linux-kernel - Re: [PATCH 5/5 v2] ARM: OMAP1: recalculate loops per jiffy after dpll1 reprogram

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Date:	Fri, 9 Dec 2011 08:42:45 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Janusz Krzysztofik <jkrzyszt@....icnet.pl>
Cc:	Tony Lindgren <tony@...mide.com>, Paul Walmsley <paul@...an.com>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5 v2] ARM: OMAP1: recalculate loops per jiffy after
	dpll1 reprogram

On Tue, Nov 29, 2011 at 01:25:32AM +0100, Janusz Krzysztofik wrote:
> However, the result of cpufreq_scale() differs from that of
> (re)calibrate_delay() by ca. 6%, i.e., 70.40 vs. 74.54. Please advise if
> this approximation is acceptable.

You don't say which figure is what.

Note that calibrate_delay() is itself inaccurate - the loops_per_jiffy
is the number of loops which can be executed between two timer ticks
_minus_ the time to process the timer interrupt itself.  So, it's
actually always a little less than the theoretical number of loops
within that time period.
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