linux-kernel - Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86

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Message-ID: <20140328081117.GA32308@gmail.com>
Date:	Fri, 28 Mar 2014 09:11:17 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	Feng Tang <feng.tang@...el.com>, tglx@...utronix.de, mingo@...e.hu,
	hpa@...or.com, linux-kernel@...r.kernel.org,
	John Stultz <john.stultz@...aro.org>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y
 for X86_64


* Clemens Ladisch <clemens@...isch.de> wrote:

> Feng Tang wrote:
> > On Fri, Mar 28, 2014 at 08:17:16AM +0100, Ingo Molnar wrote:
> >> * Feng Tang <feng.tang@...el.com> wrote:
> >>  - 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,
> 
> HPET does have the PCI vendor ID in the first register.
> 
> > only thing I can think of to identify them may be the CPU family/ID.
> 
> The HPET is implemented by some actual chip, and that chip also has lots
> of PCI devices.  (In the case of a SoC, the CPU ID would work, too).

Correct. See arch/x86/kernel/hpet.c, which has a large number of HPET 
quirks keyed off chipset PCI IDs:

  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ESB2_0,
                           ich_force_enable_hpet);
  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_0,
                           ich_force_enable_hpet);
  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_ICH6_1,
                           ich_force_enable_hpet);
  [...]

Thanks,

	Ingo
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