Commit ab688059 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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[PATCH] x86_64: Don't enable ATI apicmaintimer workaround when the machine has C2 or C3

Many laptops have problems with ticking the local APIC timer in C2/C3.
The code added earlier to use it by default on ATI didn't really work
for them. Don't enable it when the system supports C2/C3.

This doesn't fix the problem fully, but at least it's not worse than before.
Signed-off-by: default avatarAndi Kleen <>
Signed-off-by: default avatarLinus Torvalds <>
parent 2391c4b5
......@@ -30,6 +30,9 @@
#include <linux/mc146818rtc.h>
#include <linux/acpi.h>
#include <linux/sysdev.h>
#include <acpi/acpi_bus.h>
#include <asm/io.h>
#include <asm/smp.h>
......@@ -260,6 +263,8 @@ __setup("apic", enable_ioapic_setup);
And another hack to disable the IOMMU on VIA chipsets.
... and others. Really should move this somewhere else.
Kludge-O-Rama. */
void __init check_ioapic(void)
......@@ -307,6 +312,17 @@ void __init check_ioapic(void)
if (apic_runs_main_timer != 0)
/* Don't do this for laptops right
right now because their timer
doesn't necessarily tick in C2/3 */
if (acpi_fadt.revision >= 3 &&
(acpi_fadt.plvl2_lat + acpi_fadt.plvl3_lat) < 1100) {
"ATI board detected, but seems to be a laptop. Timer might be shakey, sorry\n");
"ATI board detected. Using APIC/PM timer.\n");
apic_runs_main_timer = 1;
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