linux-kernel - Re: [PATCH 2/2] arm64: dts: renesas: r9a09g047e57-smarc: Add overlay for P3T1085UK-ARD

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Message-ID: <aRzzEgeetDFlE3YC@tom-desktop>
Date: Tue, 18 Nov 2025 23:28:34 +0100
From: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: tomm.merciai@...il.com, linux-renesas-soc@...r.kernel.org,
	biju.das.jz@...renesas.com,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] arm64: dts: renesas: r9a09g047e57-smarc: Add overlay
 for P3T1085UK-ARD

Hi Wolfram,
Thank you for your review!

On Tue, Nov 18, 2025 at 05:43:44PM +0100, Wolfram Sang wrote:
> Hi Tommaso,
> 
> > +/*
> > + * #define I3C_BUS_MODE_PURE 1 (for I3C bus mode pure - default)
> > + * #define I3C_BUS_MODE_PURE 0 (for I3C bus mode mixed-fast)
> > + */
> > +#define I3C_BUS_MODE_PURE	1
> 
> Sorry, but I really think this is configuration and not hardware
> description. The board has only I3C capable devices, so unless you
> connect more devices externally, you can always use pure-i3c-mode.
> Enforcing mixed-mode is only for debugging.
> 
> > +
> > +#if I3C_BUS_MODE_PURE
> > +&i3c {
> > +	i2c-scl-hz = <400000>;
> > +	i3c-scl-hz = <12500000>;
> > +	status = "okay";
> > +};
> 
> So, the above is all that is needed. Which is the basic enablement for
> the I3C bus in general. I mean, auto-detecting devices is a key feature
> of I3C :) Which basically means IMHO that this overlay is superfluous.
> 
> 
> > +#else /* I3C_BUS_MODE_MIXED_FAST */
> > +&i3c {
> > +	status = "okay";
> > +
> > +	#address-cells = <1>;
> > +	#size-cells = <0>;
> > +
> > +	i2c-scl-hz = <400000>;
> > +	i3c-scl-hz = <12500000>;
> 
> Despite this else block being debug only...
> 
> > +
> > +	eeprom@1a {
> > +		compatible = "atmel,24c02";
> > +		reg = <0x1a 0 (I2C_FM | I2C_FILTER)>;
> > +	};
> 
> ... there is no device listening to 0x1a on this board? What do you see
> there? Did I forget something?

Ouch :'(
Sorry, my bad I forgot to remove this 0x1a (audio codec)
device from the bring-up/testing session.

> 
> > +
> > +	/* U2 */
> > +	temperature-sensor@48 {
> > +		compatible = "nxp,p3t1085";
> > +		reg = <0x48 0 (I2C_FM | I2C_FILTER)>;
> > +	};
> > +
> > +	/* U1 NOT MOUNTED as default */
> > +	temp-sense@4c {
> > +		status = "disabled";
> > +		compatible = "national,lm75";
> 
> Yes, mounting U1 is a hack I introduced. The compatible should be
> "nxp,p3t1755" BTW. But as said, the whole MIXED_MODE block is not
> hardware description, I'd say.

Ack, thanks.

Please correct me if I'm wrong.
Your suggestion is to keep only Patch 1/2 dropping alias line right?
Thanks in advance.

> 
> Happy hacking,
> 
>    Wolfram
> 

Kind Regards,
Tommaso