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

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Message-ID: <aWFPEa9HI4wmYLpn@smile.fi.intel.com>
Date: Fri, 9 Jan 2026 20:55:13 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: 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 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.

...

> +#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?

...

> +#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).

...

> +#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