[PATCH] x86_64: Add option to disable timer check
This works around the too fast timer seen on some ATI boards.
I don't feel confident enough about it yet to enable it by default, but give
users the option.
Patch and debugging from Christopher Allen Wing <wingc@engin.umich.edu>, with
minor tweaks (renamed the option and documented it)
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 44b6eea..b9e6be0 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -25,6 +25,9 @@
noapictimer Don't set up the APIC timer
+ no_timer_check Don't check the IO-APIC timer. This can work around
+ problems with incorrect timer initialization on some boards.
+
Early Console
syntax: earlyprintk=vga
diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index ac76843..80e9b49 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -42,6 +42,8 @@
int sis_apic_bug; /* not actually supported, dummy for compile */
+static int no_timer_check;
+
static DEFINE_SPINLOCK(ioapic_lock);
/*
@@ -1601,7 +1603,7 @@
* Ok, does IRQ0 through the IOAPIC work?
*/
unmask_IO_APIC_irq(0);
- if (timer_irq_works()) {
+ if (!no_timer_check && timer_irq_works()) {
nmi_watchdog_default();
if (nmi_watchdog == NMI_IO_APIC) {
disable_8259A_irq(0);
@@ -1671,6 +1673,13 @@
panic("IO-APIC + timer doesn't work! Try using the 'noapic' kernel parameter\n");
}
+static int __init notimercheck(char *s)
+{
+ no_timer_check = 1;
+ return 1;
+}
+__setup("no_timer_check", notimercheck);
+
/*
*
* IRQ's that are handled by the PIC in the MPS IOAPIC case.