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From:   Subbaraya Sundeep Bhatta <sbhatta@marvell.com>
To:     Andrew Lunn <andrew@lunn.ch>,
        Naveen Mamindlapalli <naveenm@marvell.com>,
        "richardcochran@gmail.com" <richardcochran@gmail.com>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sunil Kovvuri Goutham <sgoutham@marvell.com>
Subject: Re: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60
Thread-Topic: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60
Thread-Index: AQHYoy4zf4LbZ0cr1Uaj3A8adEB7Lg==
Date:   Fri, 29 Jul 2022 09:33:03 +0000
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 <YuMGMiFv8TAiUI11@lunn.ch>
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Hi Andrew,=0A=
=0A=
Added PTP maintainer also in v2. We fixed this to work with latest ptp4l si=
nce after debugging we found=0A=
ptp4l complains bad message for Sync packets. =0A=
Lets hear from Richard.=0A=
=0A=
Thanks,=0A=
Sundeep=0A=
=0A=
________________________________________=0A=
From: Andrew Lunn <andrew@lunn.ch>=0A=
Sent: Friday, July 29, 2022 3:27 AM=0A=
To: Naveen Mamindlapalli=0A=
Cc: davem@davemloft.net; edumazet@google.com; kuba@kernel.org; pabeni@redha=
t.com; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil Kovvuri =
Goutham; Subbaraya Sundeep Bhatta=0A=
Re: [net PATCH] octeontx2-pf: Reduce minimum mtu size to 60=0A=
=0A=
----------------------------------------------------------------------=0A=
On Thu, Jul 28, 2022 at 06:08:12PM +0530, Naveen Mamindlapalli wrote:=0A=
> From: Subbaraya Sundeep <sbhatta@marvell.com>=0A=
>=0A=
> PTP messages like SYNC, FOLLOW_UP, DELAY_REQ are of size 58 bytes.=0A=
> Using a minimum packet length as 64 makes NIX to pad 6 bytes of=0A=
> zeroes while transmission. This is causing latest ptp4l application to=0A=
> emit errors since length in PTP header and received packet are not same.=
=0A=
> Padding upto 3 bytes is fine but more than that makes ptp4l to assume=0A=
> the pad bytes as a TLV. Hence reduce the size to 60 from 64.=0A=
=0A=
Please Cc: the PTP maintainer for changes like this.=0A=
=0A=
I also don't follow your explanation. At least for the original 802.3,=0A=
you had to pad packets shorter than 64 bytes, otherwise CSMA/CD did=0A=
not work. So i would expect PTP messages should be padded to 64?=0A=
=0A=
Or is you hardware doing the padding wrong, and this is a workaround=0A=
for that bug?=0A=
=0A=
    Andrew=0A=