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 >
