diff --git a/sys/mips/atheros/ar71xxreg.h b/sys/mips/atheros/ar71xxreg.h
index 3f6b50a97fb3..5677a4eff599 100644
--- a/sys/mips/atheros/ar71xxreg.h
+++ b/sys/mips/atheros/ar71xxreg.h
@@ -214,6 +214,10 @@
  */
 #define AR71XX_MAC0_BASE	0x19000000
 #define AR71XX_MAC1_BASE	0x1A000000
+/*
+ * All 5 PHYs accessible only through MAC0 register space
+ */
+#define AR71XX_MII_BASE		0x19000000
 
 #define		AR71XX_MAC_CFG1			0x00
 #define			MAC_CFG1_SOFT_RESET		(1 << 31)
diff --git a/sys/mips/atheros/if_arge.c b/sys/mips/atheros/if_arge.c
index 6263ef1601ff..6d77edca1a63 100644
--- a/sys/mips/atheros/if_arge.c
+++ b/sys/mips/atheros/if_arge.c
@@ -162,6 +162,11 @@ DRIVER_MODULE(miibus, arge, miibus_driver, miibus_devclass, 0, 0);
  */
 extern uint32_t ar711_base_mac[ETHER_ADDR_LEN];
 
+static struct mtx miibus_mtx;
+
+MTX_SYSINIT(miibus_mtx, &miibus_mtx, "arge mii lock", MTX_SPIN);
+
+
 /*
  * Flushes all 
  */
@@ -488,23 +493,27 @@ arge_miibus_readreg(device_t dev, int phy, int reg)
 	if (phy != sc->arge_phy_num)
 		return (0);
 
-	ARGE_WRITE(sc, AR71XX_MAC_MII_CMD, MAC_MII_CMD_WRITE);
-	ARGE_WRITE(sc, AR71XX_MAC_MII_ADDR, addr);
-	ARGE_WRITE(sc, AR71XX_MAC_MII_CMD, MAC_MII_CMD_READ);
+	mtx_lock(&miibus_mtx);
+	ARGE_MII_WRITE(AR71XX_MAC_MII_CMD, MAC_MII_CMD_WRITE);
+	ARGE_MII_WRITE(AR71XX_MAC_MII_ADDR, addr);
+	ARGE_MII_WRITE(AR71XX_MAC_MII_CMD, MAC_MII_CMD_READ);
 
 	i = ARGE_MII_TIMEOUT;
-	while ((ARGE_READ(sc, AR71XX_MAC_MII_INDICATOR) & 
+	while ((ARGE_MII_READ(AR71XX_MAC_MII_INDICATOR) & 
 	    MAC_MII_INDICATOR_BUSY) && (i--))
 		DELAY(5);
 
 	if (i < 0) {
+		mtx_unlock(&miibus_mtx);
 		dprintf("%s timedout\n", __func__);
 		/* XXX: return ERRNO istead? */
 		return (-1);
 	}
 
-	result = ARGE_READ(sc, AR71XX_MAC_MII_STATUS) & MAC_MII_STATUS_MASK;
-	ARGE_WRITE(sc, AR71XX_MAC_MII_CMD, MAC_MII_CMD_WRITE);
+	result = ARGE_MII_READ(AR71XX_MAC_MII_STATUS) & MAC_MII_STATUS_MASK;
+	ARGE_MII_WRITE(AR71XX_MAC_MII_CMD, MAC_MII_CMD_WRITE);
+	mtx_unlock(&miibus_mtx);
+
 	dprintf("%s: phy=%d, reg=%02x, value[%08x]=%04x\n", __func__, 
 		 phy, reg, addr, result);
 
@@ -519,17 +528,24 @@ arge_miibus_writereg(device_t dev, int phy, int reg, int data)
 	uint32_t addr = 
 	    (phy << MAC_MII_PHY_ADDR_SHIFT) | (reg & MAC_MII_REG_MASK);
 
+
+	if (phy != sc->arge_phy_num)
+		return (-1);
+
 	dprintf("%s: phy=%d, reg=%02x, value=%04x\n", __func__, 
 	    phy, reg, data);
 
-	ARGE_WRITE(sc, AR71XX_MAC_MII_ADDR, addr);
-	ARGE_WRITE(sc, AR71XX_MAC_MII_CONTROL, data);
+	mtx_lock(&miibus_mtx);
+	ARGE_MII_WRITE(AR71XX_MAC_MII_ADDR, addr);
+	ARGE_MII_WRITE(AR71XX_MAC_MII_CONTROL, data);
 
 	i = ARGE_MII_TIMEOUT;
-	while ((ARGE_READ(sc, AR71XX_MAC_MII_INDICATOR) & 
+	while ((ARGE_MII_READ(AR71XX_MAC_MII_INDICATOR) & 
 	    MAC_MII_INDICATOR_BUSY) && (i--))
 		DELAY(5);
 
+	mtx_unlock(&miibus_mtx);
+
 	if (i < 0) {
 		dprintf("%s timedout\n", __func__);
 		/* XXX: return ERRNO istead? */
diff --git a/sys/mips/atheros/if_argevar.h b/sys/mips/atheros/if_argevar.h
index aec2cf46af34..40962ce58f11 100644
--- a/sys/mips/atheros/if_argevar.h
+++ b/sys/mips/atheros/if_argevar.h
@@ -64,6 +64,16 @@
 #define ARGE_CLEAR_BITS(sc, reg, bits)	\
 	ARGE_WRITE(sc, reg, ARGE_READ(sc, (reg)) & ~(bits))
 
+/*
+ * MII registers access macros
+ */
+#define ARGE_MII_READ(reg) \
+        *((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((AR71XX_MII_BASE + reg)))
+
+#define ARGE_MII_WRITE(reg, val) \
+        *((volatile uint32_t *)MIPS_PHYS_TO_KSEG1((AR71XX_MII_BASE + reg))) = (val)
+
+
 #define ARGE_DESC_EMPTY		(1 << 31)
 #define ARGE_DESC_MORE		(1 << 24)
 #define ARGE_DESC_SIZE_MASK	((1 << 12) - 1)