linux-kernel - Re: [PATCH] arm64: dts: rockchip: add EEPROM node for NanoPi R4S

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Date:   Mon, 7 Jun 2021 17:40:06 +0800
From:   Chen-Yu Tsai <wens@...nel.org>
To:     Johan Jonker <jbx6244@...il.com>
Cc:     Tianling Shen <cnsztl@...il.com>, Rob Herring <robh+dt@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Marty Jones <mj8263788@...il.com>, Pavel Machek <pavel@....cz>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: rockchip: add EEPROM node for NanoPi R4S

On Mon, Jun 7, 2021 at 5:31 PM Johan Jonker <jbx6244@...il.com> wrote:
>
> Hi Tianling,
>
> On 6/7/21 10:17 AM, Tianling Shen wrote:
> > NanoPi R4S has a EEPROM attached to the 2nd I2C bus (U92), which
> > stores the MAC address.
> >
> > Signed-off-by: Tianling Shen <cnsztl@...il.com>
> > ---
> >  arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts b/arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts
> > index cef4d18b599d..4a82f50a07c5 100644
> > --- a/arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts
> > +++ b/arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts
> > @@ -68,6 +68,15 @@
> >       status = "disabled";
> >  };
> >
> > +&i2c2 {
> > +     eeprom@51 {
> > +             compatible = "microchip,24c02", "atmel,24c02";
> > +             reg = <0x51>;
> > +             pagesize = <16>;
>
> > +             read-only; /* This holds our MAC */
>
> The mainline dts files should be generic I think.
> Any comment about "use", partitions or write ability should be avoided.
> It's up the user.

Per the datasheet for this specific EEPROM, the latter half (128 bytes)
is read-only in hardware by design though.

ChenYu