diff --git a/plat/st/stm32mp1/include/stm32mp1_private.h b/plat/st/stm32mp1/include/stm32mp1_private.h
index e38fca01..2da64ac 100644
--- a/plat/st/stm32mp1/include/stm32mp1_private.h
+++ b/plat/st/stm32mp1/include/stm32mp1_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -21,4 +21,5 @@
 void stm32mp1_syscfg_enable_io_compensation(void);
 void stm32mp1_syscfg_disable_io_compensation(void);
 
+uint32_t stm32mp_get_ddr_ns_size(void);
 #endif /* STM32MP1_PRIVATE_H */
diff --git a/plat/st/stm32mp1/stm32mp1_def.h b/plat/st/stm32mp1/stm32mp1_def.h
index 5dc5206..fc776ae 100644
--- a/plat/st/stm32mp1/stm32mp1_def.h
+++ b/plat/st/stm32mp1/stm32mp1_def.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -62,6 +62,9 @@
 #ifdef AARCH32_SP_OPTEE
 #define STM32MP_DDR_S_SIZE		U(0x01E00000)	/* 30 MB */
 #define STM32MP_DDR_SHMEM_SIZE		U(0x00200000)	/* 2 MB */
+#else
+#define STM32MP_DDR_S_SIZE		U(0)
+#define STM32MP_DDR_SHMEM_SIZE		U(0)
 #endif
 
 /* DDR power initializations */
diff --git a/plat/st/stm32mp1/stm32mp1_private.c b/plat/st/stm32mp1/stm32mp1_private.c
index e2dcd2a..ac45195 100644
--- a/plat/st/stm32mp1/stm32mp1_private.c
+++ b/plat/st/stm32mp1/stm32mp1_private.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -365,3 +365,24 @@
 	return BSEC_OK;
 }
 #endif
+
+/* Get the non-secure DDR size */
+uint32_t stm32mp_get_ddr_ns_size(void)
+{
+	static uint32_t ddr_ns_size;
+	uint32_t ddr_size;
+
+	if (ddr_ns_size != 0U) {
+		return ddr_ns_size;
+	}
+
+	ddr_size = dt_get_ddr_size();
+	if ((ddr_size <= (STM32MP_DDR_S_SIZE + STM32MP_DDR_SHMEM_SIZE)) ||
+	    (ddr_size > STM32MP_DDR_MAX_SIZE)) {
+		panic();
+	}
+
+	ddr_ns_size = ddr_size - (STM32MP_DDR_S_SIZE + STM32MP_DDR_SHMEM_SIZE);
+
+	return ddr_ns_size;
+}