linux-kernel - Re: [PATCH] x86/intel: Disable HPET on Intel Coffe Lake platforms

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Date:   Wed, 30 Oct 2019 16:06:13 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        Borislav Petkov <bp@...en8.de>
Cc:     "H. Peter Anvin" <hpa@...or.com>, Harry Pan <harry.pan@...el.com>,
        feng.tang@...el.com, x86@...nel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] x86/intel: Disable HPET on Intel Coffe Lake platforms

Hi Thomas,

> On Oct 16, 2019, at 18:38, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
> 
> Some Coffee Lake platforms have skewed HPET timer once the SoCs entered
> PC10, and marked TSC as unstable clocksource as result.
> 
> 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@intel.com/
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203183

Do you think it's a sane approach?

Kai-Heng

> 
> Cc: <stable@...r.kernel.org>
> Suggested-by: Feng Tang <feng.tang@...el.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
> arch/x86/kernel/early-quirks.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
> index 6f6b1d04dadf..4cba91ec8049 100644
> --- a/arch/x86/kernel/early-quirks.c
> +++ b/arch/x86/kernel/early-quirks.c
> @@ -710,6 +710,8 @@ static struct chipset early_qrk[] __initdata = {
> 	 */
> 	{ PCI_VENDOR_ID_INTEL, 0x0f00,
> 		PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet},
> +	{ PCI_VENDOR_ID_INTEL, 0x3ec4,
> +		PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet},
> 	{ PCI_VENDOR_ID_BROADCOM, 0x4331,
> 	  PCI_CLASS_NETWORK_OTHER, PCI_ANY_ID, 0, apple_airport_reset},
> 	{}
> -- 
> 2.17.1
>