Re: [PATCH v11 1/2] dt-bindings: adc: add AD7173

Ceclan Dumitru
2024-01-17T12:30:37Z

On 1/15/24 23:53, David Lechner wrote:
> On Wed, Dec 20, 2023 at 4:48 AM Dumitru Ceclan <mitrutzceclan@gmail.com> wrote:

...
>
> According to the timing diagram in the datasheet, SCLK is high during
> idle, so don't we need `spi-cpol: true` here?
>
> Likewise, data is valid on the trailing SCLK edge, so don't we need
> `spi-cpha: true` here?
>
>
V1 Rob Herring suggested that if device is not configurable, driver
should set the spi mode
>> + gpio-controller:
>> + description: Marks the device node as a GPIO controller.
>> +
>> + "#gpio-cells":
>> + const: 2
>> + description:
>> + The first cell is the GPIO number and the second cell specifies
>> + GPIO flags, as defined in <dt-bindings/gpio/gpio.h>.
>> +
>> + refin-supply:
>> + description: external reference supply, can be used as reference for conversion.
>
> If I'm understanding correctly, this represents both voltage inputs
> REF+ and REF-, correct? The datasheet says "Reference Input Negative
> Terminal. REF− can span from AVSS to AVDD1 − 1 V". It seems like they
> should be separate supplies in case REF- is non-zero. Otherwise, how
> can we know what voltage it is? (same comment applies to refin2.)
> Yes, but in that case, the value of the referenced supply should reflect
that and be equal to (REF+)-(REF-). I'll add to the description this.

...

>> +required:
>> + - compatible
>> + - reg
>> + - interrupts
>
> Why are interrupts required? What if the pin is not connected?
>
From the datasheet, the reading of the conversions seem to be only
interrupt based: "As soon as the next conversion is complete,
the data register is updated; therefore, the period in which to
read the conversion is limited." this paragraph suggests to me that
interrupts are required