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Subject: Re: [RFC] Improving udelay/ndelay on platforms where that is possible
To:     Nicolas Pitre <nicolas.pitre@linaro.org>
CC:     Russell King - ARM Linux <linux@armlinux.org.uk>,
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        Mason <slash.tmp@free.fr>
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From:   Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
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Date:   Thu, 16 Nov 2017 17:51:05 +0100
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On 16/11/2017 17:47, Nicolas Pitre wrote:

> Look at cpufreq_callback() in arch/arm/kernel/smp.c.

Are you pointing at the scaling of loops_per_jiffy done in that function?

As I wrote earlier:

If I'm reading arch/arm/kernel/smp.c correctly, loops_per_jiffy is scaled
when the frequency changes.

But arch/arm/lib/delay-loop.S starts by loading the current value of
loops_per_jiffy, computes the number of times to loop, and then loops.
If the frequency increases when the core is in __loop_delay, the
delay will be much shorter than requested.


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