Re: [PATCH net] net: stmmac: Skip PHY attach if custom PCS is in use

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi,

+Mohd

On 7/22/26 15:19, Zxyan Zhu wrote:
> When a platform provides a custom PCS via the pcs_init callback
> (e.g., for USXGMII with in-band autoneg), the MAC's phylink_pcs
> is already configured. In this case, phylink validates against
> the PCS's supported interfaces and manages link state through
> the PCS, so no traditional PHY device is needed.
> 
> Without this, stmmac_init_phy() falls through to the
> no-phy-node path and errors out with "no phy found" when
> the DT has no phy-handle for such interfaces.
> 
> Skip the PHY attach when priv->hw->phylink_pcs is already set
> and no phy-handle is specified in the device tree, allowing
> platform PCS implementations to handle the link autonomously.

Hmpf this bug again...

There have been multiple attempts at solving this, cf this thread :

https://lore.kernel.org/netdev/E1w66jW-0000000E3qS-23fW@rmk-PC.armlinux.org.uk/

Now, there wasn't any conclusion on that, but I _think_ the proper
solution is to re-apply Russell's original patch (the one in the link above)
and to add this current patch on top of it.

Russell states that this may (will ?) break qcom-ethqos, but OTOH
we're in need for a solution here, and with the pace of PCS-related
work that impacts stmmac, there's going to be a point where we may
need to think about compatibility.

TBF I don't understand the qcom-ethqos issue, maybe Mohd can help
with testing here ?

Maxime