net: dpaa2-mac: move rtnl_lock() only around phylink_{,dis}connect_phy()

After the introduction of a private mac_lock that serializes access to
priv->mac (and port_priv->mac in the switch), the only remaining purpose
of rtnl_lock() is to satisfy the locking requirements of
phylink_fwnode_phy_connect() and phylink_disconnect_phy().

But the functions these live in, dpaa2_mac_connect() and
dpaa2_mac_disconnect(), have contradictory locking requirements.
While phylink_fwnode_phy_connect() wants rtnl_lock() to be held,
phylink_create() wants it to not be held.

Move the rtnl_lock() from top-level (in the dpaa2-eth and dpaa2-switch
drivers) to only surround the phylink calls that require it, in the
dpaa2-mac library code.

This is possible because dpaa2_mac_connect() and dpaa2_mac_disconnect()
run unlocked, and there isn't any danger of an AB/BA deadlock between
the rtnl_mutex and other private locks.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c

@@ -4715,7 +4715,6 @@ static irqreturn_t dpni_irq0_handler_thread(int irq_num, void *arg)
 		dpaa2_eth_set_mac_addr(netdev_priv(net_dev));
 		dpaa2_eth_update_tx_fqids(priv);
 
-		rtnl_lock();
 		/* We can avoid locking because the "endpoint changed" IRQ
 		 * handler is the only one who changes priv->mac at runtime,
 		 * so we are not racing with anyone.
@@ -4725,7 +4724,6 @@ static irqreturn_t dpni_irq0_handler_thread(int irq_num, void *arg)
 			dpaa2_eth_disconnect_mac(priv);
 		else
 			dpaa2_eth_connect_mac(priv);
-		rtnl_unlock();
 	}
 
 	return IRQ_HANDLED;
@@ -5045,9 +5043,7 @@ static int dpaa2_eth_remove(struct fsl_mc_device *ls_dev)
 	else
 		fsl_mc_free_irqs(ls_dev);
 
-	rtnl_lock();
 	dpaa2_eth_disconnect_mac(priv);
-	rtnl_unlock();
 	dpaa2_eth_free_rings(priv);
 	free_percpu(priv->fd);
 	free_percpu(priv->sgt_cache);

drivers/net/ethernet/freescale/dpaa2/dpaa2-mac.c

@@ -430,7 +430,9 @@ int dpaa2_mac_connect(struct dpaa2_mac *mac)
 	}
 	mac->phylink = phylink;
 
+	rtnl_lock();
 	err = phylink_fwnode_phy_connect(mac->phylink, dpmac_node, 0);
+	rtnl_unlock();
 	if (err) {
 		netdev_err(net_dev, "phylink_fwnode_phy_connect() = %d\n", err);
 		goto err_phylink_destroy;
@@ -448,7 +450,10 @@ int dpaa2_mac_connect(struct dpaa2_mac *mac)
 
 void dpaa2_mac_disconnect(struct dpaa2_mac *mac)
 {
+	rtnl_lock();
 	phylink_disconnect_phy(mac->phylink);
+	rtnl_unlock();
+
 	phylink_destroy(mac->phylink);
 	dpaa2_pcs_destroy(mac);
 	of_phy_put(mac->serdes_phy);

drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c

@@ -1529,7 +1529,6 @@ static irqreturn_t dpaa2_switch_irq0_handler_thread(int irq_num, void *arg)
 	}
 
 	if (status & DPSW_IRQ_EVENT_ENDPOINT_CHANGED) {
-		rtnl_lock();
 		/* We can avoid locking because the "endpoint changed" IRQ
 		 * handler is the only one who changes priv->mac at runtime,
 		 * so we are not racing with anyone.
@@ -1539,7 +1538,6 @@ static irqreturn_t dpaa2_switch_irq0_handler_thread(int irq_num, void *arg)
 			dpaa2_switch_port_disconnect_mac(port_priv);
 		else
 			dpaa2_switch_port_connect_mac(port_priv);
-		rtnl_unlock();
 	}
 
 out:
@@ -2957,9 +2955,7 @@ static void dpaa2_switch_remove_port(struct ethsw_core *ethsw,
 {
 	struct ethsw_port_priv *port_priv = ethsw->ports[port_idx];
 
-	rtnl_lock();
 	dpaa2_switch_port_disconnect_mac(port_priv);
-	rtnl_unlock();
 	free_netdev(port_priv->netdev);
 	ethsw->ports[port_idx] = NULL;
 }