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Subject[PATCH] linux-2.4.22_clear-smi-fix_A0
Marcelo, All,

Some of our more recent hardware requires that SMIs are routed
through the IOAPIC, thus when we clear_IO_APIC() at boot time, we clear
the BIOS initialized SMI pin (which is unfortunately not described in
the MPS or ACPI tables). This basically clobbers the SMI, which can
cause problems with console redirection as well keeping us from being
able to transition into full ACPI mode.

This patch (back ported from 2.5) simply reads the apic entry in
clear_IO_APIC to make sure the delivery_mode isn't dest_SMI. If it is,
we leave the apic entry alone and return.

With this patch, booting with full ACPI works and SMIs function

Please consider for acceptance.


diff -Nru a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
--- a/arch/i386/kernel/io_apic.c Mon Aug 25 14:10:12 2003
+++ b/arch/i386/kernel/io_apic.c Mon Aug 25 14:10:12 2003
@@ -169,6 +169,14 @@
struct IO_APIC_route_entry entry;
unsigned long flags;
+ /* Check delivery_mode to be sure we're not clearing an SMI pin */
+ spin_lock_irqsave(&ioapic_lock, flags);
+ *(((int*)&entry) + 0) = io_apic_read(apic, 0x10 + 2 * pin);
+ *(((int*)&entry) + 1) = io_apic_read(apic, 0x11 + 2 * pin);
+ spin_unlock_irqrestore(&ioapic_lock, flags);
+ if (entry.delivery_mode == dest_SMI)
+ return;

* Disable it in the IO-APIC irq-routing table:

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