linux-kernel - Re: [PATCH net v3] net: ti: icssg-prueth: Fix 1 PPS sync

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Message-ID: <20241031185905.610c982f@kernel.org>
Date: Thu, 31 Oct 2024 18:59:05 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Meghana Malladi <m-malladi@...com>
Cc: <vigneshr@...com>, <grygorii.strashko@...com>, <horms@...nel.org>,
 <jan.kiszka@...mens.com>, <diogo.ivo@...mens.com>, <pabeni@...hat.com>,
 <edumazet@...gle.com>, <davem@...emloft.net>, <andrew+netdev@...n.ch>,
 <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
 <linux-arm-kernel@...ts.infradead.org>, <srk@...com>, Roger Quadros
 <rogerq@...nel.org>, <danishanwar@...com>, "Vadim Fedorenko"
 <vadim.fedorenko@...ux.dev>
Subject: Re: [PATCH net v3] net: ti: icssg-prueth: Fix 1 PPS sync

On Mon, 28 Oct 2024 16:40:52 +0530 Meghana Malladi wrote:
> The first PPS latch time needs to be calculated by the driver
> (in rounded off seconds) and configured as the start time
> offset for the cycle. After synchronizing two PTP clocks
> running as master/slave, missing this would cause master
> and slave to start immediately with some milliseconds
> drift which causes the PPS signal to never synchronize with
> the PTP master.

You're reading a 64b value in chunks, is it not possible that it'd wrap
in between reads? This can be usually detected by reading high twice and
making sure it didn't change.

Please fix or explain in the commit message why this is not a problem..
-- 
pw-bot: cr