MPU settings for external Ram with FreeRTOS

Andreas Schnitzer

Other Parts Discussed in Thread: HALCOGEN

Hello,

On a RM48 custom board want to use the external SDRAM together with FreeRTOS (approx. hdk setup)

Emif setting and test-routines are successful without FreeRTOS – with FreeRTOS any access from a (privileged) task leads to an abort, even when using the test function before any task creation /scheduler start.

Setup in halcogen (03.06.00)

This writes on sys_mpu.asm _mpuInit_

FreeRtos is also managing MPU, I don’t know if the settings of _mpuInit_ will be overwritten. However in os_port.c - prvSetupDefaultMPU( void ) is a MPU setup for FreeRtos.

There I tried some setups for the first configurable Region e.g.:

prvMpuSetRegion(portFIRST_CONFIGURABLE_REGION, 0x80000000, portMPU_SIZE_128MB | portMPU_REGION_ENABLE, portMPU_REGION_READ_WRITE | portMPU_REGION_DEVICE);

without getting the access.

So my question is how to setup the MPU/FreeRTOS for using the external SDRAM?

Thanks,

Andreas

over 11 years ago

0 Brian Fortman over 11 years ago

TI__Expert 7650 points

Hi Andreas,

We have received your inquiry. Sorry for the issues you are facing. I have forwarded it to one of our experts.

Best Regards,

Brian

0 Zhaohong Zhang over 11 years ago in reply to Brian Fortman

TI__Mastermind 22715 points

Andreas,

On Hercules devices, the Cortex-R4 MPU setting for the external SDRAM should be "device".

Thanks and regards,

Zhaohong

0 Andreas Schnitzer over 11 years ago in reply to Zhaohong Zhang

Intellectual 390 points

Hi Zhaohong,

i found that _mpuInit_ is not called when using FreeRTOS.

As described above, in the fnc prvMpuSetRegion i already tried portMPU_REGION_DEVICE without getting access.

Regards,

Andreas

0 Krzysztof Pilch over 11 years ago in reply to Andreas Schnitzer

Prodigy 40 points

Hi.

I am facing the same problem -- FreeRTOS seems to overwrite MPU settings and I am unable to use EMIF after that.

Andreas, have you found a solution for this?

Regards,

Krzysztof

0 Krzysztof Pilch over 11 years ago in reply to Krzysztof Pilch

Prodigy 40 points

I have found the solution.

Apparently FreeRTOS if run with support for MPU will restrict access to memory regions other than heap and task own stack. This means EMIF is mapped outside accessible memory for task code (but not main() function or any other function that is called before calling FreeRTOS task scheduler).

Similar issue may occure to other hardware mapped as memory that is not inside address ranges specified by FreeRTOS.

In order to gain access to such resources from tasks managed by FreeRTOS it is necesary to create task with access privilages. This page from FreeRTOS docummentation describes how to achive this.

Regards,

Krzysztof

0 Anthony F. Seely over 11 years ago in reply to Krzysztof Pilch

TI__Guru 68920 points

Kryzstof,

The link above wasn't working - I think this page is what you are referring to:

http://www.freertos.org/FreeRTOS-MPU-memory-protection-unit.html

The xTaskCreateRestricted() function takes a pxTaskDefinition argument which points to a structure that controls whether the task runs with or without privilege, and also the MPU settings for that task.

0 Krzysztof Pilch over 11 years ago in reply to Anthony F. Seely

Prodigy 40 points

You are right Anthony, that is exactly the page I was referring to. Thank you for pointing this out.

Regards,
Krzysztof

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MPU settings for external Ram with FreeRTOS