linux-kernel - RE: [PATCH net-next v3 7/7] net: dsa: microchip: Disable PTP function of KSZ8463

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <LV3PR11MB87427E7BBE2FFC011FD4410DEC49A@LV3PR11MB8742.namprd11.prod.outlook.com>
Date: Wed, 9 Jul 2025 22:54:24 +0000
From: <Tristram.Ha@...rochip.com>
To: <vadim.fedorenko@...ux.dev>
CC: <maxime.chevallier@...tlin.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<marex@...x.de>, <UNGLinuxDriver@...rochip.com>,
	<devicetree@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Woojung.Huh@...rochip.com>,
	<andrew@...n.ch>, <olteanv@...il.com>, <robh@...nel.org>,
	<krzk+dt@...nel.org>, <conor+dt@...nel.org>
Subject: RE: [PATCH net-next v3 7/7] net: dsa: microchip: Disable PTP function
 of KSZ8463

> On 09/07/2025 01:32, Tristram.Ha@...rochip.com wrote:
> > From: Tristram Ha <tristram.ha@...rochip.com>
> >
> > The PTP function of KSZ8463 is on by default.  However, its proprietary
> > way of storing timestamp directly in a reserved field inside the PTP
> > message header is not suitable for use with the current Linux PTP stack
> > implementation.  It is necessary to disable the PTP function to not
> > interfere the normal operation of the MAC.
> 
> Could you please explain the "proprietary way of storing timestamps"?
> Maybe you can provide some examples of headers with timestamps?

The PTP engine used in KSZ8463 is first generation, so it contains some
quirks and cannot be easily used in the current PTP stack implementation.
The receive timestamp and receive port information is put in the 2
reserved fields of the PTP message header.  As those reserved fields are
not used yet in v2 it does not pose an immediate problem.  Software can
ignore them.  A real problem is the hardware will update the Sync
transmit timestamp when the message is sent out and that will definitely
cause issue if the MAC is using its own PTP function.

The switch also will filter some PTP messages from reaching the MAC
because it thinks software wants it that way.

The receive timestamp and receive port information is put in the tail tag
for the second generation PTP engine used in KSZ9477 and LAN937X.

It is not likely the DSA PTP driver will be updated to support KSZ8463.