On Mon, 2011-04-04 at 14:31 +0100, Russell King - ARM Linux wrote: > On Mon, Apr 04, 2011 at 02:24:17PM +0100, Marc Zyngier wrote: > > On Mon, 2011-04-04 at 12:21 +0100, Russell King - ARM Linux wrote: > > > Whether its worth it or not is questionable - the above is more lines > > > of code than many of the existing implementations, and we're not going > > > to shrink the existing implementations by much (maybe one to three > > > lines.) The only thing we gain is the ability to select an implementation > > > at runtime. > > > > I believe this last point to be rather important if we plan to have this > > mythical single kernel covering several architectures. It's also nice > > for the A15 to be able to use some default sched_clock() implementation > > as a fallback if the generic timers are not available for some reason. > > If ARM are going to architect a set of timers into the hardware, let's > make sure that all such hardware has them so we can dig ourselves out > of this crappy mess that we find ourselves in today. As far as I know, A15 always has a set of generic timers. It may be that they are not available (frequency not programmed into the CNTFREQ register), or that someone decided to use a better alternative (for some particular interpretation of "better"). Overall, it seems like we need some degree of flexibility to have several sched_clock() implementations within a single image, whether it is to support multiple platforms, or to allow a single architecture to pick the best alternative given a set of initial conditions. M. -- Reality is an implementation detail. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
