diff --git a/sys/mips/atheros/ar71xx_chip.c b/sys/mips/atheros/ar71xx_chip.c
index 18181aef169f..f83f70317dd4 100644
--- a/sys/mips/atheros/ar71xx_chip.c
+++ b/sys/mips/atheros/ar71xx_chip.c
@@ -176,6 +176,50 @@ ar71xx_chip_set_mii_speed(uint32_t unit, uint32_t speed)
 	ATH_WRITE_REG(reg, val);
 }
 
+void
+ar71xx_chip_set_mii_if(uint32_t unit, uint32_t mii_mode)
+{
+	uint32_t val, reg, mii_if;
+
+	switch (unit) {
+	case 0:
+		reg = AR71XX_MII0_CTRL;
+		if (mii_mode == AR71XX_MII_MODE_GMII)
+			mii_if = MII0_CTRL_IF_GMII;
+		else if (mii_mode == AR71XX_MII_MODE_MII)
+			mii_if = MII0_CTRL_IF_MII;
+		else if (mii_mode == AR71XX_MII_MODE_RGMII)
+			mii_if = MII0_CTRL_IF_RGMII;
+		else if (mii_mode == AR71XX_MII_MODE_RMII)
+			mii_if = MII0_CTRL_IF_RMII;
+		else
+			printf("%s: invalid MII mode (%d) for unit %d\n",
+			    __func__, mii_mode, unit);
+			return;
+		break;
+	case 1:
+		reg = AR71XX_MII1_CTRL;
+		if (mii_mode == AR71XX_MII_MODE_RGMII)
+			mii_if = MII1_CTRL_IF_RGMII;
+		if (mii_mode == AR71XX_MII_MODE_RMII)
+			mii_if = MII1_CTRL_IF_RMII;
+		else
+			printf("%s: invalid MII mode (%d) for unit %d\n",
+			    __func__, mii_mode, unit);
+			return;
+		break;
+	default:
+		printf("%s: invalid MII unit set for arge unit: %d\n",
+		    __func__, unit);
+		return;
+	}
+
+	val = ATH_READ_REG(reg);
+	val &= ~(MII_CTRL_IF_MASK << MII_CTRL_IF_SHIFT);
+	val |= (mii_if & MII_CTRL_IF_MASK) << MII_CTRL_IF_SHIFT;
+	ATH_WRITE_REG(reg, val);
+}
+
 /* Speed is either 10, 100 or 1000 */
 static void
 ar71xx_chip_set_pll_ge(int unit, int speed)
@@ -197,6 +241,7 @@ ar71xx_chip_set_pll_ge(int unit, int speed)
 		    __func__, unit, speed);
 		return;
 	}
+
 	switch (unit) {
 	case 0:
 		ar71xx_write_pll(AR71XX_PLL_SEC_CONFIG,
@@ -213,6 +258,12 @@ ar71xx_chip_set_pll_ge(int unit, int speed)
 		    __func__, unit);
 		return;
 	}
+
+	/*
+	 * AR71xx and AR913x require this; AR724x doesn't require
+	 * an MII clock change at all.
+	 */
+	ar71xx_chip_set_mii_speed(unit, speed);
 }
 
 static void
@@ -278,6 +329,7 @@ struct ar71xx_cpu_def ar71xx_chip_def = {
 	&ar71xx_chip_device_stopped,
 	&ar71xx_chip_set_pll_ge,
 	&ar71xx_chip_set_mii_speed,
+	&ar71xx_chip_set_mii_if,
 	&ar71xx_chip_ddr_flush_ge,
 	&ar71xx_chip_get_eth_pll,
 	&ar71xx_chip_ddr_flush_ip2,
diff --git a/sys/mips/atheros/ar71xx_chip.h b/sys/mips/atheros/ar71xx_chip.h
index 4869f3110f6e..a9b4804299d1 100644
--- a/sys/mips/atheros/ar71xx_chip.h
+++ b/sys/mips/atheros/ar71xx_chip.h
@@ -31,5 +31,6 @@
 
 extern struct ar71xx_cpu_def ar71xx_chip_def;
 extern void ar71xx_chip_set_mii_speed(uint32_t unit, uint32_t speed);
+extern void ar71xx_chip_set_mii_if(uint32_t unit, uint32_t mii_if);
 
