From mboxrd@z Thu Jan  1 00:00:00 1970
From: Richard Cochran <richardcochran@gmail.com>
Subject: Re: [PATCH net-next 1/2] mlx4_en: Add PTP hardware clock
Date: Wed, 25 Dec 2013 12:49:36 +0100
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Cc: Shawn Bohrer <shawn.bohrer@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Or Gerlitz <ogerlitz@mellanox.com>,
	Amir Vadai <amirv@mellanox.com>, netdev@vger.kernel.org,
	tomk@rgmadvisors.com, Shawn Bohrer <sbohrer@rgmadvisors.com>
To: Hadar Hen Zion <hadarh@mellanox.com>
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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