linux-kernel - Re: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix clock support

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Date:   Wed, 7 Dec 2022 04:26:24 +0000
From:   <Arun.Ramadoss@...rochip.com>
To:     <olteanv@...il.com>, <ceggers@...i.de>
CC:     <andrew@...n.ch>, <linux-kernel@...r.kernel.org>,
        <UNGLinuxDriver@...rochip.com>, <vivien.didelot@...il.com>,
        <linux@...linux.org.uk>, <Tristram.Ha@...rochip.com>,
        <f.fainelli@...il.com>, <kuba@...nel.org>, <edumazet@...gle.com>,
        <pabeni@...hat.com>, <richardcochran@...il.com>,
        <netdev@...r.kernel.org>, <Woojung.Huh@...rochip.com>,
        <davem@...emloft.net>
Subject: Re: [Patch net-next v2 01/13] net: dsa: microchip: ptp: add the posix
 clock support

Hi Vladimir,
On Tue, 2022-12-06 at 12:48 +0200, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> On Tue, Dec 06, 2022 at 11:37:26AM +0100, Christian Eggers wrote:
> > > v1 -> v2
> > > - Deleted setting 8021_1as bit and added P2P bit in
> > > ksz_ptp_clock_register()
> > 
> > did I miss the discussion about this change? I thought that the
> > first goal is
> > to use KSZ switches as a boundary clock which implies using the
> > 802.1AS feature.
> > 
> > Using the KSZ in P2P transparent clock mode IMHO requires writing
> > the peer delays
> > into switch registers (which needs to be implemented in a companion
> > application/script for ptp4p).
> > 
> > As far as I remember, there is also no support using ptp4l with 1-
> > step transparent
> > clock switches.
> 
> If it was in response to something I said, I just asked to add a
> comment
> as to what the 802.1AS bit does, not to delete it...

I got confused with the review comments like Is this bit required for
p2p 1 step timestamping and also because this bit is mentioned reserved
in datasheet for KSZ9563.
When the 802.1AS bit is set in PTP_MSG_CONF1 register, it forwards all
the PTP frames to cpu port and not to other ports.
Since, the 2 step timestamping does not work in KSZ9563, this bit is
made as reserved in the datasheet.
I will revert the changes back to setting 802.1AS bit and add
appropriate comment in the code/commit description.