feat(tc): add dummy TRNG support to be able to boot pVMs

pVMs on Android 14 has a platform requirement to support
SMCCC TRNG discovery. This implementation add a
dummy TRNG support to TC2.

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: Iae0ca546cadf48a6a404ae578c7ccf5a84d057c4

plat/arm/board/tc/platform.mk

@@ -222,6 +222,10 @@ ifeq (${MEASURED_BOOT},1)
     endif
 endif
 
+ifeq (${TRNG_SUPPORT},1)
+	BL31_SOURCES	+=	plat/arm/board/tc/tc_trng.c
+endif
+
 ifneq (${PLATFORM_TEST},)
     # Add this include as first, before arm_common.mk. This is necessary
     # because arm_common.mk builds Mbed TLS, and platform_test.mk can

plat/arm/board/tc/tc_trng.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2017-2024, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arm_acle.h>
+#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <lib/mmio.h>
+#include <lib/smccc.h>
+#include <lib/utils_def.h>
+#include <plat/common/platform.h>
+#include <platform_def.h>
+#include <services/trng_svc.h>
+#include <smccc_helpers.h>
+
+DEFINE_SVC_UUID2(_plat_trng_uuid,
+	0x23523c58, 0x7448, 0x4083, 0x9d, 0x16,
+	0xe3, 0xfa, 0xb9, 0xf1, 0x73, 0xbc
+);
+uuid_t plat_trng_uuid;
+
+/* Dummy implementation */
+bool plat_get_entropy(uint64_t *out)
+{
+	*out = 0xABBAEDDAACDCDEAD;
+
+	return true;
+}
+
+void plat_entropy_setup(void)
+{
+	uint64_t dummy;
+
+	plat_trng_uuid = _plat_trng_uuid;
+
+	/* Initialise the entropy source and trigger RNG generation */
+	plat_get_entropy(&dummy);
+}