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SubjectRe: [PATCH RFC] x86/tsc: Make recalibration default on for TSC_KNOWN_FREQ cases
On Tue, May 23, 2023 at 10:11:15AM +0200, Peter Zijlstra wrote:
> On Tue, May 23, 2023 at 09:18:23AM +0800, Feng Tang wrote:
> > On Mon, May 22, 2023 at 06:11:58PM +0200, Peter Zijlstra wrote:
> > > On Mon, May 22, 2023 at 11:20:15PM +0800, Feng Tang wrote:
> > >
> > > > And I don't understand the commit log: "On Intel GOLDMONT Atom SoC
> > > > TSC is the only reliable clocksource. We mark TSC reliable to avoid
> > > > watchdog on it."
> > > >
> > > > Clearly the Denventon I found today has both HPET and ACPI_PM timer:
> > > >
> > > > [root@dnv0 ~]# grep . /sys/devices/system/clocksource/clocksource0/*
> > > > /sys/devices/system/clocksource/clocksource0/available_clocksource:tsc hpet acpi_pm
> > > > /sys/devices/system/clocksource/clocksource0/current_clocksource:tsc
> > > >
> > > > The lscpu info is:
> > > >
> > > > Architecture: x86_64
> > > > CPU op-mode(s): 32-bit, 64-bit
> > > > Address sizes: 39 bits physical, 48 bits virtual
> > > > Byte Order: Little Endian
> > > > CPU(s): 12
> > > > On-line CPU(s) list: 0-11
> > > > Vendor ID: GenuineIntel
> > > > BIOS Vendor ID: Intel(R) Corporation
> > > > Model name: Intel(R) Atom(TM) CPU C3850 @ 2.10GHz
> > > > BIOS Model name: Intel(R) Atom(TM) CPU C3850 @ 2.10GHz CPU @ 2.1GHz
> > > > BIOS CPU family: 43
> > > > CPU family: 6
> > > > Model: 95
> > > > Thread(s) per core: 1
> > > > Core(s) per socket: 12
> > > > Socket(s): 1
> > > > Stepping: 1
> > > >
> > > > Maybe this cpu model (0x5F) has been used by some type of platforms
> > > > which has met the false alarm watchdog issue.
> > >
> > > It has them; but they are not *reliable*.
> >
> > Yes, that's possible. I tried to CC the author Bin in case he can
> > provide more background or information for his statement, but his
> > email address is unreachable now.
>
> IIRC HPET stops in C10 or something stupid like that, I forgot what the
> problem with ACPI_PM is.

Yes, that HPET issue is a common one for several generations of
client platforms like Baytrail, Coffee Lake etc.

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