Re: Issues with HW RNG / SSS on Exynos 5422

[jonghwa3.lee@samsung.com]

Hi
On 2015년 08월 16일 20:21, Heiner Kallweit wrote:
> Am 16.08.2015 um 13:18 schrieb Heiner Kallweit:
>> Am 15.08.2015 um 13:19 schrieb Heiner Kallweit:
>>> 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.
>>>
>> After some more testing it seems like SSS in general has problems on Exynos 5422.
>> Also the AES implementation in s5p-sss doesn't work. dmesg output:
>>
>> [    7.116739] alg: skcipher: encryption failed on chunk test 1 for ecb-aes-s5p: ret=22
>> [    7.123673] s5p-sss driver registered
>>
> Sorry, there was a typo in the mail agent cc line.
>
I suspect Trustzone would prohibit to access SSS IP. I never tested it Exynos
hwrng under Trustzone enabled,
however some said it cannot be used manually after being protected by Secure OS.

And I don't know neither how to check whether Trustzone is enabled.
Can you access all other registers in SSS IP? If not, it might be related with it.

Thanks.
Jonghwa