Messages in this thread | | | Date | Tue, 24 Jun 2008 18:00:41 +0200 | From | Andreas Herrmann <> | Subject | Re: [PATCH] x86: enable hpet=force for AMD SB400 |
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On Sun, May 11, 2008 at 11:03:16AM +0200, Thomas Gleixner wrote: > On Sun, 11 May 2008, Alistair John Strachan wrote: > > > Well we don't have to auto-enable the hpet. Simply adding a loud "you > > > should try the hpet=force option" printk would help a lot of people. > > > > I'm a bit confused about the policy here: if we look at the Intel chipset > > overrides for HPET, they conditionally enable the HPET _without_ the > > hpet=force option if you have a chipset on the whitelist. > > > > If Intel can do this on their chipsets, why is this not being done for the ATI > > chipsets for which (presumably) AMD have specs? > > Well, we have no confirmation for the correctness of the non Intel > quirks so far. I'm happy to move them into unconditional mode once > AMD/ATI/NVidia tell us that the HPET is indeed discoverable this way. > > > One thing I'd considered was that HPET isn't actually used very often on Intel > > chipsets because on most recent Intel CPUs the TSC is stable, but I think > > Well, stable except for the C-States. We still need a backup clock > source as TSC is stopping in C3. > > > either the Intel quirk should be consistent with the hpet=force usage, > > or "known correct" HPET overrides should just always be applied. > > That's what we do. We have "known correct" for Intel and those which > work on the patch submitters box w/o confirmation of the > correctness. I guess the SB400 one can move into the "is correct" > category, Andreas ???
Sorry for the late reply, but I had to look for the spec in the first place ;-) and I have done some coding and testing since then. (Well, the patch was written as a quick hack to get HPET working on my private laptop.)
The point is that at least some revisions of IXP400/IXP450 have indeed hardware issues regarding HPET. Thus HPET works only for certain chip revisions.
Currently I am internally discussing whether it makes sense to enable (and properly configure) HPET for those chipset revisions.
BTW, if outcome of this discussion is that HPET on IXP400/IXP450 shouldn't be used then IMHO a quirk is needed to reliably disable it. I.e. disable it even if a system provides an ACPI HPET table.
Thanks for your patience.
Regards,
Andreas
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