linux-kernel - Re: [PATCH 3/3] phy: nxp-c45-tja11xx: read the tx timestamp without lock

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Date:   Wed, 22 Dec 2021 10:19:30 +0200
From:   "Radu Nicolae Pirea (NXP OSS)" <radu-nicolae.pirea@....nxp.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        christian.herber@....com, hkallweit1@...il.com,
        linux@...linux.org.uk, davem@...emloft.net, kuba@...nel.org
Subject: Re: [PATCH 3/3] phy: nxp-c45-tja11xx: read the tx timestamp without
 lock

On Mon, 2021-12-20 at 16:10 +0100, Andrew Lunn wrote:
> On Mon, Dec 20, 2021 at 02:08:59PM +0200, Radu Pirea (NXP OSS) wrote:
> > The tx timestamps are read from only one place in interrupt or
> > polling
> > mode. Locking the mutex is useless.
> 
> You cannot take a mutex in an interrupt handler. So your description
> is probably not accurate.
Actually this is the second issue.
I will improve the description.
> 
> Is it safe for other ptp operations to be performed in parallel with
> reading the TX timestamp? _nxp_c45_ptp_settime64()?
Yes, it's safe. The purpose of the mutex is to protect the access to
LTC(PTP counter).
> 
>         Andrew