Commit 0713e555 authored by Oleksij Rempel's avatar Oleksij Rempel Committed by Jakub Kicinski
Browse files

net: phy: smsc: Force predictable MDI-X state on LAN87xx 



Override the hardware strap configuration for MDI-X mode to ensure a
predictable initial state for the driver. The initial mode of the LAN87xx
PHY is determined by the AUTOMDIX_EN strap pin, but the driver has no
documented way to read its latched status.

This unpredictability means the driver cannot know if the PHY has
initialized with Auto-MDIX enabled or disabled, preventing it from
providing a reliable interface to the user.

This patch introduces a `config_init` hook that forces the PHY into a
known state by explicitly enabling Auto-MDIX.

Fixes: 05b35e7e ("smsc95xx: add phylib support")
Signed-off-by: default avatarOleksij Rempel <o.rempel@pengutronix.de>
Cc: Andre Edich <andre.edich@microchip.com>
Reviewed-by: default avatarAndrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250703114941.3243890-3-o.rempel@pengutronix.de


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent a141af8e

drivers/net/phy/smsc.c

+28 −1
Original line number Diff line number Diff line
@@ -262,6 +262,33 @@ int lan87xx_read_status(struct phy_device *phydev) 
}

EXPORT_SYMBOL_GPL(lan87xx_read_status);



static int lan87xx_phy_config_init(struct phy_device *phydev)

{

	int rc;



	/* The LAN87xx PHY's initial MDI-X mode is determined by the AUTOMDIX_EN

	 * hardware strap, but the driver cannot read the strap's status. This

	 * creates an unpredictable initial state.

	 *

	 * To ensure consistent and reliable behavior across all boards,

	 * override the strap configuration on initialization and force the PHY

	 * into a known state with Auto-MDIX enabled, which is the expected

	 * default for modern hardware.

	 */

	rc = phy_modify(phydev, SPECIAL_CTRL_STS,

			SPECIAL_CTRL_STS_OVRRD_AMDIX_ |

			SPECIAL_CTRL_STS_AMDIX_ENABLE_ |

			SPECIAL_CTRL_STS_AMDIX_STATE_,

			SPECIAL_CTRL_STS_OVRRD_AMDIX_ |

			SPECIAL_CTRL_STS_AMDIX_ENABLE_);

	if (rc < 0)

		return rc;



	phydev->mdix_ctrl = ETH_TP_MDI_AUTO;



	return smsc_phy_config_init(phydev);

}



static int lan874x_phy_config_init(struct phy_device *phydev)

{

	u16 val;
@@ -696,7 +723,7 @@ static struct phy_driver smsc_phy_driver[] = { 


	/* basic functions */

	.read_status	= lan87xx_read_status,

	.config_init	= smsc_phy_config_init,

	.config_init	= lan87xx_phy_config_init,

	.soft_reset	= smsc_phy_reset,

	.config_aneg	= lan87xx_config_aneg,