Index: sys/arm/arm/pl310.c
===================================================================
--- sys/arm/arm/pl310.c
+++ sys/arm/arm/pl310.c
@@ -529,7 +529,8 @@
 	cpufuncs.cf_l2cache_wbinv_range = pl310_wbinv_range;
 	cpufuncs.cf_l2cache_inv_range = pl310_inv_range;
 	cpufuncs.cf_l2cache_wb_range = pl310_wb_range;
-	cpufuncs.cf_l2cache_drain_writebuf = pl310_drain_writebuf;
+	if (cpufuncs.cf_l2cache_drain_writebuf == cpufunc_nullop)
+		cpufuncs.cf_l2cache_drain_writebuf = pl310_drain_writebuf;
 
 	return (0);
 }
Index: sys/arm/mv/mv_common.c
===================================================================
--- sys/arm/mv/mv_common.c
+++ sys/arm/mv/mv_common.c
@@ -115,6 +115,8 @@
 static void decode_win_sdhci_dump(u_long);
 static void decode_win_pcie_dump(u_long);
 
+static void l2cache_drainwb_coherent(void);
+
 static int fdt_get_ranges(const char *, void *, int, int *, int *);
 #ifdef SOC_MV_ARMADA38X
 int gic_decode_fdt(phandle_t iparent, pcell_t *intr, int *interrupt,
@@ -128,6 +130,7 @@
 static int cpu_wins_no = 0;
 static int eth_port = 0;
 static int usb_port = 0;
+static boolean_t plat_dma_coherent = false;
 
 static struct decode_win cpu_win_tbl[MAX_CPU_WIN];
 
@@ -568,11 +571,17 @@
 SYSINIT(mv_enter_debugger, SI_SUB_CPU, SI_ORDER_ANY, mv_enter_debugger, NULL);
 #endif
 
+static void l2cache_drainwb_coherent(void)
+{
+	/* No-op for coherent platforms */
+}
+
 int
 soc_decode_win(void)
 {
 	uint32_t dev, rev;
 	int mask, err;
+	phandle_t node;
 
 	mask = 0;
 	TUNABLE_INT_FETCH("hw.pm-disable-mask", &mask);
@@ -587,6 +596,13 @@
 	/* Retrieve our ID: some windows facilities vary between SoC models */
 	soc_id(&dev, &rev);
 
+	/* Retrieve information about DMA coherency from device tree */
+	node = OF_finddevice("/soc");
+	if ((node > 0) && OF_hasprop(node, "dma-coherent")) {
+		plat_dma_coherent = true;
+		cpufuncs.cf_l2cache_drain_writebuf = l2cache_drainwb_coherent;
+	}
+
 #ifdef SOC_MV_ARMADAXP
 	if ((err = decode_win_sdram_fixup()) != 0)
 		return(err);
@@ -1064,7 +1080,7 @@
 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 +1088,14 @@
 	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 (plat_dma_coherent)
+		attr |= 0x10;
+
+	return (attr);
 }
 
 uint32_t