[dpdk-dev] i40e rte_eth_link_get_nowait() on X722 returns wrong link_speed value 20000 instead of 10000

[Martin Weiser]

Hi,

We are using a Xeon D with an integrated X722 NIC that provides two
ports of 8086:37d2 and two ports of 8086:37d0. All four ports show the
same behavior: they return a link speed value of 20000 for a 10Gbps link.

This only seems to happen when internally the update_link_reg() function
in i40e_ethdev.c is used. This requires the application to use the
rte_eth_link_get_nowait() function and not use link status change
interrupts.
If you use e.g. testpmd with the option --no-lsc-interrupt you can
reproduce the behavior since it will suddenly show a link speed of 20000
Mbps instead of 10000 Mbps.


Here are two examples of the register values read by update_link_reg():

A 10Gbps link which produces the wrong link speed value:

I40E_PRTMAC_LINKSTA: 0x60000080
I40E_PRTMAC_MACC:    0x3d00


A 1Gbps link which produces the correct link speed value:

I40E_PRTMAC_LINKSTA: 0x48000081
I40E_PRTMAC_MACC:    0x3d00


Best regards,
Martin