diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index 067b830..d1ad31d 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -194,6 +194,8 @@
 DEFINE_SYSOP_FUNC(sev)
 DEFINE_SYSOP_TYPE_FUNC(dsb, sy)
 DEFINE_SYSOP_TYPE_FUNC(dmb, sy)
+DEFINE_SYSOP_TYPE_FUNC(dmb, st)
+DEFINE_SYSOP_TYPE_FUNC(dmb, ld)
 DEFINE_SYSOP_TYPE_FUNC(dsb, ish)
 DEFINE_SYSOP_TYPE_FUNC(dmb, ish)
 DEFINE_SYSOP_FUNC(isb)
diff --git a/include/plat/arm/common/arm_def.h b/include/plat/arm/common/arm_def.h
index b2db616..6049171 100644
--- a/include/plat/arm/common/arm_def.h
+++ b/include/plat/arm/common/arm_def.h
@@ -151,14 +151,10 @@
 #define ARM_G0_IRQS			ARM_IRQ_SEC_SGI_0,		\
 					ARM_IRQ_SEC_SGI_6
 
-#define ARM_SHARED_RAM_ATTR		((PLAT_ARM_SHARED_RAM_CACHED ?	\
-						MT_MEMORY : MT_DEVICE)	\
-						| MT_RW | MT_SECURE)
-
 #define ARM_MAP_SHARED_RAM		MAP_REGION_FLAT(		\
 						ARM_SHARED_RAM_BASE,	\
 						ARM_SHARED_RAM_SIZE,	\
-						ARM_SHARED_RAM_ATTR)
+						MT_DEVICE | MT_RW | MT_SECURE)
 
 #define ARM_MAP_NS_DRAM1		MAP_REGION_FLAT(		\
 						ARM_NS_DRAM1_BASE,	\
diff --git a/include/plat/arm/css/common/css_def.h b/include/plat/arm/css/common/css_def.h
index c900278..7a5d193 100644
--- a/include/plat/arm/css/common/css_def.h
+++ b/include/plat/arm/css/common/css_def.h
@@ -37,8 +37,6 @@
 /*************************************************************************
  * Definitions common to all ARM Compute SubSystems (CSS)
  *************************************************************************/
-#define MHU_PAYLOAD_CACHED		0
-
 #define NSROM_BASE			0x1f000000
 #define NSROM_SIZE			0x00001000
 
@@ -118,8 +116,6 @@
 
 #define SCP_BL2U_BASE			BL31_BASE
 
-#define PLAT_ARM_SHARED_RAM_CACHED	MHU_PAYLOAD_CACHED
-
 /* Load address of Non-Secure Image for CSS platform ports */
 #define PLAT_ARM_NS_IMAGE_OFFSET	0xE0000000
 
diff --git a/plat/arm/board/fvp/include/platform_def.h b/plat/arm/board/fvp/include/platform_def.h
index 0d671dc..9b85342 100644
--- a/plat/arm/board/fvp/include/platform_def.h
+++ b/plat/arm/board/fvp/include/platform_def.h
@@ -64,8 +64,6 @@
 
 #define PLAT_ARM_DRAM2_SIZE		MAKE_ULL(0x780000000)
 
-#define PLAT_ARM_SHARED_RAM_CACHED	1
-
 /*
  * Load address of BL33 for this platform port
  */
diff --git a/plat/arm/common/arm_pm.c b/plat/arm/common/arm_pm.c
index 2ddc583..1e756a9 100644
--- a/plat/arm/common/arm_pm.c
+++ b/plat/arm/common/arm_pm.c
@@ -192,11 +192,6 @@
 	assert((PLAT_ARM_TRUSTED_MAILBOX_BASE >= ARM_SHARED_RAM_BASE) &&
 		((PLAT_ARM_TRUSTED_MAILBOX_BASE + sizeof(*mailbox)) <= \
 				(ARM_SHARED_RAM_BASE + ARM_SHARED_RAM_SIZE)));
-
-	/* Flush data cache if the mail box shared RAM is cached */
-#if PLAT_ARM_SHARED_RAM_CACHED
-	flush_dcache_range((uintptr_t) mailbox, sizeof(*mailbox));
-#endif
 }
 
 /*******************************************************************************
diff --git a/plat/arm/css/common/css_scp_bootloader.c b/plat/arm/css/common/css_scp_bootloader.c
index c01f42f..4367459 100644
--- a/plat/arm/css/common/css_scp_bootloader.c
+++ b/plat/arm/css/common/css_scp_bootloader.c
@@ -77,10 +77,10 @@
 
 static void scp_boot_message_send(size_t payload_size)
 {
-	/* Make sure payload can be seen by SCP */
-	if (MHU_PAYLOAD_CACHED)
-		flush_dcache_range(BOM_SHARED_MEM,
-				   sizeof(bom_cmd_t) + payload_size);
+	/* Ensure that any write to the BOM payload area is seen by SCP before
+	 * we write to the MHU register. If these 2 writes were reordered by
+	 * the CPU then SCP would read stale payload data */
+	dmbst();
 
 	/* Send command to SCP */
 	mhu_secure_message_send(BOM_MHU_SLOT_ID);
@@ -99,9 +99,10 @@
 		panic();
 	}
 
-	/* Make sure we see the reply from the SCP and not any stale data */
-	if (MHU_PAYLOAD_CACHED)
-		inv_dcache_range(BOM_SHARED_MEM, size);
+	/* Ensure that any read to the BOM payload area is done after reading
+	 * the MHU register. If these 2 reads were reordered then the CPU would
+	 * read invalid payload data */
+	dmbld();
 
 	return *(uint32_t *) BOM_SHARED_MEM;
 }
diff --git a/plat/arm/css/common/css_scpi.c b/plat/arm/css/common/css_scpi.c
index 0a4eafe..829a174 100644
--- a/plat/arm/css/common/css_scpi.c
+++ b/plat/arm/css/common/css_scpi.c
@@ -55,10 +55,10 @@
 
 static void scpi_secure_message_send(size_t payload_size)
 {
-	/* Make sure payload can be seen by SCP */
-	if (MHU_PAYLOAD_CACHED)
-		flush_dcache_range(SCPI_SHARED_MEM_AP_TO_SCP,
-				   sizeof(scpi_cmd_t) + payload_size);
+	/* Ensure that any write to the SCPI payload area is seen by SCP before
+	 * we write to the MHU register. If these 2 writes were reordered by
+	 * the CPU then SCP would read stale payload data */
+	dmbst();
 
 	mhu_secure_message_send(SCPI_MHU_SLOT_ID);
 }
@@ -78,9 +78,10 @@
 		panic();
 	}
 
-	/* Make sure we don't read stale data */
-	if (MHU_PAYLOAD_CACHED)
-		inv_dcache_range(SCPI_SHARED_MEM_SCP_TO_AP, sizeof(*cmd));
+	/* Ensure that any read to the SCPI payload area is done after reading
+	 * the MHU register. If these 2 reads were reordered then the CPU would
+	 * read invalid payload data */
+	dmbld();
 
 	memcpy(cmd, (void *) SCPI_SHARED_MEM_SCP_TO_AP, sizeof(*cmd));
 }