[haiku-gsoc] Re: [HPET] (Fwd:) I'm in a jam.
- From: "Michael Lotz" <mmlr@xxxxxxxx>
- To: haiku-gsoc@xxxxxxxxxxxxx
- Date: Sun, 03 Aug 2008 18:26:12 +0200
> > I thought there is enough data in the separate HPET table to do
> > basic
> > setup/use of the timer. This might not expose all available timers
> > and
> > such, but it may be enough for our needs? The idea being similar to
> > that of the APIC table that provides boot code with enough MP
> > information to configure/start a SMP system without a full blown
> > AML
> > parser.
>
> I couldn't find a separate HPET block in the patched QEMU BIOS, nor
> in
> my BIOS, and found the only reference to it in the AML in my bios,
> too
> (Opened up Phoenix BIOS Editor and grepped the disassembled files)..
> appears the only reference to it is in the DSDT.
The HPET specs describe it in chapter 3.2.4. Not sure if QEMU supports
HPET, and if it does it's still possible that it doesn't do the
separate HPET descriptor table. But then that'd probably be a missing
feature of QEMU. I'm pretty sure that my board has an HPET and also
exports that separate table. Just to make sure, the board you use does
have a working HPET in other systems? I know that not all modern boards
have it present, although they've probably become more widespread since
I last checked.
> > Therefore I would like to see 3 as the best solution, as it could
> > then
> > be used in that code as well. Doing something specifically for HPET
> > would probably be a waste of time, as there are a few other things
> > that
> > will require full ACPI anyway and having it available from the
> > normal
> > module instead of duplicating specific code makes the most sense to
> > me.
> >
>
> I was leaning towards that option as well.
Doing that is of course still desirable, if only for the IOAPIC case.
Thought that one (IOAPIC) isn't really critical in early boot, it can
be switched later on when the ACPI module is available as well.
Regards
Michael
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