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x86: docs fixes to Documentation/i386/IO-APIC.txt

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Clean up spelling and grammar of IO-APIC.txt

Signed-off-by: Nick Andrew <nick@nick-andrew.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Nick Andrew 2008-02-17 18:01:42 +11:00 committed by Ingo Molnar
parent d8ff0bbf56
commit 248fb89c12
1 changed files with 17 additions and 15 deletions
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32
Documentation/i386/IO-APIC.txt
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@ -1,12 +1,14 @@
Most (all) Intel-MP compliant SMP boards have the so-called 'IO-APIC',
which is an enhanced interrupt controller, it enables us to route
hardware interrupts to multiple CPUs, or to CPU groups.
which is an enhanced interrupt controller. It enables us to route
hardware interrupts to multiple CPUs, or to CPU groups. Without an
IO-APIC, interrupts from hardware will be delivered only to the
CPU which boots the operating system (usually CPU#0).
Linux supports all variants of compliant SMP boards, including ones with
multiple IO-APICs. (multiple IO-APICs are used in high-end servers to
distribute IRQ load further).
multiple IO-APICs. Multiple IO-APICs are used in high-end servers to
distribute IRQ load further.
There are (a few) known breakages in certain older boards, which bugs are
There are (a few) known breakages in certain older boards, such bugs are
usually worked around by the kernel. If your MP-compliant SMP board does
not boot Linux, then consult the linux-smp mailing list archives first.
@ -28,18 +30,18 @@ If your box boots fine with enabled IO-APIC IRQs, then your
hell:~>
<----------------------------
some interrupts are still listed as 'XT PIC', but this is not a problem,
Some interrupts are still listed as 'XT PIC', but this is not a problem;
none of those IRQ sources is performance-critical.
in the unlikely case that your board does not create a working mp-table,
In the unlikely case that your board does not create a working mp-table,
you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This
is nontrivial though and cannot be automated. One sample /etc/lilo.conf
is non-trivial though and cannot be automated. One sample /etc/lilo.conf
entry:
append="pirq=15,11,10"
the actual numbers depend on your system, on your PCI cards and on their
The actual numbers depend on your system, on your PCI cards and on their
PCI slot position. Usually PCI slots are 'daisy chained' before they are
connected to the PCI chipset IRQ routing facility (the incoming PIRQ1-4
lines):
@ -54,7 +56,7 @@ lines):
PIRQ1 ----| |- `----| |- `----| |- `----| |--------| |
`-' `-' `-' `-' `-'
every PCI card emits a PCI IRQ, which can be INTA,INTB,INTC,INTD:
Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
,-.
INTD--| |
@ -95,21 +97,21 @@ card (IRQ11) in Slot3, and have Slot1 empty:
[value '0' is a generic 'placeholder', reserved for empty (or non-IRQ emitting)
slots.]
generally, it's always possible to find out the correct pirq= settings, just
Generally, it's always possible to find out the correct pirq= settings, just
permute all IRQ numbers properly ... it will take some time though. An
'incorrect' pirq line will cause the booting process to hang, or a device
won't function properly (if it's inserted as eg. a module).
won't function properly (e.g. if it's inserted as a module).
If you have 2 PCI buses, then you can use up to 8 pirq values. Although such
If you have 2 PCI buses, then you can use up to 8 pirq values, although such
boards tend to have a good configuration.
Be prepared that it might happen that you need some strange pirq line:
append="pirq=0,0,0,0,0,0,9,11"
use smart try-and-err techniques to find out the correct pirq line ...
Use smart trial-and-error techniques to find out the correct pirq line ...
good luck and mail to linux-smp@vger.kernel.org or
Good luck and mail to linux-smp@vger.kernel.org or
linux-kernel@vger.kernel.org if you have any problems that are not covered
by this document.