netdev - RE: [PATCH v1 1/1] net: phy: micrel: Add workaround for incomplete autonegotiation

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Message-ID:
 <PH7PR12MB7282E7132837B38AC6982B1DD77B2@PH7PR12MB7282.namprd12.prod.outlook.com>
Date: Wed, 24 Jan 2024 22:18:20 +0000
From: Asmaa Mnebhi <asmaa@...dia.com>
To: Andrew Lunn <andrew@...n.ch>
CC: "Russell King (Oracle)" <linux@...linux.org.uk>, "davem@...emloft.net"
	<davem@...emloft.net>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	David Thompson <davthompson@...dia.com>
Subject: RE: [PATCH v1 1/1] net: phy: micrel: Add workaround for incomplete
 autonegotiation

> > What is the link partner? From the datasheet
> >
> > MMD Address 1h, Register 5Ah – 1000BASE-T Link-Up Time Control
> >
> > When the link partner is another KSZ9031 device, the 1000BASE-T
> > link-up time can be long. These three bits provide an optional setting
> > to reduce the 1000BASE-T link-up time.
> > 100 = Default power-up setting
> > 011 = Optional setting to reduce link-up time when the link partner is
> > a KSZ9031 device.
> >
> > Might be worth setting it and see what happens.
> >
> > Have you tried playing with the prefer master/prefer slave options? If
> > you have identical PHYs on each end, it could be they are generating the same
> 'random'
> > number used to determine who should be master and who should be slave.
> > If they both pick the same number, they are supposed to pick a
> > different random number and try again. There have been some PHYs which
> > are broken in this respect. prefer master/prefer slave should
> > influence the random number, biasing it higher/lower.
> >
> > auto-neg should typically take a little over 1 second. 5 seconds is
> > way too long, something is not correct. You might want to sniff the
> > fast link pulses, try to decode the values and see what is going on.
> >
> > I would not be surprised if you find out this 5 second complete time
> > is somehow related to it not completing at all.
> >
> 
> The link partner is a switch (KSZ9893R) so I am not sure setting the 5Ah register
> to 011 would help.

I set the 5Ah register to 011 and that didn’t help. I also am consulting the vendor and the hardware team regarding why autonegotiation takes so long with the KSZ9031. Will report back when they get back to me.