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

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Message-ID: <HE1PR0402MB2745963E2B675BAC95A61E55FFAD0@HE1PR0402MB2745.eurprd04.prod.outlook.com>
Date:   Wed, 29 Apr 2020 03:43:15 +0000
From:   Andy Duan <fugang.duan@....com>
To:     David Miller <davem@...emloft.net>
CC:     "andrew@...n.ch" <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "cphealy@...il.com" <cphealy@...il.com>,
        Leonard Crestez <leonard.crestez@....com>
Subject: RE: [EXT] Re: [PATCH net-next] net: ethernet: fec: Prevent MII event
 after MII_SPEED write

From: David Miller <davem@...emloft.net> Sent: Wednesday, April 29, 2020 11:35 AM
> From: Andy Duan <fugang.duan@....com>
> Date: Wed, 29 Apr 2020 01:55:35 +0000
> 
> > From: David Miller <davem@...emloft.net> Sent: Wednesday, April 29,
> > 2020 5:34 AM
> >> From: Andrew Lunn <andrew@...n.ch>
> >> Date: Tue, 28 Apr 2020 19:58:33 +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.
> >> >
> >> > 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>
> >>
> >> Applied to net-next, thanks.
> >
> > David, it is too early to apply the patch, it will introduce another
> > break issue as I explain in previous mail for the patch.
> 
> So what should I do, revert?

If you can revert the patch, please do it. 
Thanks, David.