Re: [PATCH] arm64: dts: imx8mp-debix-model-a: Disable EEE for 1000T

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Oct 27, 2025 at 03:13:51PM +0000, Russell King (Oracle) wrote:
> On Sun, Oct 26, 2025 at 02:29:04PM +0200, Laurent Pinchart wrote:
> > Energy Efficient Ethernet (EEE) is broken at least for 1000T on the EQOS
> > (DWMAC) interface. When connected to an EEE-enabled peer, the ethernet
> > devices produces an interrupts storm. Disable EEE support to fix it.
> 
> We've finally got to the bottom of what's going on here. Please try
> this patch (it's building locally, but will take some time because
> I'd wound the tree back to 6.13 and 6.14, so it's going to be a full
> rebuild.) Thus, there may be compile bugs remaining.

I've applied it on top of 

I've started with a branch based on v6.18-rc3 plus "[PATCH net-next 0/5]
net: stmmac: more cleanups" ([1]) and "[PATCH net-next v2 0/6] net: add
phylink managed WoL and convert stmmac" ([2]) to make the patch apply
cleanly.

[1] https://lore.kernel.org/all/aO_HIwT_YvxkDS8D@shell.armlinux.org.uk/
[2] https://lore.kernel.org/all/aPnyW54J80h9DmhB@shell.armlinux.org.uk/

The base branch exhibits the interrupt storm issue. The patch
unfortunately doesn't fix it.

> This uncovered a latent bug in Emanuele's case - the TI PHY drivers
> report EEE capabilities despite not being capable which also needs
> fixing. The patch below will stop stmmac enabling EEE by default on
> PHYs described in firmware, which is the behaviour the driver used
> to have.
> 
> If we decide that EEE should be enabled by default, then we'll need
> to revert this change. However, given Oleksij's recent input, I'm
> wondering whether EEE should default to disabled given the issues
> with Tq. The suggestion there is that many PHYs get it wrong and thus
> are incompatible with each other when EEE is enabled.
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index fd5106880192..c18690a6804f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1208,6 +1208,24 @@ static int stmmac_init_phy(struct net_device *dev)
>  	return 0;
>  }
>  
> +static bool stmmac_has_fw_phy(struct stmmac_priv *priv)
> +{
> +	struct fwnode_handle *fwnode;
> +
> +	fwnode = priv->plat->port_node;
> +	if (!fwnode)
> +		fwnode = dev_fwnode(priv->device);
> +
> +	if (!fwnode)
> +		return false;
> +
> +	fwnode = fwnode_get_phy_node(fwnode);
> +	if (fwnode)
> +		fwnode_handle_put(fwnode);
> +
> +	return !!fwnode;
> +}
> +
>  static int stmmac_phylink_setup(struct stmmac_priv *priv)
>  {
>  	struct stmmac_mdio_bus_data *mdio_bus_data;
> @@ -1270,7 +1288,7 @@ static int stmmac_phylink_setup(struct stmmac_priv *priv)
>  		/* All full duplex speeds above 100Mbps are supported */
>  		config->lpi_capabilities = ~(MAC_1000FD - 1) | MAC_100FD;
>  		config->lpi_timer_default = eee_timer * 1000;
> -		config->eee_enabled_default = true;
> +		config->eee_enabled_default = !stmmac_has_fw_phy(priv);
>  	}
>  
>  	config->wol_phy_speed_ctrl = true;

-- 
Regards,

Laurent Pinchart