[PATCH net-next v4 0/6] net: bcmgenet: add XDP support

[Nicolai Buchwitz <nb@tipi-net.de>]

Add XDP support to the bcmgenet driver, covering XDP_PASS, XDP_DROP,
XDP_TX, XDP_REDIRECT, and ndo_xdp_xmit.

The first patch converts the RX path from the existing kmalloc-based
allocation to page_pool, which is a prerequisite for XDP. The remaining
patches incrementally add XDP functionality and per-action statistics.

Tested on Raspberry Pi CM4 (BCM2711, bcmgenet, 1Gbps link):
- XDP_PASS: 943 Mbit/s TX, 935 Mbit/s RX (no regression vs baseline)
- XDP_PASS latency: 0.164ms avg, 0% packet loss
- XDP_DROP: all inbound traffic blocked as expected
- XDP_TX: TX counter increments (packet reflection working)
- Link flap with XDP attached: no errors
- Program swap under iperf3 load: no errors
- Upstream XDP selftests (xdp.py): pass_sb, drop_sb, tx_sb passing
- XDP-based EtherCAT master (~37 kHz cycle rate, all packet processing
  in BPF/XDP), stable over multiple days

Changes since v3:
  - Fixed page leak on partial bcmgenet_alloc_rx_buffers() failure:
    free already-allocated rx_cbs before destroying page pool.
    (Simon Horman)
  - Fixed GENET_Q16_TX_BD_CNT defined as 64 instead of 32, matching
    the documented and intended BD allocation. (Simon Horman)
  - Moved XDP TX ring to a separate struct member (xdp_tx_ring)
    instead of expanding tx_rings[] to DESC_INDEX+1. (Justin Chen)
  - Added synchronize_net() before bpf_prog_put() in XDP prog swap
    to ensure NAPI is not still running the old program.
  - Removed goto drop_page inside switch; inlined page_pool_put
    calls in each failure path. (Justin Chen)
  - Removed unnecessary curly braces around case XDP_TX. (Justin Chen)
  - Moved int err hoisting from patch 2 to patch 1 where it belongs.
    (Justin Chen)
  - Kept return type on same line as function name throughout, to
    match existing driver style. (Justin Chen)
    Note: checkpatch flags one alignment CHECK on bcmgenet_xdp_xmit_frame
    as a result; keeping per Justin's preference.
  - Fixed XDP_TX xmit failure path: use xdp_return_frame_rx_napi()
    instead of page_pool_put_full_page() after xdp_convert_buff_to_frame
    to avoid double-free of the backing page.
  - Count XDP TX packets/bytes in TX reclaim so XDP traffic is visible
    in standard network stats (ip -s link show).
  - Added headroom check before TSB prepend in XDP_TX to prevent
    out-of-bounds write when bpf_xdp_adjust_head consumed headroom.

Changes since v2:
  - Fixed xdp_prepare_buff() called with meta_valid=false, causing
    bcmgenet_xdp_build_skb() to compute metasize=UINT_MAX and corrupt
    skb meta_len. Now passes true. (Simon Horman)
  - Removed bcmgenet_dump_tx_queue() for ring 16 in bcmgenet_timeout().
    Ring 16 has no netdev TX queue, so netdev_get_tx_queue(dev, 16)
    accessed beyond the allocated _tx array. (Simon Horman)
  - Fixed checkpatch alignment warnings in patches 4 and 5.

Changes since v1:
  - Fixed tx_rings[DESC_INDEX] out-of-bounds access. Expanded array
    to DESC_INDEX+1 and initialized ring 16 with dedicated BDs.
  - Use ring 16 (hardware default descriptor ring) for XDP TX,
    isolating from normal SKB TX queues.
  - Piggyback ring 16 TX completion on RX NAPI poll (INTRL2_1 bit
    collision with RX ring 0).
  - Fixed ring 16 TX reclaim: skip INTRL2_1 clear, skip BQL
    completion, use non-destructive reclaim in RX poll path.
  - Prepend zeroed TSB before XDP TX frame data (TBUF_64B_EN requires
    64-byte struct status_64 prefix on all TX buffers).
  - Tested with upstream XDP selftests (xdp.py): pass_sb, drop_sb,
    tx_sb all passing. The multi-buffer tests (pass_mb, drop_mb,
    tx_mb) fail because bcmgenet does not support jumbo frames /
    MTU changes; I plan to add ndo_change_mtu support in a follow-up
    series.

Nicolai Buchwitz (6):
  net: bcmgenet: convert RX path to page_pool
  net: bcmgenet: register xdp_rxq_info for each RX ring
  net: bcmgenet: add basic XDP support (PASS/DROP)
  net: bcmgenet: add XDP_TX support
  net: bcmgenet: add XDP_REDIRECT and ndo_xdp_xmit support
  net: bcmgenet: add XDP statistics counters

 drivers/net/ethernet/broadcom/Kconfig         |   1 +
 .../net/ethernet/broadcom/genet/bcmgenet.c    | 641 +++++++++++++++---
 .../net/ethernet/broadcom/genet/bcmgenet.h    |  19 +
 3 files changed, 564 insertions(+), 97 deletions(-)

--
2.51.0