linux-kernel - Re: [PATCH v2 4/4] arm64: dts: allwinner: a133-liontron-h-a133l: Add Ethernet support

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Message-ID: <CAGb2v64vYEkKm8D_6r_O+fg_tR4zG1Loai1BPVO5AiE-MO=DJw@mail.gmail.com>
Date: Tue, 8 Jul 2025 21:27:55 +0800
From: Chen-Yu Tsai <wens@...e.org>
To: Paul Kocialkowski <paulk@...-base.io>
Cc: Andre Przywara <andre.przywara@....com>, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.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>, 
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2 4/4] arm64: dts: allwinner: a133-liontron-h-a133l: Add
 Ethernet support

On Tue, Jul 8, 2025 at 9:22 PM Paul Kocialkowski <paulk@...-base.io> wrote:
>
> Hi,
>
> Le Tue 08 Jul 25, 16:18, Chen-Yu Tsai a écrit :
> > On Tue, Jul 8, 2025 at 7:36 AM Andre Przywara <andre.przywara@....com> wrote:
> > >
> > > On Mon,  7 Jul 2025 18:51:55 +0200
> > > Paul Kocialkowski <paulk@...-base.io> wrote:
> > >
> > > Hi Paul,
> > >
> > > > The Liontron H-A133L board features an Ethernet controller with a
> > > > JLSemi JL1101 PHY. Its reset pin is tied to the PH12 GPIO.
> > > >
> > > > Note that the reset pin must be handled as a bus-wide reset GPIO in
> > > > order to let the MDIO core properly reset it before trying to read
> > > > its identification registers. There's no other device on the MDIO bus.
> > >
> > > putting the PHY reset GPIO into the MDIO node is a clever solution, I
> > > was struggling with putting it either in the MAC or PHY node, though
> > > conceptually it would still belong in the latter, I think. But this
> > > might be a more generic problem: for most other devices we activate
> > > reset and clock gates *before* trying to access them, though this might
> > > be historically different for Ethernet PHYs.
> >
> > The phylib core has code to deal with reset GPIOs listed under the PHY node.
> > It might be worth checking why that doesn't work.
>
> While this code does exist, it's too early to be called when the mdio bus is
> trying to probe the phy. I was also surprised the existing reset gpio support
> in the phylib core didn't take effect (that's how I tried to implement it first)
> only to find that the code was never called. It's only called once the phy was
> probed and registered.

OK, that's definitely weird. The code looked like it just walked the DT
and registered PHY devices, upon which the GPIO lines would be found and
toggled.

ChenYu

> Cheers,
>
> Paul
>
> > OOTH, there's no code to deal with regulator supplies for PHYs.
> >
> > ChenYu
> >
> > > > The datasheet of the PHY mentions that the reset signal must be held
> > > > for 1 ms to take effect. Make it 2 ms (and the same for post-delay) to
> > > > be on the safe side without wasting too much time during boot.
> > > >
> > > > Signed-off-by: Paul Kocialkowski <paulk@...-base.io>
> > >
> > > Despite the above, this looks fine, and works for me:
> > >
> > > Reviewed-by: Andre Przywara <andre.przywara@....com>
> > > Tested-by: Andre Przywara <andre.przywara@....com>
> > >
> > > Cheers,
> > > Andre
> > >
> > > > ---
> > > >  .../sun50i-a133-liontron-h-a133l.dts          | 19 +++++++++++++++++++
> > > >  1 file changed, 19 insertions(+)
> > > >
> > > > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a133-liontron-h-a133l.dts b/arch/arm64/boot/dts/allwinner/sun50i-a133-liontron-h-a133l.dts
> > > > index fe77178d3e33..90a50910f07b 100644
> > > > --- a/arch/arm64/boot/dts/allwinner/sun50i-a133-liontron-h-a133l.dts
> > > > +++ b/arch/arm64/boot/dts/allwinner/sun50i-a133-liontron-h-a133l.dts
> > > > @@ -65,6 +65,25 @@ &ehci1 {
> > > >       status = "okay";
> > > >  };
> > > >
> > > > +&emac0 {
> > > > +     pinctrl-names = "default";
> > > > +     pinctrl-0 = <&rmii0_pins>;
> > > > +     phy-handle = <&rmii_phy>;
> > > > +     phy-mode = "rmii";
> > > > +     status = "okay";
> > > > +};
> > > > +
> > > > +&mdio0 {
> > > > +     reset-gpios = <&pio 7 12 GPIO_ACTIVE_LOW>; /* PH12 */
> > > > +     reset-delay-us = <2000>;
> > > > +     reset-post-delay-us = <2000>;
> > > > +
> > > > +     rmii_phy: ethernet-phy@1 {
> > > > +             compatible = "ethernet-phy-ieee802.3-c22";
> > > > +             reg = <1>;
> > > > +     };
> > > > +};
> > > > +
> > > >  &mmc0 {
> > > >       vmmc-supply = <&reg_dcdc1>;
> > > >       cd-gpios = <&pio 5 6 GPIO_ACTIVE_LOW>; /* PF6 */
> > >
> > >
>
> --
> Paul Kocialkowski,
>
> Independent contractor - sys-base - https://www.sys-base.io/
> Free software developer - https://www.paulk.fr/
>
> Expert in multimedia, graphics and embedded hardware support with Linux.