of: net: fix of_get_mac_addr_nvmem() for non-platform devices

of_get_mac_address() already supports fetching the MAC address by an
nvmem provider. But until now, it was just working for platform devices.
Esp. it was not working for DSA ports and PCI devices. It gets more
common that PCI devices have a device tree binding since SoCs contain
integrated root complexes.

Use the nvmem of_* binding to fetch the nvmem cells by a struct
device_node. We still have to try to read the cell by device first
because there might be a nvmem_cell_lookup associated with that device.
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/of/of_net.c

@@ -11,6 +11,7 @@
 #include <linux/phy.h>
 #include <linux/export.h>
 #include <linux/device.h>
+#include <linux/nvmem-consumer.h>
 
 /**
  * of_get_phy_mode - Get phy mode for given device_node
@@ -59,15 +60,39 @@ static int of_get_mac_addr(struct device_node *np, const char *name, u8 *addr)
 static int of_get_mac_addr_nvmem(struct device_node *np, u8 *addr)
 {
 	struct platform_device *pdev = of_find_device_by_node(np);
+	struct nvmem_cell *cell;
+	const void *mac;
+	size_t len;
 	int ret;
 
-	if (!pdev)
-		return -ENODEV;
-
+	/* Try lookup by device first, there might be a nvmem_cell_lookup
+	 * associated with a given device.
+	 */
+	if (pdev) {
 		ret = nvmem_get_mac_address(&pdev->dev, addr);
 		put_device(&pdev->dev);
-
 		return ret;
+	}
+
+	cell = of_nvmem_cell_get(np, "mac-address");
+	if (IS_ERR(cell))
+		return PTR_ERR(cell);
+
+	mac = nvmem_cell_read(cell, &len);
+	nvmem_cell_put(cell);
+
+	if (IS_ERR(mac))
+		return PTR_ERR(mac);
+
+	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
+		kfree(mac);
+		return -EINVAL;
+	}
+
+	memcpy(addr, mac, ETH_ALEN);
+	kfree(mac);
+
+	return 0;
 }
 
 /**