4 files changed, 16 insertions, 21 deletions
diff --git a/plat/arm/board/fvp/include/platform_def.h b/plat/arm/board/fvp/include/platform_def.h
index 9c82cbfa..c5e3095b 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 2ddc5833..1e756a9e 100644
--- a/plat/arm/common/arm_pm.c
+++ b/plat/arm/common/arm_pm.c
@@ -192,11 +192,6 @@ void arm_program_trusted_mailbox(uintptr_t address)
 	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 8bfaa87c..d3f671e2 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_start(void)
 
 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 @@ static uint32_t scp_boot_message_wait(size_t size)
 		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 9e1f9738..02d573c9 100644
--- a/plat/arm/css/common/css_scpi.c
+++ b/plat/arm/css/common/css_scpi.c
@@ -56,10 +56,10 @@ static void scpi_secure_message_start(void)
 
 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);
 }
@@ -79,9 +79,10 @@ static void scpi_secure_message_receive(scpi_cmd_t *cmd)
 		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));
 }