[PATCH net-next 0/2] net: ethernet: mtk_eth_soc: 9K jumbo frame support

[Sandeep Haemoon <sandeeph@loljews.com>]

This series makes the MediaTek SoC ethernet driver support 9K jumbo
frames on the 10G XGMII MACs (MT7988).  The driver currently advertises
a 2030-byte max_mtu and programs the MAC max-rx field for at most 2048
bytes, so MTU > 2K is rejected and 9K frames are not usable.

Patch 1 adds the MTK_NETSYS_RX_9K capability, advertises 9K max_mtu on
the XGMII MACs (from the DT phy_mode at probe, so DSA can raise the
conduit MTU before the netdev is opened), programs XMAC_RX_CFG2,
derives the shared RX buffer length from the largest MTU, sizes the RX
rings from it, and programs the PDMA RX SDL max frame.  A runtime MTU
change that would need a different ring buffer size is rejected with
-EBUSY while DMA is running; the rings are sized at the next open.

Patch 2 stops creating a page_pool for RX rings whose buffers do not
fit in an order-0 page (jumbo and HW-LRO rings).  page_pool is created
with MTK_PP_MAX_BUF_SIZE and order 0; using it for 9K buffers would
overrun.  The large-buffer path already uses mtk_max_buf_alloc().

This work is a forward-port of the MediaTek downstream jumbo series:
Mason Chang's "change default rx buffer length", "add 9k jumbo frame
support" and "add dynamic rx buffer adjustment support" (MediaTek
OpenWrt feed 999-eth-30/31/33, carried in
frank-w/BPI-Router-Linux), plus Frank Wunderlich's "try to fix crash
the right way".  The per-ring page_pool rule is added here to make the
9K path safe without disabling page_pool for every ring.

The equivalent change was tested on a BPI-R4 Pro 8X (MT7988, 10G lan6 /
MxL86252) on the 6.18.60 backport: with both ends at MTU 9000, 8K ICMP
passes and iperf3 with MSS 8900 reaches ~9.87 Gbit/s (vs ~2.57 Gbit/s
at MSS 1460); the DSA conduit is raised to 9004 at boot.  This v7.3
series is compile-tested with CONFIG_NET_MEDIATEK_SOC=y and
COMPILE_TEST=y; no hardware run of this exact tree yet.

The runtime-reallocation patch is not included: it reallocates the
shared RX rings when the MTU changes while an interface is up, removing
the -EBUSY restriction.  It is a larger change and will be sent
separately.

Sandeep Haemoon (2):
  net: ethernet: mtk_eth_soc: add 9K jumbo frame support
  net: ethernet: mtk_eth_soc: skip page_pool for large RX buffers

 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 142 ++++++++++++++++----
 drivers/net/ethernet/mediatek/mtk_eth_soc.h |   9 +-
 2 files changed, 122 insertions(+), 29 deletions(-)

base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
-- 
2.53.0