From 23c046b6f16805ff0131460189967bf261d704de Mon Sep 17 00:00:00 2001 From: Nico Huber Date: Mon, 24 Sep 2012 10:48:43 +0200 Subject: 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 Reviewed-on: http://review.coreboot.org/1624 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer --- src/arch/x86/lib/ioapic.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/arch/x86/lib/ioapic.c b/src/arch/x86/lib/ioapic.c index 57b99e283e..018a42c173 100644 --- a/src/arch/x86/lib/ioapic.c +++ b/src/arch/x86/lib/ioapic.c @@ -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 -- cgit v1.2.3