Index: head/sys/arm/mv/mv_common.c
===================================================================
--- head/sys/arm/mv/mv_common.c
+++ head/sys/arm/mv/mv_common.c
@@ -128,6 +128,7 @@
 static int cpu_wins_no = 0;
 static int eth_port = 0;
 static int usb_port = 0;
+static boolean_t platform_io_coherent = false;
 
 static struct decode_win cpu_win_tbl[MAX_CPU_WIN];
 
@@ -1064,7 +1065,7 @@
 uint32_t
 ddr_attr(int i)
 {
-	uint32_t dev, rev;
+	uint32_t dev, rev, attr;
 
 	soc_id(&dev, &rev);
 	if (dev == MV_DEV_88RC8180)
@@ -1072,10 +1073,14 @@
 	if (dev == MV_DEV_88F6781)
 		return (0);
 
-	return (i == 0 ? 0xe :
+	attr = (i == 0 ? 0xe :
 	    (i == 1 ? 0xd :
 	    (i == 2 ? 0xb :
 	    (i == 3 ? 0x7 : 0xff))));
+	if (platform_io_coherent)
+		attr |= 0x10;
+
+	return (attr);
 }
 
 uint32_t
@@ -2478,6 +2483,10 @@
 	node = OF_finddevice("/");
 	if (node == -1)
 		panic("fdt_win_setup: no root node");
+
+	/* Allow for coherent transactions on the A38x MBUS */
+	if (ofw_bus_node_is_compatible(node, "marvell,armada380"))
+		platform_io_coherent = true;
 
 	/*
 	 * Traverse through all children of root and simple-bus nodes.
Index: head/sys/arm/mv/mv_machdep.c
===================================================================
--- head/sys/arm/mv/mv_machdep.c
+++ head/sys/arm/mv/mv_machdep.c
@@ -46,10 +46,13 @@
 #include <sys/systm.h>
 #include <sys/bus.h>
 #include <sys/devmap.h>
+#include <sys/kernel.h>
 
 #include <vm/vm.h>
 #include <vm/pmap.h>
 
+#include <arm/arm/nexusvar.h>
+
 #include <machine/bus.h>
 #include <machine/fdt.h>
 #include <machine/machdep.h>
@@ -86,6 +89,39 @@
 #define MPP_PINS_PER_REG	8
 #define MPP_SEL(pin,func)	(((func) & 0xf) <<		\
     (((pin) % MPP_PINS_PER_REG) * 4))
+
+static void
+mv_busdma_tag_init(void *arg __unused)
+{
+	phandle_t node;
+	bus_dma_tag_t dmat;
+
+	/*
+	 * If this platform has coherent DMA, create the parent DMA tag to pass
+	 * down the coherent flag to all busses and devices on the platform,
+	 * otherwise return without doing anything. By default create tag
+	 * for all A38x-based platforms only.
+	 */
+	if ((node = OF_finddevice("/")) == -1)
+		return;
+	if (ofw_bus_node_is_compatible(node, "marvell,armada380") == 0)
+		return;
+
+	bus_dma_tag_create(NULL,	/* No parent tag */
+	    1, 0,			/* alignment, bounds */
+	    BUS_SPACE_MAXADDR,		/* lowaddr */
+	    BUS_SPACE_MAXADDR,		/* highaddr */
+	    NULL, NULL,			/* filter, filterarg */
+	    BUS_SPACE_MAXSIZE,		/* maxsize */
+	    BUS_SPACE_UNRESTRICTED,	/* nsegments */
+	    BUS_SPACE_MAXSIZE,		/* maxsegsize */
+	    BUS_DMA_COHERENT,		/* flags */
+	    NULL, NULL,			/* lockfunc, lockarg */
+	    &dmat);
+
+	nexus_set_dma_tag(dmat);
+}
+SYSINIT(mv_busdma_tag, SI_SUB_DRIVERS, SI_ORDER_ANY, mv_busdma_tag_init, NULL);
 
 static int
 platform_mpp_init(void)