netdev - Re: realtek PHY commit bbc4d71d63549 causes regression

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Date:   Sat, 17 Oct 2020 17:18:16 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "open list:BPF JIT for MIPS (32-BIT AND 64-BIT)" 
        <netdev@...r.kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Willy Liu <willy.liu@...ltek.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Masahisa Kojima <masahisa.kojima@...aro.org>
Subject: Re: realtek PHY commit bbc4d71d63549 causes regression

On Sat, 17 Oct 2020 at 17:11, Andrew Lunn <andrew@...n.ch> wrote:
>
> On Sat, Oct 17, 2020 at 04:46:23PM +0200, Ard Biesheuvel wrote:
> > On Sat, 17 Oct 2020 at 16:44, Andrew Lunn <andrew@...n.ch> wrote:
> > >
> > > On Sat, Oct 17, 2020 at 04:20:36PM +0200, Ard Biesheuvel wrote:
> > > > Hello all,
> > > >
> > > > I just upgraded my arm64 SynQuacer box to 5.8.16 and lost all network
> > > > connectivity.
> > >
> > > Hi Ard
> > >
> > > Please could you point me at the DT files.
> > >
> > > > This box has a on-SoC socionext 'netsec' network controller wired to
> > > > a Realtek 80211e PHY, and this was working without problems until
> > > > the following commit was merged
> > >
> > > It could be this fix has uncovered a bug in the DT file. Before this
> > > fix, if there is an phy-mode property in DT, it could of been ignored.
> > > Now the phy-handle property is correctly implemented. So it could be
> > > the DT has the wrong value, e.g. it has rgmii-rxid when maybe it
> > > should have rgmii-id.
> > >
> >
> > This is an ACPI system. The phy-mode device property is set to 'rgmii'
>
> Hi Ard
>
> Please try rgmii-id.
>
> Also, do you have the schematic? Can you see if there are any
> strapping resistors? It could be, there are strapping resistors to put
> it into rgmii-id. Now that the phy-mode properties is respected, the
> reset defaults are being over-written to rgmii, which breaks the link.
> Or the bootloader has already set the PHY mode to rgmii-id.
>
> You can also use '' as the phy-mode, which results in
> PHY_INTERFACE_MODE_NA, which effectively means, don't touch the PHY
> mode, something else has already set it up. This might actually be the
> correct way to go for ACPI. In the DT world, we tend to assume the
> bootloader has done the absolute minimum and Linux should configure
> everything. The ACPI takes the opposite view, the firmware will do the
> basic hardware configuration, and Linux should not touch it, or ask
> ACPI to modify it.
>

Indeed, the firmware should have set this up. This would mean we could
do this in the driver: it currently uses

priv->phy_interface = device_get_phy_mode(&pdev->dev);

Can we just assign that to PHY_INTERFACE_MODE_NA instead?