On Sun, 30 Dec 2007 21:13:29 +0000 Alan Cox <[EMAIL PROTECTED]> wrote:
> > But that does't mean that other ports won't have the same timings. > > Also, it doesn't mean that we really need to have exactly *those* > > timings. > > For ISA bus you want "at least" those timings. That is an easy case > anyway - ISA bus boxes, old processors and generally no TSC so we can > fall back to 0x80 - we know from 15 years experience the problem only > occurs with recent non ISA systems that have borked firmware. > > Lots of ISA hardware does really need the delays and most of it will > be on old processors as well naturally enough. If I recall correctly, the MediaGX/Geode processor does need _p for the PIT accesses, and that CPU family does have a TSC (even though the TSC stops at times so is hard to use). I also seem to remember that the breakage did not happen very often, but running a system without _p overnight usually showed one hiccup where a read from the counter got corrupted. So unless I'm wrong (which I very well could be, it's been a couple of years since I was debugging the PIT code on a misbehaving Geode SC1200 based system) there is at least one fairly modern CPU, which is used in lots of embedded systems, and in active use, which does need the _p. Just a data point... It's not only ancient systems that need _p. /Christer -- "Just how much can I get away with and still go to heaven?" Christer Weinigel <[EMAIL PROTECTED]> http://www.weinigel.se -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
