linux-kernel - Re: [PATCH 2/3] ARM: dts: imx7: add support for kamstrup flex concentrator

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Date:   Wed, 15 Jul 2020 16:21:55 +0200
From:   Bruno Thomsen <bruno.thomsen@...il.com>
To:     Fabio Estevam <festevam@...il.com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        Bruno Thomsen <bth@...strup.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Subject: Re: [PATCH 2/3] ARM: dts: imx7: add support for kamstrup flex concentrator

Den tir. 14. jul. 2020 kl. 13.54 skrev Fabio Estevam <festevam@...il.com>:
>
> Hi Bruno,
>
> On Tue, Jul 14, 2020 at 7:03 AM Bruno Thomsen <bruno.thomsen@...il.com> wrote:
>
> > I have not yet been successful in converting the deprecated properties
> > to generic phy properties, so hoping I could get a hit.
> >
> > Kernel error messages:
> > mdio_bus 30be0000.ethernet-1: MDIO device at address 1 is missing.
>
> Please double-check whether 1 is the correct address for the KSZ8051
> Ethernet PHY as per your schematics.

Hi Fabio,

Thanks for the hints.

Yes, the address is correct and configured with external resistors,
but just realised that I wrote the wrong device name in the comment,
it's actually KSZ8081RNB.

Ethernet has been working with multiple mainline kernel versions
(latest being 5.7.8)
for the last year or so when using the DTS in patch. So I am pretty sure
hardware and setup of mux is correct'ish.

Kernel trace from patch version:
kernel: Micrel KSZ8081 or KSZ8091 30be0000.ethernet-1:01: attached PHY driver
 [Micrel KSZ8081 or KSZ8091] (mii_bus:phy_addr=30be0000.ethernet-1:01, irq=POLL)

Error first occurs when switching from fec phy reset to mdio phy reset
code path,
I understand that the fec phy reset is obsolete as phy properties was wrongly
added to the mac and of course should be part of the phy (separate chip).

When debugging it I end up with the get_phy_device() call not working
inside of_mdiobus_register_phy().

Workaround at the moment seems to be extending compatible with
"ethernet-phy-id0022.1560" to disable auto detection of phy type,
and then Ethernet works again. At least the same PHY driver trace
can be found and full transmission speed can be used without packet
errors/loss.

> Are there external pull-up/pull-down resistors for strapping the
> various configuration pins for the PHY? Or are the pull-up/pull-down
> provided by the i.MX7D pins?

Config strapping is done with external resistors.

> If there are no external pull-ups, please make sure to configure the
> pinctrl_enet1 accordingly, so that the Ethernet PHY address can be
> properly configured and then mdio_bus driver can find it at the
> correct address.
>
> Please check in arch/arm/boot/dts/imx6qdl-sr-som.dtsi for an example
> on how to configure the Ethernet PHY pin strapping via iMX IOMUX.

Thanks, good examples can be hard to find.

/Bruno