From: Andrew Lunn <and...@lunn.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.d...@nxp.com>
> Suggested-by: Andy Duan <fugang.d...@nxp.com>
> Signed-off-by: Andrew Lunn <and...@lunn.ch>
Applied to net-next, thanks.
