Cc: Linus Torvalds <torvalds@...>, Rafael J. Wysocki <rjw@...>, Dmitry Torokhov <dmitry.torokhov@...>, <linux-kernel@...>, Andrew Morton <akpm@...>, Len Brown <lenb@...>, Jason Vas Dias <jason.vas.dias@...>
None of the above. This:
691874f: x86: I/O APIC: timer through 8259A second-chance
This change has fixed a problem with the timer for a lot of systems and
permitted the removal of a bunch of horrible hacks we used to have in our
I/O-APIC/timer code, including a command-line override parameter, needed
so that some systems would boot at all.
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. So in fact this machine
suffers from three configuration problems at once of which all add up to
the end result we can observe.
It is not just theory. I did actually analyse the AML code coming from
the broken DSDT and found the responsible snippets. See:
http://lkml.org/lkml/2008/6/20/442 for a reference. No SMI is involved
here -- this is native ACPI operation -- Linux calls these snippets
explicitly as required by the ACPI spec for various actions.
It will break many if not most of the systems out there which have the
PIT (rather than the master 8259A) wired to the pin #2 of the I/O APIC
and correctly reported as such with an ACPI IRQ override.
Maciej
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