STM32H750 Ethernet stops responding to ARP and ping after some time

[Artron]

Hello, 

I am using an STM32H750I-DK Discovery board with LAN8742 PHY, MII mode, FreeRTOS and LwIP.

Ethernet works initially: the STM32 IP appears in arp -a and I can ping it. After some time, the ARP entry disappears and ping gives Request timed out or Destination host unreachable.

I have already checked the IP configuration, MII configuration, PHY link, DMA, MPU/cache, and tried disabling RTP traffic, but the issue still occurs.

What could cause the STM32H750 Ethernet connection to stop responding to ARP and ping after working normally for some time? What should I check next?

[SAHSTM]

Hello,

Based on the symptoms you reported, the problem is most likely related to the Ethernet driver / LwIP / DMA / cache coherency layer rather than to the IP configuration. Since the board works initially and then stops responding to ARP and ping after some time, this suggests that Rx packet processing may be blocked, descriptors may no longer be recycled correctly, or the Ethernet interface may no longer be properly serviced by the system.

Please check whether the Ethernet interrupt is still being triggered when the issue occurs, as a loss of interrupt activity or Rx servicing would be a strong indication that packet processing has stopped.

In addition, please verify the following points:

• Rx/Tx descriptors are correctly initialized and continuously updated, and that buffers are properly returned to the DMA after reception.

• On STM32H7 devices, Ethernet buffers and descriptors must be handled carefully with respect to DCache coherency. Please verify that the memory regions used by Ethernet are configured as required, and that cache maintenance operations are correctly applied.

With Regards,

[Artron]

Thank you for the reply. I have solved this problem. It was caused by the RX and TX descriptors and the memory region settings. 

[sergey23]

If DMA buffers are placed in non-DMA-accessible region, the drive won’t work in the first place. If it works but then stops, it is an unusual situation. Could you elaborate on that please? Sounds like a different failure mode.