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Date:   Mon, 2 May 2022 20:21:10 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Francesco Dolcini <francesco.dolcini@toradex.com>
Cc:     netdev@vger.kernel.org, Andy Duan <fugang.duan@nxp.com>,
        Joakim Zhang <qiangqing.zhang@nxp.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Fabio Estevam <festevam@gmail.com>,
        Tim Harvey <tharvey@gateworks.com>,
        Chris Healy <cphealy@gmail.com>
Subject: Re: FEC MDIO read timeout on linkup
Message-ID: <YnAhFse2h0vN1FCM@lunn.ch>
References: <20220422152612.GA510015@francesco-nb.int.toradex.com>
 <20220502170527.GA137942@francesco-nb.int.toradex.com>
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> Could it be that the issue is writing the MSCR in fec_restart(),
> `writel(fep->phy_speed, fep->hwp + FEC_MII_SPEED)`?
> 
> I do see the issue on link up/down event, when this function is actually
> called.
> 
> >From what I can understand from the previous history:
> 
>   1e6114f51f9d (net: fec: fix MDIO probing for some FEC hardware blocks, 2020-10-28) 
>   f166f890c8f0 (net: ethernet: fec: Replace interrupt driven MDIO with polled IO, 2020-05-02)
> 
> writing to this register could trigger a FEC_ENET_MII interrupt actually
> creating a race condition with fec_enet_mdio_read() that is called on
> link change also.

You should read the discussion from when this code was added.

Are you planning on adding:

       if (fep->quirks & FEC_QUIRK_CLEAR_SETUP_MII) {
                /* Clear MMFR to avoid to generate MII event by writing MSCR.
                 * MII event generation condition:
                 * - writing MSCR:
                 *      - mmfr[31:0]_not_zero & mscr[7:0]_is_zero &
                 *        mscr_reg_data_in[7:0] != 0
                 * - writing MMFR:
                 *      - mscr[7:0]_not_zero
                 */
                writel(0, fep->hwp + FEC_MII_DATA);
        }

To other locations which change FEC_MII_SPEED?

   Andrew