Re: [PATCH 1/2] dt-bindings: iio: adc: Add Nuvoton MA35D1 EADC

[Chi-Wen Weng <cwweng.linux@gmail.com>]

Hi David,

Thanks for the review.

 > Datasheet says there are 4 interrupts.

Yes, the controller has four EOC interrupt outputs, ADINT0 to ADINT3.
The initial driver only uses ADINT0, but the hardware does provide four
interrupt lines.

I will update the binding to allow up to four interrupt entries and
document the order as ADINT0, ADINT1, ADINT2 and ADINT3. The example
will keep a single interrupt entry since that is the only one used by
the initial driver.

 > Should there be an optional vref-supply for the V_REF pin?

Yes, I agree. I will add an optional vref-supply property.

I will also update the driver so that it does not force the external
reference path unconditionally. If vref-supply is present, the driver
will enable it and use it to report the ADC scale. Otherwise, the driver
will use the internal reference path.

 > Should there be a dmas property? Datasheet says it supports PDMA 
transfer.

The hardware does support PDMA, but DMA support is intentionally not
included in this initial upstream version. The initial driver will only
support interrupt-driven direct raw reads, and the MA35D1 PDMA provider
is not upstream yet.

I would prefer to leave dmas/dma-names out of the initial binding and
add them later together with DMA support. Please let me know if you
would prefer optional DMA properties to be described now.

 > I assume 8 is for the internal batter voltage channel? Often, we don't
 > include fixed internal channels like this in the devicetree since they
 > are always the same and don't depend on external wiring.

Correct. Channels 0 to 7 are the external ADC input pins, while channel
8 is the internal VBAT input. I will limit the DT child channel nodes to
external channels 0 to 7.

If VBAT support is added later, it can be exposed by the driver as a
fixed internal channel rather than being described by devicetree.

 > adc.yaml already specifies minItems and maxItems, so we don't need to
 > repeat it.

Since I plan to simplify v2 and drop differential channel support from
the initial submission, I will remove diff-channels from the initial
binding.

Differential input support can be added later once the fixed hardware
pair constraints and signed output handling are implemented in the
driver.

 > This (and reg) are uint32, so don't really need minimum: 0.
 >
 > Also, I assume that 8 is for the internal battery voltage channel,
 > which wouldn't make sense as part of a differential input.

Will fix. The v2 binding will restrict child nodes to external channels
0 to 7 and drop the unnecessary minimum: 0.

Thanks,
Chi-Wen


David Lechner 於 2026/6/28 上午 04:05 寫道:
> On 6/25/26 6:06 AM, Chi-Wen Weng wrote:
>> From: Chi-Wen Weng <cwweng@nuvoton.com>
>>
>> Add devicetree binding for the Enhanced ADC controller found on
>> Nuvoton MA35D1 SoCs.
>>
>> The controller has one register region, one interrupt and one functional
>> clock. ADC inputs are described using standard channel child nodes,
>> including optional differential channel pairs.
>>
>> Signed-off-by: Chi-Wen Weng <cwweng@nuvoton.com>
>> ---
>>   .../bindings/iio/adc/nuvoton,ma35d1-eadc.yaml | 100 ++++++++++++++++++
>>   1 file changed, 100 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/adc/nuvoton,ma35d1-eadc.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/nuvoton,ma35d1-eadc.yaml b/Documentation/devicetree/bindings/iio/adc/nuvoton,ma35d1-eadc.yaml
>> new file mode 100644
>> index 000000000000..ae7ad0f7689a
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/nuvoton,ma35d1-eadc.yaml
>> @@ -0,0 +1,100 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/nuvoton,ma35d1-eadc.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Nuvoton MA35D1 Enhanced Analog to Digital Converter
>> +
>> +maintainers:
>> +  - Chi-Wen Weng <cwweng@nuvoton.com>
>> +
>> +description: |
>> +  The Nuvoton MA35D1 Enhanced Analog to Digital Converter (EADC) is a
>> +  12-bit ADC controller integrated in the MA35D1 SoC. Each enabled ADC
>> +  input is described by a child channel node.
>> +
>> +properties:
>> +  compatible:
>> +    const: nuvoton,ma35d1-eadc
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    maxItems: 1
> Datasheet says there are 4 interrupts.
>
>> +
>> +  clocks:
>> +    maxItems: 1
> Should there be an optional vref-supply for the V_REF pin?
>
> Should there be a dmas property? Datasheet says it supports
> PDMA transfer.
>
>> +
>> +  '#address-cells':
>> +    const: 1
>> +
>> +  '#size-cells':
>> +    const: 0
>> +
>> +patternProperties:
>> +  '^channel@[0-8]$':
>> +    type: object
>> +    $ref: adc.yaml
>> +    unevaluatedProperties: false
>> +
>> +    properties:
>> +      reg:
>> +        minimum: 0
>> +        maximum: 8
> I assume 8 is for the internal batter voltage channel? Often, we don't
> include fixed internal channels like this in the devicetree since they
> are always the same and don't depend on external wiring.
>
>> +
>> +      diff-channels:
>> +        minItems: 2
>> +        maxItems: 2
> adc.yaml already specifies minItems and maxItems, so we don't need to repeat it.
>
>> +        items:
>> +          minimum: 0
>> +          maximum: 8
> This (and reg) are uint32, so don't really need minimum: 0.
>
> Also, I assume that 8 is for the internal battery voltage channel, which
> wouldn't make sense as part of a differential input.
>
>> +
>> +    required:
>> +      - reg
>> +
>> +required:
>> +  - compatible
>> +  - reg
>> +  - interrupts
>> +  - clocks
>> +  - '#address-cells'
>> +  - '#size-cells'
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> +  - |
>> +    #include <dt-bindings/clock/nuvoton,ma35d1-clk.h>
>> +    #include <dt-bindings/interrupt-controller/arm-gic.h>
>> +    #include <dt-bindings/interrupt-controller/irq.h>
>> +
>> +    soc {
>> +        #address-cells = <2>;
>> +        #size-cells = <2>;
>> +
>> +        adc@40430000 {
>> +            compatible = "nuvoton,ma35d1-eadc";
>> +            reg = <0x0 0x40430000 0x0 0x10000>;
>> +            interrupts = <GIC_SPI 65 IRQ_TYPE_LEVEL_HIGH>;
>> +            clocks = <&clk EADC_GATE>;
>> +
>> +            #address-cells = <1>;
>> +            #size-cells = <0>;
>> +
>> +            channel@0 {
>> +                reg = <0>;
>> +            };
>> +
>> +            channel@1 {
>> +                reg = <1>;
>> +            };
>> +
>> +            channel@2 {
>> +                reg = <2>;
>> +                diff-channels = <2 3>;
>> +            };
>> +        };
>> +    };
>> +...