pussuw opened a new pull request #5782:
URL: https://github.com/apache/incubator-nuttx/pull/5782
- Add config "ARCH_USE_S_MODE" which controls whether the kernel
runs in M-mode or S-mode
- Add more MSTATUS and most of the SSTATUS register definitions
- Add more MIP flags for interrupt delegation
- Add handling of interrupts from S-mode
- Add handling of FPU from S-mode
- Add new context handling functions that are not dependent on the trap
handlers / ecall
Exceptions / faults are delegated to S-mode.
External interrupts are delegated to S-mode.
Only the machine timer interrupt is handled in M-mode.
Machine mode timer is used as follows:
- The timer reload happens in M-mode ISR
- The event is dispatched to S-mode ISR, which will notify the kernel
to advance time
- For some reason clearing the interrupt does not work from S-mode, so
created a call gate to clear the interrupt in M-mode
The only supported (tested) target for now is MPFS / icicle:knsh (not yet
published).
## Summary
Add option to run NuttX with RISC-V in supervisor mode.
## Impact
Enabler for CONFIG_BUILD_KERNEL=y, MMU mappings require S-mode.
## Testing
Tested with icicle:knsh (not yet published)
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