hisi_higmac: harden bare-minimum driver toward production parity (TSO, EEE, ethtool, multicast, PM)

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Context

PR #44 landed the hisi_higmac driver — a minimal mainline port of the vendor's 3000-line higmac driver from Hi3516A_SDK_V1.0.8.0. The mainline version is 990 lines and intentionally stripped to the descriptor-ring TX/RX path that QEMU emulates and that real hardware needs to boot.

Sufficient for: ifup, DHCP, ping, SSH, web management.
Insufficient for: production camera traffic patterns (high-throughput RTSP streams, dropped-frame tracking, power management).

Missing vs. vendor driver

Feature	Vendor (4.9 BSP)	Mainline hisi_higmac
TSO (TCP Segmentation Offload)	✅ via TSO_COE_CTRL (0x02E8) + descriptor tso_* flags	❌
COE checksum offload	✅ IPv4/IPv6 RX+TX checksum	❌
EEE / autoEEE	✅ separate autoeee/ sub-driver, PHY-coordinated	❌
AVS (adaptive voltage scaling)	✅ via open_pm.ko hooks	❌
Statistics / ndo_get_stats64	✅ HW counters	❌ (only core netdev counters)
ethtool ops	✅ link/speed/wol/coalesce/strings/stats	❌
Multicast hash filter	✅ 128-bit MAC filter table	❌ (runs permissive — broadcast + multicast pass)
PM suspend/resume	✅	❌ (HW defaults across suspend)
WoL (Wake-on-LAN)	✅ via PMU magic packet detect	❌
RX coalescing tuning	✅ via RX_COALESCED_* regs	❌
VLAN HW offload	✅	❌

Suggested phasing

Phase 1 — usability gaps

• ndo_get_stats64: read RX_PKT_CNT, TX_PKT_CNT, RX_OCTET_CNT, TX_OCTET_CNT, RX_DROP_CNT from HW counters. Cheap, high-value for monitoring.
• ethtool_ops with at least: get_drvinfo, get_link, get_settings, get_strings, get_stats. Lets userspace ethtool eth0 work.
• Multicast hash filter: program the 128-bit table from dev->mc.list so multicast users (IGMP, mDNS) don't all hit the slow path.

Phase 2 — performance

• TSO + COE checksum offload: vendor uses TSO_COE_CTRL to enable IPv4/IPv6 TCP segmentation in HW. Significant win for RTSP/video streaming.
• RX coalescing tuning: vendor defaults are 8 frames or 0x74 (line RX_COALESCED_FRAMES/RX_COALESCED_TIMER); make these ethtool-tunable.

Phase 3 — power

• PM suspend/resume: assert reset → restore on resume → reprogram ring base addresses, IRQ mask, port_en.
• EEE / autoEEE: significant complexity (vendor has a separate sub-driver); defer until phase 1/2 land.
• WoL + AVS: defer.

Why minimum-viable was the right scope for #44

Driver landed alongside hi3516av100_neo firmware bring-up (OpenIPC/firmware#2122). DoD was "QEMU boots + DHCP + ping" — bare-minimum meets that. Production hardening can layer on without changing the IP register layout assumptions. The driver also doesn't yet have real-hardware validation; phase 1 should arrive alongside the first hardware test of the av100_neo image.

Related

• openipc/linux arm: hisilicon: add hi3516av100 SoC support (CRG + DT + higmac driver) #44 (initial driver)
• OpenIPC/firmware #2122 (firmware build that exercises it)
• openhisilicon #170, #171 (V2A OSAL shim landings — orthogonal but same SoC bring-up effort)