diff --git a/drivers/arm/css/scp/css_pm_scmi.c b/drivers/arm/css/scp/css_pm_scmi.c
index 5de2604..8327865 100644
--- a/drivers/arm/css/scp/css_pm_scmi.c
+++ b/drivers/arm/css/scp/css_pm_scmi.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2022, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -11,6 +11,7 @@
 #include <common/debug.h>
 #include <drivers/arm/css/css_scp.h>
 #include <drivers/arm/css/scmi.h>
+#include <lib/mmio.h>
 #include <plat/arm/common/plat_arm.h>
 #include <plat/arm/css/common/css_pm.h>
 #include <plat/common/platform.h>
@@ -291,6 +292,13 @@
 	int ret;
 
 	/*
+	 * Before issuing the system power down command, set the trusted mailbox
+	 * to 0. This will ensure that in the case of a warm/cold reset, the
+	 * primary CPU executes from the cold boot sequence.
+	 */
+	mmio_write_64(PLAT_ARM_TRUSTED_MAILBOX_BASE, 0U);
+
+	/*
 	 * Disable GIC CPU interface to prevent pending interrupt from waking
 	 * up the AP from WFI.
 	 */