net: bcmgenet: synchronize EXT_RGMII_OOB_CTRL access

The EXT_RGMII_OOB_CTRL register can be written from different
contexts. It is predominantly written from the adjust_link
handler which is synchronized by the phydev->lock, but can
also be written from a different context when configuring the
mii in bcmgenet_mii_config().

The chances of contention are quite low, but it is conceivable
that adjust_link could occur during resume when WoL is enabled
so use the phydev->lock synchronizer in bcmgenet_mii_config()
to be sure.

Fixes: afe3f907 ("net: bcmgenet: power on MII block for all MII modes")
Cc: stable@vger.kernel.org
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/genet/bcmmii.c

@@ -2,7 +2,7 @@
 /*
  * Broadcom GENET MDIO routines
  *
- * Copyright (c) 2014-2017 Broadcom
+ * Copyright (c) 2014-2024 Broadcom
  */
 
 #include <linux/acpi.h>
@@ -275,6 +275,7 @@ int bcmgenet_mii_config(struct net_device *dev, bool init)
 	 * block for the interface to work, unconditionally clear the
 	 * Out-of-band disable since we do not need it.
 	 */
+	mutex_lock(&phydev->lock);
 	reg = bcmgenet_ext_readl(priv, EXT_RGMII_OOB_CTRL);
 	reg &= ~OOB_DISABLE;
 	if (priv->ext_phy) {
@@ -286,6 +287,7 @@ int bcmgenet_mii_config(struct net_device *dev, bool init)
 			reg |= RGMII_MODE_EN;
 	}
 	bcmgenet_ext_writel(priv, reg, EXT_RGMII_OOB_CTRL);
+	mutex_unlock(&phydev->lock);
 
 	if (init)
 		dev_info(kdev, "configuring instance for %s\n", phy_name);