[PATCH 5.14 738/849] net: phy: fix duplex out of sync problem while changing settings

[Greg Kroah-Hartman]

From: Heiner Kallweit <hkallweit1@xxxxxxxxx>

[ Upstream commit a4db9055fdb9cf607775c66d39796caf6439ec92 ]

As reported by Zhang there's a small issue if in forced mode the duplex
mode changes with the link staying up [0]. In this case the MAC isn't
notified about the change.

The proposed patch relies on the phylib state machine and ignores the
fact that there are drivers that uses phylib but not the phylib state
machine. So let's don't change the behavior for such drivers and fix
it w/o re-adding state PHY_FORCING for the case that phylib state
machine is used.

[0] https://lore.kernel.org/netdev/a5c26ffd-4ee4-a5e6-4103-873208ce0dc5@xxxxxxxxxx/T/

Fixes: 2bd229df5e2e ("net: phy: remove state PHY_FORCING")
Reported-by: Zhang Changzhong <zhangchangzhong@xxxxxxxxxx>
Tested-by: Zhang Changzhong <zhangchangzhong@xxxxxxxxxx>
Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Link: https://lore.kernel.org/r/7b8b9456-a93f-abbc-1dc5-a2c2542f932c@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/phy/phy.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index cbf344c5db610..451adee132139 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -815,7 +815,12 @@ int phy_ethtool_ksettings_set(struct phy_device *phydev,
 	phydev->mdix_ctrl = cmd->base.eth_tp_mdix_ctrl;
 
 	/* Restart the PHY */
-	_phy_start_aneg(phydev);
+	if (phy_is_started(phydev)) {
+		phydev->state = PHY_UP;
+		phy_trigger_machine(phydev);
+	} else {
+		_phy_start_aneg(phydev);
+	}
 
 	mutex_unlock(&phydev->lock);
 	return 0;
-- 
2.33.0