netdev - Re: [PATCH 0/3]: net: dsa: mt7530: support MT7530 in the MT7621 SoC

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Message-ID: <20181130133313.GB11747@lunn.ch>
Date:   Fri, 30 Nov 2018 14:33:13 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     gerg@...nel.org
Cc:     sean.wang@...iatek.com, vivien.didelot@...oirfairelinux.com,
        f.fainelli@...il.com, netdev@...r.kernel.org, blogic@...nwrt.org,
        neil@...wn.name
Subject: Re: [PATCH 0/3]: net: dsa: mt7530: support MT7530 in the MT7621 SoC

> 2. Maximal sized RX packets get silently dropped. So receive side packets
>    that are large (perfect case is the all-but-last packets in a fragemented
>    larger packet) appear to be dropped at the mt7621 ethernet MAC level.
>    The 7530 MIB switch register counters show receive packets at the physical
>    switch port side and at the CPU switch port - but I get no packets
>    received or errors in the 7621 ethernet MAC. If I set the mtu of the
>    server at the other end a little smaller (a few bytes is enough) then
>    I get all the packets through. It seems like the DSA/VLAN tag bytes
>    are causing a too large packet to get silently dropped somewhere.

Hi Gerg

Try increasing the MTU on the master device. Some hardware will reject
receiving packets bigger than the MTU. But if you increase the MTU by
the DSA header size, it will then receive the frame.

I have a patchset i will be posting soon to do this automatically.

  Andrew