rpi3: Introduce hardware RNG driver
Note that this is a non-secure RNG. This is only useful for educational
purposes.
Change-Id: If359c8d0f755ef8e416986de7fbca34679a523e1
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/rpi3/rpi3_rng.c b/plat/rpi3/rpi3_rng.c
new file mode 100644
index 0000000..111b3b6
--- /dev/null
+++ b/plat/rpi3/rpi3_rng.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <mmio.h>
+#include <string.h>
+
+#include "rpi3_hw.h"
+
+/* Initial amount of values to discard */
+#define RNG_WARMUP_COUNT U(0x40000)
+
+static void rpi3_rng_initialize(void)
+{
+ uint32_t int_mask, ctrl;
+
+ /* Return if it is already enabled */
+ ctrl = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET);
+ if ((ctrl & RPI3_RNG_CTRL_ENABLE) != 0U) {
+ return;
+ }
+
+ /* Mask interrupts */
+ int_mask = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET);
+ int_mask |= RPI3_RNG_INT_MASK_DISABLE;
+ mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET, int_mask);
+
+ /* Discard several values when initializing to give it time to warmup */
+ mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET, RNG_WARMUP_COUNT);
+
+ mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET,
+ RPI3_RNG_CTRL_ENABLE);
+}
+
+static uint32_t rpi3_rng_get_word(void)
+{
+ size_t nwords;
+
+ do {
+ /* Get number of available words to read */
+ nwords = (mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET)
+ >> RPI3_RNG_STATUS_NUM_WORDS_SHIFT)
+ & RPI3_RNG_STATUS_NUM_WORDS_MASK;
+ } while (nwords == 0U);
+
+ return mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_DATA_OFFSET);
+}
+
+void rpi3_rng_read(void *buf, size_t len)
+{
+ uint32_t data;
+ size_t left = len;
+ uint32_t *dst = buf;
+
+ assert(buf != NULL);
+ assert(len != 0U);
+ assert(check_uptr_overflow((uintptr_t) buf, (uintptr_t) len) == 0);
+
+ rpi3_rng_initialize();
+
+ while (left >= sizeof(uint32_t)) {
+ data = rpi3_rng_get_word();
+ *dst++ = data;
+ left -= sizeof(uint32_t);
+ }
+
+ if (left > 0U) {
+ data = rpi3_rng_get_word();
+ memcpy(dst, &data, left);
+ }
+}