Hello,
I'm working on a project that uses the Serial LTE Modem (SLM) application on a custom board. The main processor sends data to the nRF9160 over UART. The project is build using NCS v2.9.1 with TF-M, and UART2 is configured as the SLM UART.
I ran into an issue where the nRF9160 would hit an SPU fault caused by a RAM access violation right after switching to the non-secure firmware. The fault is triggered whenever the main processor TX line is high, which it is when it's idle.
The problem came from MCUBOOT. In the nrf_cleanup_peripheral() function in nrf_cleanup.c,file UARTs 0, 1, 20, and 30 are deinitialized before do_boot() jumps to the non-secure reset vector, but UART2 wasn’t included in that list. Adding UART2 to the deinitialization list solved the issue for me.
I'm not sure, but I think it might also be related to this ticket.
#if defined(NRF_UARTE_CLEANUP)
static NRF_UARTE_Type *nrf_uarte_to_clean[] = {
#if defined(NRF_UARTE0)
NRF_UARTE0,
#endif
#if defined(NRF_UARTE1)
NRF_UARTE1,
#endif
// Add UART2 to the list of UARTS to cleanup so so it won't cause an SPU fault if enabled by MCUboot in
// firmware that builds with TF-M
#if defined(NRF_UARTE2)
NRF_UARTE2,
#endif
#if defined(NRF_UARTE20)
NRF_UARTE20,
#endif
#if defined(NRF_UARTE30)
NRF_UARTE30,
#endif
};
Regards,
Mike