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

["Russell King (Oracle)" <linux@armlinux.org.uk>]

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.

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;

-- 
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