Re: [PATCH] x86/hpet: Disable HPET on Intel Coffe Lake

[Kai-Heng Feng]

at 20:13, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> On Thu, 29 Aug 2019, Kai-Heng Feng wrote:
>
> > Some Coffee Lake platforms have skewed HPET timer once the SoCs entered
> > PC10, and marked TSC as unstable clocksource as result.
>
> So here you talk about Coffee Lake and in the patch you use KABYLAKE.

Coffeelake has the same model number as Kabylake.

> > Harry Pan identified it's a firmware bug [1].
> >
> > To prevent creating a circular dependency between HPET and TSC, let's
> > disable HPET on affected platforms.
> >
> > [1]:  
> > https://lore.kernel.org/lkml/20190516090651.1396-1-harry.pan@xxxxxxxxx/
> > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203183
>
> Please use Link:// for reference not [1] and not Bugzilla:

Ok.

> > +static const struct x86_cpu_id hpet_blacklist[] __initconst = {
> > +	{ X86_VENDOR_INTEL, 6, INTEL_FAM6_KABYLAKE_MOBILE },
> > +	{ X86_VENDOR_INTEL, 6, INTEL_FAM6_KABYLAKE_DESKTOP },
>
> So this disables HPET on all Kaby Lake variants not just on the affected
> Coffee Lakes. I know that I rejected the initial patch with the random
> stepping cutoff...
>
>   https://lore.kernel.org/lkml/alpine.DEB.2.21.1904081403220.1748@xxxxxxxxxxxxxxxxxxxxxxx
>
> In the other attempt to 'fix' this I asked for clarification, but silence
> from Intel after this:
>
>   https://lore.kernel.org/lkml/alpine.DEB.2.21.1905182015320.3019@xxxxxxxxxxxxxxxxxxxxxxx
>
> Can Intel please provide some useful information about this finally?

Hopefully Intel can provide more info.

I know we should find the root cause rather than stopping at "itâs a  
firmware bugâ, but users are already affected by this issue [1].
Is there any better short-term workaround?

[1] https://bugzilla.kernel.org/show_bug.cgi?id=204537

Kai-Heng

> Thanks,
>
> 	tglx