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Message-ID: <1349286d7f93aabec3b7b43aba9089f96214944e.camel@redhat.com>
Subject: Re: [PATCH net] net: ethernet: ti: am65-cpts: Fix PTPv1 message
 type on TX packets
From: Paolo Abeni <pabeni@redhat.com>
To: Ravi Gunasekaran <r-gunasekaran@ti.com>, s-vadapalli@ti.com, 
	rogerq@kernel.org
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, 
	richardcochran@gmail.com, jreeder@ti.com, netdev@vger.kernel.org, 
	linux-kernel@vger.kernel.org, srk@ti.com
Date: Tue, 23 Apr 2024 13:44:48 +0200
In-Reply-To: <52c7352f-a91b-3604-5ae0-88d7bb814e51@ti.com>
References: <20240419080547.10682-1-r-gunasekaran@ti.com>
	 <4a92f794480b12c21eaeeeb66521dbe978f08414.camel@redhat.com>
	 <52c7352f-a91b-3604-5ae0-88d7bb814e51@ti.com>
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On Tue, 2024-04-23 at 16:36 +0530, Ravi Gunasekaran wrote:
> On 4/23/24 3:31 PM, Paolo Abeni wrote:
> > On Fri, 2024-04-19 at 13:35 +0530, Ravi Gunasekaran wrote:
> > > From: Jason Reeder <jreeder@ti.com>
> > >=20
> > > The CPTS, by design, captures the messageType (Sync, Delay_Req, etc.)
> > > field from the second nibble of the PTP header which is defined in th=
e
> > > PTPv2 (1588-2008) specification. In the PTPv1 (1588-2002) specificati=
on
> > > the first two bytes of the PTP header are defined as the versionType
> > > which is always 0x0001. This means that any PTPv1 packets that are
> > > tagged for TX timestamping by the CPTS will have their messageType se=
t
> > > to 0x0 which corresponds to a Sync message type. This causes issues
> > > when a PTPv1 stack is expecting a Delay_Req (messageType: 0x1)
> > > timestamp that never appears.
> > >=20
> > > Fix this by checking if the ptp_class of the timestamped TX packet is
> > > PTP_CLASS_V1 and then matching the PTP sequence ID to the stored
> > > sequence ID in the skb->cb data structure. If the sequence IDs match
> > > and the packet is of type PTPv1 then there is a chance that the
> > > messageType has been incorrectly stored by the CPTS so overwrite the
> > > messageType stored by the CPTS with the messageType from the skb->cb
> > > data structure. This allows the PTPv1 stack to receive TX timestamps
> > > for Delay_Req packets which are necessary to lock onto a PTP Leader.
> > >=20
> > > Signed-off-by: Jason Reeder <jreeder@ti.com>
> > > Signed-off-by: Ravi Gunasekaran <r-gunasekaran@ti.com>
> >=20
> > Please provide a suitable fixes tag, thanks!
>=20
> am65_cpts_match_tx_ts() was added in the very first commit of the file.
> Would that be a suitable fixes tag?=C2=A0

It looks like it is, since such function exposed the buggy behaviour
since the beginning.

> I understand that the purpose of
> the fixes tag is to know to which all previous kernels, the fix needs to
> be applied.=20

Yes, it's used by stable team(s) to filter fixes relevant for a given
stable tree. A correct hash allow to do that automatically.


Cheers,

Paolo