CI/Doc: Add tests for 32-bit/64-bit Datapath.

[enjoy-digital]

@lschuermann, @david-sawatzke: Thanks a lot for the work on the 32-bit/64-bit Datapath. Would you mind listing here the tests/commands you are currently running to verify your changes (at least in simulation)? This will be useful now for the PRs reviews/eventual modifications and will be useful for later to document these and add CI. Thanks!

[david-sawatzke]

I have used a couple different approaches depending on the issue at hand:

• ARP works by just resolving the IP (tests the MAC, hybrid mac and hardware stack)
• tftp works to copy data from the bios (variable length data gets received via sram.py)
• ping with varying lengths to exercise the last_be options and verify the Packetizer/Depacketizer works with different last_bes
  • The icmp checksum fails if data is missing
• etherbone to read data, primarily with the crossbar uart to check the data is valid.

Usually coupled with wireshark and the debug prints in the bios to take a look at the packets.

I've also tested the MAC & SRAM stack on the colorlight 5a-75b, with the bios and firmware (smoltcp) that handles (hacky) telnet and some art-net udp.

For #88 we mostly worked with ping.

The simulation is a bit hacky, but I usually test with ./litex_sim.py --with-sdram --ethernet-phy-model=gmii --with-etherbone --with-ethernet and adjusting the code in litex_sim to test the correct thing. For #88 I mostly used https://gist.github.com/david-sawatzke/d0463060d84ce1748370c0888b1f6343.

EDIT:

For #90 upstream for 8 bit testing and https://gist.github.com/david-sawatzke/daca60f6e8dc196895e30387c928dd57 for 32 bit testing. And https://gist.github.com/david-sawatzke/34acfa65b411672fee73e5367371e818 with ./colorlight_5a_75x.py --board 5a-75b --with-etherbone --revision 6.1 --build --sys-clk-freq 50e6 --load

[enjoy-digital]

Thanks @david-sawatzke, I indeed mostly wanted to know the used commands to also be able to run similar simulations.