Re: [PATCH u-boot-mvebu v3 17/18] misc: turris_omnia_mcu: Add support for rng provided by MCU

Stefan Roese
2024-03-28T10:25:26Z

On 3/27/24 17:23, Marek Behún wrote:
> Add support for true random number generator provided by the MCU on
> Turris Omnia. The MCU firmware supports TRNG if the FEAT_TRNG bit is set
> in features. In that case we bind the rng driver.
>
> Signed-off-by: Marek Behún <kabel@kernel.org>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

> ---
> configs/turris_omnia_defconfig | 1 +
> drivers/misc/Kconfig | 1 +
> drivers/misc/turris_omnia_mcu.c | 57 +++++++++++++++++++++++++++++++++
> 3 files changed, 59 insertions(+)
>
> diff --git a/configs/turris_omnia_defconfig b/configs/turris_omnia_defconfig
> index 0df0f3c90b..4c21635ec9 100644
> --- a/configs/turris_omnia_defconfig
> +++ b/configs/turris_omnia_defconfig
> @@ -107,6 +107,7 @@ CONFIG_NVME_PCI=y
> CONFIG_PCI_MVEBU=y
> CONFIG_PINCTRL=y
> CONFIG_PINCTRL_ARMADA_38X=y
> +CONFIG_DM_RNG=y
> CONFIG_DM_RTC=y
> CONFIG_RTC_ARMADA38X=y
> CONFIG_SERIAL_PROBE_ALL=y
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 844a21be47..a08f02196f 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -509,6 +509,7 @@ config TURRIS_OMNIA_MCU
> bool "Enable Turris Omnia MCU driver"
> depends on DM_I2C
> depends on DM_GPIO
> + depends on DM_RNG
> depends on SYSRESET
> default y if TARGET_TURRIS_OMNIA
> help
> diff --git a/drivers/misc/turris_omnia_mcu.c b/drivers/misc/turris_omnia_mcu.c
> index 77a0424d61..6b2f17c000 100644
> --- a/drivers/misc/turris_omnia_mcu.c
> +++ b/drivers/misc/turris_omnia_mcu.c
> @@ -5,15 +5,20 @@
> */
>
> #include <common.h>
> +#include <console.h>
> #include <dm.h>
> #include <dm/lists.h>
> #include <i2c.h>
> +#include <rng.h>
> #include <sysreset.h>
> #include <turris-omnia-mcu-interface.h>
> #include <asm/byteorder.h>
> #include <asm/gpio.h>
> +#include <linux/delay.h>
> #include <linux/log2.h>
>
> +#define CMD_TRNG_MAX_ENTROPY_LEN 64
> +
> struct turris_omnia_mcu_info {
> u32 features;
> };
> @@ -282,6 +287,49 @@ U_BOOT_DRIVER(turris_omnia_mcu_sysreset) = {
> .ops = &omnia_sysreset_ops,
> };
>
> +static int omnia_rng_read(struct udevice *dev, void *data, size_t count)
> +{
> + u8 buf[1 + CMD_TRNG_MAX_ENTROPY_LEN];
> + size_t len;
> + int ret;
> +
> + while (count) {
> + ret = dm_i2c_read(dev->parent, CMD_TRNG_COLLECT_ENTROPY, buf,
> + sizeof(buf));
> + if (ret)
> + return ret;
> +
> + len = min_t(size_t, buf[0],
> + min_t(size_t, CMD_TRNG_MAX_ENTROPY_LEN, count));
> +
> + if (!len) {
> + /* wait 500ms (fail if interrupted), then try again */
> + for (int i = 0; i < 5; ++i) {
> + mdelay(100);
> + if (ctrlc())
> + return -EINTR;
> + }
> + continue;
> + }
> +
> + memcpy(data, &buf[1], len);
> + data += len;
> + count -= len;
> + }
> +
> + return 0;
> +}
> +
> +static const struct dm_rng_ops omnia_rng_ops = {
> + .read = omnia_rng_read,
> +};
> +
> +U_BOOT_DRIVER(turris_omnia_mcu_trng) = {
> + .name = "turris-omnia-mcu-trng",
> + .id = UCLASS_RNG,
> + .ops = &omnia_rng_ops,
> +};
> +
> static int turris_omnia_mcu_bind(struct udevice *dev)
> {
> /* bind MCU GPIOs as a child device */
> @@ -336,6 +384,15 @@ static int turris_omnia_mcu_probe(struct udevice *dev)
> return ret;
> }
>
> + /* bind rng if trng is supported */
> + if (info->features & FEAT_TRNG) {
> + ret = device_bind_driver_to_node(dev, "turris-omnia-mcu-trng",
> + "turris-omnia-mcu-trng",
> + dev_ofnode(dev), NULL);
> + if (ret < 0)
> + return ret;
> + }
> +
> return 0;
> }
>

Viele Grüße,
Stefan Roese

--
DENX Software Engineering GmbH, Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: sr@denx.de