google/CFU-Playground

program results are messy when displayed on my terminal

Siris-Li opened this issue · 5 comments

Siris-Li commented

Hello! I follow setup guide to build my cfu-playground by using Arty A7 35T on my VM ubuntu 20.04.
Everything works well except that the information displayed on my terminal is in a mess.
I run the project in proj/proj_template, adding export EXTRA_LITEX_ARGS="--cpu-variant=perf+cfu" in Makefile to turn perf counters on.
Followings are some of my golden test results.

 Counter |  Total | Starts | Average |   Raw
---------+--------+--------+---------+--------------
       |     0  |     0  |   n/a   |            0
    1    |      |     0  |   n/a   |            0
    2    |     0  |     0|   n/a   |            0
    3    |     0  |     0  |   n/a   |            0
    4    |     0  |     0  |   n/a   |          0
    5    |     0  |     0  |   n/a   |            0
       |     0  |     0  |   n/a   |            0
    7    |      |     0  |   n/a   |            0
   212M (    212233017 ) ycles total

It's obvious that the output missed a lot of things. For example, in Counter column, number 0 and 6 were missed. In the last row, cycles missed one letter c.
I have run several times and the missing parts are different each time, which means it is totally random.
I also try another Arty A7 35T, but got the same result. So, I think it's not due to the board.
How can I address this problem? Thanks in advance!

tcal-x commented

Hi @limingxuan-pku , yes, this appears to be corruption on the serial link. I am a bit surprised you're seeing exactly the same thing with a different board.

In any case, the first thing I'd try is reducing UART_SPEED from the default 1843200. Either temporarily modify the value set in proj/proj.mk, or specify it on all make commands:

make UART_SPEED=115200 prog
make UART_SPEED=115200 load
Siris-Li commented

@tcal-x Thanks! I pretty agree with your idea. LGTM. :)

tcal-x commented

@limingxuan-pku please let me know if my suggested workaround fixes the issue. You can try speeds between 115200 and 1843200 to see where it starts seeing corruption.

Siris-Li commented

please let me know if my suggested workaround fixes the issue.

Hi! @tcal-x I found out some interesting results.
When I use VM Ubuntu20.04 in software Orcale VM VirtualBox, I try three URAT speeds: 115200, 57600, 38400. It turns out that only when I lower the speed to 38400 can I print the normal text without missing.
However, when it comes to using VM Ubuntu20.04 in software VMware Workstation Pro 16, things are different. Even with default speed 1843200 can the terminal print the correct text.
A little confused result, but that's what I got.

tcal-x commented

Thanks @limingxuan-pku for following up! I don't have much experience running CFU-Playground in a VM (other than Linux on ChromeOS). But correct handling of USB-connected devices is often an issue.