netdev - Re: net: phy: micrel KSZ9031 ifdown ifup issue

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Date:   Mon, 16 Sep 2019 09:54:49 -0400
From:   Paul Thomas <pthomas8589@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: net: phy: micrel KSZ9031 ifdown ifup issue

Hi Andrew,

I did some more investigation, and what seems to be happening is the
device get's stuck in auto-negotiation. I looked at this using
phytool:
https://github.com/wkz/phytool

When it is in the good state I see that reg 0x01 is 0x796d where bit
1.2 reports 'Link is up' and bit 1.5 reports 'Auto-negotiation process
complete'. However, once I get to the bad state (it may take several
tries of ifdown, ifup to get there) then reg 0x01 is 0x7649 reporting
'Link is down' and 'Auto-negotiation process not completed'. This can
be fixed by resetting the phy './phytool write eth0/3/0 0x9140'

So, I guess that means the driver is doing what it is supposed to?
Could we add quirk or something to reset the phy again from the driver
if auto-negotiation doesn't complete with x seconds?

> Are you using interrupts, or polling? If interrupts, try polling?
> Seems unlikely, but you could be missing an interrupt.
It must be polling, the interrupt from the PHY is run in the
schematic, but it is not used in the hw or device-tree configuration.

>
> There is a fix from Antoine Tenart which suggests asym pause can be an
> issue? What pause setup are you using? But this is a known issue,
> which 5.2 should have the fix for.
Yes, this kernel includes this asym pause workaround. Reg 4.11:10 is 0
# ./phytool read eth0/3/4
0x01e1

This is the last little Ethernet issue that we are having, it would be
nice if we could find a solution.

thanks,
Paul