--- /dev/null
+From 06efc9b8a1360cad83cae6e71558e5458cc1fbf3 Mon Sep 17 00:00:00 2001
+From: Vladimir Oltean <vladimir.oltean@nxp.com>
+Date: Tue, 29 Nov 2022 16:12:14 +0200
+Subject: [PATCH 07/14] net: dpaa2-eth: assign priv->mac after
+ dpaa2_mac_connect() call
+
+There are 2 requirements for correct code:
+
+- Any time the driver accesses the priv->mac pointer at runtime, it
+ either holds NULL to indicate a DPNI-DPNI connection (or unconnected
+ DPNI), or a struct dpaa2_mac whose phylink instance was fully
+ initialized (created and connected to the PHY). No changes are made to
+ priv->mac while it is being used. Currently, rtnl_lock() watches over
+ the call to dpaa2_eth_connect_mac(), so it serves the purpose of
+ serializing this with all readers of priv->mac.
+
+- dpaa2_mac_connect() should run unlocked, because inside it are 2
+ phylink calls with incompatible locking requirements: phylink_create()
+ requires that the rtnl_mutex isn't held, and phylink_fwnode_phy_connect()
+ requires that the rtnl_mutex is held. The only way to solve those
+ contradictory requirements is to let dpaa2_mac_connect() take
+ rtnl_lock() when it needs to.
+
+To solve both requirements, we need to identify the writer side of the
+priv->mac pointer, which can be wrapped in a mutex private to the driver
+in a future patch. The dpaa2_mac_connect() cannot be part of the writer
+side critical section, because of an AB/BA deadlock with rtnl_lock().
+
+So the strategy needs to be that where we prepare the DPMAC by calling
+dpaa2_mac_connect(), and only make priv->mac point to it once it's fully
+prepared. This ensures that the writer side critical section has the
+absolute minimum surface it can.
+
+The reverse strategy is adopted in the dpaa2_eth_disconnect_mac() code
+path. This makes sure that priv->mac is NULL when we start tearing down
+the DPMAC that we disconnected from, and concurrent code will simply not
+see it.
+
+No locking changes in this patch (concurrent code is still blocked by
+the rtnl_mutex).
+
+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>
+---
+ .../net/ethernet/freescale/dpaa2/dpaa2-eth.c | 21 +++++++++++--------
+ 1 file changed, 12 insertions(+), 9 deletions(-)
+
+--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
++++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+@@ -4443,9 +4443,8 @@ static int dpaa2_eth_connect_mac(struct
+ err = dpaa2_mac_open(mac);
+ if (err)
+ goto err_free_mac;
+- priv->mac = mac;
+
+- if (dpaa2_eth_is_type_phy(priv)) {
++ if (dpaa2_mac_is_type_phy(mac)) {
+ err = dpaa2_mac_connect(mac);
+ if (err && err != -EPROBE_DEFER)
+ netdev_err(priv->net_dev, "Error connecting to the MAC endpoint: %pe",
+@@ -4454,11 +4453,12 @@ static int dpaa2_eth_connect_mac(struct
+ goto err_close_mac;
+ }
+
++ priv->mac = mac;
++
+ return 0;
+
+ err_close_mac:
+ dpaa2_mac_close(mac);
+- priv->mac = NULL;
+ err_free_mac:
+ kfree(mac);
+ return err;
+@@ -4466,15 +4466,18 @@ err_free_mac:
+
+ static void dpaa2_eth_disconnect_mac(struct dpaa2_eth_priv *priv)
+ {
+- if (dpaa2_eth_is_type_phy(priv))
+- dpaa2_mac_disconnect(priv->mac);
++ struct dpaa2_mac *mac = priv->mac;
++
++ priv->mac = NULL;
+
+- if (!dpaa2_eth_has_mac(priv))
++ if (!mac)
+ return;
+
+- dpaa2_mac_close(priv->mac);
+- kfree(priv->mac);
+- priv->mac = NULL;
++ if (dpaa2_mac_is_type_phy(mac))
++ dpaa2_mac_disconnect(mac);
++
++ dpaa2_mac_close(mac);
++ kfree(mac);
+ }
+
+ static irqreturn_t dpni_irq0_handler_thread(int irq_num, void *arg)
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