Re: [PATCH v4] rng: Add Turris Mox rTWM RNG driver

Hi Max,

mostly some nitpicking comments below.

On 2/11/24 14:04, Max Resch wrote:

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

Changes in v4:

• wrongful/missing git rebase

Changes in v3:

• More meaningful variable names in accordance with review

Changes in v2:

• Removed ring buffer implementation

drivers/rng/Kconfig | 8 +++ drivers/rng/Makefile | 1 + drivers/rng/turris_rwtm_rng.c | 122 ++++++++++++++++++++++++++++++++++ 3 files changed, 131 insertions(+) create mode 100644 drivers/rng/turris_rwtm_rng.c

diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig index a89c899568..cd72852a47 100644 --- a/drivers/rng/Kconfig +++ b/drivers/rng/Kconfig @@ -105,4 +105,12 @@ config RNG_JH7110 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 7e64c4cdfc..ecae1a3da3 100644 --- a/drivers/rng/Makefile +++ b/drivers/rng/Makefile @@ -17,3 +17,4 @@ obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o obj-$(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 0000000000..ec2cb0bca3 --- /dev/null +++ b/drivers/rng/turris_rwtm_rng.c @@ -0,0 +1,122 @@ +// 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);
  

Return code check missing here.

• 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);

Please drop this empty line before the ret check.

• 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),

+};

Thanks, Stefan