Messages in this thread | | | Subject | Re: [PATCH] x86 ACPI: Blacklist two HP machines with buggy BIOSes (Re: 2.6.27-rc8+ - first impressions) | From | Andi Kleen <> | Date | Mon, 06 Oct 2008 22:59:37 +0200 |
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"Maciej W. Rozycki" <macro@linux-mips.org> writes: > > This single instance of a piece of some HP gear being twisted beyond > belief is IMO a minor annoyance and price to pay compared to the gain. > Please note that apart from the DSDT being buggy on this machine, it has > an incorrect IRQ 0 override in the ACPI table pointing to the pin #2 of > the I/O APIC, which is in fact routed to the output of the master 8259A. > Additionally the pin #0 of the I/O APIC which is indeed routed to the > output of the 8254 does not receive any interrupts, presumably because of > some misconfiguration during BIOS initialisation.
The real reason is actually a workaround in the BIOS for problems in the older Linux code that caused duplicated timer interrupts. The old Linux would fall into "enable both IO-APIC and 8259" fallback mode and the resulted in duplicated timer events, which made everything unhappy. They instead configured the northbridge in a way that one of the inputs is ignored.
You won't be able to DMI list it, that workaround is widely used in lots of different systems.
-andi
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