linux-kernel - Re: [PATCH v3 2/6] iio: frequency: adf41513: driver implementation

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Message-ID: <6hcqrcy3meskddrklb3jtlpca2snrs4upwms56lhq7mkes7krm@vdiaqkfc6lgg>
Date: Mon, 12 Jan 2026 09:56:25 +0000
From: Rodrigo Alencar <455.rodrigo.alencar@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>, 
	rodrigo.alencar@...log.com
Cc: linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>, 
	David Lechner <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>, 
	Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH v3 2/6] iio: frequency: adf41513: driver implementation

On 26/01/09 08:55PM, Andy Shevchenko wrote:
> On Thu, Jan 08, 2026 at 12:14:51PM +0000, Rodrigo Alencar via B4 Relay wrote:
> > 
> > The driver is based on existing PLL drivers in the IIO subsystem and
> > implements the following key features:
> > 
> > - Integer-N and fractional-N (fixed/variable modulus) synthesis modes
> > - High-resolution frequency calculations using microhertz (µHz) precision
> >   to handle sub-Hz resolution across multi-GHz frequency ranges
> > - IIO debugfs interface for direct register access
> > - FW property parsing from devicetree including charge pump settings,
> >   reference path configuration and muxout options
> > - Power management support with suspend/resume callbacks
> > - Lock detect GPIO monitoring
> > 
> > The driver uses 64-bit microhertz values throughout PLL calculations to
> > maintain precision when working with frequencies that exceed 32-bit Hz
> > representation while requiring fractional Hz resolution.
> 
> ...
> 
> > +/* Specifications */
> > +#define ADF41510_MAX_RF_FREQ			(10000ULL * HZ_PER_MHZ)
> > +#define ADF41513_MIN_RF_FREQ			(1000ULL * HZ_PER_MHZ)
> > +#define ADF41513_MAX_RF_FREQ			(26500ULL * HZ_PER_MHZ)
> 
> We need HZ_PER_GHZ. I think it's easy to have one be present in units.h.
>

26.5 GHz is not going to use HZ_PER_GHZ, so for consistency I think it makes
sense to keep HZ_PER_MHZ for the others.
 
> ...
> 
> > +#define ADF41513_MIN_REF_FREQ			(10U * HZ_PER_MHZ)
> > +#define ADF41513_MAX_REF_FREQ			(800U * HZ_PER_MHZ)
> > +#define ADF41513_MAX_REF_FREQ_DOUBLER		(225U * HZ_PER_MHZ)
> 
> How does "U" help here?

not much really, will remove.

> ...
> 
> > +#define ADF41513_MIN_INT_4_5			20
> > +#define ADF41513_MAX_INT_4_5			511
> > +#define ADF41513_MIN_INT_8_9			64
> > +#define ADF41513_MAX_INT_8_9			1023
> 
> Not sure if we want (BIT(x) - 1) for the limits as we have non-0 minimums.
> 
> ...
> 
> > +#define ADF41513_MAX_CLK_DIVIDER		4095
> 
> Sounds like a candidate for (BIT(12) - 1).
>

limits for INT are taken from the datasheet as is, so I think it makes to leave them
like this, as for CLK1/CLK2 max divider, indeed I can make it (BIT(12) - 1) as it
refers to a 12-bit register field.
 
> ...
> 
> > +#define ADF41513_MAX_PHASE_MICRORAD		6283185UL
> 
> Basically I'm replying to this just for this line. 180° is PI radians, which is
> something like 31415926... Can we use here (2 * 314...) where PI is provided in
> one of the used form? This will help to grep and replace in case we will have a
> common PI constant defined in the kernel (units.h).
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 

kind regards,

Rodrigo Alencar