[dpdk-dev] [Bug 250] i40e: rte_eth_link_get_nowait() on X722 returns wrong link_speed value 20000 instead of 10000

[dpdk-dev] [Bug 250] i40e: rte_eth_link_get_nowait() on X722 returns wrong link_speed value 20000 instead of 10000

[bugzilla]

https://bugs.dpdk.org/show_bug.cgi?id=250

            Bug ID: 250
           Summary: i40e: rte_eth_link_get_nowait() on X722 returns wrong
                    link_speed value 20000 instead of 10000
           Product: DPDK
           Version: 18.11
          Hardware: All
                OS: Linux
            Status: CONFIRMED
          Severity: normal
          Priority: Normal
         Component: ethdev
          Assignee: dev@dpdk.org
          Reporter: martin.weiser@allegro-packets.com
  Target Milestone: ---

When 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.

To reproduce use e.g. testpmd with the option --no-lsc-interrupt:
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

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