Re: [PATCH 0/8] net: mrmac: Fix Rx packet loss on back-to-back frames

On Thu, 20 Aug 2026 at 10:26, Padmarao Begari <[email protected]> wrote:
>
> The MRMAC Rx path drops frames when two arrive back to back. recv()
> always starts at rx_bd[0] and clears the status of both descriptors,
> and the status field is the only record that a frame arrived, so the
> second frame is lost without any error being reported. This shows up
> with multiple boards on a switch, where the extra traffic makes
> back-to-back arrivals common and network transfers time out.

Out of interest is this using the legacy IP or LWIP stack?

> Fixing that needs an Rx ring the driver can index, so the series first
> makes the ring scalable and then fixes the bug:
>
>   1-3  Independent cleanups: check memalign() failures, give the
>        driver its own Rx buffer pool instead of borrowing the shared
>        net_rx_packets[], and read the link speed from the standard
>        max-speed property.
>
>   4-6  Make the descriptor ring scale: index the contiguous BD blocks
>        directly, build the Rx chain in a loop over RX_DESC, and
>        program CURDESC only once the ring is complete in memory.
>
>   7    Track the descriptor to consume next in rx_bd_idx and take
>        completion from the per-descriptor COMPLETE bit, so a
>        descriptor goes back to hardware only after the network stack
>        has read it.
>
>   8    Size the Rx ring from ETH_PACKETS_BATCH_RECV, so a full
>        eth_rx() call can be served without hardware running out of
>        descriptors.
>
> Padmarao Begari (8):
>   net: mrmac: check memalign() return values
>   net: mrmac: use a driver-owned RX buffer pool
>   net: mrmac: switch to max-speed property
>   net: mrmac: use contiguous BD arrays
>   net: mrmac: initialize the Rx BD ring in a loop
>   net: mrmac: write CURDESC after ring setup
>   net: mrmac: fix Rx packet loss on back-to-back frames
>   net: mrmac: increase the Rx BD ring
>
>  drivers/net/xilinx_axi_mrmac.c | 235 +++++++++++++++++----------------
>  drivers/net/xilinx_axi_mrmac.h |  20 ++-
>  2 files changed, 137 insertions(+), 118 deletions(-)
>
> --
> 2.34.1
>