From: Feng Tang <feng.tang@intel.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Clemens Ladisch <clemens@ladisch.de>,
tglx@linutronix.de, mingo@elte.hu, hpa@zytor.com,
linux-kernel@vger.kernel.org,
John Stultz <john.stultz@linaro.org>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64
Date: Fri, 18 Apr 2014 15:18:23 +0800 [thread overview]
Message-ID: <20140418071823.GA4533@feng-snb> (raw)
In-Reply-To: <20140416065148.GB1193@gmail.com>
Hi All,
On Wed, Apr 16, 2014 at 08:51:48AM +0200, Ingo Molnar wrote:
>
> * Feng Tang <feng.tang@intel.com> wrote:
> > > > > > > >
> > > > > > > > > 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);
> > > > > > > [...]
> > > > > >
> > > > > > I just gave it another thought, that the HPET on our platform
> > > > > > currently do have some problem to be used as clocksource/clockevent,
> > > > > > but it may get fixed in future version (by Silicon or BIOS).
> > > > > >
> > > > > > If I add quirk to block it now, I may revert this code in future
> > > > > > when it get fixed, same problem applis for the future generation of
> > > > > > platform.
> > > > >
> > > > > If the hardware or BIOS gets fixed then that will be visible in the
> > > > > revision level of the hardware, right?
> > > >
> > > > AFAIK, if it is fixed in a new silicon version, we should be able to
> > > > detect it by the "stepping", but the PCI DEV ID is not likely to
> > > > change.
> > > >
> > > > If it is fixed by BIOS or PUNIT FW, then we may go through the
> > > > DMI info to check the BIOS version, One problem is there is some
> > > > Baytrail tablet platforms that doesn't provide DMI info as its
> > > > FW is not UEFI/Legacy BIOS compatible version.
> > >
> > > So just turn it off for the current hardware, via PCI ID. When you
> > > get a fix, you can turn it back on again by refining the quirk
> > > check, for that specific hardware.
> >
> > got it, thanks!
>
> Btw., note that such narrow quirk refinings are pretty uncontroversial
> and have a pretty fast path upstream, once you have the initial quirk
> in there.
During implementing, I found the arch/x86/kerne/quirks.c doesn't fit
well as the DECLARE_PCI_FIXUP_HEADER/EARLY/FINAL() way of quirk happens
inside the pci subsystem init phase, while the hpet_enable() will be
called before that.
Then by searching the arch/x86/, the early-quirks.c can be used to
add such a quirk as the early quirks are checked earlier than
hpet_enable()
I'll post a RFC patch soon.
Thanks,
Feng
next prev parent reply other threads:[~2014-04-18 7:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-28 2:55 [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64 Feng Tang
2014-03-28 7:17 ` Ingo Molnar
2014-03-28 7:37 ` Feng Tang
2014-03-28 8:08 ` Clemens Ladisch
2014-03-28 8:11 ` Ingo Molnar
2014-03-28 8:20 ` Feng Tang
2014-04-15 7:44 ` Feng Tang
2014-04-15 9:00 ` Ingo Molnar
2014-04-15 9:55 ` Feng Tang
2014-04-15 10:42 ` Ingo Molnar
2014-04-15 14:12 ` Feng Tang
2014-04-16 6:51 ` Ingo Molnar
2014-04-18 7:18 ` Feng Tang [this message]
2014-04-18 7:49 ` [RFC PATCH] x86, hpet: Add quirk to disable HPET for baytrail platform Feng Tang
2014-04-18 8:15 ` Ingo Molnar
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