Hi Greg,

On Nov 18, 2019, at 23:55, gregkh@linuxfoundation.org gregkh@linuxfoundation.org wrote:

This is a note to let you know that I've just added the patch titled

x86/quirks: Disable HPET on Intel Coffe Lake platforms

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-quirks-disable-hpet-on-intel-coffe-lake-platforms.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

This patch depends on commit c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets"). Otherwise the system may freeze at boot. So please also include that commit.

Kai-Heng

From fc5db58539b49351e76f19817ed1102bf7c712d0 Mon Sep 17 00:00:00 2001 From: Kai-Heng Feng kai.heng.feng@canonical.com Date: Wed, 16 Oct 2019 18:38:16 +0800 Subject: x86/quirks: Disable HPET on Intel Coffe Lake platforms

From: Kai-Heng Feng kai.heng.feng@canonical.com

commit fc5db58539b49351e76f19817ed1102bf7c712d0 upstream.

Some Coffee Lake platforms have a skewed HPET timer once the SoCs entered PC10, which in consequence marks TSC as unstable because HPET is used as watchdog clocksource for TSC.

Harry Pan tried to work around it in the clocksource watchdog code [1] thereby creating a circular dependency between HPET and TSC. This also ignores the fact, that HPET is not only unsuitable as watchdog clocksource on these systems, it becomes unusable in general.

Disable HPET on affected platforms.

Suggested-by: Feng Tang feng.tang@intel.com Signed-off-by: Kai-Heng Feng kai.heng.feng@canonical.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203183 Link: https://lore.kernel.org/lkml/20190516090651.1396-1-harry.pan@intel.com/ [1] Link: https://lkml.kernel.org/r/20191016103816.30650-1-kai.heng.feng@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

---

arch/x86/kernel/early-quirks.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/early-quirks.c +++ b/arch/x86/kernel/early-quirks.c @@ -699,6 +699,8 @@ static struct chipset early_qrk[] __init */ { 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}, {}

Patches currently in stable-queue which might be from kai.heng.feng@canonical.com are

queue-4.4/x86-quirks-disable-hpet-on-intel-coffe-lake-platforms.patch