Re: [PATCH net v4 0/2] stmmac crash/stall fixes when under memory pressure

[Sam Edwards]

On Thu, Apr 2, 2026 at 10:16 AM Russell King (Oracle)
<linux@xxxxxxxxxxxxxxx> wrote:
> I've tested this on my Jetson Xavier platform. One of the issues I've
> had is that running iperf3 results in the receive side stalling because
> it runs out of descriptors. However, despite the receive ring
> eventually being re-filled and the hardware appropriately prodded, it
> steadfastly refuses to restart, despite the descriptors having been
> updated.

Hi Russell,

Just to make sure I understand correctly: before my patches, you've
been observing this problem on Xavier for a while (no interrupts, ring
goes dry); with my patches, the ring is refilled, but the dwmac5
doesn't resume DMA. (Ah, just saw your follow-up email.)

> Any ideas?

Off the top of my head, my hypothesis is that dwmac5 has an additional
tripwire when the receive DMA is exhausted, and the
stmmac_set_rx_tail_ptr()/stmmac_enable_dma_reception() at the end of
stmmac_rx_refill() aren't sufficient to wake it back up.

I think this is new to dwmac5, because my RK3588 (dwmac4.20 iirc)
happily resumes after the same condition.

You gave a lot of info; thanks! I'll try to scrape up some
documentation on dwmac5 to see if there's something more
stmmac_rx_refill() ought to be doing. I think I have a Xavier NX
around here somewhere, I'll see if I can repro the problem.

Cheers,
Sam