diff --git a/sys/dev/etherswitch/arswitch/arswitch_7240.c b/sys/dev/etherswitch/arswitch/arswitch_7240.c
index c4b6ba87c09b..32769f69bcc9 100644
--- a/sys/dev/etherswitch/arswitch/arswitch_7240.c
+++ b/sys/dev/etherswitch/arswitch/arswitch_7240.c
@@ -66,11 +66,6 @@
 
 /* XXX belongs in arswitch_7240_reg.h */
 
-#define	AR7240_REG_CPU_PORT		0x78
-#define		AR7240_MIRROR_PORT_MASK		0x000000f0
-#define		AR7240_MIRROR_PORT_S		4
-#define		AR7240_CPU_PORT_EN		0x00000100
-
 #define	AR7240_REG_TAG_PRIORITY		0x70
 
 /*
@@ -81,9 +76,8 @@ ar7240_hw_setup(struct arswitch_softc *sc)
 {
 
 	/* Enable CPU port; disable mirror port */
-	arswitch_writereg(sc->sc_dev, AR7240_REG_CPU_PORT,
-	    AR7240_CPU_PORT_EN |
-	    (15 << AR7240_MIRROR_PORT_S));
+	arswitch_writereg(sc->sc_dev, AR8X16_REG_CPU_PORT,
+	    AR8X16_CPU_PORT_EN | AR8X16_CPU_MIRROR_DIS);
 
 	/*
 	 * Let things settle; probing PHY4 doesn't seem reliable
diff --git a/sys/dev/etherswitch/arswitch/arswitchreg.h b/sys/dev/etherswitch/arswitch/arswitchreg.h
index 37175738d3cf..ad0b4d5a5d8d 100644
--- a/sys/dev/etherswitch/arswitch/arswitchreg.h
+++ b/sys/dev/etherswitch/arswitch/arswitchreg.h
@@ -122,6 +122,9 @@
 
 #define	AR8X16_REG_CPU_PORT		0x0078
 #define		AR8X16_MIRROR_PORT_SHIFT	4
+#define		AR8X16_MIRROR_PORT_MASK		(0xf << AR8X16_MIRROR_PORT_SHIFT)
+#define		AR8X16_CPU_MIRROR_PORT(_p)	((_p) << AR8X16_MIRROR_PORT_SHIFT)
+#define		AR8X16_CPU_MIRROR_DIS		AR8X16_CPU_MIRROR_PORT(0xf)
 #define		AR8X16_CPU_PORT_EN		(1 << 8)
 
 #define	AR8X16_REG_MIB_FUNC0		0x0080