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

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Message-ID:
 <OSCPR01MB14647796989C230D7E1866C86FF9CA@OSCPR01MB14647.jpnprd01.prod.outlook.com>
Date: Mon, 19 May 2025 08:56:09 +0000
From: John Madieu <john.madieu.xa@...renesas.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
CC: "geert+renesas@...der.be" <geert+renesas@...der.be>,
	"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 Geert,

> -----Original Message-----
> From: Geert Uytterhoeven <geert@...ux-m68k.org>
> Sent: Monday, May 19, 2025 10:29 AM
> To: John Madieu <john.madieu.xa@...renesas.com>
> Subject: Re: [PATCH] arm64: dts: renesas: r9a09g047e57-smarc: Reduce I2C2
> clock frequency
> 
> Hi John,
> 
> 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.
> >

Thanks for the feedback.

> 
> > --- 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.

> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-
> m68k.org
> 
Regards,
John