cpu/nrf5x_common: map hwrng to SoC library if SoftDevice is present

[PeterKietzmann]

Contribution description

According to this comment which bases on Nordic documentation, the hardware RNG can't be accessed when the SoftDevice is used. The fix maps our hwrng_read() function the the respective library function call (see here for reference)

Testing procedure

(i)

Build/flash/term examples/gnrc_networking for an nrf5X based board.

(ii)

Build/flash/term tests/periph_hwrng for an nrf5x based board and include the SoftDevice package. E.g.:
USEPKG=nordic_softdevice_ble BOARD=nrf52dk make -C tests/periph_hwrng flash term

W/o this fix, there is no output as the initialization hangs before main() is called. W/ this fix, everything should work as expected.

Issues/PRs references

Fixes #11091

[PeterKietzmann]

@Citrullin please test

[ghost]

Does not compile for examples/gnrc_networking and tests/periph_hwrng on nrf52840dk.

Also the example does not open a shell on nrf52dk (the same for master, so unrelated but not testable), when using the softdevice. Does open a shell with nrfmin though.

tests/periph_hwrng goes through on nrf52dk.

[PeterKietzmann]

Does not compile for examples/gnrc_networking and tests/periph_hwrng on nrf52840dk.

I just found that it doesn't even compile on master when USEPKG=nordic_softdevice_ble. I'm not very familiar with the nordic hardware nor with the softdevice. Is this feature expected on the nrf52840?

Also the example does not open a shell on nrf52dk

I can't reproduce that. Everything works smooth on my machine. Did you check out my branch or merge/pick the commit somehow? Otherwise this seems like a toolchain issue. I'm on:

Operating System Environment
-----------------------------
       Operating System: "Ubuntu" "18.04.2 LTS (Bionic Beaver)"
                 Kernel: Linux 4.15.0-50-generic x86_64 x86_64

Installed compiler toolchains
-----------------------------
             native gcc: gcc (Ubuntu 7.4.0-1ubuntu1~18.04) 7.4.0
      arm-none-eabi-gcc: arm-none-eabi-gcc (GNU Tools for Arm Embedded Processors 7-2018-q3-update) 7.3.1 20180622 (release) [ARM/embedded-7-branch revision 261907]
                avr-gcc: missing
       mips-mti-elf-gcc: missing
             msp430-gcc: msp430-gcc (GCC) 4.6.3 20120301 (mspgcc LTS 20120406 unpatched)
   riscv-none-embed-gcc: missing
   xtensa-esp32-elf-gcc: missing
   xtensa-lx106-elf-gcc: missing
                  clang: missing

Installed compiler libs
-----------------------
   arm-none-eabi-newlib: "3.0.0"
    mips-mti-elf-newlib: missing
riscv-none-embed-newlib: missing
xtensa-esp32-elf-newlib: missing
xtensa-lx106-elf-newlib: missing
               avr-libc: missing (missing)

Installed development tools
---------------------------
                  cmake: cmake version 3.10.2
               cppcheck: missing
                doxygen: 1.8.13
                 flake8: 3.6.0 (mccabe: 0.6.1, pycodestyle: 2.4.0, pyflakes: 2.0.0) CPython 3.6.7 on Linux
                    git: git version 2.17.1
                   make: GNU Make 4.1
                openocd: Open On-Chip Debugger 0.10.0
                 python: Python 2.7.15rc1
                python2: Python 2.7.15rc1
                python3: Python 3.6.7
             coccinelle: missing

[haukepetersen]

Just checked, the fix seems to do the job for nrf52832-based boards. I do however have some improvements regarding the code in mind -> see PeterKietzmann#11

AFAIK the softdevice was never verified to work with the nrf52840, so no surprise this is not working. I opened a PR introducing an explicit feature to resolve this -> #11769

[PeterKietzmann]

Thanks @haukepetersen! I've reviewed, tested and merged your changes into my branch and rebased + squashed this PR afterwards to run CI

[miri64]

Should also be (void)ret;'ed, in case assert resolves to NOP.

[haukepetersen]

yes, I have missed that.

@PeterKietzmann I think its the easiest if you fix that in your branch directly?!

[PeterKietzmann]

Ok. Ready to squash?

[haukepetersen]

yes, please go ahead

[haukepetersen]

ACK, works as expected and code is valid

[PeterKietzmann]

Squashed

[haukepetersen]

Merged :-)