diff options
author | H. Peter Anvin <hpa@zytor.com> | 2008-05-30 20:19:03 -0400 |
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committer | H. Peter Anvin <hpa@zytor.com> | 2008-05-30 20:19:03 -0400 |
commit | 23deb06821442506615f34bd92ccd6a2422629d7 (patch) | |
tree | 5e95dba1471007a161e19844fab2d60d422f5423 /Documentation/i386/IO-APIC.txt | |
parent | 4039feb5bae72a5fed9ba6bc1a9cfd8dfe0a8613 (diff) |
x86: move x86-specific documentation into Documentation/x86
The current organization of the x86 documentation makes it appear as
if the "i386" documentation doesn't apply to x86-64, which is does.
Thus, move that documentation into Documentation/x86, and move the
x86-64-specific stuff into Documentation/x86/x86_64 with the eventual
goal to move stuff that isn't actually 64-bit specific back into
Documentation/x86.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/i386/IO-APIC.txt')
-rw-r--r-- | Documentation/i386/IO-APIC.txt | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/Documentation/i386/IO-APIC.txt b/Documentation/i386/IO-APIC.txt deleted file mode 100644 index 30b4c714fbe1..000000000000 --- a/Documentation/i386/IO-APIC.txt +++ /dev/null | |||
@@ -1,119 +0,0 @@ | |||
1 | Most (all) Intel-MP compliant SMP boards have the so-called 'IO-APIC', | ||
2 | which is an enhanced interrupt controller. It enables us to route | ||
3 | hardware interrupts to multiple CPUs, or to CPU groups. Without an | ||
4 | IO-APIC, interrupts from hardware will be delivered only to the | ||
5 | CPU which boots the operating system (usually CPU#0). | ||
6 | |||
7 | Linux supports all variants of compliant SMP boards, including ones with | ||
8 | multiple IO-APICs. Multiple IO-APICs are used in high-end servers to | ||
9 | distribute IRQ load further. | ||
10 | |||
11 | There are (a few) known breakages in certain older boards, such bugs are | ||
12 | usually worked around by the kernel. If your MP-compliant SMP board does | ||
13 | not boot Linux, then consult the linux-smp mailing list archives first. | ||
14 | |||
15 | If your box boots fine with enabled IO-APIC IRQs, then your | ||
16 | /proc/interrupts will look like this one: | ||
17 | |||
18 | ----------------------------> | ||
19 | hell:~> cat /proc/interrupts | ||
20 | CPU0 | ||
21 | 0: 1360293 IO-APIC-edge timer | ||
22 | 1: 4 IO-APIC-edge keyboard | ||
23 | 2: 0 XT-PIC cascade | ||
24 | 13: 1 XT-PIC fpu | ||
25 | 14: 1448 IO-APIC-edge ide0 | ||
26 | 16: 28232 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet | ||
27 | 17: 51304 IO-APIC-level eth0 | ||
28 | NMI: 0 | ||
29 | ERR: 0 | ||
30 | hell:~> | ||
31 | <---------------------------- | ||
32 | |||
33 | Some interrupts are still listed as 'XT PIC', but this is not a problem; | ||
34 | none of those IRQ sources is performance-critical. | ||
35 | |||
36 | |||
37 | In the unlikely case that your board does not create a working mp-table, | ||
38 | you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This | ||
39 | is non-trivial though and cannot be automated. One sample /etc/lilo.conf | ||
40 | entry: | ||
41 | |||
42 | append="pirq=15,11,10" | ||
43 | |||
44 | The actual numbers depend on your system, on your PCI cards and on their | ||
45 | PCI slot position. Usually PCI slots are 'daisy chained' before they are | ||
46 | connected to the PCI chipset IRQ routing facility (the incoming PIRQ1-4 | ||
47 | lines): | ||
48 | |||
49 | ,-. ,-. ,-. ,-. ,-. | ||
50 | PIRQ4 ----| |-. ,-| |-. ,-| |-. ,-| |--------| | | ||
51 | |S| \ / |S| \ / |S| \ / |S| |S| | ||
52 | PIRQ3 ----|l|-. `/---|l|-. `/---|l|-. `/---|l|--------|l| | ||
53 | |o| \/ |o| \/ |o| \/ |o| |o| | ||
54 | PIRQ2 ----|t|-./`----|t|-./`----|t|-./`----|t|--------|t| | ||
55 | |1| /\ |2| /\ |3| /\ |4| |5| | ||
56 | PIRQ1 ----| |- `----| |- `----| |- `----| |--------| | | ||
57 | `-' `-' `-' `-' `-' | ||
58 | |||
59 | Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD: | ||
60 | |||
61 | ,-. | ||
62 | INTD--| | | ||
63 | |S| | ||
64 | INTC--|l| | ||
65 | |o| | ||
66 | INTB--|t| | ||
67 | |x| | ||
68 | INTA--| | | ||
69 | `-' | ||
70 | |||
71 | These INTA-D PCI IRQs are always 'local to the card', their real meaning | ||
72 | depends on which slot they are in. If you look at the daisy chaining diagram, | ||
73 | a card in slot4, issuing INTA IRQ, it will end up as a signal on PIRQ4 of | ||
74 | the PCI chipset. Most cards issue INTA, this creates optimal distribution | ||
75 | between the PIRQ lines. (distributing IRQ sources properly is not a | ||
76 | necessity, PCI IRQs can be shared at will, but it's a good for performance | ||
77 | to have non shared interrupts). Slot5 should be used for videocards, they | ||
78 | do not use interrupts normally, thus they are not daisy chained either. | ||
79 | |||
80 | so if you have your SCSI card (IRQ11) in Slot1, Tulip card (IRQ9) in | ||
81 | Slot2, then you'll have to specify this pirq= line: | ||
82 | |||
83 | append="pirq=11,9" | ||
84 | |||
85 | the following script tries to figure out such a default pirq= line from | ||
86 | your PCI configuration: | ||
87 | |||
88 | echo -n pirq=; echo `scanpci | grep T_L | cut -c56-` | sed 's/ /,/g' | ||
89 | |||
90 | note that this script wont work if you have skipped a few slots or if your | ||
91 | board does not do default daisy-chaining. (or the IO-APIC has the PIRQ pins | ||
92 | connected in some strange way). E.g. if in the above case you have your SCSI | ||
93 | card (IRQ11) in Slot3, and have Slot1 empty: | ||
94 | |||
95 | append="pirq=0,9,11" | ||
96 | |||
97 | [value '0' is a generic 'placeholder', reserved for empty (or non-IRQ emitting) | ||
98 | slots.] | ||
99 | |||
100 | Generally, it's always possible to find out the correct pirq= settings, just | ||
101 | permute all IRQ numbers properly ... it will take some time though. An | ||
102 | 'incorrect' pirq line will cause the booting process to hang, or a device | ||
103 | won't function properly (e.g. if it's inserted as a module). | ||
104 | |||
105 | If you have 2 PCI buses, then you can use up to 8 pirq values, although such | ||
106 | boards tend to have a good configuration. | ||
107 | |||
108 | Be prepared that it might happen that you need some strange pirq line: | ||
109 | |||
110 | append="pirq=0,0,0,0,0,0,9,11" | ||
111 | |||
112 | Use smart trial-and-error techniques to find out the correct pirq line ... | ||
113 | |||
114 | Good luck and mail to linux-smp@vger.kernel.org or | ||
115 | linux-kernel@vger.kernel.org if you have any problems that are not covered | ||
116 | by this document. | ||
117 | |||
118 | -- mingo | ||
119 | |||