How to use RTC while using Root of Trust on the NUCLEO-N657X0-Q board.

[young_seo]

I am a user of the NUCLEO-N657X0-Q board.

 

I am using the NUCLEO-N657X0-Q board with Root of Trust enabled, and I want to use the RTC.
Out of the 3 stages  (FSBL → Secure App → Non-Secure App)  I want to use the RTC in the Non-Secure App.

 

My development environment is as follows:
1> Development tool: Keil uVision V5.42
2> Example source: STM32Cube\Repository\STM32Cube_FW_N6_V1.2.0\Projects\NUCLEO-N657X0-Q\Applications\ROT\OEMuROT_Appli
3> Development board: NUCLEO-N657X0-Q

 

The biggest problem is that when HAL_RTC_Init() is called in the Non-Secure App, it hangs.

 

The source for STM32Cube_FW_N6_V1.2.0\Projects\NUCLEO-N657X0-Q\Applications\ROT\OEMuROT_Appli was created by referencing STM32Cube_FW_N6_V1.2.0\Projects\STM32N6570-DK\Applications\ROT\OEMuROT_Appli.

 

The code I added is as follows.

1. Added to the main function of the Secure App.

HAL_RIF_RISC_SetSlaveSecureAttributes(RIF_RCC_PERIPH_INDEX_RTC, RIF_ATTRIBUTE_NSEC);




2. Added a function to the Non-Secure App.


RTC_HandleTypeDef RtcHandle;

void rtc_Init(void)
{
    memset(&RtcHandle, 0,  sizeof(RTC_HandleTypeDef));

    RtcHandle.Instance            = RTC;
    RtcHandle.Init.HourFormat     = RTC_HOURFORMAT_24;
    RtcHandle.Init.AsynchPrediv   = 0x7F;
    RtcHandle.Init.SynchPrediv    = 0xF9;
    RtcHandle.Init.OutPut         = RTC_OUTPUT_DISABLE;
    RtcHandle.Init.OutPutRemap    = RTC_OUTPUT_REMAP_NONE;
    RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
    RtcHandle.Init.OutPutType     = RTC_OUTPUT_TYPE_OPENDRAIN;
    RtcHandle.Init.OutPutPullUp   = RTC_OUTPUT_PULLUP_NONE;
    RtcHandle.Init.BinMode        = RTC_BINARY_NONE;

    printf("rtc_Init() start 111...\r\n");

    if (HAL_RTC_Init(&RtcHandle) != HAL_OK)
    {
        printf("rtc_Init() Fail!\r\n");
        return;
    }
    printf("rtc_Init() OK!\r\n");
}



void HAL_RTC_MspInit(RTC_HandleTypeDef *hrtc)
{
    RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};

    if (hrtc->Instance == RTC)
    {
        HAL_PWR_EnableBkUpAccess();

        PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC;
        PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;
        HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) ;


        __HAL_RCC_RTC_CLK_ENABLE();
        __HAL_RCC_RTCAPB_CLK_ENABLE();

        printf("HAL_RTC_MspInit() end...\r\n") ;

    }
}


int main(void)
{
.
.
.

#ifdef PRINT_BOOT_TIME
  printf("\r\nBoot time : %u ms at %u MHz", (unsigned int)(time), (unsigned int)(SystemCoreClock/1000000U));
  printf("\r\n");
#endif
  printf("\r\n======================================================================");
  printf("\r\n=              (C) COPYRIGHT 2024 STMicroelectronics                 =");
  printf("\r\n=                                                                    =");
  printf("\r\n=                          User App #%c                               =", *pUserAppId);
  printf("\r\n======================================================================");
  printf("\r\n\r\n");

  /* User App firmware runs*/

  rtc_Init() ;

  FW_APP_Run();

.
.
.  


}

 

 

The execution result is as follows.

 

======================================================================
              (C) COPYRIGHT 2024 STMicroelectronics                 =
                                                                    =
                          User App #A                               =
======================================================================

rtc_Init() start 111...
HAL_RTC_MspInit() end…

 

 

 

 

 

if (HAL_RTC_Init(&RtcHandle) != HAL_OK) //// ==> It hangs at this point.

 

 

I would like to inquire about how to use RTC in a ROT (Root of Trust) environment.
The actual RTC usage is in the Non-Secure App.

 

Thank you.