linux-kernel - Re: [PATCH 2/3] riscv: dts: spacemit: add 24c02 eeprom on BPI-F3

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Message-ID: <2A310AE601C62BAA+aNH7IfsDeD7-Vrxf@LT-Guozexi>
Date: Tue, 23 Sep 2025 09:42:57 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Yixun Lan <dlan@...too.org>, linux-kernel@...r.kernel.org,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
	"open list:RISC-V ARCHITECTURE" <linux-riscv@...ts.infradead.org>,
	"open list:RISC-V SPACEMIT SoC Support" <spacemit@...ts.linux.dev>
Cc: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: Re: [PATCH 2/3] riscv: dts: spacemit: add 24c02 eeprom on BPI-F3

On Mon, Sep 22, 2025 at 06:49:35AM +0200, Aurelien Jarno wrote:
> Hi,
> 
> On 2025-09-22 11:21, Yixun Lan wrote:
> > Hi Aurelien,
> > 
> > On 23:01 Sun 21 Sep     , Aurelien Jarno wrote:
> > > The BPI-F3 contains a 24c02 eeprom, that contains among other things the
> > > MAC addresses of the two network interfaces. For this reason, mark it as
> > > read-only.
> > > 
> > > Signed-off-by: Aurelien Jarno <aurelien@...el32.net>
> > > ---
> > >  arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts | 11 ++++++++++-
> > >  1 file changed, 10 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > index 3b6e4f52e9aad..574d10fdf9b82 100644
> > > --- a/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > +++ b/arch/riscv/boot/dts/spacemit/k1-bananapi-f3.dts
> > > @@ -115,6 +115,15 @@ &i2c2 {
> > >  	pinctrl-0 = <&i2c2_0_cfg>;
> > >  	pinctrl-names = "default";
> > >  	status = "okay";
> > > +
> > > +	eeprom@50 {
> > > +		compatible = "atmel,24c02";
> > > +		reg = <0x50>;
> > > +		vcc-supply = <&vcc1v8_sys>;
> > > +		pagesize = <16>;
> > ..
> > > +		read-only;
> > so you're sure there is no demand to write data to eeprom?
> > (update info at linux env)
> 
> It seems to only contains board infos (mac addresses), but if there are 
> other use cases, that can indeed be dropped.
Then you can split the EEPROM into different parts.
Each part can be described as an individual nvmem cell in the device tree.
Some of them can be marked as read-only, while others remain writable.

Documentation/devicetree/bindings/eeprom/at24.yaml +15:
```
  - $ref: /schemas/nvmem/nvmem-deprecated-cells.yaml
```

                - Troy
> 
> > > +		size = <256>;
> > > +	};
> > >  };
> > >  
> > >  &i2c8 {
> > > @@ -143,7 +152,7 @@ buck2 {
> > >  				regulator-always-on;
> > >  			};
> > >  
> > > -			buck3 {
> > > +			vcc1v8_sys: buck3 {
> > I'm not sure if adding an alias here is a good idea, it occurs buck3
> > serve the suppy for many devices, besides, to me it's more proper to
> > name it as eeprom_vcc1v8 for the eeprom according to schematics in
> > this case..
> 
> We need to add a label to be able to reference it for the eeprom 
> vcc-supply, but we'll have to also reference it for other devices (e.g.  
> emmc, wifi, phys, etc... It tried to choose a common name, ie the right 
> most one on the schematics. Another option could be to call it buck3, 
> but other name suggestions are welcome.
> 
> -- 
> Aurelien Jarno                          GPG: 4096R/1DDD8C9B
> aurelien@...el32.net                     http://aurel32.net
> 
> _______________________________________________
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> linux-riscv@...ts.infradead.org
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