linux-kernel - Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi type IRQ handlers

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Date:	Mon, 20 Nov 2006 07:41:25 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org, dwalker@...sta.com
Subject: Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi
	type IRQ handlers


>     This is not implicit -- CPU has to read INTACK reg. on OpenPIC.

Which is what I meant... "implicit by reading the vector".

> Really implicit method is in action on x86 where CPU issues dual ACK bus cycle to get 
> the vector form 8259...

Which you can do on OpenPIC too. It's the same idea. The concept that
obtaining the vector performs the ack.

> > EOI is a more "high level" thing that some "intelligent" PICs that
> > automatically raise the priority do to restore the priority to what it
> > was before the interrupt occured.
> 
>     Thank you, I know. Even 8259 has the notion of priority and EOI works the 
> same way here.

Ok, so why would you need an ack there then while eoi is just what you
need ? :-)

Also, that's interesting what you are saying about 8259... I should be
able to convert ppc's i8259 to use fasteoi too...

Ben.


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