linux-kernel - Re: DSA mv88e6xxx RX frame errors and TCP/IP RX failure

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Date:   Wed, 30 Aug 2017 17:22:42 -0700
From:   Tim Harvey <tharvey@...eworks.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Fugang Duan <fugang.duan@....com>
Subject: Re: DSA mv88e6xxx RX frame errors and TCP/IP RX failure

On Wed, Aug 30, 2017 at 3:06 PM, Andrew Lunn <andrew@...n.ch> wrote:
> On Wed, Aug 30, 2017 at 12:53:56PM -0700, Tim Harvey wrote:
>> Greetings,
>>
>> I'm seeing RX frame errors when using the mv88e6xxx DSA driver on
>> 4.13-rc7. The board I'm using is a GW5904 [1] which has an IMX6 FEC
>> MAC (eth0) connected via RGMII to a MV88E6176 with its downstream
>> P0/P1/P2/P3 to front panel RJ45's (lan1-lan4).
>
> Hi Tim
>
> Can you confirm the counter is this one:
>
>                        /* Report late collisions as a frame error. */
>                         if (status & (BD_ENET_RX_NO | BD_ENET_RX_CL))
>                                 ndev->stats.rx_frame_errors++;
>
> I don't see anywhere else frame errors are counted, but it would be
> good to prove we are looking in the right place.
>

Andrew,

(adding IMX FEC driver maintainer to CC)

Yes, that's one of them being hit. It looks like ifconfig reports
'frame' as the accumulation of a few stats so here are some more
specifics from /sys/class/net/eth0/statistics:

root@...ial:/sys/devices/soc0/soc/2100000.aips-bus/2188000.ethernet/net/eth0/statistics#
for i in `ls rx_*`; do echo $i:$(cat $i); done
rx_bytes:103229
rx_compressed:0
rx_crc_errors:22
rx_dropped:0
rx_errors:22
rx_fifo_errors:0
rx_frame_errors:22
rx_length_errors:22
rx_missed_errors:0
rx_nohandler:0
rx_over_errors:0
rx_packets:1174
root@...ial:/sys/devices/soc0/soc/2100000.aips-bus/2188000.ethernet/net/eth0/statistics#
ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:D0:12:41:F3:E7
          inet6 addr: fe80::2d0:12ff:fe41:f3e7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1207 errors:22 dropped:0 overruns:0 frame:66
          TX packets:42 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:106009 (103.5 KiB)  TX bytes:4604 (4.4 KiB)

Instrumenting fec driver I see the following getting hit:

status & BD_ENET_RX_LG /* rx_length_errors: Frame too long */
status & BD_ENET_RX_CR  /* rx_crc_errors: CRC Error */
status & BD_ENET_RX_CL /* rx_frame_errors: Collision? */

Is this a frame size issue where the MV88E6176 is sending frames down
that exceed the MTU because of headers added?

Tim