[PATCH v1] smsc911x: add second read of EEPROM mac when possible corruption seen

[Colin Foster]

When the EEPROM MAC is read by way of ADDRH, it can return all 0s the
first time. Subsequent reads succeed.

Re-read the ADDRH when this behaviour is observed, in an attempt to
correctly apply the EEPROM MAC address.

Signed-off-by: Colin Foster <colin.foster@xxxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/smsc/smsc911x.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/smsc/smsc911x.c b/drivers/net/ethernet/smsc/smsc911x.c
index a2e511912e6a9..63ed221edc00a 100644
--- a/drivers/net/ethernet/smsc/smsc911x.c
+++ b/drivers/net/ethernet/smsc/smsc911x.c
@@ -2162,8 +2162,20 @@ static const struct net_device_ops smsc911x_netdev_ops = {
 static void smsc911x_read_mac_address(struct net_device *dev)
 {
 	struct smsc911x_data *pdata = netdev_priv(dev);
-	u32 mac_high16 = smsc911x_mac_read(pdata, ADDRH);
-	u32 mac_low32 = smsc911x_mac_read(pdata, ADDRL);
+	u32 mac_high16, mac_low32;
+
+	mac_high16 = smsc911x_mac_read(pdata, ADDRH);
+	mac_low32 = smsc911x_mac_read(pdata, ADDRL);
+
+	/*
+	 * The first mac_read always returns 0. Re-read it to get the
+	 * full MAC
+	 */
+	if (mac_high16 == 0) {
+		SMSC_TRACE(pdata, probe, "Re-read MAC ADDRH\n");
+		mac_high16 = smsc911x_mac_read(pdata, ADDRH);
+	}
+
 	u8 addr[ETH_ALEN];
 
 	addr[0] = (u8)(mac_low32);
-- 
2.43.0