Messages in this thread Patch in this message | | | Date | Sat, 14 Aug 2010 13:38:01 -0700 | From | Yinghai Lu <> | Subject | [PATCH] x86: Don't write io_apic ID if it is not changed |
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For 32bit mptable path, setup_ids_from_mpc() always write io apic id register, even there is no change needed.
So try to do that when they are different bewteen reading out and mptable
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
--- arch/x86/kernel/apic/io_apic.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
Index: linux-2.6/arch/x86/kernel/apic/io_apic.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c +++ linux-2.6/arch/x86/kernel/apic/io_apic.c @@ -2125,7 +2125,6 @@ void __init setup_ioapic_ids_from_mpc(vo physids_or(phys_id_present_map, phys_id_present_map, tmp); } - /* * We need to adjust the IRQ routing table * if the ID changed. @@ -2137,9 +2136,12 @@ void __init setup_ioapic_ids_from_mpc(vo = mp_ioapics[apic_id].apicid; /* - * Read the right value from the MPC table and - * write it into the ID register. + * Update the ID register according to the right value from + * the MPC table if they are different. */ + if (mp_ioapics[apic_id].apicid == reg_00.bits.ID) + continue; + apic_printk(APIC_VERBOSE, KERN_INFO "...changing IO-APIC physical APIC ID to %d ...", mp_ioapics[apic_id].apicid);
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