[dpdk-users] DPDK16.11.2 LTS: i40e PMD fails to start X710 port

[Dumitru Ceara]

Hi all,

With DPDK 16.11.2 LTS we see "intermittent" errors when trying to
start an X710 interface (latest firmware - FW 5.05).

Due to the fact that the i40e PMD requires the port to be stopped when
setting MTU we use the following sequence in our code:
1. rte_eth_dev_ stop
2. rte_eth_dev_set_mtu
3. rte_eth_dev_start

If rte_eth_dev_start is called shortly after stop (as is in our case),
the i40e_phy_conf_link sometimes fails and returns -ENOTSUP. This
happens because i40e_aq_get_phy_capabilities returns status
I40E_ERR_UNKNOWN_PHY. I double checked and the transceivers we use are
Intel FTLX8571D3BCV-IT.

Moreover, if we introduce a delay (e.g., 10 seconds) after
rte_eth_dev_stop then rte_eth_dev_start works fine.

In order to eliminate potential issues with our code I tried to
replicate with test-pmd with "disable-link-check" in order to avoid
the delay introduced by link state checking:

# $RTE_SDK/tools/dpdk-devbind.py -s

Network devices using DPDK-compatible driver
============================================
0000:82:00.0 'Ethernet Controller X710 for 10GbE SFP+' drv=igb_uio unused=
0000:82:00.1 'Ethernet Controller X710 for 10GbE SFP+' drv=igb_uio unused=

# $RTE_SDK/x86_64-native-linuxapp-gcc/build/app/test-pmd/testpmd -w
0000:82:00.0 -w 0000:82:00.1 -- --disable-link-check -i
EAL: Detected 32 lcore(s)
EAL: Probing VFIO support...
EAL: PCI device 0000:82:00.0 on NUMA socket 1
EAL:   probe driver: 8086:1572 net_i40e
PMD: eth_i40e_dev_init(): FW 5.0 API 1.5 NVM 05.00.05 eetrack 8000289d
EAL: PCI device 0000:82:00.1 on NUMA socket 1
EAL:   probe driver: 8086:1572 net_i40e
PMD: eth_i40e_dev_init(): FW 5.0 API 1.5 NVM 05.00.05 eetrack 8000289d
Interactive-mode selected
USER1: create a new mbuf pool <mbuf_pool_socket_0>: n=395456,
size=2176, socket=0
Configuring Port 0 (socket 0)
Port 0: 3C:FD:FE:9C:79:F0
Configuring Port 1 (socket 0)
Port 1: 3C:FD:FE:9C:79:F1
Done
testpmd> port stop 1
Stopping ports...
Done
testpmd> port start 1
Port 1: 3C:FD:FE:9C:79:F1
Done
testpmd> port stop 1
Stopping ports...
Done
testpmd> port start 1
Fail to start port 1
Please stop the ports first    <<<<<<< Here we fail to stop port 1
Done

I saw there were some more reports of similar I40E_ERR_UNKNOWN_PHY
issues but I'm not sure if they were related to the device stop/start
sequence. Is this a known limitation of the driver/firmware? Is the
application supposed to deal with this specific behavior of the X710?
If so, how would an application detect that the rte_eth_dev_stop
operation has completed? Or are we missing some hardware specific
initialization?

Thanks,
Dumitru