S32k344 NVIC_SystemReset() not working. no reset occurs.

[not_a_duck]

I was testing some fault handling and explicitly called NVIC_SystemReset() to trigger a reset.
It does not seem to work. I confirmed that the SYSRESETREQ bit is set and the processor is just running the NOP indefinitely. 

/**
  \brief   System Reset
  \details Initiates a system reset request to reset the MCU.
 */
__NO_RETURN __STATIC_INLINE void __NVIC_SystemReset(void)
{
  __DSB();                                                          /* Ensure all outstanding memory accesses included
                                                                       buffered write are completed before reset */
  SCB->AIRCR  = (uint32_t)((0x5FAUL << SCB_AIRCR_VECTKEY_Pos)    |
                           (SCB->AIRCR & SCB_AIRCR_PRIGROUP_Msk) |
                            SCB_AIRCR_SYSRESETREQ_Msk    );         /* Keep priority group unchanged */
  __DSB();                                                          /* Ensure completion of memory access */

  for(;;)                                                           /* wait until reset */
  {
    __NOP();
  }
}

also tested commenting out __DSB() and writing directly to SCB->AIRCR 

SCB->AIRCR = 0x05fA0004;

same result. reset does not occur.

also tested removing the debugger and doing a powercycle and it just boots up and then gets stuck in the NOP. 

[not_a_duck · Accepted solution]

So I think the answer here is that Cortex M7 reset request (SCB->AIRCR "SYSRESETREQ") is not implemented in the s32k344.
(@petervlna please let me know if I'm mistaken about this.)

If someone else stumbles upon this and needs to perform functional or destructive resets from software here is a distilled version of what the POWER IP module does.

/// S32K344_MC_ME.h

    /* MC_ME - Peripheral instance base addresses */
    /** Peripheral MC_ME base address */
    #define IP_MC_ME_BASE                            (0x402DC000u)
    /** Peripheral MC_ME base pointer */
    #define IP_MC_ME                                 ((MC_ME_Type *)IP_MC_ME_BASE)
/// S32K344_MC_ME.h

void perform_functional_reset(void)
{
    // functional reset request
    IP_MC_ME->MODE_CONF = 0x2U;

    IP_MC_ME->MODE_UPD = 0x1U;
    IP_MC_ME->CTL_KEY = 0x00005AF0U;
    IP_MC_ME->CTL_KEY = 0x0000A50FU;
}

void perform_destructive_reset(void)
{
    // destructive reset request
    IP_MC_ME->MODE_CONF = 0x1U;

    IP_MC_ME->MODE_UPD = 0x1U;
    IP_MC_ME->CTL_KEY = 0x00005AF0U;
    IP_MC_ME->CTL_KEY = 0x0000A50FU; 
}

 
also probably good practice to check Functional and destructive reset reason on boot up and clear the flags for FES.

uint32_t f_reset_reason = IP_MC_RGM->FES;
uint32_t d_reset_reason = IP_MC_RGM->DES;

// clear the reset reason
IP_MC_RGM->FES = f_reset_reason;

[danielmartynek]

Hi @not_a_duck,

Yes, that's correct.

https://community.nxp.com/t5/S32K/S32K344-software-reset-fail/m-p/1454018#M15288

Regards,

Daniel