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x86: I/O APIC: AEOI timer acknowledgement clean-ups

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The code that used to be in do_slow_gettimeoffset() that relied on the
IRR bit of the master 8259A PIC for IRQ0 to check the state of the output
timer 0 of the PIT is no longer there.  As a result, there is no need to
use the POLL command to acknowledge the timer interrupt in the "8259A
Virtual Wire", except for the NMI watchdog when the i82489DX APIC is used
(this is because this particular APIC treats NMIs as level-triggered and
keeping the input asserted would keep motherboard NMI sources held off for
too long).  Remove the unneeded bits and adjust comments accordingly.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Maciej W. Rozycki
2008-05-21 22:09:11 +01:00
committed by Ingo Molnar
parent a0176e2485
commit d11d5794e0
4 changed files with 13 additions and 19 deletions
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3
arch/x86/kernel/time_32.c
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@@ -84,8 +84,7 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
if (timer_ack) {
/*
* Subtle, when I/O APICs are used we have to ack timer IRQ
* manually to reset the IRR bit for do_slow_gettimeoffset().
* This will also deassert NMI lines for the watchdog if run
* manually to deassert NMI lines for the watchdog if run
* on an 82489DX-based system.
*/
spin_lock(&i8259A_lock);