2015-08-16 20:18 GMT+09:00 Heiner Kallweit [off-list ref]:

Am 15.08.2015 um 13:19 schrieb Heiner Kallweit:

quoted

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.

Indeed... Status has value 0x3 which means that buffer is not full,
seed setup is done and PRNG engine is idle. I tried this also on
Trats2 board (Exynos 4412) with exactly the same result. No idea.

quoted

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.

It's okay. Accepted values for engine are only from 0 to 5. The bit no
4 (start init bit) is automatically cleared by hardware.

Best regards,
Krzysztof