How to disable data cache on stm32H743?

[SKS2CNC]

I'm using STM32H743 in my project.
If anyone knows how to disable D-cache, please help!
D-cache really interferes with my work - I'm tired of fighting it!
SCB_DisableDCache() - leads to nothing.

[LCE]

Just don't enable it, the source code shouldn't do that on its own.

Don't know about CubeMx, though... 

BTW, if CubeMx tells you that you need the cache for any peripheral / middleware to work: that's wrong.

[SKS2CNC]

Thank you for your participation. In my projects, I use Cube very sparingly - it often cannot help, but only loads the processor with unnecessary code. Unfortunately, the cache works by default - this is indicated in the documentation and in the debugger. I also observe this when processing arrays - the data does not appear immediately, but with a delay of several milliseconds - in my project this is critical. Flushing the cache by address or shared takes 50 microseconds - too much time and breaks the logic of the state machine. I will accept any advice on how to turn off the cache completely.

[mƎALLEm]

You can disable the Cache on a specific memory region using the MPU by configuring it as Shared memory.

Example:

 

void MPU_Config(void)
{
 MPU_Region_InitTypeDef MPU_InitStruct;
 
 /* Disable the MPU */
 HAL_MPU_Disable();
 /* Configure the MPU attributes as WB-WA for SRAM */
 MPU_InitStruct.Enable = MPU_REGION_ENABLE;
 MPU_InitStruct.BaseAddress = <Your memeory start address>;
 MPU_InitStruct.Size = MPU_REGION_SIZE_<of your memeory region>;
 MPU_InitStruct.AccessPermission = MPU_REGION_FULL_ACCESS;
 MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;
 MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
 MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
 MPU_InitStruct.Number = MPU_REGION_NUMBER0;
 MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
 MPU_InitStruct.SubRegionDisable = 0x00;
 MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_ENABLE;

 HAL_MPU_ConfigRegion(&MPU_InitStruct);

 /* Enable the MPU */
 HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);
}

 

 

[Pavel A.]

Try LL_MPU_CTRL_HFNMI_PRIVDEF instead of LL_MPU_CTRL_HFNMI_PRIVDEF_NONE.

 

[SKS2CNC]

Sorry for the long answer - I was testing!
Thanks to everyone - advice with LL_MPU_CTRL_HFNMI_PRIVDEF - the cache is disabled for the necessary memory areas - this is what you need!

[mƎALLEm]

Hello @SKS2CNC  if your question has been answered please mark Accepted as Solution the comment that answered your question.

[LCE]

I don't see that any cache is enabled by default, neither in the AN4839 (see 4 Mistakes to avoid and tips, the advice to invalidate cache before enabling it sounds like it's OFF at CPU start), nor in my H723/733/735 source code (not using HAL). I'm not using any cache, and I'm not disabling it.

[SKS2CNC]

Thanks for the links to AN4839 and PM0253 - it helped for general understanding.

[mƎALLEm]

Did the config I provided solved your issue? 

[SKS2CNC]

I don't use the cube much - it was enough for me to solve
LL_MPU_Enable(LL_MPU_CTRL_HFNMI_PRIVDEF);
By the way, for some reason I didn’t find these LowLevel functions in the UM2217 ;)