[PATCH 6.12 092/244] net: lan743x: fix duplex configuration in mac_link_up

Greg Kroah-Hartman
2026-03-31T16:50:03Z

From: Thangaraj Samynathan <thangaraj.s@microchip.com>

[ Upstream commit 71399707876b93240f236f48b8062f3423a5fe97 ]

The driver does not explicitly configure the MAC duplex mode when
bringing the link up. As a result, the MAC may retain a stale duplex
setting from a previous link state, leading to duplex mismatches with
the link partner and degraded network performance.

Update lan743x_phylink_mac_link_up() to set or clear the MAC_CR_DPX_
bit according to the negotiated duplex mode.

This ensures the MAC configuration is consistent with the phylink
resolved state.

Fixes: a5f199a8d8a03 ("net: lan743x: Migrate phylib to phylink")
Signed-off-by: Thangaraj Samynathan <thangaraj.s@microchip.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/20260323065345.144915-1-thangaraj.s@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/microchip/lan743x_main.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 8c4c28a1d6575..b897d071fc452 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -3055,6 +3055,11 @@ static void lan743x_phylink_mac_link_up(struct phylink_config *config,
else if (speed == SPEED_100)
mac_cr |= MAC_CR_CFG_L_;

+ if (duplex == DUPLEX_FULL)
+ mac_cr |= MAC_CR_DPX_;
+ else
+ mac_cr &= ~MAC_CR_DPX_;
+
lan743x_csr_write(adapter, MAC_CR, mac_cr);

lan743x_ptp_update_latency(adapter, speed);
--
2.51.0