It was <2024-06-18 wto 15:45>, when Sam Protsenko wrote:
> On some Exynos chips like Exynos850 the access to Security Sub System
> (SSS) registers is protected with TrustZone, and therefore only possible
> from EL3 monitor software. The Linux kernel is running in EL1, so the
> only way for the driver to obtain TRNG data is via SMC calls to EL3
> monitor. Implement such SMC operation and use it when EXYNOS_SMC flag is
> set in the corresponding chip driver data.
>
> Signed-off-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> ---
> Changes in v2:
> - Used the "reversed Christmas tree" style in the variable declaration
> block in exynos_trng_do_read_smc()
> - Renamed .quirks to .flags in the driver structure
> - Added Krzysztof's R-b tag
>
> drivers/char/hw_random/exynos-trng.c | 133 +++++++++++++++++++++++++--
> 1 file changed, 123 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/char/hw_random/exynos-trng.c b/drivers/char/hw_random/exynos-trng.c
> index 99a0b271ffb7..497d6018c6ba 100644
> --- a/drivers/char/hw_random/exynos-trng.c
> +++ b/drivers/char/hw_random/exynos-trng.c
> @@ -10,6 +10,7 @@
> * Krzysztof Kozłowski <krzk@xxxxxxxxxx>
> */
[...]
> +static int exynos_trng_init_smc(struct hwrng *rng)
> +{
> + struct arm_smccc_res res;
> +
> + arm_smccc_smc(SMC_CMD_RANDOM, HWRNG_INIT, 0, 0, 0, 0, 0, 0, &res);
> + if (res.a0 != HWRNG_RET_OK)
> + return -EIO;
> +
> + return 0;
> +}
> +
Does this driver requiers some vendor-specifig bootloading code?
I am testing the code on a WinLink E850-96 board booted with the
upstream u-boot and it fails during init (res0.a is -1).
[ 1.883413] exynos-trng 12081400.rng: Could not register hwrng device
[ 1.893394] exynos-trng 12081400.rng: probe with driver exynos-trng failed with error -5
If an additional code outside the kernel is required for this to run,
then maybe the error message should reflect that.
Kind regards,
--
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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