Re: [PATCH] Blacklist Dell Optiplex 320 from using the HPET

Andi Kleen
2007-05-04T23:18:58Z

On Friday 04 May 2007 23:29:04 john stultz wrote:
> One of the 2.6.21 regressions was Guilherme's problem seeing his box
> lock up when the system detected an unstable TSC and dropped back to
> using the HPET.
>
> In digging deeper, we found the HPET is not actually incrementing on
> this system. And in fact, the reason why this issue just cropped up was
> because of Thomas's clocksource watchdog code was comparing the TSC to
> the HPET (which wasn't moving) and thought the TSC was broken.
>
> Anyway, Guliherme checked for a BIOS update and did not find one, so
> I've added a DMI blacklist against his system so the HPET is not used.
>
> Many thanks to Guilherme for the slow and laborious testing that finally
> narrowed down this issue.

Before going to hard to maintain DMI black lists we should first check
if it's a more general problem and can't it be solved better? Most likely
that system isn't the one with this issue and I don't want to apply
DMI patches forever.

In particular: what lspci chipset does it have? If it's Intel it might be
worth checking the datasheet if there is some "HPET stop" bit -- perhaps it
could be fixed up.

We seem to have a couple of Intel systems recently with HPET trouble.

-Andi