Re: IO-APIC on nforce2 [PATCH]

[Len Brown]

Re: IRQ0 XT-PIC timer issue

Since the hardware is connected to APIC pin0, it is a BIOS bug
that an ACPI interrupt source override from pin2 to IRQ0 exists.

With this simple 2.6.5 patch you can specify "acpi_skip_timer_override"
to ignore that bogus BIOS directive.  The result is with your
ACPI-enabled APIC-enabled kernel, you'll get IRQ0 IO-APIC-edge timer.

Probably there is a more clever way to trigger this workaround
automatcially instead of via boot parameter.

cheers,
-Len

===== Documentation/kernel-parameters.txt 1.44 vs edited =====
--- 1.44/Documentation/kernel-parameters.txt	Mon Mar 22 16:03:22 2004
+++ edited/Documentation/kernel-parameters.txt	Tue Apr 13 17:47:11 2004
@@ -122,6 +122,10 @@
 
 	acpi_serialize	[HW,ACPI] force serialization of AML methods
 
+	acpi_skip_timer_override [HW,ACPI]]
+			Recognize IRQ0/pin2 Interrupt Source Override
+			and ignore it -- for broken nForce2 BIOS.
+
 	ad1816=		[HW,OSS]
 			Format: <io>,<irq>,<dma>,<dma2>
 			See also Documentation/sound/oss/AD1816.
===== arch/i386/kernel/setup.c 1.115 vs edited =====
--- 1.115/arch/i386/kernel/setup.c	Fri Apr  2 07:21:43 2004
+++ edited/arch/i386/kernel/setup.c	Tue Apr 13 17:41:31 2004
@@ -614,6 +614,12 @@
 		else if (!memcmp(from, "acpi_sci=low", 12))
 			acpi_sci_flags.polarity = 3;
 
+		else if (!memcmp(from, "acpi_skip_timer_override", 24)) {
+			extern int acpi_skip_timer_override;
+
+			acpi_skip_timer_override = 1;
+		}
+
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* disable IO-APIC */
 		else if (!memcmp(from, "noapic", 6))
===== arch/i386/kernel/acpi/boot.c 1.57 vs edited =====
--- 1.57/arch/i386/kernel/acpi/boot.c	Tue Mar 30 17:05:19 2004
+++ edited/arch/i386/kernel/acpi/boot.c	Tue Apr 13 17:50:14 2004
@@ -62,6 +62,7 @@
 
 acpi_interrupt_flags acpi_sci_flags __initdata;
 int acpi_sci_override_gsi __initdata;
+int acpi_skip_timer_override __initdata;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
@@ -327,6 +328,12 @@
 		acpi_sci_ioapic_setup(intsrc->global_irq,
 			intsrc->flags.polarity, intsrc->flags.trigger);
 		return 0;
+	}
+
+	if (acpi_skip_timer_override &&
+		intsrc->bus_irq == 0 && intsrc->global_irq == 2) {
+			printk(PREFIX "BIOS IRQ0 pin2 override ignored.\n");
+			return 0;
 	}
 
 	mp_override_legacy_irq (


===== Documentation/kernel-parameters.txt 1.44 vs edited =====
--- 1.44/Documentation/kernel-parameters.txt	Mon Mar 22 16:03:22 2004
+++ edited/Documentation/kernel-parameters.txt	Tue Apr 13 17:47:11 2004
@@ -122,6 +122,10 @@
 
 	acpi_serialize	[HW,ACPI] force serialization of AML methods
 
+	acpi_skip_timer_override [HW,ACPI]]
+			Recognize IRQ0/pin2 Interrupt Source Override
+			and ignore it -- for broken nForce2 BIOS.
+
 	ad1816=		[HW,OSS]
 			Format: <io>,<irq>,<dma>,<dma2>
 			See also Documentation/sound/oss/AD1816.
===== arch/i386/kernel/setup.c 1.115 vs edited =====
--- 1.115/arch/i386/kernel/setup.c	Fri Apr  2 07:21:43 2004
+++ edited/arch/i386/kernel/setup.c	Tue Apr 13 17:41:31 2004
@@ -614,6 +614,12 @@
 		else if (!memcmp(from, "acpi_sci=low", 12))
 			acpi_sci_flags.polarity = 3;
 
+		else if (!memcmp(from, "acpi_skip_timer_override", 24)) {
+			extern int acpi_skip_timer_override;
+
+			acpi_skip_timer_override = 1;
+		}
+
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* disable IO-APIC */
 		else if (!memcmp(from, "noapic", 6))
===== arch/i386/kernel/acpi/boot.c 1.57 vs edited =====
--- 1.57/arch/i386/kernel/acpi/boot.c	Tue Mar 30 17:05:19 2004
+++ edited/arch/i386/kernel/acpi/boot.c	Tue Apr 13 17:50:14 2004
@@ -62,6 +62,7 @@
 
 acpi_interrupt_flags acpi_sci_flags __initdata;
 int acpi_sci_override_gsi __initdata;
+int acpi_skip_timer_override __initdata;
 
 #ifdef CONFIG_X86_LOCAL_APIC
 static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
@@ -327,6 +328,12 @@
 		acpi_sci_ioapic_setup(intsrc->global_irq,
 			intsrc->flags.polarity, intsrc->flags.trigger);
 		return 0;
+	}
+
+	if (acpi_skip_timer_override &&
+		intsrc->bus_irq == 0 && intsrc->global_irq == 2) {
+			printk(PREFIX "BIOS IRQ0 pin2 override ignored.\n");
+			return 0;
 	}
 
 	mp_override_legacy_irq (