linux-kernel - Re: [PATCH 2/4] iio: adc: Add support for the Renesas RZ/N1 ADC

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Message-ID: <aPHiAObA61OVf8mY@ninjato>
Date: Fri, 17 Oct 2025 08:28:16 +0200
From: Wolfram Sang <wsa+renesas@...g-engineering.com>
To: "Herve Codina (Schneider Electric)" <herve.codina@...tlin.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-iio@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Pascal Eberhard <pascal.eberhard@...com>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/4] iio: adc: Add support for the Renesas RZ/N1 ADC

Hi Herve,

On Wed, Oct 15, 2025 at 04:28:14PM +0200, Herve Codina (Schneider Electric) wrote:
> The Renesas RZ/N1 ADC controller is the ADC controller available in the
> Renesas RZ/N1 SoCs family. It can use up to two internal ACD cores (ADC1

ADC cores

> and ADC2) those internal cores are not directly accessed but are handled
> through ADC controller virtual channels.
> 
> Signed-off-by: Herve Codina (Schneider Electric) <herve.codina@...tlin.com>

Very high level review.

> +/*                  ADC1 ADC2
> + * RZ/N1D, BGA 400   y    y
> + * RZ/N1D, BGA 324   y    n
> + * RZ/N1S, BGA 324   y    n
> + * RZ/N1S, BGA 196   y    n
> + * RZ/N1L, BGA 196   y    n
> + */

I think this table can go. N1D is the only variant supported by Linux
because others have no SDRAM controller. Maybe a comment after the
copyright is helpful stating that the second ADC core is utilized when
the adc2-* bindings are supplied?

> +static void rzn1_adc_vc_setup_conversion(struct rzn1_adc *rzn1_adc, u32 ch,
> +					 int adc1_ch, int adc2_ch)
> +{
> +	u32 vc = 0;
> +
> +	if (adc1_ch != -1)
> +		vc |= RZN1_ADC_VC_ADC1_ENABLE | RZN1_ADC_VC_ADC1_CHANNEL_SEL(adc1_ch);
> +
> +	if (adc2_ch != -1)
> +		vc |= RZN1_ADC_VC_ADC2_ENABLE | RZN1_ADC_VC_ADC2_CHANNEL_SEL(adc2_ch);

Are you open to either use an errno (maybe EACCES) or define something
custom (maybe RZN1_ADC_NO_CHANNEL) instead of hardcoded -1? I think I
like the latter a tad more.

Happy hacking,

   Wolfram


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