 #endif
diff --git a/sys/mips/atheros/ar71xx_cpudef.h b/sys/mips/atheros/ar71xx_cpudef.h
index ce472f51a2e4..1fe2e096ce63 100644
--- a/sys/mips/atheros/ar71xx_cpudef.h
+++ b/sys/mips/atheros/ar71xx_cpudef.h
@@ -37,6 +37,7 @@ struct ar71xx_cpu_def {
 	int (* ar71xx_chip_device_stopped) (uint32_t);
 	void (* ar71xx_chip_set_pll_ge) (int, int);
 	void (* ar71xx_chip_set_mii_speed) (uint32_t, uint32_t);
+	void (* ar71xx_chip_set_mii_if) (uint32_t, ar71xx_mii_mode);
 	void (* ar71xx_chip_ddr_flush_ge) (int);
 	uint32_t (* ar71xx_chip_get_eth_pll) (unsigned int, int);
 
@@ -90,6 +91,11 @@ static inline void ar71xx_device_set_mii_speed(int unit, int speed)
 	ar71xx_cpu_ops->ar71xx_chip_set_mii_speed(unit, speed);
 }
 
+static inline void ar71xx_device_set_mii_if(int unit, ar71xx_mii_mode mii_cfg)
+{
+	ar71xx_cpu_ops->ar71xx_chip_set_mii_if(unit, mii_cfg);
+}
+
 static inline void ar71xx_device_flush_ddr_ge(int unit)
 {
 	ar71xx_cpu_ops->ar71xx_chip_ddr_flush_ge(unit);
diff --git a/sys/mips/atheros/ar724x_chip.c b/sys/mips/atheros/ar724x_chip.c
index d56a26c73da7..d15529765d1b 100644
--- a/sys/mips/atheros/ar724x_chip.c
+++ b/sys/mips/atheros/ar724x_chip.c
@@ -56,6 +56,7 @@ __FBSDID("$FreeBSD$");
 
 #include <mips/atheros/ar71xx_cpudef.h>
 #include <mips/atheros/ar71xx_setup.h>
+#include <mips/atheros/ar71xx_chip.h>
 #include <mips/atheros/ar724x_chip.h>
 
 #include <mips/sentry5/s5reg.h>
@@ -130,6 +131,13 @@ ar724x_chip_set_mii_speed(uint32_t unit, uint32_t speed)
 	return;
 }
 
+/*
+ * XXX TODO: set the PLL for arge0 only on AR7242.
+ * The PLL/clock requirements are different.
+ *
+ * Otherwise, it's a NULL function for AR7240, AR7241 and
+ * AR7242 arge1.
+ */
 static void
 ar724x_chip_set_pll_ge(int unit, int speed)
 {
@@ -229,6 +237,7 @@ struct ar71xx_cpu_def ar724x_chip_def = {
 	&ar724x_chip_device_stopped,
 	&ar724x_chip_set_pll_ge,
 	&ar724x_chip_set_mii_speed,
+	&ar71xx_chip_set_mii_if,
 	&ar724x_chip_ddr_flush_ge,
 	&ar724x_chip_get_eth_pll,
 	&ar724x_chip_ddr_flush_ip2,
diff --git a/sys/mips/atheros/ar91xx_chip.c b/sys/mips/atheros/ar91xx_chip.c
index c88518f1cb22..d2fec2f326da 100644
--- a/sys/mips/atheros/ar91xx_chip.c
+++ b/sys/mips/atheros/ar91xx_chip.c
@@ -147,6 +147,7 @@ ar91xx_chip_set_pll_ge(int unit, int speed)
 		    __func__, unit);
 		return;
 	}
+	ar71xx_chip_set_mii_speed(unit, speed);
 }
 
 static void
@@ -211,6 +212,7 @@ struct ar71xx_cpu_def ar91xx_chip_def = {
 	&ar91xx_chip_device_stopped,
 	&ar91xx_chip_set_pll_ge,
 	&ar71xx_chip_set_mii_speed,
+	&ar71xx_chip_set_mii_if,
 	&ar91xx_chip_ddr_flush_ge,
 	&ar91xx_chip_get_eth_pll,
 	&ar91xx_chip_ddr_flush_ip2,