Hi,
> -----Original Message-----
> From: U-Boot <u-boot-boun...@lists.denx.de> On Behalf Of Heinrich
> Schuchardt
> Sent: Sunday, October 29, 2023 8:26 AM
> To: Rick Chen <r...@andestech.com>; Leo <ycli...@andestech.com>
> Cc: Sughosh Ganu <sughosh.g...@linaro.org>; u-boot@lists.denx.de; Heinrich
> Schuchardt <heinrich.schucha...@canonical.com>
> Subject: [RFC 1/1] rng: Provide a RNG based on the RISC-V Zkr ISA
> extension
>
> The Zkr ISA extension (ratified Nov 2021) introduced the seed CSR. It
> provides an interface to a physical entropy source.
>
> A RNG driver based on the seed CSR is provided. It depends on
> mseccfg.sseed being set in the SBI firmware.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com>
This works fine on my qemu risv with your opensbi patch and KASLR has been
tested as well.
Feel free to add my reviewed/tested-by tag.
Reviewed-by: Chanho Park <chanho61.p...@samsung.com>
Tested-by: Chanho Park <chanho61.p...@samsung.com>
Best Regards,
Chanho Park
> ---
> drivers/rng/Kconfig | 11 ++++
> drivers/rng/Makefile | 1 +
> drivers/rng/riscv_zkr_rng.c | 102 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 114 insertions(+)
> create mode 100644 drivers/rng/riscv_zkr_rng.c
>
> diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> index 994cc35b27..f8f1d91ed2 100644
> --- a/drivers/rng/Kconfig
> +++ b/drivers/rng/Kconfig
> @@ -48,6 +48,17 @@ config RNG_OPTEE
> accessible to normal world but reserved and used by the OP-TEE
> to avoid the weakness of a software PRNG.
>
> +config RNG_RISCV_ZKR
> + bool "RISC-V Zkr random number generator"
> + depends on RISCV_SMODE
> + help
> + This driver provides a Random Number Generator based on the
> + Zkr RISC-V ISA extension which provides an interface to an
> + NIST SP 800-90B or BSI AIS-31 compliant physical entropy source.
> +
> + Using this driver will lead to an exception if the M-mode
> firmware
> + has not set mseccfg.sseed=1.
> +
> config RNG_STM32
> bool "Enable random number generator for STM32"
> depends on ARCH_STM32 || ARCH_STM32MP
> diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> index 47b323e61e..a5d3ca4130 100644
> --- a/drivers/rng/Makefile
> +++ b/drivers/rng/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_RNG_MSM) += msm_rng.o
> obj-$(CONFIG_RNG_NPCM) += npcm_rng.o
> obj-$(CONFIG_RNG_OPTEE) += optee_rng.o
> obj-$(CONFIG_RNG_STM32) += stm32_rng.o
> +obj-$(CONFIG_RNG_RISCV_ZKR) += riscv_zkr_rng.o
> obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
> obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
> obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o
> diff --git a/drivers/rng/riscv_zkr_rng.c b/drivers/rng/riscv_zkr_rng.c
> new file mode 100644
> index 0000000000..f48ae35410
> --- /dev/null
> +++ b/drivers/rng/riscv_zkr_rng.c
> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The RISC-V Zkr extension provides CSR seed which provides access to a
> + * random number generator.
> + */
> +
> +#define LOG_CATEGORY UCLASS_RNG
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <rng.h>
> +
> +#define DRIVER_NAME "riscv_zkr"
> +
> +enum opst {
> + /** @BIST: built in self test running */
> + BIST = 0b00,
> + /** @WAIT: sufficient amount of entropy is not yet available */
> + WAIT = 0b01,
> + /** @ES16: 16bits of entropy available */
> + ES16 = 0b10,
> + /** @DEAD: unrecoverable self-test error */
> + DEAD = 0b11,
> +};
> +
> +static unsigned long read_seed(void)
> +{
> + unsigned long ret;
> +
> + __asm__ __volatile__("csrrw %0, seed, x0" : "=r" (ret) : :
> "memory");
> +
> + return ret;
> +}
> +
> +static int riscv_zkr_read(struct udevice *dev, void *data, size_t len)
> +{
> + u8 *ptr = data;
> +
> + while (len) {
> + u32 val;
> +
> + val = read_seed();
> +
> + switch (val >> 30) {
> + case BIST:
> + continue;
> + case WAIT:
> + continue;
> + case ES16:
> + *ptr++ = val & 0xff;
> + if (--len) {
> + *ptr++ = val >> 8;
> + --len;
> + }
> + break;
> + case DEAD:
> + return -ENODEV;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * riscv_zkr_probe() - check if the seed register is available
> + *
> + * If the SBI software has not set mseccfg.sseed=1 or the Zkr
> + * extension is not available this probe function will result
> + * in an exception. Currently we cannot recover from this.
> + *
> + * @dev: RNG device
> + * Return: 0 if successfully probed
> + */
> +static int riscv_zkr_probe(struct udevice *dev)
> +{
> + u32 val;
> +
> + do {
> + val = read_seed();
> + val >>= 30;
> + } while (val == BIST || val == WAIT);
> +
> + if (val == DEAD)
> + return -ENODEV;
> +
> + return 0;
> +}
> +
> +static const struct dm_rng_ops riscv_zkr_ops = {
> + .read = riscv_zkr_read,
> +};
> +
> +U_BOOT_DRIVER(riscv_zkr) = {
> + .name = DRIVER_NAME,
> + .id = UCLASS_RNG,
> + .ops = &riscv_zkr_ops,
> + .probe = riscv_zkr_probe,
> +};
> +
> +U_BOOT_DRVINFO(cpu_riscv_zkr) = {
> + .name = DRIVER_NAME,
> +};
> --
> 2.40.1
