On Mon, 19 Apr 2004, Jun Sun wrote: > Solution > -------- > > All the boards that I am really concerned right now have cpu count/compare > registers. I believe this will even more so in the future. > > Therefore I like to propose a separate time support for systems that use > cpu timer as their system timer. > > As you can see from the patch, the new code is much simpler. It makes it separate again -- more maintenance burden and a bigger opportunity to have functional divergence, sigh... Additionally I don't think using the CP0 Count & Compare registers for the system timer is the way to go. It's rather a way to escape when there's no other possibility. A lot of systems have a reliable external timer interrupt source and using it actually would free the CP0 registers for other uses, like profiling or a programmable interval timer. > The hidden agenda > ----------------- > > OK, I admit there is another motivation in all of this. Linux is moving > to have higher resolution timer. For example, see the introduction of high resolution > posix timer (http://sourceforge.net/projects/high-res-timers/). Having a MIPS common > time routine based on cpu timer makes it much easier to support > such a feature for MIPS boards. We don't need to mess with individual board timer > anymore. > > In addition I think in 2.7 time frame Linux needs to replace its ancient jiffy > time system with a natively higher resolution time system. A MIPS cpu timer based > routine would evolve much better into the future. Well, I don't think the two issues are coupled together, although, there may be certain dependencies. E.g. an external time source may actually have a good resolution. Anyway, the details may be worth discussing when 2.7 spins off, preferably on the LKML, as this is about generic support. Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@xxxxxxxxxxxxx, PGP key available +
