Custom Accelerator in FreedomStudio

Archive General
1

Hi, I have built Freedom E300 with custom Accelerator (AccumulatorExampleModule) from Rocketchip. I can run demo_gpio on the Arty with this new generated image. Now I would like to test the accelerator and I would like to compile and run it in FreedomStudio. My understanding is that since I am using built in accelerator on ROCC interface so I don’t need to rebuilt the tool. Am I right? From this https://github.com/seldridge/rocket-rocc-examples I get header file rocc.h and accumulator.h. And add the following line in demo_gpio after reset_demo

doWrite(y, addr, data[0]);

As per the repository mention before. But I am getting unhandled trap and program exit with code 03. Is there any thing I am missing? Do I need to make any changes in any *.s file to switch on the accerator?

Regards
Nauman

2

How are you running the program? If you are using the pk you will need to modify its boot process to enable accelerators.

That would involve adding a write_csr(mstatus, MSTATUS_XS) somewhere in minit.c presumably around here

3

Hi, I am running the code through FreedomStudio and following Freedom E300 Arty FPGA Dev Kit Getting Started Guide and https://github.com/riscv/riscv-gnu-toolchain/issues/190#issuecomment-264083212. About this write_csr(mstatus, MSTATUS_XS) when I use it in my main program I don’t get the error but nothing happening it’s like accelerator is not working. And as per the Riscv instruction set manual (Privileged Architectures V1.10) page 23 XS[1:0] is read only so I am not sure whether I should write it or not.

4

Hello Nauman,
did you make any progress on that issue? I am trying to do the same thing and have the same issue of the unhandled trap.
Thanks
Lukas

5

Hi, I was able to run it by including write_csr(mstatus, MSTATUS_XS). Did you try it? Are you building the example accumulator accelerator from rocket chip?

6

Not yet. I was going to try that next. I just need to integrate write_csr somewhere in my program before I call the accelerator? And did you somehow modify the original freedom sourcecodes? Because to me it looks like the Accumulator example is included in the freedom-e300-arty by default.

7

Please see this for the changes in Freedom code https://github.com/sifive/freedom/issues/37. For the software I used https://github.com/seldridge/rocket-rocc-examples. You need write_scr at the start of your code.

8

Okay, this looks more promising than anything I have found on RoCC myself so far. I probably won’t be able to try it before the weekend, I am kinda swamped in work here, but I’ll try it saturday and get back to you if more questions arise.
Thanks a lot
Lukas

9

Hello @Nauman,
Did you test it the Accumulator Rocc accelerator? I’ve build and deploy on Artix board, but it seems to not work as expected, I mean:

core freq at 32000000 Hz
[INFO] Write R[1] = 0xdead
[INFO] Read R[1]
[INFO] Received 0x0 (expected 0xdead)
[INFO] Accum R[1] with 0xffffe042
[INFO] Read R[1]
[INFO] Received 0x0 (expected 0xbeef)

What about your results?