linux-kernel - Re: [PATCH v4 2/2] dt-bindings: iio: filter: Add lpf/hpf freq margins

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Message-ID: <Z79K8Ag4SJYtJTtM@65YTFL3.secure.tethers.com>
Date: Wed, 26 Feb 2025 12:10:08 -0500
From: Sam Winchenbach <sam.winchenbach@...mepointer.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: linux-kernel@...r.kernel.org, lars@...afoo.de,
	Michael.Hennerich@...log.com, antoniu.miclaus@...log.com,
	jic23@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
	conor+dt@...nel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/2] dt-bindings: iio: filter: Add lpf/hpf freq margins

On Wed, Feb 26, 2025 at 09:03:13AM +0100, Krzysztof Kozlowski wrote:
> On Tue, Feb 25, 2025 at 08:46:12AM -0500, Sam Winchenbach wrote:
> > Adds two properties to add a margin when automatically finding the
> > corner frequencies.
> > 
> > Signed-off-by: Sam Winchenbach <sam.winchenbach@...mepointer.org>
> > ---
> >  .../bindings/iio/filter/adi,admv8818.yaml          | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> 
> Bindings are before users (see DT submitting patches), so this should be
> re-ordered.
> 
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/filter/adi,admv8818.yaml b/Documentation/devicetree/bindings/iio/filter/adi,admv8818.yaml
> > index b77e855bd594..2acdbd8d84cb 100644
> > --- a/Documentation/devicetree/bindings/iio/filter/adi,admv8818.yaml
> > +++ b/Documentation/devicetree/bindings/iio/filter/adi,admv8818.yaml
> > @@ -44,6 +44,18 @@ properties:
> >    '#clock-cells':
> >      const: 0
> >  
> > +  adi,lpf-margin-hz:
> > +    description:
> > +      Sets minimum low-pass corner frequency to the frequency of rf_in plus
> > +      this value when in auto mode.
> > +    default: 0
> > +
> > +  adi,hpf-margin-hz:
> > +    description:
> > +      Sets maximum high-pass corner frequency to the frequency of rf_in minus
> > +      this value when in auto mode.
> 
> IIUC, these are two bounds - lower and upper - in relation to something
> else (like rf_in frequency)? If so, make it an array (naming to be
> discuss, I assume you know better what's that):

It is true that these are both related to rf_in but both the low and high pass
filters can operate independently. Logically, IMO, it makes more sense to have
them as separate controls but I am happy to put them into an array if that is
the idiomatic approach to situations like this. That said, I am having a
difficult time getting dt_binding_check to pass when I have an array of uint64.

When listing two items, as in your example below, I get the following:
adi,admv8818.example.dtb: admv8818@0: adi,filter-margins-hz: [[0, 30000000], [0, 30000000]] is too long

I have tried specifying the scheme for each item, setting minItems/maxItems.

Any advice on this would be appreciated.
Thanks.

> 
> adi,filter-margin-hz:
>   items:
>     - description: low-pass corner frequency to the freq.....
>       minimum: xxxx?
>       maximum: xxxx?
>       default: 0
>     - description: high-pass ....
>       minimum: xxxx?
>       maximum: xxxx?
>       default: 0
> 
> Best regards,
> Krzysztof
>