netdev - Re: sun7i-dwmac: link detection failure with 1000Mbit parters

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Date:   Fri, 1 Nov 2019 09:49:20 +0000
From:   Priit Laes <plaes@...es.org>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "linux-sunxi@...glegroups.com" <linux-sunxi@...glegroups.com>,
        "wens@...e.org" <wens@...e.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "peppe.cavallaro@...com" <peppe.cavallaro@...com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>
Subject: Re: sun7i-dwmac: link detection failure with 1000Mbit parters

On Thu, Oct 31, 2019 at 10:38:41AM +0000, Russell King - ARM Linux admin wrote:
> On Thu, Oct 31, 2019 at 08:39:06AM +0000, Jose Abreu wrote:
> > ++ Florian, Andrew, Heiner, Russell
> > 
> > Can you please attach your dmesg log ? PHYLINK provides some useful 
> > debug logs.
> > 
> > From: Priit Laes <plaes@...es.org>
> > Date: Oct/30/2019, 20:21:17 (UTC+00:00)
> > 
> > > Heya!
> > > 
> > > I have noticed that with sun7i-dwmac driver (OLinuxino Lime2 eMMC), link
> > > detection fails consistently with certain 1000Mbit partners (for example Huawei
> > > B525s-23a 4g modem ethernet outputs and RTL8153-based USB3.0 ethernet dongle),
> > > but the same hardware works properly with certain other link partners (100Mbit GL AR150
> > > for example).
> > > 
> > > (Just need to test with another 1000Mbit switch at the office).
> > > 
> > > I first thought it could be a regression, but I went from current master to as far back
> > > as 5.2.0-rc6 where it was still broken.
> 
> The stmmac conversion to phylink was v5.3-rc1, so that's likely not the
> issue if v5.2-rc6 also exhibits this behaviour.
> 
> My guess is that the problem lies in phylib, especially as the link LEDs
> go off when the link is configured.  I notice that it's using the
> generic PHY driver rather than a specific driver.

Yup, it turned out to be a phy-related issue - I was using generic PHY
driver, but the board is using Micrel KSZ9031 which has some quirks that
MICREL_PHY=y managed to work around.

> 
>   mii-diag -v eth0
> 
> would be useful to see for the case where the link has failed, without
> replugging the ethernet cable.

mii-diag seems to be quite an useful tool, but unfortunately has not been
packaged anymore on newer distro releases like Debian stable and latest
Ubuntu LTS.

> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up