dpaa2-mac: return -EPROBE_DEFER from dpaa2_mac_open in case the fwnode is not set

We could get into a situation when the fwnode of the parent device is
not yet set because its probe didn't yet finish. When this happens, any
caller of the dpaa2_mac_open() will not have the fwnode available, thus
cause problems at the PHY connect time.

Avoid this by just returning -EPROBE_DEFER from the dpaa2_mac_open when
this happens.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -54,6 +54,12 @@ static struct fwnode_handle *dpaa2_mac_get_node(struct device *dev,
 		parent = of_fwnode_handle(dpmacs);
 	} else if (is_acpi_node(fwnode)) {
 		parent = fwnode;
+	} else {
+		/* The root dprc device didn't yet get to finalize it's probe,
+		 * thus the fwnode field is not yet set. Defer probe if we are
+		 * facing this situation.
+		 */
+		return ERR_PTR(-EPROBE_DEFER);
 	}
 
 	if (!parent)
@@ -330,6 +336,7 @@ int dpaa2_mac_open(struct dpaa2_mac *mac)
 {
 	struct fsl_mc_device *dpmac_dev = mac->mc_dev;
 	struct net_device *net_dev = mac->net_dev;
+	struct fwnode_handle *fw_node;
 	int err;
 
 	err = dpmac_open(mac->mc_io, 0, dpmac_dev->obj_desc.id,
@@ -349,7 +356,13 @@ int dpaa2_mac_open(struct dpaa2_mac *mac)
 	/* Find the device node representing the MAC device and link the device
 	 * behind the associated netdev to it.
 	 */
-	mac->fw_node = dpaa2_mac_get_node(&mac->mc_dev->dev, mac->attr.id);
+	fw_node = dpaa2_mac_get_node(&mac->mc_dev->dev, mac->attr.id);
+	if (IS_ERR(fw_node)) {
+		err = PTR_ERR(fw_node);
+		goto err_close_dpmac;
+	}
+
+	mac->fw_node = fw_node;
 	net_dev->dev.of_node = to_of_node(mac->fw_node);
 
 	return 0;