[PATCH net-next v1 2/5] net: lan743x: start phylink last and stop it first

[Chris Babroski <cbabroski@nvidia.com>]

lan743x_netdev_open() starts phylink before the RX and TX rings exist,
and lan743x_netdev_close() only stops it after the rings are freed. The
mac_link_up() callback wakes all TX queues, so it can run while there is
no TX ring to transmit on.

For ndo_open and ndo_stop the qdisc is not active at that point, but the
suspend and resume paths call lan743x_netdev_close() and
lan743x_netdev_open() directly with the qdisc still attached. A link up
event in either window lets the stack call ndo_start_xmit() on a channel
whose ring is not allocated yet or has just been freed.

The error path of lan743x_netdev_open() is also wrong: a
lan743x_ptp_open() failure jumps past lan743x_phylink_disconnect(),
leaving phylink started and the PHY attached after open has failed.
Every later open then fails because the PHY is already attached.

Connect and start phylink as the last step of open and stop it as the
first step of close, as other phylink users do. If phylink fails to
connect, nothing is attached, so the error path only needs to unwind the
rings, PTP, MAC and interrupts.

Fixes: a5f199a8d8a0 ("net: lan743x: Migrate phylib to phylink")
Assisted-by: LLM
Signed-off-by: Chris Babroski <cbabroski@nvidia.com>
---
 drivers/net/ethernet/microchip/lan743x_main.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index 9e1276cf313c..583f631df701 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -3334,6 +3334,8 @@ static int lan743x_netdev_close(struct net_device *netdev)
 	struct lan743x_adapter *adapter = netdev_priv(netdev);
 	int index;
 
+	lan743x_phylink_disconnect(adapter);
+
 	for (index = 0; index < adapter->used_tx_channels; index++)
 		lan743x_tx_close(&adapter->tx[index]);
 
@@ -3342,8 +3344,6 @@ static int lan743x_netdev_close(struct net_device *netdev)
 
 	lan743x_ptp_close(adapter);
 
-	lan743x_phylink_disconnect(adapter);
-
 	lan743x_mac_close(adapter);
 
 	lan743x_intr_close(adapter);
@@ -3365,10 +3365,6 @@ static int lan743x_netdev_open(struct net_device *netdev)
 	if (ret)
 		goto close_intr;
 
-	ret = lan743x_phylink_connect(adapter);
-	if (ret)
-		goto close_mac;
-
 	ret = lan743x_ptp_open(adapter);
 	if (ret)
 		goto close_mac;
@@ -3387,6 +3383,10 @@ static int lan743x_netdev_open(struct net_device *netdev)
 			goto close_tx;
 	}
 
+	ret = lan743x_phylink_connect(adapter);
+	if (ret)
+		goto close_tx;
+
 	if (netdev->phydev)
 		phy_support_eee(netdev->phydev);
 
@@ -3414,8 +3414,6 @@ static int lan743x_netdev_open(struct net_device *netdev)
 			lan743x_rx_close(&adapter->rx[index]);
 	}
 	lan743x_ptp_close(adapter);
-	if (adapter->phylink)
-		lan743x_phylink_disconnect(adapter);
 
 close_mac:
 	lan743x_mac_close(adapter);
-- 
2.34.1