mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-27 06:34:11 +08:00
c98be0c96d
Fixed multiple spelling errors. Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Carlos E. Garcia <carlos@cgarcia.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
120 lines
4.8 KiB
Plaintext
120 lines
4.8 KiB
Plaintext
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. 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.
|
|
|
|
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.
|
|
|
|
If your box boots fine with enabled IO-APIC IRQs, then your
|
|
/proc/interrupts will look like this one:
|
|
|
|
---------------------------->
|
|
hell:~> cat /proc/interrupts
|
|
CPU0
|
|
0: 1360293 IO-APIC-edge timer
|
|
1: 4 IO-APIC-edge keyboard
|
|
2: 0 XT-PIC cascade
|
|
13: 1 XT-PIC fpu
|
|
14: 1448 IO-APIC-edge ide0
|
|
16: 28232 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet
|
|
17: 51304 IO-APIC-level eth0
|
|
NMI: 0
|
|
ERR: 0
|
|
hell:~>
|
|
<----------------------------
|
|
|
|
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,
|
|
you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This
|
|
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
|
|
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):
|
|
|
|
,-. ,-. ,-. ,-. ,-.
|
|
PIRQ4 ----| |-. ,-| |-. ,-| |-. ,-| |--------| |
|
|
|S| \ / |S| \ / |S| \ / |S| |S|
|
|
PIRQ3 ----|l|-. `/---|l|-. `/---|l|-. `/---|l|--------|l|
|
|
|o| \/ |o| \/ |o| \/ |o| |o|
|
|
PIRQ2 ----|t|-./`----|t|-./`----|t|-./`----|t|--------|t|
|
|
|1| /\ |2| /\ |3| /\ |4| |5|
|
|
PIRQ1 ----| |- `----| |- `----| |- `----| |--------| |
|
|
`-' `-' `-' `-' `-'
|
|
|
|
Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
|
|
|
|
,-.
|
|
INTD--| |
|
|
|S|
|
|
INTC--|l|
|
|
|o|
|
|
INTB--|t|
|
|
|x|
|
|
INTA--| |
|
|
`-'
|
|
|
|
These INTA-D PCI IRQs are always 'local to the card', their real meaning
|
|
depends on which slot they are in. If you look at the daisy chaining diagram,
|
|
a card in slot4, issuing INTA IRQ, it will end up as a signal on PIRQ4 of
|
|
the PCI chipset. Most cards issue INTA, this creates optimal distribution
|
|
between the PIRQ lines. (distributing IRQ sources properly is not a
|
|
necessity, PCI IRQs can be shared at will, but it's a good for performance
|
|
to have non shared interrupts). Slot5 should be used for videocards, they
|
|
do not use interrupts normally, thus they are not daisy chained either.
|
|
|
|
so if you have your SCSI card (IRQ11) in Slot1, Tulip card (IRQ9) in
|
|
Slot2, then you'll have to specify this pirq= line:
|
|
|
|
append="pirq=11,9"
|
|
|
|
the following script tries to figure out such a default pirq= line from
|
|
your PCI configuration:
|
|
|
|
echo -n pirq=; echo `scanpci | grep T_L | cut -c56-` | sed 's/ /,/g'
|
|
|
|
note that this script won't work if you have skipped a few slots or if your
|
|
board does not do default daisy-chaining. (or the IO-APIC has the PIRQ pins
|
|
connected in some strange way). E.g. if in the above case you have your SCSI
|
|
card (IRQ11) in Slot3, and have Slot1 empty:
|
|
|
|
append="pirq=0,9,11"
|
|
|
|
[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
|
|
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 (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
|
|
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 trial-and-error techniques to find out the correct pirq line ...
|
|
|
|
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.
|
|
|
|
-- mingo
|
|
|