linux-kernel - Re: [PATCH] arm64: dts: renesas: rzt2h-n2h-evk: Add VCC supply for EEPROM

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Message-ID: <CA+V-a8vUKJDFCwQ3tMyhuMEaoR1DhpEhhHfwRnmMwNerdBM49w@mail.gmail.com>
Date: Wed, 15 Oct 2025 20:12:18 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Magnus Damm <magnus.damm@...il.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Bartosz Golaszewski <bgolaszewski@...libre.com>, Linux I2C <linux-i2c@...r.kernel.org>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] arm64: dts: renesas: rzt2h-n2h-evk: Add VCC supply for EEPROM

Hi Geert,

On Wed, Oct 15, 2025 at 4:36 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> CC at24, regulator
>
> On Tue, 14 Oct 2025 at 17:33, Prabhakar <prabhakar.csengg@...il.com> wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > The R1EX24016 EEPROM on the RZ/T2H-N2H Evaluation Kit is powered from
> > the 3.3V rail. Add the regulator phandle for the VCC supply to reflect
> > this in the device tree and avoid the fallback to the dummy regulator:
> >
> >     at24 0-0050: supply vcc not found, using dummy regulator
> >
> > Fixes: 0176c9e82e10 ("arm64: dts: renesas: rzt2h-n2h-evk-common: Enable EEPROM on I2C0")
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Thanks for your patch!
>
> > --- a/arch/arm64/boot/dts/renesas/rzt2h-n2h-evk-common.dtsi
> > +++ b/arch/arm64/boot/dts/renesas/rzt2h-n2h-evk-common.dtsi
> > @@ -160,6 +160,7 @@ eeprom: eeprom@50 {
> >                 compatible = "renesas,r1ex24016", "atmel,24c16";
> >                 reg = <0x50>;
> >                 pagesize = <16>;
> > +               vcc-supply = <&reg_3p3v>;
> >         };
> >  };
>
> "vcc-supply" is not a required property, according to the DT bindings,
> and I believe the 3.3V supply can be considered always-on (but see
> below to encounter dragons).
> I was always under the impression that these "supply not found, using
> dummy regulator"-messages are just informational, and can be ignored,
> but they are at the KERN_WARNING level.
> So should we add real dummy supplies to DTS, or not?
>
Agreed, I get your point. Let's drop this patch.

Cheers,
Prabhakar