[PATCH net-next v2 0/2] net: stmmac: dwmac-sun8i: Jumbo frames and an RX_TH fix

[Arun Iyengar via B4 Relay <devnull+aiyengar1990.gmail.com@kernel.org>]

The sun8i EMAC advertises a maximum MTU of 3712, but drops every frame
longer than 1518 bytes. Patch 2 sets the receiver's jumbo frame enable
bit and limits the MTU to what fits in one normal descriptor buffer
(2018). Patch 1 corrects two swapped RX threshold values; no in-tree
Allwinner board uses RX threshold mode, so none is affected.

Tested on an Orange Pi Zero2 (H616, RTL8211F over RGMII) at 1 Gbit/s,
with a 7.3 kernel carrying both patches:
- MTU 2000 and 2018: pings with DF set up to the full MTU pass in both
  directions, iperf3 gives 955 Mbit/s to the board and 905 Mbit/s from
  it, and the rx_length and rx_crc_errors counters stay at 0.
- Setting MTU 2019 is refused.
- At MTU 1500, a 90 minute run (bulk transfers up to 256 MiB both ways,
  iperf3 853/873 Mbit/s, 1000 pings each of 56, 1472 and 8000 bytes)
  had no loss and no new error counters.

In that 7.3 kernel, frames longer than 2044 bytes were dropped by a
local norm_desc change; v7.4-rc2 does the same through commit
834ec9530832 ("net: stmmac: drop split frames on AF_XDP zero-copy RX"),
which patch 2 now relies on.

These patches were developed with Claude (Anthropic) as a coding
assistant. It investigated the problem and wrote the code and the commit
messages; I reviewed them, and they were tested on an Orange Pi Zero2
(H616) as described above.

---
Changes in v2:
- Patch 1: add the Fixes: tag, and correct the commit message: RX
  threshold mode depends on snps,force_thresh_dma_mode, not on RX
  checksum offload (Sashiko AI review)
- Cc Corentin Labbe (author of the Fixes: target)
- Rebased onto current net-next; patch 2 unchanged
- Link to v1: https://patch.msgid.link/20261110-sun8i-emac-jumbo-v1-0-84bf00e9ffa3@gmail.com

---
Arun Iyengar (2):
      net: stmmac: dwmac-sun8i: Fix the RX_TH threshold encoding
      net: stmmac: dwmac-sun8i: Enable jumbo frames up to MTU 2018

 drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 29 +++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)
---
base-commit: c88fd6989aea9237a60a4859139a265bfb7ddc0b
change-id: 20261110-sun8i-emac-jumbo-4839f984a6a9

Best regards,
--  
Arun Iyengar <aiyengar1990@gmail.com>