netdev - [PATCH net-next 1/3] net: stmmac: clear half-duplex caps where unsupported

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Message-Id: <E1vlmOQ-00000006zuz-0ffN@rmk-PC.armlinux.org.uk>
Date: Fri, 30 Jan 2026 11:10:26 +0000
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next 1/3] net: stmmac: clear half-duplex caps where
 unsupported

Where a core supports hardware features, but does not indicate support
for half-duplex, clear phylink's half-duplex 1G, 100M and 10M
capability bits to disallow half-duplex operation and advertisement of
these link modes.

This will avoid the need for special code in the PCS driver to do this
based on the ESTATUS register bits, as the support in the PCS is
dependent on the same synthesis choice as the MAC core.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c | 2 --
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c   | 3 +++
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
index ca81bb1cae39..49893b9fb88c 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwxgmac2_core.c
@@ -46,8 +46,6 @@ static void dwxgmac2_update_caps(struct stmmac_priv *priv)
 {
 	if (!priv->dma_cap.mbps_10_100)
 		priv->hw->link.caps &= ~(MAC_10 | MAC_100);
-	else if (!priv->dma_cap.half_duplex)
-		priv->hw->link.caps &= ~(MAC_10HD | MAC_100HD);
 }
 
 static void dwxgmac2_set_mac(void __iomem *ioaddr, bool enable)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 788b884f9c89..a3c155cccd9b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -906,6 +906,9 @@ static unsigned long stmmac_mac_get_caps(struct phylink_config *config,
 	/* Refresh the MAC-specific capabilities */
 	stmmac_mac_update_caps(priv);
 
+	if (priv->hw_cap_support && !priv->dma_cap.half_duplex)
+		priv->hw->link.caps &= ~(MAC_1000HD | MAC_100HD | MAC_10HD);
+
 	config->mac_capabilities = priv->hw->link.caps;
 
 	if (priv->plat->max_speed)
-- 
2.47.3