On Wed, 20 Jul 2022 at 15:30, Sughosh Ganu wrote:
>
> The TPM device has a builtin random number generator(RNG)
> functionality. Expose the RNG functions of the TPM device to the
> driver model so that they can be used by the EFI_RNG_PROTOCOL if the
> protocol is installed.
>
> Also change the function arguments and return type of the random
> number functions to comply with the driver model api.
>
> Signed-off-by: Sughosh Ganu
> ---
> Changes since V6:
> * Remove the changes made in tpm-v[12].c to return -EIO instead of
> TPM_LIB_ERROR as suggested by Simon
>
> drivers/rng/Kconfig | 9 +
> drivers/rng/Makefile | 1 +
> drivers/rng/tpm_rng.c | 23 +++
> lib/Kconfig | 1 +
> lib/tpm_api.c | 6 +++---
> 5 files changed, 37 insertions(+), 3 deletions(-)
> create mode 100644 drivers/rng/tpm_rng.c
>
> diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> index 21a9ff0195..16143681da 100644
> --- a/drivers/rng/Kconfig
> +++ b/drivers/rng/Kconfig
> @@ -74,4 +74,13 @@ config RNG_SMCCC_TRNG
> Enable random number generator for platforms that support Arm
> SMCCC TRNG interface.
>
> +config TPM_RNG
> + bool "Enable random number generator on TPM device"
> + depends on TPM
> + default y
> + help
> + The TPM device has an inbuilt random number generator
> + functionality. Enable random number generator on TPM
> + devices.
> +
> endif
We could probably skip the extra Kconfig and just look for a TPM. But
let's leave it as is for now, it's an easy change if we ever want that
> diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> index 2494717d7c..78f61051ac 100644
> --- a/drivers/rng/Makefile
> +++ b/drivers/rng/Makefile
> @@ -13,3 +13,4 @@ obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
> obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
> obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
> obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o
> +obj-$(CONFIG_TPM_RNG) += tpm_rng.o
> diff --git a/drivers/rng/tpm_rng.c b/drivers/rng/tpm_rng.c
> new file mode 100644
> index 00..1a5e9e2e4b
> --- /dev/null
> +++ b/drivers/rng/tpm_rng.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2022, Linaro Limited
> + */
> +
> +#include
> +#include
> +#include
> +
> +static int rng_tpm_random_read(struct udevice *dev, void *data, size_t count)
> +{
> + return tpm_get_random(dev_get_parent(dev), data, count);
> +}
> +
> +static const struct dm_rng_ops tpm_rng_ops = {
> + .read = rng_tpm_random_read,
> +};
> +
> +U_BOOT_DRIVER(tpm_rng) = {
> + .name = "tpm-rng",
> + .id = UCLASS_RNG,
> + .ops= _rng_ops,
> +};
> diff --git a/lib/Kconfig b/lib/Kconfig
> index 7dd777b56a..e888c29245 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -360,6 +360,7 @@ source lib/crypt/Kconfig
> config TPM
> bool "Trusted Platform Module (TPM) Support"
> depends on DM
> + imply DM_RNG
> help
> This enables support for TPMs which can be used to provide security
> features for your board. The TPM can be connected via LPC or I2C
> diff --git a/lib/tpm_api.c b/lib/tpm_api.c
> index 4ac4612c81..032f383ca0 100644
> --- a/lib/tpm_api.c
> +++ b/lib/tpm_api.c
> @@ -269,7 +269,7 @@ u32 tpm_get_random(struct udevice *dev, void *data, u32
> count)
> if (tpm_is_v1(dev))
> return tpm1_get_random(dev, data, count);
> else if (tpm_is_v2(dev))
> - return -ENOSYS; /* not implemented yet */
> - else
> - return -ENOSYS;
> + return tpm2_get_random(dev, data, count);
> +
> + return -ENOSYS;
> }
> --
> 2.34.1
>
Reviewed-by: Ilias Apalodimas
