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SubjectRe: device driver for the SGI system clock, mmtimer
On Thu, Sep 16, 2004 at 10:54:51AM -0600, Bjorn Helgaas wrote:
> On Thursday 16 September 2004 10:32 am, Christoph Lameter wrote:
> > On Thu, 16 Sep 2004, Bjorn Helgaas wrote:
> > > Christoph Lameter wrote:
> > > > The timer hardware was designed around the multimedia timer specification by Intel
> > > > but to my knowledge only SGI has implemented that standard. The driver was written
> > > > by Jesse Barnes.
> > >
> > > As far as I can see, drivers/char/hpet.c talks to the same hardware.
> > > HP sx1000 machines (and probably others) also implement the HPET.
> >
> > The Intel Multimedia Standard is a earlier and different timer spec.
>
> I have a spec that's labelled "IA-PC Multimedia Timers", preliminary
> draft of June 2000, revision 0.97, which looks like the one mentioned
> in your patch.
>
> I also have something labelled "IA-PC HPET (High Precision Event
> Timers) Specification", draft of February 2002, revision 0.98,
> which is what drivers/char/hpet.c supports.
>
> I admit I haven't compared them in great detail, but they certainly
> *look* like they're close enough that the same driver could support
> both, and the 0.98 revision history only mentions fairly cosmetic
> changes (like the name :)).

Indeed, I coded the x86-64 HPET support using the 0.97 spec, and then
only did a few minor fixups when I got the 0.98 spec.

> Is there something specific that drivers/char/hpet.c expects that
> your hardware doesn't implement?

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Vojtech Pavlik
SuSE Labs, SuSE CR
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