Re: [PATCH RFC 1/4] dt-bindings: iio: adc: ad7380: add adaq4370-4 and adaq4380-4 compatible parts

Julien Stephan
2024-10-21T13:25:36Z

Le dim. 20 oct. 2024 à 15:21, Jonathan Cameron <jic23@kernel.org> a écrit :
>
> On Tue, 15 Oct 2024 11:09:06 +0200
> Julien Stephan <jstephan@baylibre.com> wrote:
>
> > adaq4370-4 (2MSPS) and adaq4380-4 (4MSPS) are quad-channel precision data
> > acquisition signal chain μModule solutions compatible with the ad738x
> > family, with the following differences:
> >
> > - configurable gain in front of each 4 adc
> As per quick review I gave for the driver code, I'm not seeing why
> a configurable gain is a DT thing on an ADC vs something that belongs
> in userspace control. I may be missing something though.
>
> It exists for the ad4000 because the control isn't via registers
> but via pin straps so we can't control it sensibly from userspace.

Hi Jonathan,
I indeed based my work on ad4000. I think my commit description is
erroneous and confusing.
On the first page of the datasheet
(https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4380-4.pdf)
it's written : Pin selectable Gain/attenuation. So I guess adaq4380-4
and adaq4370-4 are working the same way as the adaq4000 series.
I'll rewrite my commit message. Also, I didn't want to restrict users
to the gain values in the datasheet, because I thought they are just
examples and users can always use additional resistance to change the
gain. Am I correct? Or should I use the datasheet values (as adaq4000
series does) ?

Cheers
Julien

>
> Jonathan
>
> > - internal reference is 3V derived from refin-supply (5V)
> > - additional supplies
> >
> > To configure the gain a new patternProperties is added to describe each
> > channel. It is restricted to adaq devices.
> >
> > Signed-off-by: Julien Stephan <jstephan@baylibre.com>
> > ---
> > .../devicetree/bindings/iio/adc/adi,ad7380.yaml | 117 +++++++++++++++++++++
> > 1 file changed, 117 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml
> > index 74d82721637c..3007d8e39684 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml
> > @@ -25,6 +25,8 @@ description: |
> > * https://www.analog.com/en/products/ad7386-4.html
> > * https://www.analog.com/en/products/ad7387-4.html
> > * https://www.analog.com/en/products/ad7388-4.html
> > + * https://www.analog.com/en/products/adaq4370-4.html
> > + * https://www.analog.com/en/products/adaq4380-4.html
> >
> >
> > $ref: /schemas/spi/spi-peripheral-props.yaml#
> > @@ -46,6 +48,8 @@ properties:
> > - adi,ad7386-4
> > - adi,ad7387-4
> > - adi,ad7388-4
> > + - adi,adaq4370-4
> > + - adi,adaq4380-4
> >
> > reg:
> > maxItems: 1
> > @@ -59,6 +63,9 @@ properties:
> > vlogic-supply: true
> > refio-supply: true
> > refin-supply: true
> > + vs-p-supply: true
> > + vs-n-supply: true
> > + ldo-supply: true
> >
> > aina-supply:
> > description:
> > @@ -86,12 +93,43 @@ properties:
> > specify the ALERT interrupt.
> > maxItems: 1
> >
> > + '#address-cells':
> > + const: 1
> > +
> > + '#size-cells':
> > + const: 0
> > +
> > required:
> > - compatible
> > - reg
> > - vcc-supply
> > - vlogic-supply
> >
> > +patternProperties:
> > + "^channel@([0-3])$":
> > + $ref: adc.yaml
> > + type: object
> > +
> > + properties:
> > + reg:
> > + description:
> > + The channel number. From 0 to 3 corresponding to channels A,B,C,D
> > + items:
> > + minimum: 0
> > + maximum: 3
> > +
> > + adi,gain-milli:
> > + description:
> > + The hardware gain applied to the ADC input (in milli units).
> > + If not present, default to 1000 (no actual gain applied).
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + default: 1000
> > +
> > + required:
> > + - reg
> > +
> > + additionalProperties: false
> > +
> > unevaluatedProperties: false
> >
> > allOf:
> > @@ -128,7 +166,21 @@ allOf:
> > ainc-supply: false
> > aind-supply: false
> >
> > + # Using channel to declare gain property only applies to adaq devices
> > + - if:
> > + properties:
> > + compatible:
> > + not:
> > + contains:
> > + enum:
> > + - adi,adaq4370-4
> > + - adi,adaq4380-4
> > + then:
> > + patternProperties:
> > + "^channel@([0-3])$": false
> > +
> > # ad7380-4 uses refin-supply as external reference.
> > + # adaq devices use internal reference only, derived from refin-supply
> > # All other chips from ad738x family use refio as optional external reference.
> > # When refio-supply is omitted, internal reference is used.
> > - if:
> > @@ -136,6 +188,8 @@ allOf:
> > compatible:
> > enum:
> > - adi,ad7380-4
> > + - adi,adaq4370-4
> > + - adi,adaq4380-4
> > then:
> > properties:
> > refio-supply: false
> > @@ -145,6 +199,24 @@ allOf:
> > properties:
> > refin-supply: false
> >
> > + # adaq devices need more supplies
> > + - if:
> > + properties:
> > + compatible:
> > + enum:
> > + - adi,adaq4370-4
> > + - adi,adaq4380-4
> > + then:
> > + required:
> > + - vs-p-supply
> > + - vs-n-supply
> > + - ldo-supply
> > + else:
> > + properties:
> > + vs-p-supply: false
> > + vs-n-supply: false
> > + ldo-supply: false
> > +
> > examples:
> > - |
> > #include <dt-bindings/interrupt-controller/irq.h>
> > @@ -169,3 +241,48 @@ examples:
> > refio-supply = <&supply_2_5V>;
> > };
> > };
> > +
> > + - |
> > + #include <dt-bindings/interrupt-controller/irq.h>
> > +
> > + spi {
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + adc@0 {
> > + compatible = "adi,adaq4380-4";
> > + reg = <0>;
> > +
> > + spi-cpol;
> > + spi-cpha;
> > + spi-max-frequency = <80000000>;
> > +
> > + interrupts = <27 IRQ_TYPE_EDGE_FALLING>;
> > + interrupt-parent = <&gpio0>;
> > +
> > + vcc-supply = <&supply_3_3V>;
> > + vlogic-supply = <&supply_3_3V>;
> > + refin-supply = <&supply_5V>;
> > + vs-p-supply = <&supply_5V>;
> > + vs-n-supply = <&supply_0V>;
> > + ldo-supply = <&supply_5V>;
> > +
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > +
> > + channel@0 {
> > + reg = <0>;
> > + adi,gain-milli = <300>;
> > + };
> > +
> > + channel@2 {
> > + reg = <2>;
> > + adi,gain-milli = <600>;
> > + };
> > +
> > + channel@3 {
> > + reg = <3>;
> > + adi,gain-milli = <1000>;
> > + };
> > + };
> > + };
> >
>