Re: [PATCH v2 5/7] hwrng: exynos: Add SMC based TRNG operation
From: Lukasz Stelmach <l.stelmach@samsung.com>
Date: 2024-06-20 13:46:12
Also in:
linux-crypto, linux-devicetree, linux-samsung-soc, lkml
It was <2024-06-18 wto 15:45>, when Sam Protsenko wrote:
quoted hunk
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@linaro.org> Reviewed-by: Krzysztof Kozlowski <redacted> --- 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@kernel.org> */
[...]
+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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