[PATCH net-next v2 0/8] net: macb: Add XDP support and page pool integration

[Paolo Valerio <pvalerio@redhat.com>]

Tested on Raspberry Pi 5.
All the changes are intended for gem only.

The series consists of two main changes:

- Migration from netdev_alloc_skb() to page pool allocation model,
  enabling skb recycling.
  This also adds support for multi-descriptor frame reception,
  removing the previous single-descriptor approach and avoiding
  potentially large contiguous allocations for e.g. jumbo frames
  with CONFIG_PAGE_SIZE_4KB.

- XDP support: Initial XDP implementation supporting major
  verdicts (XDP_PASS, XDP_DROP, XDP_REDIRECT, XDP_TX) along with
  the ndo_xdp_xmit function for packet redirection.

The driver now advertises NETDEV_XDP_ACT_BASIC, NETDEV_XDP_ACT_REDIRECT,
NETDEV_XDP_ACT_NDO_XMIT capabilities.

Some numbers (Andrew)
=====================

  Initially reported numbers (Mbps, w/ drops on the rx side):
  
  https://lore.kernel.org/netdev/b0bff7a8-a004-4eb7-bf1d-2137182e59f9@lunn.ch/
  
  The numbers are essentially always the same with these two packet sizes.
  cpu0 doesn't appear overloaded. Not sure if there's a bottlneck at the
  interface level on my hw, but it seems cpu can handle more.
  
  Second test run (with no drops on the rx side):
  
  tx side: iperf3 sending UDP (256B) packets roughly at line rate (no drops
  on the receiving side).
  
  rx side:
  - fixed cpu frequency
  - single rxq on cpu 0
  - iperf3 server on cpu 1-3
  - average w/ mpstat 20s interval 20s count
  
  Baseline:
  
  Average:     CPU    %usr    %sys    %soft  %idle
  Average:     all    3.64   15.05     0.87  80.42
  Average:       0    0.05    0.15    10.23  89.56
  Average:       1    4.20   16.98     0.00  78.81
  Average:       2    3.67   15.53     0.00  80.79
  Average:       3    4.07   16.83     0.00  79.09
  
  Page pool:
  
  Average:     CPU    %usr    %sys    %soft  %idle
  Average:     all    3.76   14.91     0.74  80.57
  Average:       0    0.05    0.12     7.81  91.98
  Average:       1    3.88   15.53     0.00  80.58
  Average:       2    4.35   17.23     0.00  78.42
  Average:       3    4.22   16.63     0.00  79.11


Previous versions
=================
  - v1: https://lore.kernel.org/netdev/20260115222531.313002-1-pvalerio@redhat.com/
  - RFC v2: https://lore.kernel.org/netdev/20251220235135.1078587-1-pvalerio@redhat.com/
  - RFC v1: https://lore.kernel.org/netdev/20251119135330.551835-1-pvalerio@redhat.com/

v1 -> v2
========
  - Fix potential NULL pointer dereference in gem_rx() when receiving an
    unexpected non-starting frame without an active skb (Jakub Kicinski).
  - Make sure to release both the pending skb and the current buff in fragment
    overflow error path (Jakub Kicinski).
  - Reuse the existing page pool instead of creating a new one in HRESP error
    recovery (Jakub Kicinski).
  - s/page/buffer/ in netdev_err() print out (Théo Lebrun)
  - Ensure pending queue->skb is released in gem_free_rx_buffers() (Théo Lebrun).
  - Use NET_SKB_PAD for the headroom when no xdp program is attached
  - Add netdev to pp_params (for pp stats)
  - Move ip_summed handling when RX_EOF is set as RX_SUM may not be reliable when
    RX_EOF is not set.
  - Sync for device no longer relies on PP_FLAG_DMA_SYNC_DEV reducing the
    sync size.
  - Introduce rx_ip_align field in struct macb
  - Fix incorrect DMA direction for page pool when attaching XDP program by 
    restoring close/open sequence as in a previous version (Jakub Kicinski).
  - Rename release_buff() to macb_tx_release_buff() for clarity (Théo Lebrun).
  - Do not unmap dma for XDP_TX buffers by ensuring tx_buff->mapping is zero for
    MACB_TYPE_XDP_TX buff_type (Jakub Kicinski).
  - Always return memory to pool on xdp_convert_buff_to_frame()
    failure (Jakub Kicinski).
  - Remove skip_xdp label (Théo, this is a bit different from your suggestion,
    let me know if you have a strong preference here)


RFC v2 -> v1
============
  - Removed bp->macbgem_ops.mog_init_rings(bp) call from macb_open()
  - Fixed includes (remove unneeded, moved one from header to macb_main.c)
  - Reverse xmas tree ordering (gem_rx, gem_rx_refill)
  - print_hex_dump_debug() instead of print_hex_dump()
  - Replaced rx frame length check with MACB_BIT(RX_EOF) for data_len
    calculation
  - Removed NET_IP_ALIGN handling in rx buffer size calculation
  - Updated debug format string to include rx_headroom and total size
  - Changed types to unsigned int in helper functions and variable
  - Removed unneeded line break

RFC v1 -> RFC v2
================
  - Squashed 1/6 and 2/6
  - Reworked rx_buffer_size computation. It no longer takes into
    accounts extra room.
  - A bunch of renaming (rx_offset => rx_headroom, removed MACB_MAX_PAD,
    MACB_PP_HEADROOM => XDP_PACKET_HEADROOM, data => ptr, xdp_q => xdp_rxq,
    macb_xdp() => gem_xdp(), macb_xdp_xmit() => gem_xdp_xmit())
  - Deduplicated buffer size computation in gem_xdp_valid_mtu()
    and gem_xdp_setup()
  - gem_xdp_setup() no longer close()/open()
  - Renaming from rx_skbuff to rx_buff is now got split in a separate commit
  - Open-coded gem_page_pool_get_buff()
  - Added missing rx_buff re-initialization in the error path during rx
  - Page pool creation failure now fails the device open
  - Moved xdp buff preparation inside gem_xdp_run()
  - Added missing rcu_access_pointer()
  - Turned return value in -EOPNOTSUPP for macb_xdp() on failure
  - moved tx_skb to tx_buff renaming to a separate commit
  - Removed some unneeded code and set MACB_TYPE_SKB for lp->rm9200_txq[desc].type as well
  - Replaced !!addr with a dedicated bool in macb_xdp_submit_frame()

Paolo Valerio (7):
  net: macb: rename rx_skbuff into rx_buff
  net: macb: Add page pool support handle multi-descriptor frame rx
  net: macb: use the current queue number for stats
  net: macb: add XDP support for gem
  net: macb: make macb_tx_skb generic
  net: macb: make tx path skb agnostic
  net: macb: introduce xmit support

Théo Lebrun (1):
  net: macb: move Rx buffers alloc from link up to open

 drivers/net/ethernet/cadence/Kconfig     |   1 +
 drivers/net/ethernet/cadence/macb.h      |  41 +-
 drivers/net/ethernet/cadence/macb_main.c | 850 ++++++++++++++++++-----
 3 files changed, 689 insertions(+), 203 deletions(-)

-- 
2.52.0