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Date:   Tue, 28 Apr 2020 20:34:39 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     fugang.duan@....com
Cc:     andrew@...n.ch, netdev@...r.kernel.org, cphealy@...il.com,
        leonard.crestez@....com
Subject: Re: [EXT] Re: [PATCH net-next] net: ethernet: fec: Prevent MII
 event after MII_SPEED write

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?

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