Re: [PATCH v3 2/3] dt-bindings: iio: dac: Add adi,ad3530r.yaml

[David Lechner]

On 4/3/25 6:15 AM, Nuno Sá wrote:
> 
> Hi Kim,
> 
> On Thu, 2025-04-03 at 13:33 +0800, Kim Seer Paller wrote:
>> Document the AD3530/AD3530R (8-channel) and AD3531/AD3531R (4-channel)
>> low-power, 16-bit, buffered voltage output DACs with software-
>> programmable gain controls. They provide full-scale output spans of 2.5V
>> or 5V for reference voltages of 2.5V. These devices operate on a single
>> 2.7V to 5.5V supply and are guaranteed to be monotonic by design.
>> The "R" variants include a 2.5V, 5ppm/°C internal reference, which is
>> disabled by default.
>>
>> Signed-off-by: Kim Seer Paller <kimseer.paller@xxxxxxxxxx>
>> ---
>>  .../devicetree/bindings/iio/dac/adi,ad3530r.yaml   | 99
>> ++++++++++++++++++++++
>>  MAINTAINERS                                        |  7 ++
>>  2 files changed, 106 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad3530r.yaml
>> b/Documentation/devicetree/bindings/iio/dac/adi,ad3530r.yaml
>> new file mode 100644
>> index
>> 0000000000000000000000000000000000000000..cf4a3eb98f1fa30afdeb0740bba7f052d8ec
>> 2cd4
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3530r.yaml
>> @@ -0,0 +1,99 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/dac/adi,ad3530r.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Analog Devices AD3530R and Similar DACs
>> +
>> +maintainers:
>> +  - Kim Seer Paller <kimseer.paller@xxxxxxxxxx>
>> +
>> +description: |
>> +  The AD3530/AD3530R (8-channel) and AD3531/AD3531R (4-channel) are low-
>> power,
>> +  16-bit, buffered voltage output digital-to-analog converters (DACs) with
>> +  software-programmable gain controls, providing full-scale output spans of
>> 2.5V
>> +  or 5V for reference voltages of 2.5V. These devices operate from a single
>> 2.7V
>> +  to 5.5V supply and are guaranteed monotonic by design. The "R" variants
>> +  include a 2.5V, 5ppm/°C internal reference, which is disabled by default.
>> +  Datasheet can be found here:
>> + 
>> https://www.analog.com/media/en/technical-documentation/data-sheets/ad3530_ad530r.pdf
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - adi,ad3530
>> +      - adi,ad3530r
>> +      - adi,ad3531
>> +      - adi,ad3531r
>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  spi-max-frequency:
>> +    maximum: 50000000
>> +
>> +  vdd-supply:
>> +    description: Power Supply Input.
>> +
>> +  iovdd-supply:
>> +    description: Digital Power Supply Input.
>> +
>> +  io-channels:
>> +    description:
>> +      ADC channel used to monitor internal die temperature, output voltages,
>> and
>> +      current of a selected channel via the MUXOUT pin.
>> +    maxItems: 1
>>
> 
> I'm a bit puzzled... Isn't this device the provider of such a channel?
> Therefore, I believe we should have #io-channel-cells, right?

Nope. :-)

The MUXOUT is an analog output pin, so this property is to read back from
an external ADC what the analog value of MUXOUT is. The DAC doesn't have an
internal ADC for measuring these values.

Comes from Jonathan's suggestion on a similar chip:
https://lore.kernel.org/linux-iio/20240413160610.4cec010b@jic23-huawei/

> 
> - Nuno Sá
> 
>