netdev - Re: [PATCH net-next 1/2] mlx4_en: Add PTP hardware clock

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Message-ID: <20131225114934.GA5378@netboy>
Date:	Wed, 25 Dec 2013 12:49:36 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	Hadar Hen Zion <hadarh@...lanox.com>
Cc:	Shawn Bohrer <shawn.bohrer@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Amir Vadai <amirv@...lanox.com>, netdev@...r.kernel.org,
	tomk@...advisors.com, Shawn Bohrer <sbohrer@...advisors.com>
Subject: Re: [PATCH net-next 1/2] mlx4_en: Add PTP hardware clock

On Tue, Dec 24, 2013 at 05:38:35PM +0200, Hadar Hen Zion wrote:
> 
> The spin lock is needed when reading hardware registers.

Or when using a structure of fields that act together as one object.

> My suggestion is to stay with spin locks in all the places
> protecting timecounter_read()/timecounter_init() and just remove the
> spin lock from timecounter_cyc2time()

If you look at the implementation of timecounter_cyc2time, you will
see that locks are, in fact, needed.

See also the comments in clocksource.h.

Thanks,
Richard
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