[PATCH 1/1] dt-bindings: iio: adc: add missing vref-supply

[Marco Felsch]

Hi,

On 23-02-03, Alexander Stein wrote:

...

> > > > > > +  vref-supply:
> > > > > > +    description: External ADC reference voltage supply on VREFH
> > > > > > pad.
> > > > > 
> > > > > Please add it to the list of required properties, we can remove it as
> > > > > soon as the driver has support for the internal reference voltages.
> > > > 
> > > > I was thinking in doing so before as well. But DT describes the
> > > > hardware, and this ADC apparently would be functioning without a
> > > > reference voltage on that pad, using a different one. What the driver
> > > > actual does is a different matter.> 
> > > I have also thought about it first but than I checked the RM which says
> > > that "multi-reference selection" is chip dependent.
> 
> Nice for pointing this out. I wasn't aware that there are differences.
> 
> > Oh goody. So is it detectable?
> 
> That's my problem. I didn't find any source of information which chips do 
> support multiple references and which don't.
> Marco, do you have some information on this?

You can download the RM from the NXP website but you need an account for
it:
https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-processors/i-mx-8-applications-processors/i-mx-8-family-arm-cortex-a53-cortex-a72-virtualization-vision-3d-graphics-4k-video:i.MX8

Or is this the wrong model? The naming scheme is quite confusing to me.

> > If we are going to stick to a single compatible rather than adding them for
> > the variants with and without this feature, should probably add a note at
> > least to say it is required for some parts.
> 
> That's a good idea. I'm okay with that, until there is more information 
> available.

According the RM there is a bit which can be read: Multi Vref
Implemented (MVI).

Regards,
  Marco