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SubjectRe: [RT] MPIC edge sensitive issues with hardirq preemption
On Tue, Jul 01, 2008 at 02:41:19PM +0400, Sergei Shtylyov wrote:
> Hello.
> Anton Vorontsov wrote:
>> But how this could be a bug in the PIC code? IMO this is a bug in the
>> kernel/irq code, since it assumes that fasteoi PIC will retrigger masked
>> edge sources... This isn't true for at least MPIC. To make this work for
>> all fasteoi PICs, we should mask edge sensitive interrupts very very
>> carefully.
> I guess it assumed this based on 8259's behavior (not sure about I/O
> APIC).
> Hm, but the 8259 code never used "fasteoi" path for some obscure
> reason...
>> jammed with the idea that MPIC irq type 0 is low level sensitive, but the
>> true thing is that it is rising edge sensitive. (Ah, I know where I got
>> confused, type 0 is active-low for ISA PICs).
> You mean in the device tree?

Yes, simply changing device tree.

>> So in all my previous emails I was wrong when I was saying "mpic is
>> programmed to low level sensitive". It was programmed for rising edge
>> sensitive. An all my further reasonings were flawed because of this.
> Gah. I'm surprised how it could work at all then...
>> Re-programming MPIC to high level sensitive also makes IDE work. But
>> this doesn't mean that IRQ code is correct.
> I wonder why. :-O
> Your ULi IDE is in native mode, so it should be generating a PCI
> interrupt -- which is *low* level sensitive.

Exactly. This is another reason why I was so confused.

Anton Vorontsov

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