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SubjectRe: HPET regression in 2.6.26 versus 2.6.25 -- connection between HPET and lockups found

* David Witbrodt <> wrote:

> > Just to make sure: on a working kernel, do you get the HPET
> > messages? I.e. does the hpet truly work in that case?
> On the "fileserver", where 2.6.25 works but 2.6.26 locks up, the HPET
> _does_ work on a working kernel:
> $ uname -r
> 2.6.26.revert1
> $ dmesg | grep -i hpet
> ACPI: HPET 77FE80C0, 0038 (r1 RS690 AWRDACPI 42302E31 AWRD 98)
> ACPI: HPET id: 0x10b9a201 base: 0xfed00000
> hpet clockevent registered
> hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0
> hpet0: 4 32-bit timers, 14318180 Hz
> hpet_resources: 0xfed00000 is busy

btw., you might also want to look into drivers/char/hpet.c and
instrument that a bit. In particular the ioremap()s done there will show
exactly how the hpet is mapped.

In particular this bit:

if (hpet_is_known(hdp)) {
printk(KERN_DEBUG "%s: 0x%lx is busy\n",
__func__, hdp->hd_phys_address);

suggests that you've got multiple hpets listed by the BIOS?

> What I didn't realize is that the "desktop" machine, where 2.6.26 has
> always "worked", does NOT have a working HPET after all, even though I
> have enabled all HPET options in .config:

that's OK - you've still got a regression.

> (I don't know what is going on with "desktop": does the motherboard
> lack HPET, or does the Linux kernel not support the HPET hardware on
> the motherboard?)

Whether the system has a hpet listed in the BIOS data structures can be
seen in acpidump [in the pmtools package]

Even if the BIOS does not list it, the system might have hpet in the
chipset - hpet=force can be tried to force-enable it.


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