rng: Add Turris Mox rTWM RNG driver
A RNG driver for Armada 3720 boards running the Turris Mox rWTM firmware
from CZ.NIC in the secure processor.
Signed-off-by: Max Resch <resch.max@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
index a89c899..cd72852 100644
--- a/drivers/rng/Kconfig
+++ b/drivers/rng/Kconfig
@@ -105,4 +105,12 @@
help
Enable True Random Number Generator in StarFive JH7110 SoCs.
+config RNG_TURRIS_RWTM
+ bool "Turris Mox TRNG in Secure Processor"
+ depends on DM_RNG && ARMADA_3700
+ help
+ Use TRNG in Turris Mox Secure Processor Firmware. Can be used
+ on other Armada-3700 devices (like EspressoBin) if Secure
+ Firmware from CZ.NIC is used.
+
endif
diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
index 7e64c4c..ecae1a3 100644
--- a/drivers/rng/Makefile
+++ b/drivers/rng/Makefile
@@ -17,3 +17,4 @@
obj-$(CONFIG_RNG_ARM_RNDR) += arm_rndr.o
obj-$(CONFIG_TPM_RNG) += tpm_rng.o
obj-$(CONFIG_RNG_JH7110) += jh7110_rng.o
+obj-$(CONFIG_RNG_TURRIS_RWTM) += turris_rwtm_rng.o
diff --git a/drivers/rng/turris_rwtm_rng.c b/drivers/rng/turris_rwtm_rng.c
new file mode 100644
index 0000000..ca808c4
--- /dev/null
+++ b/drivers/rng/turris_rwtm_rng.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause
+/*
+ * Copyright (c) 2024, Max Resch
+ */
+
+#include <dm.h>
+#include <malloc.h>
+#include <rng.h>
+#include <asm/dma-mapping.h>
+#include <asm/types.h>
+#include <mach/mbox.h>
+
+/* size of entropy buffer */
+#define RNG_BUFFER_SIZE 128U
+
+struct turris_rwtm_rng_priv {
+ phys_addr_t buffer;
+};
+
+static int turris_rwtm_rng_fill_entropy(phys_addr_t entropy, size_t size)
+{
+ u32 args[3] = { 1, (u32)entropy, size };
+ int ret;
+
+ /* flush data cache */
+ flush_dcache_range(entropy, entropy + size);
+
+ /*
+ * get entropy
+ * args[0] = 1 copies BYTES array in args[1] of length args[2]
+ */
+ ret = mbox_do_cmd(MBOX_CMD_GET_RANDOM, args, 3, NULL, 0);
+ if (ret < 0)
+ return ret;
+
+ /* invalidate data cache */
+ invalidate_dcache_range(entropy, entropy + size);
+
+ return 0;
+}
+
+static int turris_rwtm_rng_random_read(struct udevice *dev, void *data, size_t count)
+{
+ struct turris_rwtm_rng_priv *priv = dev_get_priv(dev);
+ phys_addr_t phys;
+ size_t size;
+ int ret;
+
+ phys = priv->buffer;
+
+ while (count) {
+ size = min_t(size_t, RNG_BUFFER_SIZE, count);
+
+ ret = turris_rwtm_rng_fill_entropy(phys, size);
+ if (ret < 0)
+ return ret;
+
+ memcpy(data, (void *)phys, size);
+ count -= size;
+ data = (u8 *)data + size;
+ }
+
+ return 0;
+}
+
+static int turris_rwtm_rng_probe(struct udevice *dev)
+{
+ struct turris_rwtm_rng_priv *priv = dev_get_priv(dev);
+ u32 args[] = { 0 };
+ int ret;
+
+ /*
+ * check if the random command is supported
+ * args[0] = 0 would copy 16 DWORDS entropy to out but we ignore them
+ */
+ ret = mbox_do_cmd(MBOX_CMD_GET_RANDOM, args, ARRAY_SIZE(args), NULL, 0);
+ if (ret < 0)
+ return ret;
+
+ /* entropy buffer */
+ priv->buffer = 0;
+
+ /* buffer address need to be aligned */
+ dma_alloc_coherent(RNG_BUFFER_SIZE, (unsigned long *)&priv->buffer);
+ if (!priv->buffer)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static int turris_rwtm_rng_remove(struct udevice *dev)
+{
+ struct turris_rwtm_rng_priv *priv = dev_get_priv(dev);
+ phys_addr_t phys = priv->buffer;
+
+ dma_free_coherent((void *)phys);
+
+ return 0;
+}
+
+static const struct dm_rng_ops turris_rwtm_rng_ops = {
+ .read = turris_rwtm_rng_random_read,
+};
+
+/*
+ * only Turris MOX firmware has the RNG but allow all probable devices to be
+ * probed the default firmware will just reject the probe
+ */
+static const struct udevice_id turris_rwtm_rng_match[] = {
+ { .compatible = "cznic,turris-mox-rwtm" },
+ { .compatible = "marvell,armada-3700-rwtm-firmware" },
+ {},
+};
+
+U_BOOT_DRIVER(turris_rwtm_rng) = {
+ .name = "turris-rwtm-rng",
+ .id = UCLASS_RNG,
+ .of_match = turris_rwtm_rng_match,
+ .ops = &turris_rwtm_rng_ops,
+ .probe = turris_rwtm_rng_probe,
+ .remove = turris_rwtm_rng_remove,
+ .priv_auto = sizeof(struct turris_rwtm_rng_priv),
+};