[PATCH net] net: lan743x: fix duplex configuration in mac_link_up

[PATCH net] net: lan743x: fix duplex configuration in mac_link_up

[Thangaraj Samynathan]

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>
---
 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 866f6a3da0d9..2939b5e933d2 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -3056,6 +3056,11 @@ 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);
-- 
2.34.1

Re: [PATCH net] net: lan743x: fix duplex configuration in mac_link_up

[Russell King (Oracle)]

On Mon, Mar 23, 2026 at 12:23:45PM +0530, Thangaraj Samynathan wrote:
> 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>

Thanks!

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Re: [PATCH net] net: lan743x: fix duplex configuration in mac_link_up

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 23 Mar 2026 12:23:45 +0530 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net] net: lan743x: fix duplex configuration in mac_link_up
    https://git.kernel.org/netdev/net/c/71399707876b

You are awesome, thank you!
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