netdev - Re: [PATCH net-next 04/10] idpf: negotiate PTP capabilities and get PTP clock

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Message-ID: <20250402093731.1230cff9@kernel.org>
Date: Wed, 2 Apr 2025 09:37:31 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: "Olech, Milena" <milena.olech@...el.com>
Cc: "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "davem@...emloft.net"
 <davem@...emloft.net>, "pabeni@...hat.com" <pabeni@...hat.com>, "Dumazet,
 Eric" <edumazet@...gle.com>, "andrew+netdev@...n.ch"
 <andrew+netdev@...n.ch>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>, "Kolacinski, Karol"
 <karol.kolacinski@...el.com>, "richardcochran@...il.com"
 <richardcochran@...il.com>, "Lobakin, Aleksander"
 <aleksander.lobakin@...el.com>, Willem de Bruijn <willemb@...gle.com>,
 "Mina Almasry" <almasrymina@...gle.com>, "Salin, Samuel"
 <samuel.salin@...el.com>
Subject: Re: [PATCH net-next 04/10] idpf: negotiate PTP capabilities and get
 PTP clock

On Wed, 2 Apr 2025 15:23:53 +0000 Olech, Milena wrote:
> >So hi is latched when lo is read? Or the timer may wrap between 
> >the reads? Can reads happen in parallel (re-latching hi)?  
> 
> Actually we have HW support to latch both values simultaneously.
> 
> Hi and Lo are latched in idpf_ptp_enable_shtime function, so I will move
> lo right after ptp_read_system_postts.

You may need a lock, too, with two concurrent readers one can "re-latch"
the value for the other?