rpi3: Move rng driver to drivers

To allow sharing the driver between the RPi3 and RPi4, move the random
number generator driver into the generic driver directory.

Change-Id: Iae94d7cb22c6bce3af9bff709d76d4caf87b14d1
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/drivers/rpi3/rng/rpi3_rng.c b/drivers/rpi3/rng/rpi3_rng.c
new file mode 100644
index 00000000..b6bf0052
--- /dev/null
+++ b/drivers/rpi3/rng/rpi3_rng.c
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <string.h>
+
+#include <lib/mmio.h>
+
+#include <rpi_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);
+	}
+}