Linux 2.4.13-ac4

Linux 2.4.13-ac4

Post by Vojtech Pavli » Wed, 31 Oct 2001 02:50:15




> > bytes read from the 8254 get swapped. I've got some indirect evidence
> > that this also could happen with the original i8254.

> Im hoping not. That would imply we interrupted someone half way through
> reading the counter which means the locking is screwed up.

> > By the way, if we made the 8254 accesses (spinlock?) protected (which
> > should be done anyway, right now definitely more than one CPU can access
> > the registers at once), I think we could remove the outb(0, 0x43);,
> > saving some cycles.

> Some chipsets need the outb

I'm looking at how to cleanly fix the timer accesses. And I think a
common inline function that does the

lock
outb
inb
inb
check - via, other bugs
unlock

would make sense. What do you think?

--
Vojtech Pavlik
SuSE Labs
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Linux 2.4.13-ac4

Post by Maciej W. Rozyck » Wed, 31 Oct 2001 20:40:10



> >  Hmm, has anyone tried using the "read back" 8254 command for latching,
> > instead?  Chances are it's less buggy...

> We can try, but I think that it's more likely to be more buggy, because
> it isn't widely used by software. And at least according to the 8254
> docs they should be equivalent in what they do.

 Are you sure it isn't used?  Do you have sources of various operating
systems to check?  I don't.

--
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+

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