diff --git a/plat/st/stm32mp1/stm32mp1_security.c b/plat/st/stm32mp1/stm32mp1_security.c
index 0cdf305..e783c14 100644
--- a/plat/st/stm32mp1/stm32mp1_security.c
+++ b/plat/st/stm32mp1/stm32mp1_security.c
@@ -16,6 +16,46 @@
 #include "platform_def.h"
 
 /*******************************************************************************
+ * Initialize the TrustZone Controller. Configure Region 0 with Secure RW access
+ * and allow Non-Secure masters full access.
+ ******************************************************************************/
+static void init_tzc400(void)
+{
+	unsigned long long region_base, region_top;
+	unsigned long long ddr_base = STM32MP1_DDR_BASE;
+	unsigned long long ddr_size = (unsigned long long)dt_get_ddr_size();
+
+	tzc400_init(STM32MP1_TZC_BASE);
+
+	tzc400_disable_filters();
+
+	/* Region 1 set to cover all DRAM at 0xC000_0000. Apply the
+	 * same configuration to all filters in the TZC.
+	 */
+	region_base = ddr_base;
+	region_top = ddr_base + (ddr_size - 1U);
+	tzc400_configure_region(STM32MP1_FILTER_BIT_ALL, 1,
+			region_base,
+			region_top,
+			TZC_REGION_S_RDWR,
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_A7_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_GPU_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_LCD_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_MDMA_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_DMA_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_USB_HOST_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_USB_OTG_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_SDMMC_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_ETH_ID) |
+			TZC_REGION_ACCESS_RDWR(STM32MP1_TZC_DAP_ID));
+
+	/* Raise an exception if a NS device tries to access secure memory */
+	tzc400_set_action(TZC_ACTION_ERR);
+
+	tzc400_enable_filters();
+}
+
+/*******************************************************************************
  * Initialize the TrustZone Controller.
  * Early initialization create only one region with full access to secure.
  * This setting is used before and during DDR initialization.
@@ -76,3 +116,12 @@
 {
 	early_init_tzc400();
 }
+
+/*******************************************************************************
+ * Initialize the secure environment. At this moment only the TrustZone
+ * Controller is initialized.
+ ******************************************************************************/
+void stm32mp1_security_setup(void)
+{
+	init_tzc400();
+}