linux-kernel - RE: [PATCH v3 1/2] dt-bindings: iio: adf4371: add rdiv2 and doubler

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID:
 <CY4PR03MB3399CB671D685BA8164E0F3B9B352@CY4PR03MB3399.namprd03.prod.outlook.com>
Date: Mon, 2 Dec 2024 09:47:21 +0000
From: "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>
To: Jonathan Cameron <jic23@...nel.org>
CC: "robh@...nel.org" <robh@...nel.org>,
        "conor+dt@...nel.org"
	<conor+dt@...nel.org>,
        "linux-iio@...r.kernel.org"
	<linux-iio@...r.kernel.org>,
        "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "linux-pwm@...r.kernel.org"
	<linux-pwm@...r.kernel.org>
Subject: RE: [PATCH v3 1/2] dt-bindings: iio: adf4371: add rdiv2 and doubler



--
Antoniu Miclăuş

> -----Original Message-----
> From: Jonathan Cameron <jic23@...nel.org>
> Sent: Saturday, November 30, 2024 6:40 PM
> To: Miclaus, Antoniu <Antoniu.Miclaus@...log.com>
> Cc: robh@...nel.org; conor+dt@...nel.org; linux-iio@...r.kernel.org;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> pwm@...r.kernel.org
> Subject: Re: [PATCH v3 1/2] dt-bindings: iio: adf4371: add rdiv2 and doubler
> 
> [External]
> 
> On Fri, 29 Nov 2024 17:33:52 +0200
> Antoniu Miclaus <antoniu.miclaus@...log.com> wrote:
> 
> > Add support for reference doubler enable and reference divide by 2
> > clock.
> >
> > Both of these blocks are optional on the frequency path within the
> > chip and can be adjusted depending on the custom needs of the
> > applications.
> Thanks for the additional info!
> >
> > The doubler is useful for increasing the PFD comparison frequency
> > which will result in a noise performance of the system.
> 
> So I'll play devil's advocate. Improved noise performance sounds
> good. If it doesn't take me out of range of allowed frequencies, why
> would I not turn it on?  What is it about the surrounding circuitry
> etc that would make this a bad idea for some uses of this chip
> but not others?
> 
> >
> > The reference divide by 2 divides the reference signal by 2,
> > resulting in a 50% duty cycle PFD frequency.
> 
> why would I want one of those? My 'guess' is this makes sense
> if the reference frequency is too high after the application of
> the scaling done by the 5 bit counter.  In effect it means the
> division circuitry does divide by 1-31, 2-64 in steps of 2.
> 
> That could all be wrapped up in the existing control of the
> frequency, and so far I'm still not seeing a strong reason why
> it belongs in DT.
> 
> The 50% cycle thing is a bit of a red herring as assuming it
> is triggered on say the rising edge of the high frequency signal
> to toggle the divided signal, that will always be a 50% duty cycle.
> 
As mentioned in the cover letter this was mostly a request from
customers that are using adf4371 on a large scale and they need
these features to be controllable somehow by the user.

Since these attributes were already validated as devicetree properties
for adf4350 on mainline, I found this as the best approach to satisfy
both ends.

Antoniu
> Jonathan
> 
> >
> > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > ---
> > changes in v3:
> >  - add explanation in commit body
> >  .../devicetree/bindings/iio/frequency/adf4371.yaml    | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> > index 1cb2adaf66f9..ef241c38520c 100644
> > --- a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> > +++ b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> > @@ -40,6 +40,17 @@ properties:
> >        output stage will shut down until the ADF4371/ADF4372 achieves lock
> as
> >        measured by the digital lock detect circuitry.
> >
> > +  adi,reference-doubler-enable:
> > +    type: boolean
> > +    description:
> > +      If this property is present, the reference doubler block is enabled.
> > +
> > +  adi,adi,reference-div2-enable:
> > +    type: boolean
> > +    description:
> > +      If this property is present, the reference divide by 2 clock is enabled.
> > +      This feature can be used to provide a 50% duty cycle signal to the PFD.
> > +
> >  required:
> >    - compatible
> >    - reg