netdev - thunderx sgmii interface hang

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Date:   Tue, 12 Dec 2017 15:05:00 -0800
From:   Tim Harvey <tharvey@...eworks.com>
To:     netdev <netdev@...r.kernel.org>,
        Sunil Goutham <sgoutham@...ium.com>
Subject: thunderx sgmii interface hang

Greetings,

We are experiencing an issue on a CN80XX with an SGMII interface
coupled to a TI DP83867IS phy. We have the same PHY connected to the
RGMII interface on the same board design and everything is working as
expected on that nic both before and after triggering the hang.

The nic appears to work fine (pings, TCP etc) up until a performance
test is attempted.
When an iperf bandwidth test is attempted the nic ends up in a state
where truncated-ip packets are being sent out (per a tcpdump from
another board):

2016-02-11 16:40:23.996660 IP truncated-ip - 1454 bytes missing! (tos
0x0, ttl 64, id 39570, offset 0, flags [DF], proto TCP (6), length
1500, bad cksum 172a (->7033)!)
    192.168.1.5.0 > 192.168.168.0.0:  tcp 1480 [bad hdr length 0 - too
short, < 20]

Prior to 'net: thunderx: Fix BGX transmit stall due to underflow'
unplugging the cable and re-plugging would resolve the issue to a
point where it could no longer be created. Prior to this patch a link
status change would disable and re-enable the BGX so perhaps that
helps shed some light on what's going on.

I'm using 4.14.4 with the following patches (although the issue
existed with 4.14.0 as well):
2615c91 net: thunderx: Fix TCP/UDP checksum offload for IPv4 pkts
763d8b3 net: thunderx: Fix TCP/UDP checksum offload for IPv6 pkts
93b2e67 net: thunderx: fix double free error

The issue persists regardless of the DP83867 PHY driver being in the
kernel. Any ideas or details that can help troubleshoot this?

Best Regards,

Tim