[PATCH net] net: phy: dp83869: Set auto mdix bit for forced 100Base-Tx mode
From: Meghana Malladi
Date: Wed Feb 11 2026 - 08:10:54 EST
When using DP83869 in force 100Base-Tx mode, the PHY is required
to have robust Auto-MDIX feature enabled from register 1Eh.
Refer to 7.4.1.2 100BASE-TX section in the TRM [1] for more details.
[1]: https://www.ti.com/lit/ds/symlink/dp83869hm.pdf
Signed-off-by: Meghana Malladi <m-malladi@xxxxxx>
---
drivers/net/phy/dp83869.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
index 1f381d7b13ff..70d759c45c6a 100644
--- a/drivers/net/phy/dp83869.c
+++ b/drivers/net/phy/dp83869.c
@@ -110,6 +110,7 @@
/* CFG4 bits */
#define DP83869_INT_OE BIT(7)
+#define DP83869_CFG4_ENABLE_AUTO_MDIX_100FD BIT(9)
/* OP MODE */
#define DP83869_OP_MODE_MII BIT(5)
@@ -900,6 +901,23 @@ static int dp83869_phy_reset(struct phy_device *phydev)
return dp83869_config_init(phydev);
}
+static void dp83869_link_change_notify(struct phy_device *phydev)
+{
+ int cfg4;
+
+ /* When using DP83869 in force 100Base-Tx mode, the PHY is required
+ * to have robust Auto-MDIX feature enabled
+ */
+ if (phydev->autoneg == AUTONEG_DISABLE &&
+ phydev->speed == SPEED_100 &&
+ phydev->duplex == DUPLEX_FULL) {
+ cfg4 = phy_read(phydev, DP83869_CFG4);
+ if (cfg4 >= 0) {
+ cfg4 |= DP83869_CFG4_ENABLE_AUTO_MDIX_100FD;
+ phy_write(phydev, DP83869_CFG4, cfg4);
+ }
+ }
+}
#define DP83869_PHY_DRIVER(_id, _name) \
{ \
@@ -918,6 +936,7 @@ static int dp83869_phy_reset(struct phy_device *phydev)
.set_wol = dp83869_set_wol, \
.suspend = genphy_suspend, \
.resume = genphy_resume, \
+ .link_change_notify = dp83869_link_change_notify, \
}
static struct phy_driver dp83869_driver[] = {
base-commit: e9a5073a98d940837cbb95e71eed1f28f48e7b30
--
2.43.0