From: Dmitry Torokhov <dtor_core@ameritech.net>
To: Andrew Morton <akpm@osdl.org>,
       Alessandro Suardi <alessandro.suardi@oracle.com>
Subject: Re: 2.6.2-rc2-bk1 oopses on boot (ACPI patch)
Date: Tue, 27 Jan 2004 23:37:55 -0500
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On Tuesday 27 January 2004 09:42 pm, Andrew Morton wrote:
> Alessandro Suardi <alessandro.suardi@oracle.com> wrote:
> > Already reported, but I'll do so once again, since it looks like
> >   in a short while I won't be able to boot official kernels in my
> >   current config...
> >
> > Original report here:
> >
> > http://www.ussg.iu.edu/hypermail/linux/kernel/0312.3/0442.html
>
> Divide by zero.  Looks like ACPI is now passing bad values into the
> frequency change notifier.

It is a common problem with Dell's DSDT implementation which does not
follow ACPI spec and it's been going on for ages. From the original
report:

cpufreq: CPU0 - ACPI performance management activated
 cpufreq: *P0: 1Mhz, 0 mW, 0 uS
 cpufreq: P1: 0Mhz, 0 mW, 0 uS
 divide error: 0000 [#1]

As you can see all data is bogus... Patching DSDT cures it for sure,
sometimes CONFIG_ACPI_RELAXED_AML helps as well.

I suppose ACPI P-states driver could check frequencies/latencies and
refuse to activate if the are bogus.

-- 
Dmitry
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