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

From: [email-masked] (Rob Herring)
Date: Sun, 11 Dec 2011 21:57:55 -0600

On 12/09/2011 09:33 AM, Marc Zyngier wrote:
> 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.
> 
> Cc: Imre Kaloz <[email-masked]>
> Cc: Krzysztof Halasa <[email-masked]>
> Cc: Tony Lindgren <[email-masked]>
> Cc: Eric Miao <[email-masked]>
> Cc: Colin Cross <[email-masked]>
> Cc: Erik Gilling <[email-masked]>
> Cc: Olof Johansson <[email-masked]>
> Cc: Linus Walleij <[email-masked]>
> Cc: Sascha Hauer <[email-masked]>
> Cc: Alessandro Rubini <[email-masked]>
> Cc: STEricsson <[email-masked]>
> Cc: Lennert Buytenhek <[email-masked]>
> Cc: Nicolas Pitre <[email-masked]>
> Cc: Ben Dooks <[email-masked]>
> Cc: Kukjin Kim <[email-masked]>
> Cc: Jamie Iles <[email-masked]>
> Tested-by: Jamie Iles <[email-masked]>
> Acked-by: Linus Walleij <[email-masked]>
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
> I'm reposting this patch with the hope that it (or Russell's
> alternative patch http://patchwork.ozlabs.org/patch/115961/)
> will get merged in 3.3. It doesn't look intrusive enough to be
> left on the side of the road for yet another cycle...
> 

Please! I've been holding off on (re)doing and submitting sched_clock
support for highbank until this goes in.

Rob