[PATCH v4] ARM: sched_clock: allow sched_clock to be selected at runtime

Krzysztof Halasa khc at pm.waw.pl
Tue Dec 13 08:22:34 EST 2011

Marc Zyngier <marc.zyngier at arm.com> writes:

> sched_clock() is yet another blocker on the road to the single
> image. This patch implements an idea by Russell King:
> http://www.spinics.net/lists/linux-omap/msg49561.html
> Instead of asking the platform to implement both sched_clock()
> itself and the rollover callback, simply register a read()
> function, and let the ARM code care about sched_clock() itself,
> the conversion to ns and the rollover. sched_clock() uses
> this read() function as an indirection to the platform code.
> If the platform doesn't provide a read(), the code falls back
> to the jiffy counter (just like the default sched_clock).
> This allow some simplifications and possibly some footprint gain
> when multiple platforms are compiled in. Among the drawbacks,
> the removal of the *_fixed_sched_clock optimization which could
> negatively impact some platforms (sa1100, tegra, versatile
> and omap).
> Tested on 11MPCore, OMAP4 and Tegra.

The IXP4xx part looks good to me,
Acked-By: Krzysztof Halasa <khc at pm.waw.pl>
Krzysztof Halasa

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