r8169: add random MAC address fallback

It was reported that the GPD MicroPC is broken in a way that no valid
MAC address can be read from the network chip. The vendor driver deals
with this by assigning a random MAC address as fallback. So let's do
the same.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -6650,13 +6650,36 @@ static int rtl_get_ether_clk(struct rtl8169_private *tp)
 	return rc;
 }
 
+static void rtl_init_mac_address(struct rtl8169_private *tp)
+{
+	struct net_device *dev = tp->dev;
+	u8 *mac_addr = dev->dev_addr;
+	int rc, i;
+
+	rc = eth_platform_get_mac_address(tp_to_dev(tp), mac_addr);
+	if (!rc)
+		goto done;
+
+	rtl_read_mac_address(tp, mac_addr);
+	if (is_valid_ether_addr(mac_addr))
+		goto done;
+
+	for (i = 0; i < ETH_ALEN; i++)
+		mac_addr[i] = RTL_R8(tp, MAC0 + i);
+	if (is_valid_ether_addr(mac_addr))
+		goto done;
+
+	eth_hw_addr_random(dev);
+	dev_warn(tp_to_dev(tp), "can't read MAC address, setting random one\n");
+done:
+	rtl_rar_set(tp, mac_addr);
+}
+
 static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
-	/* align to u16 for is_valid_ether_addr() */
-	u8 mac_addr[ETH_ALEN] __aligned(2) = {};
 	struct rtl8169_private *tp;
 	struct net_device *dev;
-	int chipset, region, i;
+	int chipset, region;
 	int jumbo_max, rc;
 
 	dev = devm_alloc_etherdev(&pdev->dev, sizeof (*tp));
@@ -6748,16 +6771,7 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	u64_stats_init(&tp->rx_stats.syncp);
 	u64_stats_init(&tp->tx_stats.syncp);
 
-	/* get MAC address */
-	rc = eth_platform_get_mac_address(&pdev->dev, mac_addr);
-	if (rc)
-		rtl_read_mac_address(tp, mac_addr);
-
-	if (is_valid_ether_addr(mac_addr))
-		rtl_rar_set(tp, mac_addr);
-
-	for (i = 0; i < ETH_ALEN; i++)
-		dev->dev_addr[i] = RTL_R8(tp, MAC0 + i);
+	rtl_init_mac_address(tp);
 
 	dev->ethtool_ops = &rtl8169_ethtool_ops;