linux-kernel - Re: [PATCH v2 1/2] dt-bindings: net/nfc: ti,trf7970a: Add ti,rx-gain-reduction option

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Message-ID: <20250626082953.3963992-1-paul.geurts@prodrive-technologies.com>
Date: Thu, 26 Jun 2025 10:29:53 +0200
From: Paul Geurts <paul.geurts@...drive-technologies.com>
To: <andrew@...n.ch>
CC: <mgreer@...malcreek.com>, <krzk@...nel.org>, <andrew+netdev@...n.ch>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <robh@...nel.org>, <conor+dt@...nel.org>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<martijn.de.gouw@...drive-technologies.com>
Subject: Re: [PATCH v2 1/2] dt-bindings: net/nfc: ti,trf7970a: Add ti,rx-gain-reduction option

> On Tue, Jun 24, 2025 at 02:42:46PM +0200, Paul Geurts wrote:
> > Add option to reduce the RX antenna gain to be able to reduce the
> > sensitivity.
> > 
> > Signed-off-by: Paul Geurts <paul.geurts@...drive-technologies.com>
> > ---
> >  Documentation/devicetree/bindings/net/nfc/ti,trf7970a.yaml | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/nfc/ti,trf7970a.yaml b/Documentation/devicetree/bindings/net/nfc/ti,trf7970a.yaml
> > index d0332eb76ad2..066a7abc41e0 100644
> > --- a/Documentation/devicetree/bindings/net/nfc/ti,trf7970a.yaml
> > +++ b/Documentation/devicetree/bindings/net/nfc/ti,trf7970a.yaml
> > @@ -55,6 +55,12 @@ properties:
> >      description: |
> >        Regulator for supply voltage to VIN pin
> >  
> > +  ti,rx-gain-reduction:
> 
> You should include the units, "ti,rx-gain-reduction-db"

Well, Currently it's not really a dB value (see below).

> 
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +    description: |
> > +      Specify a RX gain reduction to reduce antenna sensitivity with 5dB per
> > +      increment, with a maximum of 15dB.
> 
> Given that description i think you can provide a list of values, [0,
> 5, 10, 15] and the tools will validate values in .dts files.
> 
> > +
> >  required:
> >    - compatible
> >    - interrupts
> > @@ -95,5 +101,6 @@ examples:
> >              irq-status-read-quirk;
> >              en2-rf-quirk;
> >              clock-frequency = <27120000>;
> > +            ti,rx-gain-reduction = <3>;
> 
> Err, how does 3 fit into 5dB increments?

I implemented it in a way that the value of ti,rx-gain-reduction is programmed
directly into the RX_GAIN reduction register, and there it means 5 dB/LSB. My
description probably was not clear enough about that. So a value of 3 here actually
means 15dB.
So I could either improve the description here that this is the case, or make the
value in here in actual dB, and do some calculations in the driver. What has your
preference?

> 
> 	Andrew
> 

Thanks!

Paul