1 files changed, 80 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 00000000..124821b8
--- /dev/null
+++ b/plat/arm/board/juno/juno_trng.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <mmio.h>
+#include <string.h>
+#include <utils_def.h>
+#include "juno_def.h"
+
+#define NSAMPLE_CLOCKS	1 /* min 1 cycle, max 231 cycles */
+#define NRETRIES	5
+
+static inline int 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)
+			break;
+	}
+	if (i >= NRETRIES)
+		return 0; /* No output data available. */
+	return 1;
+}
+
+/*
+ * This function fills `buf` with `len` bytes of entropy.
+ * It uses the Trusted Entropy Source peripheral on Juno.
+ * Returns 0 when the buffer has been filled with entropy
+ * successfully and -1 otherwise.
+ */
+int juno_getentropy(void *buf, size_t len)
+{
+	uint8_t *bp = buf;
+
+	assert(buf);
+	assert(len);
+	assert(!check_uptr_overflow((uintptr_t)bp, len));
+
+	/* 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);
+
+	while (len > 0) {
+		int i;
+
+		/* Start TRNG. */
+		mmio_write_32(TRNG_BASE + TRNG_CONTROL, 1);
+
+		/* Check if output is valid. */
+		if (!output_valid())
+			return -1;
+
+		/* Fill entropy buffer. */
+		for (i = 0; i < TRNG_NOUTPUTS; i++) {
+			size_t n;
+			uint32_t val;
+
+			val = mmio_read_32(TRNG_BASE + i * sizeof(uint32_t));
+			n = MIN(len, sizeof(uint32_t));
+			memcpy(bp, &val, n);
+			bp += n;
+			len -= n;
+			if (len == 0)
+				break;
+		}
+
+		/* Reset TRNG outputs. */
+		mmio_write_32(TRNG_BASE + TRNG_STATUS, 1);
+	}
+
+	return 0;
+}