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    SubjectRe: [ACPI] Re: PROBLEM: ACPI freezes 2.6.1 on boot
    Linus Torvalds writes:
    >
    >
    > On Thu, 22 Jan 2004, Mikael Pettersson wrote:
    >
    > > Karol Kozimor writes:
    > > >
    > > > diff -Bru linux-2.6.0-test8/arch/i386/kernel/apic.c patched/arch/i386/kernel/apic.c
    > > > --- linux-2.6.0-test8/arch/i386/kernel/apic.c 2003-10-18 05:43:36.000000000 +0800
    > > > +++ patched/arch/i386/kernel/apic.c 2003-10-30 23:17:50.000000000 +0800
    > > > @@ -836,8 +836,8 @@
    > > > {
    > > > unsigned int lvtt1_value, tmp_value;
    > > >
    > > > - lvtt1_value = SET_APIC_TIMER_BASE(APIC_TIMER_BASE_DIV) |
    > > > - APIC_LVT_TIMER_PERIODIC | LOCAL_TIMER_VECTOR;
    > > > + lvtt1_value = APIC_LVT_TIMER_PERIODIC | LOCAL_TIMER_VECTOR;
    > > > +
    > > > apic_write_around(APIC_LVTT, lvtt1_value);
    > >
    > > What is the purpose of this change?
    > > I don't remember seeing this before on LKML. (I don't have time to read bugzilla.)
    >
    > Hmm.. It does seem to fix things for a couple of people, so it looks
    > interesting.
    >
    > As far as I can tell, the _only_ thing it does is to change the timer base
    > from "DIV" to "CLKIN". I seem to have misplaced my ia-32 "volume 3" thing,
    > but I have an old one for a pentium, and that one doesn't actually
    > haev the timer-base thing at all - and marks those bits as "reserved".
    >
    > So it is entirely possible that the only safe value to write there is 0.

    Confirmed. Those bits (18 and 19 in LVTT) are marked reserved in the
    latest IA32 Volume 3. I have no idea where this APIC_TIMER_BASE came
    from (maybe some ancient discrete LAPIC thing?), but we almost certainly
    shouldn't write anything but zero to them.

    > So I'm inclined to apply the patch, but it would be better if somebody who

    I agree. The patch should be applied.

    /Mikael
    -
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