Public Hi Peter,
> From: Peter Robinson <[email protected]> > Sent: Thursday, August 20, 2026 3:59 PM > To: Begari, Padmarao <[email protected]> > Cc: [email protected]; Simek, Michal <[email protected]>; git > (AMD-Xilinx) <[email protected]> > Subject: 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? Presently using LWIP but we tested it on both. Regards Padmarao > > > 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 > >
