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

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Date:	Wed, 03 Sep 2014 10:03:39 -0700
From:	Mike Turquette <mturquette@...aro.org>
To:	Leigh Brown <leigh@...inno.co.uk>,
	"Gregory CLEMENT" <gregory.clement@...e-electrons.com>
Cc:	linux-kernel@...r.kernel.org,
	"Jason Cooper" <jason@...edaemon.net>,
	"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

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.

Regards,
Mike
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