RoCEv2: Add DCQCN congestion control

[ruck314]

Summary

Adds DCQCN (Data Center Quantized Congestion Notification) congestion control to the RoCEv2 engine, plus the supporting IPv4/UDP and AXI-Stream changes needed to carry ECN/CNP signaling.

Originally developed on FilMarini/surf:dcqcnEn; migrated here and merged up to current pre-release (conflict-free).

Changes

DCQCN core (new modules under ethernet/RoCEv2/rtl/)

• Dcqcn.vhd, AlphaUpdate.vhd, RateIncProc.vhd, RateDecProc.vhd — rate control state machine
• TokenBucket.vhd, AxisBucket.vhd, TokenCalc.vhd — token-bucket rate limiter
• AxiStreamMonDcqcn.vhd — rate/throughput monitoring
• RoceEngineWrapper.vhd — wiring + Dcqcn_en enable parameter; CNP output port

ECN/CNP signaling path

• IpV4Engine.vhd / IpV4EngineTx.vhd — DSCP + ECN fields in the IPv4 header
• EthMacRxRoCEv2.vhd, RocePkg.vhd, UdpEngineWrapper.vhd — plumbing
• Sgmii88E1111LvdsUltraScale.vhd — RoceV2_en parameter for the RJ45 PHY path

blue-rdma regen — mkQP.v, mkAxisTransportLayer.v, mkTransportLayer.v (QP destroy fix, RNR-retry-with-fragmentation fix, full 2-byte address, sequential pipeline for timing)

AXI-Stream — AxiStreamCompact.vhd reworked for the congestion-control data path

Software — python/surf/ethernet/roce/_RoceEngine.py DCQCN RemoteVariable register map

Review notes

• AxiStreamCompact.vhd is a full rewrite of an existing shared surf module (not a new file). This is the main item to scrutinize — confirm it preserves behavior for existing non-DCQCN users.
• DCQCN is gated behind the Dcqcn_en generic; default-off behavior should be confirmed.

Status

Draft — pending FW review and register cross-check.

[ruck314]

I tested this using slaclab/Simple-10GbE-RUDP-KCU105-Example#11 + rogue@pre-release (latest) and confirmed that it works

Simple-10GbE-RUDP-KCU105-Example/software$ python scripts/runDispatch.py
Rogue/pyrogue version v6.13.0-83-gf1f2b3a74. https://github.com/slaclab/rogue
Connected to Root at localhost:9099
INFO:dispatch:--- RoCEv2 connection parameters ---
INFO:dispatch:  ConnectionState : Connected
INFO:dispatch:  Host QPN        : 0x12
INFO:dispatch:  Host GID        : 0000:0000:0000:0000:0000:ffff:c0a8:0201
INFO:dispatch:  Host RQ PSN     : 0x1140ce
INFO:dispatch:  Host SQ PSN     : 0x736e9
INFO:dispatch:  MR addr         : 0x791bf84ca000
INFO:dispatch:  MR rkey         : 0x316
INFO:dispatch:  FPGA lkey       : 0x42508e2b
INFO:dispatch:  FPGA QPN        : 0x468bf
INFO:dispatch:  FPGA GID        : 0000:0000:0000:0000:0000:ffff:c0a8:020a
INFO:dispatch:  MaxPayload      : 9000
INFO:dispatch:  RxQueueDepth    : 256
INFO:dispatch:  MrLen           : 2304000
INFO:dispatch:  Payload (= MaxPayload) : 9000
INFO:dispatch:  AddrWrapCount   : 256
INFO:dispatch:------------------------------------
INFO:dispatch:Setting UDP engine destination to 192.168.2.1:4791
INFO:dispatch:Resetting counters...
INFO:dispatch:Dispatching 1 packet(s) of 9000 bytes...
INFO:dispatch:Correctly received 1 / 1 packet(s)