netdev - Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method

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Message-ID: <20120322064107.GB2182@netboy.at.omicron.at>
Date:	Thu, 22 Mar 2012 07:41:07 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	chetan loke <loke.chetan@...il.com>
Cc:	"Keller, Jacob E" <jacob.e.keller@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"Ronciak, John" <john.ronciak@...el.com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of
 the timecompare method

On Wed, Mar 21, 2012 at 05:50:34PM -0400, chetan loke wrote:
> 
> Richard - Intent is to make the readers(get_time) wait (or return last
> read value if the seq_counter tripped because you know that this value
> was recent) and let the tx/rx path continue. I haven't looked in more
> details but as Jake mentioned you will also need to change the way you
> read the values(by not using timecounter_read in get_time).

I don't get what you guys are saying. How can you avoid the spin lock
around the two time register reads? How about a patch or some pseudo
code?

Thanks,
Richard
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