cv32e41p - Prompt not answering

[pcotret]

Still working on porting the cv32e41p. LiteX boots but the prompt doesn't answering (when litex_sim --cpu-type=cv32e41p)...

• As everything boots, I assume hardware connections to the core are OK.
• The prompt blinks but doesn't print anything from my keyboard.

What could be the problem?
Something related to interrupts maybe? (litex/bios/isr has been modified).

[mithro]

My guess would be interrupts too...

[pcotret]

Thanks, I'll get a closer look at it.

[enjoy-digital]

@pcotret: To confirm it's related to interrupts, can you add self.add_constant("UART_POLLING") to your SoC? It will switch the UART to polling mode (as we are doing for CPUs not supporting interrupts:

litex/litex/soc/integration/soc.py

Line 1253 in 8f5d971

self.add_constant("UART_POLLING")

).

[pcotret]

As I'm testing my core with litex_sim --cpu-type=cv32e41p, I've added a flag in my core/cv32e41p/core.py :

    # GCC Flags.
    @property
    def gcc_flags(self):
        flags = GCC_FLAGS[self.variant]
        flags += "-D__cv32e41p__ "
+       flags += f" -DUART_POLLING"

So, if I understand correctly, guilty part is related to the UART interrupt? (may not be correctly configured)

[enjoy-digital]

@pcotret: If it's working correctly when defining UART_POLLING the issue is indeed related to interrupts.

[pcotret]

Found my problem!
In fact, the UART interrupt was mapped on read-only bits in related CSRs...