netdev - Re: [RFC] increase MDIO i2c poll timeout gradually (including patch)

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Message-ID: <aM6Ng7tnEYdWmI1F@shell.armlinux.org.uk>
Date: Sat, 20 Sep 2025 12:18:27 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Janpieter Sollie <janpieter.sollie@...elmail.de>
Cc: Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [RFC] increase MDIO i2c poll timeout gradually (including patch)

On Sat, Sep 20, 2025 at 12:00:50PM +0200, Janpieter Sollie wrote:
> Op 19/09/2025 om 19:04 schreef Andrew Lunn:
> > On Fri, Sep 19, 2025 at 03:52:55PM +0200, Janpieter Sollie wrote:
> > > Hello everyone,
> > Please ensure you Cc: the correct Maintainers.
> > 
> > ./scripts/get_maintainer.pl drivers/net/phy/sfp.c
> > Russell King <linux@...linux.org.uk> (maintainer:SFF/SFP/SFP+ MODULE SUPPORT)
> > Andrew Lunn <andrew@...n.ch> (maintainer:ETHERNET PHY LIBRARY)
> > Heiner Kallweit <hkallweit1@...il.com> (maintainer:ETHERNET PHY LIBRARY)
> > "David S. Miller" <davem@...emloft.net> (maintainer:NETWORKING DRIVERS)
> > Eric Dumazet <edumazet@...gle.com> (maintainer:NETWORKING DRIVERS)
> > Jakub Kicinski <kuba@...nel.org> (maintainer:NETWORKING DRIVERS)
> > Paolo Abeni <pabeni@...hat.com> (maintainer:NETWORKING DRIVERS)
> > netdev@...r.kernel.org (open list:SFF/SFP/SFP+ MODULE SUPPORT)
> > linux-kernel@...r.kernel.org (open list)
> Done, sorry, this is my first post here
> > 
> > > I tested a SFP module where the i2c bus is "unstable" at best.
> > Please tell us more about the hardware.
> > 
> > Also, what speed do you have the I2C bus running at? Have you tried
> > different clock-frequency values to slow down the I2C bus? Have you
> > checked the pull-up resistors? I2C problems are sometimes due to too
> > strong pull-ups.
> The hardware is a bananapi R4 2xSFP using a MT7988a SoC.
> The SFP+ module is a RJ45 rollball module using a AQR113C phy, but needs a
> quirk in sfp.c (added below)
> I'm not a i2c expert at all,
> but about the i2c bus speed, the SFP cage seems to be behind a muxer, not a i2c root.
> I could not find anything about i2c bus speed in /proc or /sys, maybe it's impossible to tell?
> 
> The dtsi or dtso files do not mention anything about bus speeds, so I honestly do not know.

As you have not include the author of the SFP support (me) in your
initial email, and have not provided a repeat of the description,
I'm afraid I have no idea what the issue is that you're encountering.

Thanks.

-- 
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