How to enable LEGACY_DCQCN (ROCE_CC_LEGACY_DCQCN) for ConnectX-6?

Infrastructure & Networking Adapters and Cables InfiniBand/VPI Adapter Cards
1

Hello,
I am trying to enable LEGACY_DCQCN for my ConnectX-6 NIC by setting the ROCE_CC_LEGACY_DCQCN parameter to 1 using mlxconfig. However, I encountered the following error:

sudo mlxconfig -d /dev/mst/mt4123_pciconf0 s ROCE_CC_LEGACY_DCQCN=0

Device #1:
----------

Device type:        ConnectX6           
Name:               MCX653105A-ECA_Ax   
Description:        ConnectX-6 VPI adapter card; 100Gb/s (HDR100; EDR IB and 100GbE); single-port QSFP56; PCIe3.0 x16; tall bracket; ROHS R6
Device:             /dev/mst/mt4123_pciconf0

Configurations:                                          Next Boot       New
-E- The Device doesn't support ROCE_CC_LEGACY_DCQCN parameter

My environment is as follows:

  • OS: Ubuntu 24.04
  • Kernel: 6.11.0
  • MLNX_OFED version: MLNX_OFED_LINUX-24.10-2.1.8.0
  • Firmware version: 20.42.1000

Has the ROCE_CC_LEGACY_DCQCN parameter been deprecated in recent OFED versions or firmware? If so, how can I enable LEGACY_DCQCN congestion control mode for RoCE traffic on my ConnectX-6 NIC?

Any guidance or confirmation regarding support for LEGACY_DCQCN in current OFED or firmware versions would be highly appreciated.

Thanks in advance!

2

I also tried the mlxreg method mentioned in Scaling Zero Touch RoCE Technology with Round Trip Time Congestion Control , but it didn’t work as well:

sudo mlxreg -d /dev/mst/mt4123_pciconf0 --reg_id 0x506e --reg_len 0x40 --get 
Sending access register...

-E- Failed send access register: ME_ICMD_OPERATIONAL_ERROR
3

Hi wenqiluonju,

You can try this guide EnterpriseSupport

Thanks,
Quanying

4

In general, the ConnectX-6 only supports the legacy DCQCN. The new HW (PCC) is supported from ConnectX-6Dx onwards. So, you do not need this knob.
Regards,
Yaniv