[PATCH -rt] powerpc update
sshtylyov at ru.mvista.com
Sun Oct 29 01:05:16 EST 2006
Ingo Molnar wrote:
> * Daniel Walker <dwalker at mvista.com> wrote:
>>Pay close attention to the fasteoi interrupt threading. I added usage
>>of mask/unmask instead of using level handling, which worked well on
> 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;
>>+ goto out;
> and you even tried to hide your tracks:
> 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
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
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?
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