openhwgroup/cv32e40p

Incorporating FPU

vidushiy25 opened this issue · 2 comments

vidushiy25 commented

Hi, I have some questions regarding incorporating the FPU. I read the documentation but found some bits confusing. When trying to incorporate the FPU do I just set the FPU parameter to 1? The docs say :
As mentioned in RISC-V Privileged Architecture specification, mstatus.FS should be set to Initial to be able to use FP instructions. If mstatus.FS = Off (reset value), any instruction that attempts to read or write the Floating-Point state (F registers or F CSRs) will cause an illegal instruction exception.

So do I need to set mstatus_fs to Initial somewhere? If yes, where?

vidushiy25 commented

Solved it!

pascalgouedo commented

Nothing confusing. You don't have to incorporate anything.
As explained you just have to take all the design files including the new top level module cv32e40p_top and set FPU to 1.

FS is a field of MSTATUS CSR. Initializing it is at Initial state should be done in the software with a csrw instruction.

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