linux-kernel - Re: fc6 kernel 2.6.18-1.2798 breaks acpi on HP laptop n5430

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Date:	Thu, 02 Nov 2006 04:23:29 +0000
From:	Sergio Monteiro Basto <sergio@...giomb.no-ip.org>
To:	Dave Jones <davej@...hat.com>
Cc:	Stephen Clark <Stephen.Clark@...lark.us>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: fc6 kernel 2.6.18-1.2798 breaks acpi on HP laptop n5430

On Wed, 2006-11-01 at 22:03 -0500, Dave Jones wrote:
> On Wed, Nov 01, 2006 at 08:08:31PM -0500, Stephen Clark wrote:
> 
>  > booting without lapic allowed it to boot but now I get
>  > ...
>  > Local APIC disabled by BIOS -- you can enable it with "lapic"
>  > ...
>  > Local APIC not detected. Using dummy APIC emulation.
>  >   which means more processor overhead - right?
>  > 
>  > also cpuspeed doesn't work anymore - I don't have a cpufreq dir
> 
> The Duron had powernow ?

This story of trying enable lapic when BIOS don't, has been triggered on
kernel2.6.18, but in my opinion is not a bug if lapic on those computers
don't work.

If you boot without enable lapic, you will see cat /proc/interrupts with
interrupts in XT-PIC.
if you try enable lapic, somehow IRQ routing should change 
and if /proc/interrupts still the same, with IRQs in XT-PIC.
I think, lapic still not enabled and the most you can get it's problems.
Unless you know that lapic works (it is programmed and BIOS wrongly
disable it), you shouldn't try enable lapic because it is probable that
just give problems, to you. 
Historically: In 2002/3 was a very common bug, when kernel was compiled
to support lapic and try enable lapic (even when BIOS don't) and
computer hangs on boot. 
-- 
Sérgio M.B.

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