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

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Message-ID: <20250828214452.11683-1-colin.foster@in-advantage.com>
Date: Thu, 28 Aug 2025 16:44:52 -0500
From: Colin Foster <colin.foster@...advantage.com>
To: linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Steve Glendinning <steve.glendinning@...well.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Colin Foster <colin.foster@...advantage.com>
Subject: [PATCH v1] smsc911x: add second read of EEPROM mac when possible corruption seen

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@...advantage.com>
---
 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