data cache issue for ethernet in stm32h753 (Assertion "pbuf_free: p->ref > 0" failed at line 753)

[Rahul3]

I have read quite a few threads about ethernet on the H7, along with several internet posts. 

I've followed this guide:

https://community.st.com/s/article/How-to-create-project-for-STM32H7-with-Ethernet-and-LwIP-stack-working?t=1679361727348

As well as this guide:

https://github.com/AnielShri/STM32H745_Ethernet/blob/master/Documentation/lwip_nortos.md

They are similar, with some slight differences with the MPU cache settings.

My first test is just basic ICMP - which doesn't work. That is, until I comment out this line:

SCB_EnableDCache();

So, of course, that implies something with the data cache, and memory locations.

So, my settings looks like these:

LWIP settings:

I've added the following to the linker script:

  /* Modification start */
  .lwip_sec (NOLOAD) : {
    . = ABSOLUTE(0x30040000);
    *(.RxDecripSection) 
    
    . = ABSOLUTE(0x30040060);
    *(.TxDecripSection)
    
    . = ABSOLUTE(0x30040200);
    *(.RxArraySection) 
  } >RAM_D2

Sometimes, I get this error upon each ICMP packet that is received:

 Assertion "pbuf_free: p->ref > 0" failed at line 753 in ../Middlewares/Third_Party/LwIP/src/core/pbuf.c

Again, it goes away when I disable the dcache. I'm not sure what else to try. I must have something not quite right.

Thanks.

[mƎALLEm · Accepted solution]

Hello,

Probably an issue in the LWIP heap memory region:

I suggest you to check again the MPU config (Bufferability, Sharability, Cachability and TEX level) as described in https://community.st.com/s/article/How-to-create-project-for-STM32H7-with-Ethernet-and-LwIP-stack-working?t=1679361727348: