intel: clear 'PLAT_SEC_ENTRY' in early platform setup

Ensure 'PLAT_SEC_ENTRY' is cleared during early platform
setup. This is to prevent the slave CPU cores jump to the stale
entry point after warm reset when using U-Boot SPL as first
stage boot loader.
Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
Change-Id: I3294ce2f74aa691d0cf311fa30f27f9d4fb8800a

plat/intel/soc/agilex/bl31_plat_setup.c

 /*
- * Copyright (c) 2019, ARM Limited and Contributors. All rights reserved.
- * Copyright (c) 2019, Intel Corporation. All rights reserved.
+ * Copyright (c) 2019-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2020, Intel Corporation. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -39,6 +39,8 @@ void bl31_early_platform_setup2(u_register_t arg0, u_register_t arg1,
 {
 	static console_t console;
 
+	mmio_write_64(PLAT_SEC_ENTRY, PLAT_SEC_WARM_ENTRY);
+
 	console_16550_register(PLAT_UART0_BASE, PLAT_UART_CLOCK, PLAT_BAUDRATE,
 		&console);
 	/*

plat/intel/soc/common/include/platform_def.h

@@ -134,6 +134,8 @@
 #define PLAT_CPUID_RELEASE	(BL_DATA_LIMIT - 16)
 #define PLAT_SEC_ENTRY		(BL_DATA_LIMIT - 8)
 
+#define PLAT_SEC_WARM_ENTRY	0
+
 /*******************************************************************************
  * Platform specific page table and MMU setup constants
  ******************************************************************************/

plat/intel/soc/stratix10/bl31_plat_setup.c

 /*
- * Copyright (c) 2019, ARM Limited and Contributors. All rights reserved.
- * Copyright (c) 2019, Intel Corporation. All rights reserved.
+ * Copyright (c) 2019-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2020, Intel Corporation. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -47,6 +47,8 @@ void bl31_early_platform_setup2(u_register_t arg0, u_register_t arg1,
 {
 	static console_t console;
 
+	mmio_write_64(PLAT_SEC_ENTRY, PLAT_SEC_WARM_ENTRY);
+
 	console_16550_register(PLAT_UART0_BASE, PLAT_UART_CLOCK, PLAT_BAUDRATE,
 		&console);
 	/*