On Sun, Jun 21, 2020 at 11:51 PM Ishikawa, Masayuki (SHES) <masayuki.ishik...@sony.com> wrote: > > Hi, Brennan, > > Did you check up_get_newintctx() ? > > The function is called from up_initial_state() to create a new task > and needs to return (MSTATUS_MPPM | MSTATUS_MPIE).
Yeah I had that already setup and I could not figure out what was going on which is why I stepped back to make sure I was not missing something more fundamental. After much digging which I guess was not for nothing since I understand the RISC-V opcodes much better, I figured out what was going on. When the syscall is made via ecall the handler does the work of restoring the context, including setting the MPIE bit in the mstatus register (if required). Then at the end mret is called which will do the proper jump and move the value in MPIE bit to MIE bit. Unfortunately this core takes a shortcut here in the RTL to save space and does not support reading or writing the MPIE bit in mstatus, so interrupts would always be disabled out of a context switch. I have not quite figured out how to work around this unfortunately, need to dig into the RTL a bit more for the core and see what I might be able to do here. Thanks for the pointer though. --Brennan
