On Thu, Jun 20, 2024 at 8:46 AM Lukasz Stelmach <l.stelmach@xxxxxxxxxxx> wrote: > > 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). > This series was only tested (and works fine) with LittleKernel based bootloader [1]. It's officially recommended and the only feature complete bootloader at the moment. And you are right, the reason why TRNG probe fails when you boot the kernel from U-Boot is that the LDFW (Loadable Firmware) loading is not implemented in U-Boot right now, which makes HWRNG_INIT SMC command fail and return -1. In fact, I'm adding LDFW loading in U-Boot right now and expect it to be ready in 1 week or so. For now, can you please check with LK [1] instead? I'm happy to help if you have any related questions. > [ 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. > Good idea! Will send v3 soon, with proper error message added. Thanks! [1] https://gitlab.com/Linaro/96boards/e850-96/lk > Kind regards, > -- > Łukasz Stelmach > Samsung R&D Institute Poland > Samsung Electronics