Issues using HW TRNG on XU4

[hkallweit]

I'm interested in using the hardware true random number generator of the Exynos 5422. The related driver exyswd-rng under drivers/char/hw_random is disabled in the default config. I tried to make it work however the TRNG init SMC call exynos_smc(SMC_CMD_RANDOM, HWRNG_INIT, 0, 0) returns -1. I was discussing this with Krzysztof Kozlowski and he recommended to check with you as the firmware might have been customized.

• Does the firmware provided by hardkernel support the SMC call for controling the TRNG?
• If yes: What's the cmd id, the one mentioned in the driver (0x81000030)?
• If not: Is there a specific reason and could it be added?

[tbe]

@tobetter could you get some details about this. Is this a missing feature in TZSW or are there other implementation limitations? It would be great if we could put the TRNG to work, and provide some patches for the kernel.