linux-kernel - Re: [PATCH V2 0/4] clk: mvebu: Improve clock drift

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Date:	Wed, 3 Sep 2014 13:11:41 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	Leigh Brown <leigh@...inno.co.uk>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	linux-arm-kernel@...ts.infradead.org,
	Lior Amsalem <alior@...vell.com>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Raphael Rigo <ml-arm@...call.eu>,
	Arnaud Ebalard <arno@...isbad.org>,
	Simon Boulay <simon.boulay@...ec.com>
Subject: Re: [PATCH V2 0/4] clk: mvebu: Improve clock drift

On Wed, Sep 03, 2014 at 10:03:39AM -0700, Mike Turquette wrote:
> Quoting Leigh Brown (2014-09-03 07:40:56)
> > On 2014-09-02 09:15, Gregory CLEMENT wrote:
> > > Few users reported a timer drift on the Armada 370 based board such as
> > > the mirabox or the Netgear ReadyNAS 102. This is the second series
> > > with few improvements after the review of the 1st version.
> > > 
> > > The reason is that when the SSCG (Spread Spectrum Clock Generator) is
> > > enabled, it shifts the frequency of the clock. The percentage is no
> > > more than 1% but when the clock is used for a timer it leads to a
> > > clock drift.
> > > 
> > > This series allows to correct the affected clock when the SSCG is
> > > enabled. This drift can happen on all the mvebu SoC on the cpu clock
> > > block (ie cpu, ddr and l2 cache). Currently the only notable effect is
> > > for the Armada 370 because this SoC use the l2cache clock as source
> > > for the timer. That's why even if the series allow any of the mvebu
> > > SoC to benefit to this correction, Armada 370 is the only user of it.
> > > 
> > > The first 2 patches should go through the clk subsystem, whereas the
> > > third one should go to the arm-soc through the mvebu tree.
> > > 
> > > The last one is just to fix a typo I found while I was reading the clk
> > > code.
> > 
> > This is working superbly for me on my Mirabox, and ntpd is now 
> > completely stable.
> > 
> > Tested-by: Leigh Brown <leigh@...inno.co.uk>
> > 
> 
> Clock patches look good to me.

Ok, I'll pull it together into a clock branch and so forth.

thx,

Jason.
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