Re: [PATCH -rt] powerpc update

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Hello.

Ingo Molnar wrote:
* Daniel Walker <[email protected]> wrote:
Pay close attention to the fasteoi interrupt threading. I added usage of mask/unmask instead of using level handling, which worked well on PPC.
this is wrong - it should be doing mask+ack.
 It's what it was doing effectively. And what was wrong was calling ack()
which OpenPIC driver didn't (and was not obliged to) support.
also note that you changed:
-		goto out_unlock;
to:
+		goto out;
and you even tried to hide your tracks:


out:
	desc->chip->eoi(irq);
-out_unlock:
	spin_unlock(&desc->lock);
:-)
really, the ->eoi() op should only be called for true fasteoi cases.
 Why is that? eoi() is effectively the same as ack() in this case. I must
note that what's the "standard" 8259 driver is doing in mask_ack() seems
misleading since it actually masks IRQ and sends EOI there.
What we want here is to turn the fasteoi handler into a handler that does mask+ack and then unmask. Not 'mask+eoi ... unmask' as your patch does.
 That's effectively the same for OpenPIC. Maybe that implemetation just
didn't look graceful but it was *correct*. And the current one is at least
incomplete.
   I can see 3 ways to get out of this situation now:

1. Revert this change and use mask() + eoi() approach suggested by Daniel.

2. Add the ack() handler to OpenPIC driver -- and point it to mpic_eoi().

3. Do the same as x86 APIC driver does and use level/egde flows instead of fasteoi for the case when IRQs are threaded -- that ensues doing (2) as well.
 Note that all three aproaches lead to the effectively the same behavior
WRT OpenPIC (except for the edge-triggered IRQs in 3rd case). Opinions?
	Ingo
WBR, Sergei
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