netdev - Re: [RESENT PATCH net--stat 1/1] net: ethernet: fec: Revert "net: ethernet: fec: Replace interrupt driven MDIO with polled IO"

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Date:   Mon, 27 Jul 2020 20:37:17 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Chris Healy <cphealy@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Fugang Duan <fugang.duan@....com>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Martin Fuzzey <martin.fuzzey@...wbird.group>
Subject: Re: [RESENT PATCH net--stat 1/1] net: ethernet: fec: Revert "net:
 ethernet: fec: Replace interrupt driven MDIO with polled IO"

Hi Chris,

On Mon, Jul 27, 2020 at 08:41:23AM -0700, Chris Healy wrote:
> On Mon, Jul 27, 2020 at 8:24 AM Laurent Pinchart wrote:
> > On Mon, Jul 27, 2020 at 02:05:45PM +0200, Andrew Lunn wrote:
> > > On Sun, Jul 26, 2020 at 08:01:25PM -0700, Chris Healy wrote:
> > > > It appears quite a few boards were affected by this micrel PHY driver change:
> > > >
> > > > 2ccb0161a0e9eb06f538557d38987e436fc39b8d
> > > > 80bf72598663496d08b3c0231377db6a99d7fd68
> > > > 2de00450c0126ec8838f72157577578e85cae5d8
> > > > 820f8a870f6575acda1bf7f1a03c701c43ed5d79
> > > >
> > > > I just updated the phy-mode with my board from rgmii to rgmii-id and
> > > > everything started working fine with net-next again:
> > >
> > > Hi Chris
> > >
> > > Is this a mainline supported board? Do you plan to submit a patch?
> > >
> > > Laurent, does the change also work for your board? This is another one
> > > of those cases were a bug in the PHY driver, not respecting the
> > > phy-mode, has masked a bug in the device tree, using the wrong
> > > phy-mode. We had the same issue with the Atheros PHY a while back.
> >
> > Yes, setting the phy-mode to rgmii-id fixes the issue.
> >
> > Thank you everybody for your quick responses and very useful help !
> >
> > On a side note, when the kernel boots, there's a ~10s delay for the
> > ethernet connection to come up:
> >
> > [    4.050754] Micrel KSZ9031 Gigabit PHY 30be0000.ethernet-1:01: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=30be0000.ethernet-1:01, irq=POLL)
> > [   15.628528] fec 30be0000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
> > [   15.676961] Sending DHCP requests ., OK
> > [   15.720925] IP-Config: Got DHCP answer from 192.168.2.47, my address is 192.168.2.210
> >
> > The LED on the connected switch confirms this, it lits up synchronously
> > with the "Link is up" message. It's not an urgent issue, but if someone
> > had a few pointers on how I could debug that, it would be appreciated.
> 
> Here's a few suggestions that could help in learning more:
> 
> 1) Review the KSZ9031 HW errata and compare against the PHY driver
> code.  There's a number of errata that could cause this from my quick
> review.

I'll have a look at that, thanks.

> 2) Based on what I read in the HW errata, try different link partners
> that utilize different copper PHYs to see if it results in different
> behaviour.

I have limited available test equipment, but I can give it a try.

> 3) Try setting your autonegotiate advertisement to only advertise
> 100Mbps and see if this affects the timing.  Obviously this would not
> be a solution but might help in better understanding the issue.

I've tested this, and the link then comes up in ~2 seconds instead of
~10. That's clearly an improvement, but I have no idea what it implies
:-)

[    4.090655] Micrel KSZ9031 Gigabit PHY 30be0000.ethernet-1:01: attached PHY driver [Micrel KSZ9031 Gigabit PHY] (mii_bus:phy_addr=30be0000.ethernet-1:01, irq=POLL)
[    6.188347] fec 30be0000.ethernet eth0: Link is Up - 100Mbps/Full - flow control rx/tx
[    6.236843] Sending DHCP requests ., OK
[    6.280807] IP-Config: Got DHCP answer from 192.168.2.47, my address is 192.168.2.210

-- 
Regards,

Laurent Pinchart