[BUG] RP2040/RP2350 with configNUMBER_OF_CORES=1 hang in debug mode

[rgrr]

Describe the bug
If one compiles a program for RP2040/RP2350 in single core mode and tries to debug with pyocd, TIMER0 (and perhaps TIMER1 on RP2350) is not running because DBGPAUSE=7 which required both cores to be active.

In my case execution hangs in timer_busy_wait_until() which is called during USB initialization.

Target

• Development board: Pico2, RP2350
• Instruction Set Architecture: ARM
• IDE and version: Eclipse
• Toolchain and version: PicoSDK 2.2.0

Host

• Host OS: Linux
• Version: Debian testing

To Reproduce

• Use project https://github.com/rgrr/yapicoprobe as target software
• set configNUMBER_OF_CORES=1
• debug with pyocd

Expected behavior
I would expect that the target behaves the same with and without debugger. But as said, TIMER0 is not running in debug mode.

Solution

In single core mode invoke multicore_reset_core1() on startup. My actual fix:

int main(void)
{
#if configNUMBER_OF_CORES != 2
    // this is actually just for debugging the probe firmware running with just one core (good for pyocd)
    // allow to run TIMER0 even in debug pause which would otherwise be inhibited because TIMER0.DBGPAUSE=7
    multicore_reset_core1();
#endif

But I think this fix belongs into FreeRTOS and not every user application.

But honestly I'm not sure if this is an SDK issue.

[cookpate]

The RP2040 port in portable/ThirdParty in this repository doesn't have a linker script that would make it easy to add this routine at startup. Interesting behavior. Is this observed only under a debug probe?

[rgrr]

yes, it only happens in debug mode. The RP2040/235x timer has a feature which allows to stop it in debug sessions.