Index: head/sys/arm/mv/armada38x/armada38x.c
===================================================================
--- head/sys/arm/mv/armada38x/armada38x.c
+++ head/sys/arm/mv/armada38x/armada38x.c
@@ -32,10 +32,14 @@
 #include <sys/systm.h>
 #include <sys/bus.h>
 
+#include <machine/fdt.h>
+
 #include <arm/mv/mvwin.h>
 #include <arm/mv/mvreg.h>
 #include <arm/mv/mvvar.h>
 
+int armada38x_win_set_iosync_barrier(void);
+
 uint32_t
 get_tclk(void)
 {
@@ -52,3 +56,25 @@
 	else
 		return (TCLK_200MHZ);
 }
+
+int
+armada38x_win_set_iosync_barrier(void)
+{
+	bus_space_handle_t vaddr_iowind;
+	int rv;
+
+	rv = bus_space_map(fdtbus_bs_tag, (bus_addr_t)MV_MBUS_BRIDGE_BASE,
+	    MV_CPU_SUBSYS_REGS_LEN, 0, &vaddr_iowind);
+	if (rv != 0)
+		return (rv);
+
+	/* Set Sync Barrier flags for all Mbus internal units */
+	bus_space_write_4(fdtbus_bs_tag, vaddr_iowind, MV_SYNC_BARRIER_CTRL,
+	    MV_SYNC_BARRIER_CTRL_ALL);
+
+	bus_space_barrier(fdtbus_bs_tag, vaddr_iowind, 0,
+	    MV_CPU_SUBSYS_REGS_LEN, BUS_SPACE_BARRIER_WRITE);
+	bus_space_unmap(fdtbus_bs_tag, vaddr_iowind, MV_CPU_SUBSYS_REGS_LEN);
+
+	return (rv);
+}
Index: head/sys/arm/mv/mv_machdep.c
===================================================================
--- head/sys/arm/mv/mv_machdep.c
+++ head/sys/arm/mv/mv_machdep.c
@@ -66,6 +66,9 @@
 void armadaxp_init_coher_fabric(void);
 void armadaxp_l2_init(void);
 #endif
+#if defined(SOC_MV_ARMADA38X)
+int armada38x_win_set_iosync_barrier(void);
+#endif
 
 #define MPP_PIN_MAX		68
 #define MPP_PIN_CELLS		2
@@ -249,6 +252,12 @@
 #endif
 	armadaxp_l2_init();
 #endif
+
+#if defined(SOC_MV_ARMADA38X)
+	/* Set IO Sync Barrier bit for all Mbus devices */
+	if (armada38x_win_set_iosync_barrier() != 0)
+		printf("WARNING: could not map CPU Subsystem registers\n");
+#endif
 }
 
 #define FDT_DEVMAP_MAX	(MV_WIN_CPU_MAX + 2)
Index: head/sys/arm/mv/mvwin.h
===================================================================
--- head/sys/arm/mv/mvwin.h
+++ head/sys/arm/mv/mvwin.h
@@ -305,6 +305,16 @@
 #define	MV_WIN_SATA_BASE(n)		(0x10 * (n) + 0x34)
 #define	MV_WIN_SATA_MAX			4
 
+#if defined(SOC_MV_ARMADA38X)
+#define	MV_BOOTROM_MEM_ADDR	0xFFF00000
+#define	MV_BOOTROM_WIN_SIZE	0xF
+#define	MV_CPU_SUBSYS_REGS_LEN	0x100
+
+/* Internal Units Sync Barrier Control Register */
+#define	MV_SYNC_BARRIER_CTRL		0x84
+#define	MV_SYNC_BARRIER_CTRL_ALL	0xFFFF
+#endif
+
 #define WIN_REG_IDX_RD(pre,reg,off,base)					\
 	static __inline uint32_t						\
 	pre ## _ ## reg ## _read(int i)						\