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| author | Andi Kleen <ak@suse.de> | 2006-02-26 04:18:52 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-26 09:53:31 -0800 |
| commit | ab9b32ee626e9b6df4ce2560a70ae15e62423cf4 (patch) | |
| tree | 4bae7b0a38b9e69d33dc7b80ad434274019d9e38 /Documentation | |
| parent | e8b917775b572bc27de105f1317c2de4335db5b3 (diff) | |
| download | lwn-ab9b32ee626e9b6df4ce2560a70ae15e62423cf4.tar.gz lwn-ab9b32ee626e9b6df4ce2560a70ae15e62423cf4.zip | |
[PATCH] x86_64: Better ATI timer fix
The previous experiment for using apicmaintimer on ATI systems didn't
work out very well. In particular laptops with C2/C3 support often
don't let it tick during idle, which makes it useless. There were also
some other bugs that made the apicmaintimer often not used at all.
I tried some other experiments - running timer over RTC and some other
things but they didn't really work well neither.
I rechecked the specs now and it turns out this simple change is
actually enough to avoid the double ticks on the ATI systems. We just
turn off IRQ 0 in the 8254 and only route it directly using the IO-APIC.
I tested it on a few ATI systems and it worked there. In fact it worked
on all chipsets (NVidia, Intel, AMD, ATI) I tried it on.
According to the ACPI spec routing should always work through the
IO-APIC so I think it's the correct thing to do anyways (and most of the
old gunk in check_timer should be thrown away for x86-64).
But for 2.6.16 it's best to do a fairly minimal change:
- Use the known to be working everywhere-but-ATI IRQ0 both over 8254
and IO-APIC setup everywhere
- Except on ATI disable IRQ0 in the 8254
- Remove the code to select apicmaintimer on ATI chipsets
- Add some boot options to allow to override this (just paranoia)
In 2.6.17 I hope to switch the default over to this for everybody.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/x86_64/boot-options.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt index 153740f460a6..1921353259ae 100644 --- a/Documentation/x86_64/boot-options.txt +++ b/Documentation/x86_64/boot-options.txt @@ -52,6 +52,10 @@ APICs apicmaintimer. Useful when your PIT timer is totally broken. + disable_8254_timer / enable_8254_timer + Enable interrupt 0 timer routing over the 8254 in addition to over + the IO-APIC. The kernel tries to set a sensible default. + Early Console syntax: earlyprintk=vga |