netdev - Re: racing ndo_open()/phylink*connect() with phy

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Message-ID: <229b5a82-1086-40be-8ee5-16b7f3a03b30@lunn.ch>
Date: Wed, 1 May 2024 17:07:44 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Andrew Halaney <ahalaney@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com, netdev@...r.kernel.org,
	alexandre.torgue@...s.st.com, joabreu@...opsys.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, mcoquelin.stm32@...il.com, hkallweit1@...il.com,
	linux@...linux.org.uk
Subject: Re: racing ndo_open()/phylink*connect() with phy_probe()

On Tue, Apr 30, 2024 at 04:02:19PM -0500, Andrew Halaney wrote:
> Hi,
> 
> I've been taking a look at the following error message:
> 
>     qcom-ethqos 23000000.ethernet end1: __stmmac_open: Cannot attach to PHY (error: -19)
> 
> end1 is using a phy on the mdio bus of end0, not on its own bus. Something
> like this devicetree snippet highlights the relationship:
> 
>     // end0
>     &ethernet0 {
>             phy-mode = "sgmii";
>             phy-handle = <&sgmii_phy0>;
> 
>             mdio {
>                     compatible = "snps,dwmac-mdio";
>                     sgmii_phy0: phy@8 {
>                             compatible = "ethernet-phy-id0141.0dd4";
>                             reg = <0x8>;
>                             device_type = "ethernet-phy";
>                     };
> 
>                     sgmii_phy1: phy@a {
>                             compatible = "ethernet-phy-id0141.0dd4";
>                             reg = <0xa>;
>                             device_type = "ethernet-phy";
>                     };
>             };
>     };
> 
>     // end1
>     &ethernet1 {
>             phy-mode = "sgmii";
>             phy-handle = <&sgmii_phy1>;
>     };

I agree with Russell here. You need to determine where the ENODEV
comes from.

It seems unlikely, but one possibility is:

static int stmmac_xgmac2_mdio_read_c22(struct mii_bus *bus, int phyaddr,
                                       int phyreg)
{
        struct net_device *ndev = bus->priv;
        struct stmmac_priv *priv;
        u32 addr;

        priv = netdev_priv(ndev);

        /* Until ver 2.20 XGMAC does not support C22 addr >= 4 */
        if (priv->synopsys_id < DWXGMAC_CORE_2_20 &&
            phyaddr > MII_XGMAC_MAX_C22ADDR)
                return -ENODEV;

Maybe if the interface is down, priv->synopsys_id has not been set
yet? Your devices are at address 8 and 10, so if priv->synopsys_id
where 0, this would give you the ENODEV.

Once you know the root cause, we might be able to make suggests how to
fix it.

      Andrew