Re: [PATCH net] net: stmmac: Clear DMA errors for multi-channel interrupts

On Fri, 2026-10-30 at 11:22 +0100, Maxime Chevallier wrote:

The Multi-MSI interrupt handler doesn't clear the DMA error
interrupts,
and this leads to interrupt storms when one of these interrupts
starts
firing :

 - The RBU (rx buff unav) which triggers under high traffic load

   This triggers easily with iperf3 and small udp packets, and shows
   when running the netpoll kselftest

 - The RPS (rx process stop) which triggers when we stop the DMA RX.

   This one shows when restarting the RX logic without doing a
down/up
   cycle, like when attaching an XDP program. The XSK kselftests
   triggers it.

Let's make sure we clear these interrupts for multi-MSI cases. It's
already properly done for the single-chan interrupt, and for that
introduce an "ERR" DMA dir, as we don't want to touch the RI/TI bits
when handling these interrupts.

To avoid duplication, the DMA TX error handling is factored out in a
dedicated helper (in the same commit to ease backporting).

Both of the above storms have been found on dwmac-motorcomm (YT8601),
and are triggered by the xdp.py, xsk_reconfig.py, xdp_features.py,
ring_reconfig.py and netpoll_basic kernel selftests.

This seems to only affect dwmac4, there's no multi-msi mode on
dwmac1000, and on dwxgmac these interrupts are masked as of today.

Fixes: 6ccf12ae111e ("net: stmmac: use interrupt mode INTM=1 for
multi-MSI")
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---

[..,]

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>

thanks,
Nicolai

-- 
Nicolai Buchwitz [off-list ref]