example_dma_external: interrupt service routine never runs

[grinningmosfet]

Summary

In the example_dma_external example, the interrupt service routine should print D on the serial output via the PRINTF macro when an end of DMA transaction (DMA_TRANS_END_INTR) interrupt is triggered:

void dma_intr_handler_trans_done()
{
    PRINTF("D");
}

But it does not. The interrupt does not seem to be fired or handled.

Steps to reproduce

Run the example_dma_external example according to the docs.

• Clone the X-HEEP repository
• Open a shell in the x-heep directory and issue the following commands:
• conda activate core-v-mini-mcu
• make mcu-gen
• Edit x-heep/sw/applications/example_dma_external/main.c by replacing the line #define PRINTF_IN_SIM 0 by #define PRINTF_IN_SIM 1
• make app PROJECT=example_dma_external
• make verilator-sim
• cd ./build/openhwgroup.org_systems_core-v-mini-mcu_0/sim-verilator
• ./Vtestharness +firmware=../../../sw/build/main.hex
• cat uart0.log

Expected behaviour

Finding some Ds into the uart0.log logs file.

Actual behaviour

uart0.log logs the following:

 ===================================

  TESTING DMA ON EXTERNAL PERIPHERAL

 ===================================

 tran: 0        Ok!
 load: 0        Ok!
 laun: 0        Ok!
 >> Finished transaction.
 External DMA success

The program exit value is 0. There is not a single standalone D printed.

[JuanSapriza]

Hello! Firstly, thank you @grinningmosfet for the detailed issue!

This might be related to #423 and #382. As mentioned in this comment the issue might be caused by the overriding of the weak implementations.

I will not have time to tackle this in the following weeks, but if @grinningmosfet needs it and wants to take a look at these ToDos we can try to debug it asynchronously here.

ToDo's

• [ ] Check if the fix of the aforementioned comment also fixes this
• [ ] Find the first commit that breaks this (to tell if the problem comes from the interrupt side or the file inclusion side)

[grinningmosfet]

Hey @JuanSapriza,

While working on PR #417, I've found a way (already implemented in the DMA's HAL) to register external ISRs; see below.

Adding the following lines before the DMA initialization fixes this issue:

if(plic_Init()) {return EXIT_FAILURE;};
if(plic_irq_set_priority(EXT_INTR_0, 1)) {return EXIT_FAILURE;};
if(plic_irq_set_enabled(EXT_INTR_0, kPlicToggleEnabled)) {return EXIT_FAILURE;};

plic_assign_external_irq_handler(EXT_INTR_0, &handler_irq_iffifo);

For more context, you can check out this commit.