juno: Add a check to verify BL2 to BL31 plat. param

This concerns only debug builds. In BL2, we now pass a special value
to BL3-1 through x1. In BL3-1, we check that we receive the correct
value. This ensures that any platform set value is correctly passed
from BL2 to BL3-1.

Change-Id: Icb94d0e99ca445dcbe574a7d5e291659bba2209e

plat/juno/bl2_plat_setup.c

@@ -142,6 +142,10 @@ bl31_params_t *bl2_plat_get_bl31_params(void)
  ******************************************************************************/
 struct entry_point_info *bl2_plat_get_bl31_ep_info(void)
 {
+#if DEBUG
+	bl31_params_mem.bl31_ep_info.args.arg1 = JUNO_BL31_PLAT_PARAM_VAL;
+#endif
+
 	return &bl31_params_mem.bl31_ep_info;
 }
 

plat/juno/bl31_plat_setup.c

@@ -111,12 +111,17 @@ void bl31_early_platform_setup(bl31_params_t *from_bl2,
 
 	/*
 	 * Check params passed from BL2 should not be NULL,
-	 * We are not checking plat_params_from_bl2 as NULL as we are not
-	 * using it on Juno
 	 */
 	assert(from_bl2 != NULL);
 	assert(from_bl2->h.type == PARAM_BL31);
 	assert(from_bl2->h.version >= VERSION_1);
+	/*
+	 * In debug builds, we pass a special value in 'plat_params_from_bl2'
+	 * to verify platform parameters from BL2 to BL3-1.
+	 * In release builds, it's not used.
+	 */
+	assert(((unsigned long long)plat_params_from_bl2) ==
+		JUNO_BL31_PLAT_PARAM_VAL);
 
 	/*
 	 * Copy BL3-2 and BL3-3 entry point information.

plat/juno/juno_def.h

@@ -31,6 +31,9 @@
 #ifndef __JUNO_DEF_H__
 #define __JUNO_DEF_H__
 
+/* Special value used to verify platform parameters from BL2 to BL3-1 */
+#define JUNO_BL31_PLAT_PARAM_VAL        0x0f1e2d3c4b5a6978ULL
+
 /*******************************************************************************
  * Juno memory map related constants
  ******************************************************************************/