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SubjectRe: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64
Hi Ingo,

Thanks for reviewing this

On Fri, Mar 28, 2014 at 08:17:16AM +0100, Ingo Molnar wrote:
>
> * Feng Tang <feng.tang@intel.com> wrote:
>
> > On many new phone/tablet platforms like Baytrail/Merrifield etc, the
> > HPET are either defeatured or has some problem to be used as a
> > reliable timer. As these platforms also have X86_64, we should not
> > make HPET_TIMER default y for all X86_64.
>
> NAK!
>
> If the HPET is unreliable on a specific platform then any of the
> following solutions would address the problem (in order of
> preference):
>
> - the hardware should not expose it. Why waste silicon on something
> that does not work?
>
> - or the firmware should not expose it. Why expose something that
> does not work?

Agreed, I've raised problem to BIOS vendor, but the response is very slow,
and those hardware/BIOS may already hit the market as a product.

>
> - or the kernel should have a quirk to reliably disable it. Why
> should we crash or misbehave if a driver is built into the
> kernel?

I thought about this before, HPET doesn't have PCI ID like stuff, only
thing I can think of to identify them may be the CPU family/ID.
Runtime check the reliability of HPET may be difficult, as we don't
know if the 8254 or the TSC are the golden timer to check HPET.

Thanks,
Feng



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