net: fec: remove .ndo_poll_controller to avoid deadlocks

There is a deadlock issue found in sungem driver, please refer to the
commit ac0a230 ("eth: sungem: remove .ndo_poll_controller to avoid
deadlocks"). The root cause of the issue is that netpoll is in atomic
context and disable_irq() is called by .ndo_poll_controller interface
of sungem driver, however, disable_irq() might sleep. After analyzing
the implementation of fec_poll_controller(), the fec driver should have
the same issue. Due to the fec driver uses NAPI for TX completions, the
.ndo_poll_controller is unnecessary to be implemented in the fec driver,
so fec_poll_controller() can be safely removed.

Fixes: 7f5c6ad ("net/fec: add poll controller function for fec nic")
Signed-off-by: Wei Fang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Wei Fang

drivers/net/ethernet/freescale/fec_main.c

@@ -3674,29 +3674,6 @@ fec_set_mac_address(struct net_device *ndev, void *p)
 	return 0;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/**
- * fec_poll_controller - FEC Poll controller function
- * @dev: The FEC network adapter
- *
- * Polled functionality used by netconsole and others in non interrupt mode
- *
- */
-static void fec_poll_controller(struct net_device *dev)
-{
-	int i;
-	struct fec_enet_private *fep = netdev_priv(dev);
-
-	for (i = 0; i < FEC_IRQ_NUM; i++) {
-		if (fep->irq[i] > 0) {
-			disable_irq(fep->irq[i]);
-			fec_enet_interrupt(fep->irq[i], dev);
-			enable_irq(fep->irq[i]);
-		}
-	}
-}
-#endif
-
 static inline void fec_enet_set_netdev_features(struct net_device *netdev,
 	netdev_features_t features)
 {
@@ -4003,9 +3980,6 @@ static const struct net_device_ops fec_netdev_ops = {
 	.ndo_tx_timeout		= fec_timeout,
 	.ndo_set_mac_address	= fec_set_mac_address,
 	.ndo_eth_ioctl		= phy_do_ioctl_running,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= fec_poll_controller,
-#endif
 	.ndo_set_features	= fec_set_features,
 	.ndo_bpf		= fec_enet_bpf,
 	.ndo_xdp_xmit		= fec_enet_xdp_xmit,