netdev - Re: realtek PHY commit bbc4d71d63549 causes regression

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Message-Id: <20201018232058.53a22758eba397695adc0352@kernel.org>
Date:   Sun, 18 Oct 2020 23:20:58 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Alex Bennée <alex.bennee@...aro.org>,
        steve@...val.com, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        "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>
Subject: Re: realtek PHY commit bbc4d71d63549 causes regression

On Sun, 18 Oct 2020 00:19:25 +0200
Ard Biesheuvel <ardb@...nel.org> wrote:

> (cc'ing some folks who may care about functional networking on SynQuacer)
> 
> On Sat, 17 Oct 2020 at 21:49, Andrew Lunn <andrew@...n.ch> wrote:
> >
> > > So we can fix this firmware by just setting phy-mode to the empty
> > > string, right?
> >
> > I've never actually tried it, but i think so. There are no DT files
> > actually doing that, so you really do need to test it and see. And
> > there might be some differences between device_get_phy_mode() and
> > of_get_phy_mode().
> >
> 
> Yes, that works fine. Fixed now in the latest firmware build [0]

Great! I've just started chasing that bug this Friday.
Thanks!

> But that still leaves the question whether and how to work around this
> for units in the field. Ignoring the PHY mode in the driver would
> help, as all known hardware ships with firmware that configures the
> PHY with the correct settings, but we will lose the ability to use
> other PHY modes in the future, in case the SoC is ever used with DT
> based minimal firmware that does not configure networking.
> 
> Since ACPI implies rich firmware, we could make ACPI probing of the
> driver ignore the phy-mode setting in the DSDT. But if we don't do the
> same for DT, it would mean DT users are forced to upgrade their
> firmware, and hopefully do so before upgrading to a kernel that breaks
> networking. (These boxes are often used headless, so this can be
> annoying)
> 
> 
> [0] http://snapshots.linaro.org/components/kernel/leg-96boards-developerbox-edk2/83/


-- 
Masami Hiramatsu <mhiramat@...nel.org>