linux-kernel - Re: [PATCH v2 3/5] arm64: dts: allwinner: a523: Add EMAC0 ethernet MAC

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Message-ID: <20250425104128.14f953f3@donnerap.manchester.arm.com>
Date: Fri, 25 Apr 2025 10:41:28 +0100
From: Andre Przywara <andre.przywara@....com>
To: Chen-Yu Tsai <wens@...e.org>
Cc: Yixun Lan <dlan@...too.org>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Jernej
 Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>,
 Maxime Ripard <mripard@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, Corentin Labbe <clabbe.montjoie@...il.com>,
 <devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
 <linux-sunxi@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
 <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] arm64: dts: allwinner: a523: Add EMAC0 ethernet
 MAC

On Fri, 25 Apr 2025 13:26:25 +0800
Chen-Yu Tsai <wens@...e.org> wrote:

Hi Chen-Yu,

> On Thu, Apr 24, 2025 at 6:09 PM Yixun Lan <dlan@...too.org> wrote:
> >
> > Add EMAC0 ethernet MAC support which found on A523 variant SoCs,
> > including the A527/T527 chips. MAC0 is compatible to the A64 chip which
> > requires an external PHY. This patch only add RGMII pins for now.
> >
> > Signed-off-by: Yixun Lan <dlan@...too.org>
> > ---
> >  arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi | 40 ++++++++++++++++++++++++++
> >  1 file changed, 40 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi b/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > index ee485899ba0af69f32727a53de20051a2e31be1d..c9a9b9dd479af05ba22fe9d783e32f6d61a74ef7 100644
> > --- a/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > +++ b/arch/arm64/boot/dts/allwinner/sun55i-a523.dtsi
> > @@ -126,6 +126,15 @@ pio: pinctrl@...0000 {
> >                         interrupt-controller;
> >                         #interrupt-cells = <3>;
> >
> > +                       rgmii0_pins: rgmii0-pins {
> > +                               pins = "PH0", "PH1", "PH2", "PH3", "PH4",
> > +                                      "PH5", "PH6", "PH7", "PH9", "PH10",
> > +                                      "PH14", "PH15", "PH16", "PH17", "PH18";
> > +                               allwinner,pinmux = <5>;
> > +                               function = "emac0";
> > +                               drive-strength = <40>;  
> 
> We should probably add
> 
>                                   bias-disable;
> 
> to explicitly turn off pull-up and pull-down.

Should we? I don't see this anywhere else for sunxi, probably because it is
the (reset) default (0b00).
I wonder if we have a hidden assumption about this? As in: if no bias is
specified, we assume bias-disable? Then we should maybe enforce this is in
the driver?

Cheers,
Andre