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lowRISC / lowrisc-chip

The root repo for lowRISC project and FPGA demos.
http://www.lowrisc.org/
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RoCC with Lowrisc #61

Closed clare7 closed 7 years ago

clare7 commented 7 years ago

Any guideline on using rocc with lowrisc rocket chip? would the procedure similar to that of the rocketchip developed by Berkeley?

jrrk commented 7 years ago

The goal of lowRISC is to make a security enhanced and usable Linux system based on Berkley Chisel and Xilinx FPGA IP.

As such the source base diverged quite a bit from their methodology, and we have yet to see a new version from them

which has all the functionality of the previous code base that our chip is based on. For example the L2 cache is missing

in the rewritten code. At the same time there have been quite a few changes in CSRs which make it difficult to track the

latest compiler technology.

An investigation is underway to solve the problems of rebasing at the moment, but as of now I would suggest avoiding any

modifications other than the ones we explicitly suggest on our website, until you reach experienced user status.

On 10/08/17 09:08, clare7 wrote:

Any guideline on using rocc with lowrisc rocket chip? would the procedure similar to that of the rocketchip developed by Berkeley?

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wsong83 commented 7 years ago

As Jonathan said, RoCC is not something you can easily plug and play. The RoCC in the upstream Rocket-Chip is not stable and lag from latest development anyway. If RoCC is your main goal to use lowRISC, I think it is unavoidable that you need to understand the interface to a level of feeling comfortable with revising the Chisel code yourself. When you reach there, probably configuring lowRISC to enable your own RoCC component is no longer an issue.

Right now for lowRISC, we use the old Rocket code around Summer 2016 and it does come along with a RoCC interface, although this interface is disabled by all configurations we provide right now. You need to change the top level Chisel configuration to enable it. As I mentioned earlier, it is not plug and play, so proving instructions to enable the interface before you understand the interface itself is useless. Once you understand it, enabling it will be easy peasy.

I would suggest you to have a careful look of this repository: https://bitbucket.org/taylor-bsg/bsg_riscv

The document and code there will help you understand the RoCC interface. I believe the RoCC interface there is not much different with ours.

Since we do not use the RoCC interface (we do not understand it much to be frank), there is very little support from lowRISC.

wsong83 commented 7 years ago

Feel free to open it again.