linux-kernel - Re: [PATCH] arm64: dts: renesas: r9a09g047e57-smarc: Reduce I2C2 clock frequency

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Message-ID: <CAMuHMdU4poOJ46NEVZUpuDDNjU-F7o6Wn62triNd=jqHq466Wg@mail.gmail.com>
Date: Fri, 23 May 2025 17:39:02 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: John Madieu <john.madieu.xa@...renesas.com>
Cc: "magnus.damm@...il.com" <magnus.damm@...il.com>, "robh@...nel.org" <robh@...nel.org>, 
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>, 
	Biju Das <biju.das.jz@...renesas.com>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: renesas: r9a09g047e57-smarc: Reduce I2C2
 clock frequency

Hi John,

On Mon, 19 May 2025 at 10:56, John Madieu <john.madieu.xa@...renesas.com> wrote:
> > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > On Mon, 19 May 2025 at 00:08, John Madieu <john.madieu.xa@...renesas.com>
> > wrote:
> > > Lower the I2C2 bus clock frequency on the RZ/G3E SMARC SoM from 1MHz
> > > to 400KHz to improve compatibility with a wider range of I2C
> > > peripherals. The previous 1MHz setting was too aggressive for some
> > > devices on the bus, which experienced timing issues at such a frequency.
> > >
> > > --- a/arch/arm64/boot/dts/renesas/rzg3e-smarc-som.dtsi
> > > +++ b/arch/arm64/boot/dts/renesas/rzg3e-smarc-som.dtsi
> > > @@ -85,7 +85,7 @@ &gpu {
> > >  &i2c2 {
> > >         pinctrl-0 = <&i2c2_pins>;
> > >         pinctrl-names = "default";
> > > -       clock-frequency = <1000000>;
> > > +       clock-frequency = <400000>;
> > >         status = "okay";
> > >
> > >         raa215300: pmic@12 {
> >
> > Can you please clarify which devices on this bus do not support 1 MHz?
> > Or perhaps this is a board layout issue?
>
> This is mainly the case for the GreenPAK device, that is programmed to
> Operate at 400KHz.

Thanks for the clarification!

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
i.e. will queue in renesas-devel as a fix for v6.16, with the clarification
added.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds