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From:   Joel Stanley <joel@jms.id.au>
Date:   Tue, 17 May 2022 09:20:41 +0000
Message-ID: <CACPK8XfS+orcdGxGtDy4_gjT9Za9B4umELVcWVYAJv1MWhV4qQ@mail.gmail.com>
Subject: Re: [PATCH net v2] net: ftgmac100: Disable hardware checksum on AST2600
To:     Dylan Hung <dylan_hung@aspeedtech.com>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        David Wilder <dwilder@us.ibm.com>,
        "openbmc@lists.ozlabs.org" <openbmc@lists.ozlabs.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        David Wilder <wilder@us.ibm.com>
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On Fri, 13 May 2022 at 01:46, Dylan Hung <dylan_hung@aspeedtech.com> wrote:
>
> > -----Original Message-----
> > From: joel.stan@gmail.com [mailto:joel.stan@gmail.com] On Behalf Of Joel
> > Stanley
> > Sent: Friday, May 13, 2022 7:20 AM
> > To: David S . Miller <davem@davemloft.net>; Jakub Kicinski
> > <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Benjamin
> > Herrenschmidt <benh@kernel.crashing.org>; Dylan Hung
> > <dylan_hung@aspeedtech.com>; David Wilder <dwilder@us.ibm.com>
> > Cc: openbmc@lists.ozlabs.org; netdev@vger.kernel.org;
> > linux-kernel@vger.kernel.org; David Wilder <wilder@us.ibm.com>
> > Subject: [PATCH net v2] net: ftgmac100: Disable hardware checksum on
> > AST2600
> >
> > The AST2600 when using the i210 NIC over NC-SI has been observed to
> > produce incorrect checksum results with specific MTU values. This was first
> > observed when sending data across a long distance set of networks.
> >
> > On a local network, the following test was performed using a 1MB file of
> > random data.
> >
> > On the receiver run this script:
> >
> >  #!/bin/bash
> >  while [ 1 ]; do
> >         # Zero the stats
> >         nstat -r  > /dev/null
> >         nc -l 9899 > test-file
> >         # Check for checksum errors
> >         TcpInCsumErrors=$(nstat | grep TcpInCsumErrors)
> >         if [ -z "$TcpInCsumErrors" ]; then
> >                 echo No TcpInCsumErrors
> >         else
> >                 echo TcpInCsumErrors = $TcpInCsumErrors
> >         fi
> >  done
> >
> > On an AST2600 system:
> >
> >  # nc <IP of  receiver host> 9899 < test-file
> >
> > The test was repeated with various MTU values:
> >
> >  # ip link set mtu 1410 dev eth0
> >
> > The observed results:
> >
> >  1500 - good
> >  1434 - bad
> >  1400 - good
> >  1410 - bad
> >  1420 - good
> >
> > The test was repeated after disabling tx checksumming:
> >
> >  # ethtool -K eth0 tx-checksumming off
> >
> > And all MTU values tested resulted in transfers without error.
> >
> > An issue with the driver cannot be ruled out, however there has been no bug
> > discovered so far.
> >
> > David has done the work to take the original bug report of slow data transfer
> > between long distance connections and triaged it down to this test case.
> >
> > The vendor suspects this this is a hardware issue when using NC-SI. The fixes
> > line refers to the patch that introduced AST2600 support.
> >
> > Fixes: 39bfab8844a0 ("net: ftgmac100: Add support for DT phy-handle
> > property")
> > Reported-by: David Wilder <wilder@us.ibm.com>
> > Signed-off-by: Joel Stanley <joel@jms.id.au>

> Reviewed-by: Dylan Hung <dylan_hung@aspeedtech.com>

Thank you Dylan. I've added your r-b to v3, as the only changes are to
the wrapping of the commit message.