netdev - Re: Re: realtek PHY commit bbc4d71d63549 causes regression

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Date:   Fri, 13 Nov 2020 14:50:14 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Jernej Škrabec <jernej.skrabec@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Ard Biesheuvel <ardb@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Alex Bennée <alex.bennee@...aro.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steve McIntyre <steve@...val.com>,
        "open list:BPF JIT for MIPS (32-BIT AND 64-BIT)" 
        <netdev@...r.kernel.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>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: Re: Re: realtek PHY commit bbc4d71d63549 causes regression

On Thu, Nov 5, 2020 at 6:28 PM Jernej Škrabec <jernej.skrabec@...il.com> wrote:
> Dne četrtek, 29. oktober 2020 ob 15:46:44 CET je Ilias Apalodimas napisal(a):
> > On Thu, Oct 29, 2020 at 03:39:34PM +0100, Andrew Lunn wrote:
> > > > What about reverting the realtek PHY commit from stable?
> > > > As Ard said it doesn't really fix anything (usage wise) and causes a
> bunch of
> > > > problems.
> > > >
> > > > If I understand correctly we have 3 options:
> > > > 1. 'Hack' the  drivers in stable to fix it (and most of those hacks will
> take
> > > >    a long time to remove)
> > > > 2. Update DTE of all affected devices, backport it to stable and force
> users to
> > > > update
> > > > 3. Revert the PHY commit
> > > >
> > > > imho [3] is the least painful solution.

There is also the option of patching the dtb in memory while booting one
of the affected machines.

> > > The PHY commit is correct, in that it fixes a bug. So i don't want to
> > > remove it.
> >
> > Yea I meant revert the commit from were ever it was backported, not on
> current
> > upstream. I agree it's correct from a coding point of view, but it never
> > actually fixes anything functionality wise of the affected platforms.
>
> Sadly, there is one board - Pine64 Plus - where HW settings are wrong and it
> actually needs SW override. Until this Realtek PHY driver fix was merged, it
> was unclear what magic value provided by Realtek to board manufacturer does.
>
> Reference:
> https://lore.kernel.org/netdev/20191001082912.12905-3-icenowy@aosc.io/

I have merged the fixes from the allwinner tree now, but I still think we
need something better than this, as the current state breaks any existing
dtb file that has the incorrect values, and this really should not have been
considered for backporting to stable kernels.

       Arnd