Re: [ACPI] Re: PROBLEM: ACPI freezes 2.6.1 on boot

[Mikael Pettersson <mikpe@csd.uu.se>]

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