linux-kernel - Re: [PATCHv4 13/17] ntp: add hardpps implementation

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Date:	Sat, 20 Nov 2010 17:27:18 +0100
From:	Rodolfo Giometti <giometti@...eenne.com>
To:	Alexander Gordeev <lasaine@....cs.msu.su>
Cc:	linux-kernel@...r.kernel.org,
	"Nikita V. Youshchenko" <yoush@...msu.su>,
	linuxpps@...enneenne.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Stultz <johnstul@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCHv4 13/17] ntp: add hardpps implementation

On Thu, Nov 18, 2010 at 07:01:06PM +0300, Alexander Gordeev wrote:
> This commit adds hardpps() implementation based upon the original one
> from the NTPv4 reference kernel code from David Mills. However, it is
> highly optimized towards very fast syncronization and maximum stickness
> to PPS signal. The typical error is less then a microsecond.
> To make it sync faster I had to throw away exponential phase filter so
> that the full phase offset is corrected immediately. Then I also had to
> throw away median phase filter because it gives a bigger error itself
> if used without exponential filter.
> Maybe we will find an appropriate filtering scheme in the future but
> it's not necessary if the signal quality is ok.

This patch (and follows) adds a new functionality to PPS subsystem, so
let me suggest to you splitting in two parts this patch set: a first
patch set who fixes up the current PPS implementation, and a second
patch set who adds kernel consumer (and follows).

Ciao,

Rodolfo

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