1 files changed, 108 insertions, 0 deletions
diff --git a/plat/arm/board/juno/juno_trng.c b/plat/arm/board/juno/juno_trng.c
new file mode 100644
index 0000000..09552a6
--- /dev/null
+++ b/plat/arm/board/juno/juno_trng.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2017-2018, 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/utils_def.h>
+#include <platform_def.h>
+
+#include <lib/smccc.h>
+#include <services/trng_svc.h>
+#include <smccc_helpers.h>
+
+#include <plat/common/platform.h>
+
+#define NSAMPLE_CLOCKS	1 /* min 1 cycle, max 231 cycles */
+#define NRETRIES	5
+
+/* initialised to false */
+static bool juno_trng_initialized;
+
+static bool output_valid(void)
+{
+	int i;
+
+	for (i = 0; i < NRETRIES; i++) {
+		uint32_t val;
+
+		val = mmio_read_32(TRNG_BASE + TRNG_STATUS);
+		if (val & 1U)
+			return true;
+	}
+	return false; /* No output data available. */
+}
+
+DEFINE_SVC_UUID2(_plat_trng_uuid,
+	0x23523c58, 0x7448, 0x4083, 0x9d, 0x16,
+	0xe3, 0xfa, 0xb9, 0xf1, 0x73, 0xbc
+);
+uuid_t plat_trng_uuid;
+
+static uint32_t crc_value = ~0U;
+
+/*
+ * Uses the Trusted Entropy Source peripheral on Juno to return 8 bytes of
+ * entropy. Returns 'true' when done successfully, 'false' otherwise.
+ */
+bool plat_get_entropy(uint64_t *out)
+{
+	uint64_t ret;
+
+	assert(out);
+	assert(!check_uptr_overflow((uintptr_t)out, sizeof(*out)));
+
+	if (!juno_trng_initialized) {
+		/* Disable interrupt mode. */
+		mmio_write_32(TRNG_BASE + TRNG_INTMASK, 0);
+		/* Program TRNG to sample for `NSAMPLE_CLOCKS`. */
+		mmio_write_32(TRNG_BASE + TRNG_CONFIG, NSAMPLE_CLOCKS);
+		/* Abort any potentially pending sampling. */
+		mmio_write_32(TRNG_BASE + TRNG_CONTROL, 2);
+		/* Reset TRNG outputs. */
+		mmio_write_32(TRNG_BASE + TRNG_STATUS, 1);
+
+		juno_trng_initialized = true;
+	}
+
+	if (!output_valid()) {
+		/* Start TRNG. */
+		mmio_write_32(TRNG_BASE + TRNG_CONTROL, 1);
+
+		if (!output_valid())
+			return false;
+	}
+
+	/* CRC each two 32-bit registers together, combine the pairs */
+	crc_value = __crc32w(crc_value, mmio_read_32(TRNG_BASE + 0));
+	crc_value = __crc32w(crc_value, mmio_read_32(TRNG_BASE + 4));
+	ret = (uint64_t)crc_value << 32;
+
+	crc_value = __crc32w(crc_value, mmio_read_32(TRNG_BASE + 8));
+	crc_value = __crc32w(crc_value, mmio_read_32(TRNG_BASE + 12));
+	*out = ret | crc_value;
+
+	/* Acknowledge current cycle, clear output registers. */
+	mmio_write_32(TRNG_BASE + TRNG_STATUS, 1);
+	/* Trigger next TRNG cycle. */
+	mmio_write_32(TRNG_BASE + TRNG_CONTROL, 1);
+
+	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);
+}