TMS570LS3137: Unexpected HALcoGen MPU Background Region Enable Function Behaviour

Hi Tyler Bailey,

Is it possible to share your project to re-create the issue at my end?

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Thanks & regards,
Jagadish.

Hi Jagadish,

My apologies for the late reply. Unfortuntately, I'm unable to share the full project, however here are the details necessary to recreate the issue:

1. Create a HALcoGen project for the TMS570LS3137 with FreeRTOS.
2. Within os_port.c, make the changes detailed below to perform a read from the EMIF CS0 region with the MPU background region enabled using the HALcoGen provided MPU functions within sys_mpu.h:

   1. static void prvSetupDefaultMPU( void )
      {
      	/* make sure MPU is disabled */
      	prvMpuDisable();
      
      	/* First setup the entire flash for unprivileged read only access. */
      	prvMpuSetRegion(portUNPRIVILEGED_FLASH_REGION,  0x00000000, portMPU_SIZE_4MB | portMPU_REGION_ENABLE, portMPU_PRIV_RO_USER_RO_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Setup the first 32K for privileged only access.  This is where the kernel code is
      	placed. */
      	prvMpuSetRegion(portPRIVILEGED_FLASH_REGION,  0x00000000, portMPU_SIZE_32KB | portMPU_REGION_ENABLE, portMPU_PRIV_RO_USER_NA_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Setup the the entire RAM region for privileged read-write and unprivileged read only access */
      	prvMpuSetRegion(portPRIVILEGED_RAM_REGION,  0x08000000, portMPU_SIZE_512KB | portMPU_REGION_ENABLE, portMPU_PRIV_RW_USER_RO_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Default peripherals setup */
      	prvMpuSetRegion(portGENERAL_PERIPHERALS_REGION,  0xF0000000,
      					portMPU_SIZE_256MB | portMPU_REGION_ENABLE | portMPU_SUBREGION_1_DISABLE | portMPU_SUBREGION_2_DISABLE | portMPU_SUBREGION_3_DISABLE | portMPU_SUBREGION_4_DISABLE,
      					portMPU_PRIV_RW_USER_RW_NOEXEC | portMPU_DEVICE_NONSHAREABLE);
      
      	/* Privilege System Region setup */
      	prvMpuSetRegion(portPRIVILEGED_SYSTEM_REGION,  0xFFF80000, portMPU_SIZE_512KB | portMPU_REGION_ENABLE, portMPU_PRIV_RW_USER_RO_NOEXEC | portMPU_DEVICE_NONSHAREABLE);
      	
      	/* START ADDED FOR TEST 1. */
      	_mpuEnableBackgroundRegion_();
      	/* END ADDED FOR TEST 1. */
      
      	/* Enable MPU */
      	prvMpuEnable();
      
      	/* START ADDED FOR TEST 2. */
      	// Perform a read at EMIF CS 0
      	uint8_t data = *(uint8_t*)(0x80000000U);
      	/* END ADDED FOR TEST 2. */
      }

3. When debugging the modified code in CCS, add a breakpoint on the line which performs a read from EMIF memory. When stepping over this breakpoint, no data abort occurs.
4. Now, to perform a test of the case where the MPU background region is disabled, modify the prvSetupDefaultMPU() function as follows:

   1. static void prvSetupDefaultMPU( void )
      {
      	/* make sure MPU is disabled */
      	prvMpuDisable();
      
      	/* First setup the entire flash for unprivileged read only access. */
      	prvMpuSetRegion(portUNPRIVILEGED_FLASH_REGION,  0x00000000, portMPU_SIZE_4MB | portMPU_REGION_ENABLE, portMPU_PRIV_RO_USER_RO_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Setup the first 32K for privileged only access.  This is where the kernel code is
      	placed. */
      	prvMpuSetRegion(portPRIVILEGED_FLASH_REGION,  0x00000000, portMPU_SIZE_32KB | portMPU_REGION_ENABLE, portMPU_PRIV_RO_USER_NA_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Setup the the entire RAM region for privileged read-write and unprivileged read only access */
      	prvMpuSetRegion(portPRIVILEGED_RAM_REGION,  0x08000000, portMPU_SIZE_512KB | portMPU_REGION_ENABLE, portMPU_PRIV_RW_USER_RO_EXEC | portMPU_NORMAL_OIWTNOWA_SHARED);
      
      	/* Default peripherals setup */
      	prvMpuSetRegion(portGENERAL_PERIPHERALS_REGION,  0xF0000000,
      					portMPU_SIZE_256MB | portMPU_REGION_ENABLE | portMPU_SUBREGION_1_DISABLE | portMPU_SUBREGION_2_DISABLE | portMPU_SUBREGION_3_DISABLE | portMPU_SUBREGION_4_DISABLE,
      					portMPU_PRIV_RW_USER_RW_NOEXEC | portMPU_DEVICE_NONSHAREABLE);
      
      	/* Privilege System Region setup */
      	prvMpuSetRegion(portPRIVILEGED_SYSTEM_REGION,  0xFFF80000, portMPU_SIZE_512KB | portMPU_REGION_ENABLE, portMPU_PRIV_RW_USER_RO_NOEXEC | portMPU_DEVICE_NONSHAREABLE);
      	
      	/* START ADDED FOR TEST 1. */
      	_mpuDisableBackgroundRegion_();
      	/* END ADDED FOR TEST 1. */
      
      	/* Enable MPU */
      	prvMpuEnable();
      
      	/* START ADDED FOR TEST 2. */
      	// Perform a read at EMIF CS 0
      	uint8_t data = *(uint8_t*)(0x80000000U);
      	/* END ADDED FOR TEST 2. */
      }

5. When debugging the modified code in CCS, again add a breakpoint on the line which performs a read from EMIF memory. When stepping over this breakpoint, a data abort occurs.

These results illustrate the inverted behaviour I've described - when the MPU background region is "enabled", no data abort occurs - this is the opposite of what I'm expecting given the details provided about the TMS570LS3137's Cortex-R4F MPU.

Thanks,

Tyler

Hi Tyler,

Thanks for your code, i will go through it and i will try to provide my updates as soon as possible.

--
Thanks & regards,
Jagadish.

Hi Tyler,

Apologies for the delay in late response, i was stuck with other issues in this mean time.

I found something:

I think you should need to disable the region-1 to test the Background region enable check:

Please refer below highlighted sentences in the core reference manual:

Can you please once again test the behavior of BR bit by disabling the region-1 once.

--
Thanks & regards,
Jagadish.