Re: racing ndo_open()/phylink*connect() with phy_probe()

Russell King (Oracle)
2024-05-01T15:19:26Z

On Wed, May 01, 2024 at 05:07:44PM +0200, Andrew Lunn wrote:
> 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.

Yes, I did look at that, but didn't read the DT snippet to realise
that the addresses would be trapped by that. So, looking at where
priv->synopsys_id is set... is in stmmac_hwif_init(), which is
called from stmmac_hw_init(), which in turn is called from
stmmac_dvr_probe(). This is the only path that leads here.

This all happens before the MDIO bus is registered, so the value of
priv->synopsys_id should be set by the time the MDIO bus is registered.

So I'm unconvinced... but I think Andrew Halaney needs to delve
deeper into debugging what is going on when the failure occurs.

--
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