Re: [PATCH v2] x86/intel: Disable HPET on another Intel Coffee Lake platform

["Krzysztof Wilczyński" <kw@linux.com>]

Hi Jakub,

> My Lenovo T490s with i7-8665U had been marking TSC as unstable
> since v5.13, resulting in very sluggish desktop experience...
> 
> Kernel logs show:
> 
>   clocksource: timekeeping watchdog on CPU3: hpet read-back delay of 316000ns, attempt 4, marking unstable
>   tsc: Marking TSC unstable due to clocksource watchdog
>   TSC found unstable after boot, most likely due to broken BIOS. Use 'tsc=unstable'.
>   sched_clock: Marking unstable (14539801827657, -530891666)<-(14539319241737, -48307500)
>   clocksource: Checking clocksource tsc synchronization from CPU 3 to CPUs 0-2,6-7.
>   clocksource: Switched to clocksource hpet
> 
> I have a 8086:3e34 bridge, also known as "Host bridge: Intel
> Corporation Coffee Lake HOST and DRAM Controller (rev 0c)".
> Add it to the list.
> 
> We should perhaps consider applying this quirk more widely.
> The Intel documentation does not list my device [1], but
> linuxhw [2] does, and it seems to list a few more bridges
> we do not currently cover (3e31, 3ecc, 3e35, 3e0f).

I wish someone from Intel would be a little more forthcoming and chimed in
about the other devices.  I guess, we will cross that bridge when we get to
it, so to speak.

> [1] https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/8th-gen-core-family-datasheet-vol-2.pdf
> [2] https://github.com/linuxhw/DevicePopulation/blob/master/README.md
> 
> Cc: stable@vger.kernel.org # v5.13+
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> v2: - add the dmesg output
> ---
>  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 38837dad46e6..7d2de04f8750 100644
> --- a/arch/x86/kernel/early-quirks.c
> +++ b/arch/x86/kernel/early-quirks.c
> @@ -716,6 +716,8 @@ static struct chipset early_qrk[] __initdata = {
>  		PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet},
>  	{ PCI_VENDOR_ID_INTEL, 0x3e20,
>  		PCI_CLASS_BRIDGE_HOST, PCI_ANY_ID, 0, force_disable_hpet},
> +	{ PCI_VENDOR_ID_INTEL, 0x3e34,
> +		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_INTEL, 0x8a12,

Thank you!

Acked-by: Krzysztof Wilczyński <kw@linux.com>

	Krzysztof