linux-kernel - RE: [PATCH] ARM: twd: Adjust localtimer frequency with cpufreqnotifiers

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Date:	Sat, 5 Mar 2011 13:49:00 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Colin Cross <ccross@...roid.com>,
	Rob Herring <robherring2@...il.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Srinidhi KASAGAR <srinidhi.kasagar@...ricsson.com>,
	Harald Gustafsson <harald.gustafsson@...csson.com>,
	Linus Walleij <linus.ml.walleij@...il.com>,
	linux-kernel@...r.kernel.org,
	Rickard ANDERSSON <rickard.andersson@...ricsson.com>,
	Varun Swara <Varun.Swara@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	martin persson <martin.persson@...ricsson.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: RE: [PATCH] ARM: twd: Adjust localtimer frequency with cpufreqnotifiers

Collin, Rob,
> -----Original Message-----
> From: linux-arm-kernel-bounces@...ts.infradead.org [mailto:linux-
> arm-kernel-bounces@...ts.infradead.org] On Behalf Of Colin Cross
> Sent: Saturday, March 05, 2011 3:03 AM
> To: Rob Herring
> Cc: Russell King; Srinidhi KASAGAR; Harald Gustafsson; Linus
> Walleij; linux-kernel@...r.kernel.org; Rickard ANDERSSON; Varun
> Swara; Catalin Marinas; martin persson; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH] ARM: twd: Adjust localtimer frequency with
> cpufreqnotifiers
>
[...]

>
> Using a clock along with the cpufreq notifiers would simplify my
> patch
> some.  Maybe we can use the traction this patch has among platforms
> that use the twd to get the necessary clocks added.  Can you post a
> version of your patch that assumes the presence of a twd clock, and
> I'll work on getting the necessary clocks added and updating my
> patch on top of yours?
>

Some time back I also fixed the TWD scaling problem based on more
or less similar idea of pre-scaler and CPUFREQ notifiers.
Rob's clock idea was neat and useful to re-calibration

While doing this patch for OMAP I also found that
CPUFREQ notifiers does delays scaling timer frequency
and there is a tick deviation(3-4 ms) around 1st tick and
last tick around twd rescaling.

Another issue was not able to select higher fixed twd rate
and found fix for the same.

Regards,
Santosh
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