I'm having issues making the hardware RNG work on a Samsung Exynos 5422 (Odroid XU4) with kernel 4.2rc6.
No random number generation is started if I write the appropriate value (0x18) to the hash control register.
What I did so far:
Splitted the sss DT node in exynos5420.dtsi into one for the s5p-sss driver and one for the exynos-rng driver.
(s5p-sss doesn't seem to need the hash registers from offset 0x400)
sss: sss@10830000 {
icompatible = "samsung,exynos4210-secss";
reg = <0x10830000 0x400>;
interrupts = <0 112 0>;
clocks = <&clock CLK_SSS>;
clock-names = "secss";
};
rng: rng@10830400 {
compatible = "samsung,exynosrng-secss";
reg = <0x10830400 0x300>;
clocks = <&clock CLK_SSS>;
clock-names = "secss";
};
The DT binding is just for testing and after adding some DT glue logic (of_device_id table) to the exynos-rng driver
it binds to the rng platform device.
The clock also seems to be ok with a rate of 266 MHz.
As is the driver hangs in a loop because the PRNG_DONE in the status register bit never gets set.
I traced it back to the hash control register not accepting value 0x8 (or 0x18 incl. the start bit) for the PRNG.
Writing a value and reading it back works for values from 0 to 5 only.
As I have no SSS datasheet my only other reference is drivers/crypto/ace_sha.h in the uboot source code
which also uses the HW RNG.
Any hint would be appreciated.
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