > @@ -0,0 +1,99 @@
> > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/adc/adi,ad7091r8.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Analog Devices AD7091R8 8-Channel 12-Bit ADC
> > +
> > +maintainers:
> > +  - Marcelo Schmitt <marcelo.schmitt@analog.com>
> > +
> > +description: |
> > +  Analog Devices AD7091R-8 8-Channel 12-Bit ADC
> > +  https://www.analog.com/media/en/technical-documentation/data-sheets/AD7091R-2_7091R-4_7091R-8.pdf
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - adi,ad7091r2
> > +      - adi,ad7091r4
> > +      - adi,ad7091r8
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> 
> Missing other supplies? Like vdd-supply and vdrive-supply?
> 

I used the name that would work with ad7091r-base.c.
If I'm not misinterpreting the datasheet, vdd-supply and vdrive-supply are
for powering the ADC and setting SPI lanes logic level, respectively.
They don't have any impact on ADC readings.
By the way, should maybe I extend ad7091r5 dt doc instead of creating this
new one?

> > +  vref-supply: true
> 
> refin-supply might be a better name to match the datasheet pin name.
> 

Agree, though I guess changing the name now would break users of ad7091r5 if
they happen to update the driver without updating their device tree.

> > +
> > +  adi,conversion-start-gpios:
> 
> gpios usually don't get a vendor prefix do they?
> 
> convst-gpios could be a better name to match the pin name on the datasheet.

Ack, will do for v4.

> 
> > +    description:
> > +      GPIO connected to the CONVST pin.
> > +      This logic input is used to initiate conversions on the analog
> > +      input channels.
> > +    maxItems: 1
> > +
> > +  reset-gpios:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> 
> A description of what the interrupt is attached to (ALERT/BUSY/GPO0
> pin) would be helpful.
> 

Ack, will do for v4.

> > +
> > +patternProperties:
> > +  "^channel@[0-7]$":
> > +    $ref: adc.yaml
> > +    type: object
> > +    description: Represents the external channels which are connected to the ADC.
> > +
> > +    properties:
> > +      reg:
> > +        minimum: 0
> > +        maximum: 7
> 
> Shouldn't this be:
> 
>         items:
>           - minimum: 0
>             maximum: 7
> 

Ack

> > +
> > +    required:
> > +      - reg
> 
> Missing `unevaluatedProperties: false` for channels?
> 
> Bigger picture: since no other properties besides `reg` are included
> here, do we actually need channel nodes?
> 

The channel nodes are not used by the drivers so we can remove them if we want.
I thought they would be required as documentation even if they were not used
in drivers.
Looks like they're not required so will remove them in v4.

> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - adi,conversion-start-gpios
> > +
> > +allOf:
> > +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +  # AD7091R-2 does not have ALERT/BUSY/GPO pin
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            enum:
> > +              - adi,ad7091r4
> > +              - adi,ad7091r8
> > +    then:
> > +      properties:
> > +        interrupts: true
> 
> Interrupts is already true. Maybe better to only match chips without
> interrupts and set false?
> 

Agree, that should simplify the constrain logic. Will do for v4.

> > +    else:
> > +      properties:
> > +        interrupts: false
> > +
> > +unevaluatedProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/irq.h>
> > +    #include <dt-bindings/gpio/gpio.h>
> > +    spi {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        adc@0 {
> > +                compatible = "adi,ad7091r8";
> > +                reg = <0x0>;
> > +                spi-max-frequency = <45454545>;
> > +                vref-supply = <&adc_vref>;
> > +                adi,conversion-start-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
> > +                reset-gpios = <&gpio 27 GPIO_ACTIVE_LOW>;
> > +                interrupts = <22 IRQ_TYPE_EDGE_FALLING>;
> > +                interrupt-parent = <&gpio>;
> > +        };
> > +    };
> > +...
> > --
> > 2.42.0
> >
> >