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Fix reading of number of interrupts for IO-APICs 

The number read from the io-apic register represents the index of the
highest interrupt redirection entry, i.e. the number of interrupts
minus one.

Change-Id: I54c992e4ff400de24bb9fef5d82251078f92c588
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/1624
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
This commit is contained in:
Nico Huber 2012-09-24 10:48:43 +02:00 committed by Patrick Georgi
parent f4ff56f617
commit 23c046b6f1
1 changed files with 5 additions and 2 deletions
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7
src/arch/x86/lib/ioapic.c
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@ -85,8 +85,11 @@ void setup_ioapic(u32 ioapic_base, u8 ioapic_id)
/* Read the available number of interrupts. */
ioapic_interrupts = (io_apic_read(ioapic_base, 0x01) >> 16) & 0xff;
if (!ioapic_interrupts || ioapic_interrupts == 0xff)
ioapic_interrupts = 24;
if (ioapic_interrupts == 0xff)
ioapic_interrupts = 23;
ioapic_interrupts += 1; /* Bits 23-16 specify the maximum redirection
entry, which is the number of interrupts
minus 1. */
printk(BIOS_DEBUG, "IOAPIC: %d interrupts\n", ioapic_interrupts);
#if CONFIG_IOAPIC_INTERRUPTS_ON_FSB