linux-kernel - Re: [PATCH v1] net: phy: dp83867: Disable EEE support as not implemented

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Message-ID: <aPyN7z8Vk4EiS20b@shell.armlinux.org.uk>
Date: Sat, 25 Oct 2025 09:44:31 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Emanuele Ghidoli <ghidoliemanuele@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>,
	Emanuele Ghidoli <emanuele.ghidoli@...adex.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v1] net: phy: dp83867: Disable EEE support as not
 implemented

On Thu, Oct 23, 2025 at 04:48:53PM +0200, Emanuele Ghidoli wrote:
> While the DP83867 PHYs report EEE capability through their feature
> registers, the actual hardware does not support EEE (see Links).
> When the connected MAC enables EEE, it causes link instability and
> communication failures.
> 
> The issue is reproducible with a iMX8MP and relevant stmmac ethernet port.
> Since the introduction of phylink-managed EEE support in the stmmac driver,
> EEE is now enabled by default, leading to issues on systems using the
> DP83867 PHY.

Wasn't it enabled before? See commit 4218647d4556 ("net: stmmac:
convert to phylink managed EEE support").

stmmac's mac_link_up() was:

-       if (phy && priv->dma_cap.eee) {
-               phy_eee_rx_clock_stop(phy, !(priv->plat->flags &
-                                            STMMAC_FLAG_RX_CLK_RUNS_IN_LPI));
-               priv->tx_lpi_timer = phy->eee_cfg.tx_lpi_timer;
-               stmmac_eee_init(priv, phy->enable_tx_lpi);
                stmmac_set_eee_pls(priv, priv->hw, true);
-       }

So, if EEE is enabled in the core synthesis, then EEE will be
configured depending on what phylib says.

In stmmac_init_phy(), there was this:

-               if (priv->dma_cap.eee)
-                       phy_support_eee(phydev);
-
                ret = phylink_connect_phy(priv->phylink, phydev);

So phylib was told to enable EEE support on the PHY if the dwmac
core supports EEE.

So, from what I can see, converting to phylink managed EEE didn't
change this. So what really did change?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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