Merge pull request #523 from jcastillo-arm/jc/genfw-791

ARM platforms: rationalise memory attributes of shared memory

1 files changed, 8 insertions, 7 deletions

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;
 }