[PATCH] PowerPC: MPIC ack interrupts at mpic_teardown_this_cpu()

[Olof Johansson]

On Fri, Apr 04, 2008 at 07:38:27PM +0200, Segher Boessenkool wrote:
>>>> We really need to ack interrupts at mpic_teardown, since
>>>> not all platforms reset mpic at kernel start-up. For example,
>>>> kexec'ed kernel hangs on P.A. Semi if mpic_eoi() isn't called.
>>>>
>>>> Signed-off-by: Valentine Barshak <vbarshak at ru.mvista.com>
>>>> ---
>>>
>>> Would be interesting to find out why it hangs tho... it shouldn't .
>>
>> I haven't reproduced the problem and looked at hardware state yet, but  
>> I
>> would expect it to be because the openpic won't send another interrupt
>> until the previous is EOI'd, and the IPI is never EOI'd as far as I
>> can tell.
>>
>> The XICS code does it explicitly already. I'm surprised it doesn't  
>> break
>> on the 970-based platforms actually...
>
> platforms/maple/setup.c and platforms/powermac/pic.c use  
> MPIC_WANTS_RESET.
> Is there a reason why we don't do that on every MPIC?  If there is such
> a reason, the default should be to reset, only pseries and chrp and cell
> and now pasemi do not use it.  It's the only sane way to get an MPIC  
> into
> a sane known state starting from <whatever> state.

I used to have the reset there on pasemi but due to some other issues I
ended up taking it out.

It's not like doing a final EOI is a big deal, I really don't see why
there's hassle about this patch.


-Olof