linux-kernel - [PATCH] tg3: replace placeholder MAC address with device property

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Message-ID: <20251023160946.380127-1-paul.sage@42.fr>
Date: Thu, 23 Oct 2025 18:08:42 +0200
From: Paul SAGE <paul.sage@...fr>
To: paul.sage@...fr,
	vinc@...fr
Cc: Pavan Chebbi <pavan.chebbi@...adcom.com>,
	Michael Chan <mchan@...adcom.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] tg3: replace placeholder MAC address with device property

On some systems (e.g. iMac 20,1 with BCM57766), the tg3 driver reads a default placeholder mac address (00:10:18:00:00:00) from the mailbox.
The correct value on those systems are stored in the 'local-mac-address' property.

This patch, detect the default value and tries to retrieve the correct address from the device_get_mac_address function instead.

The patch has been tested on two different systems:
- iMac 20,1 (BCM57766) model which use the local-mac-address property
- iMac 13,2 (BCM57766) model which can use the mailbox, NVRAM or MAC control registers

Co-developed-by: Vincent MORVAN <vinc@...fr>
Signed-off-by: Vincent MORVAN <vinc@...fr>
Signed-off-by: Paul SAGE <paul.sage@...fr>
---
 drivers/net/ethernet/broadcom/tg3.c | 12 ++++++++++++
 drivers/net/ethernet/broadcom/tg3.h |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index d78cafdb2094..55c2f2804df5 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -17042,6 +17042,14 @@ static int tg3_get_invariants(struct tg3 *tp, const struct pci_device_id *ent)
 	return err;
 }
 
+static int tg3_is_default_mac_address(u8 *addr)
+{
+	u32 addr_high = (addr[0] << 16) | (addr[1] << 8) | addr[2];
+	u32 addr_low = (addr[3] << 16) | (addr[4] <<  8) | addr[5];
+
+	return addr_high == BROADCOM_OUI && addr_low == 0;
+}
+
 static int tg3_get_device_address(struct tg3 *tp, u8 *addr)
 {
 	u32 hi, lo, mac_offset;
@@ -17115,6 +17123,10 @@ static int tg3_get_device_address(struct tg3 *tp, u8 *addr)
 
 	if (!is_valid_ether_addr(addr))
 		return -EINVAL;
+
+	if (tg3_is_default_mac_address(addr))
+		device_get_mac_address(&tp->pdev->dev, addr);
+
 	return 0;
 }
 
diff --git a/drivers/net/ethernet/broadcom/tg3.h b/drivers/net/ethernet/broadcom/tg3.h
index a9e7f88fa26d..9fb226772e79 100644
--- a/drivers/net/ethernet/broadcom/tg3.h
+++ b/drivers/net/ethernet/broadcom/tg3.h
@@ -14,6 +14,8 @@
 #ifndef _T3_H
 #define _T3_H
 
+#define BROADCOM_OUI			0x00001018
+
 #define TG3_64BIT_REG_HIGH		0x00UL
 #define TG3_64BIT_REG_LOW		0x04UL
 
-- 
2.51.0