netdev - Re: [PATCH net-next v2] net: ethernet: fec: Prevent MII event after MII

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Date:   Sat, 2 May 2020 00:49:37 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, fugang.duan@....com, cphealy@...il.com
Subject: Re: [PATCH net-next v2] net: ethernet: fec: Prevent MII event after
 MII_SPEED write

On Fri, May 01, 2020 at 03:29:54PM -0700, David Miller wrote:
> From: Andrew Lunn <andrew@...n.ch>
> Date: Wed, 29 Apr 2020 22:53:23 +0200
> 
> > The change to polled IO for MDIO completion assumes that MII events
> > are only generated for MDIO transactions. However on some SoCs writing
> > to the MII_SPEED register can also trigger an MII event. As a result,
> > the next MDIO read has a pending MII event, and immediately reads the
> > data registers before it contains useful data. When the read does
> > complete, another MII event is posted, which results in the next read
> > also going wrong, and the cycle continues.
> > 
> > By writing 0 to the MII_DATA register before writing to the speed
> > register, this MII event for the MII_SPEED is suppressed, and polled
> > IO works as expected.
> > 
> > v2 - Only infec_enet_mii_init()
> > 
> > Fixes: 29ae6bd1b0d8 ("net: ethernet: fec: Replace interrupt driven MDIO with polled IO")
> > Reported-by: Andy Duan <fugang.duan@....com>
> > Suggested-by: Andy Duan <fugang.duan@....com>
> > Signed-off-by: Andrew Lunn <andrew@...n.ch>
> 
> Hmmm, I reverted the Fixes: tag patch so you'll need to respin this I think.

Ah.

We wanted the fix reverting, but not that the fix was fixing. Sorry,
we were unclear.

   Andrew