From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933245AbWKSUid (ORCPT ); Sun, 19 Nov 2006 15:38:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933230AbWKSUid (ORCPT ); Sun, 19 Nov 2006 15:38:33 -0500 Received: from h155.mvista.com ([63.81.120.155]:1198 "EHLO imap.sh.mvista.com") by vger.kernel.org with ESMTP id S933245AbWKSUic (ORCPT ); Sun, 19 Nov 2006 15:38:32 -0500 Message-ID: <4560C121.30403@ru.mvista.com> Date: Sun, 19 Nov 2006 23:40:01 +0300 From: Sergei Shtylyov Organization: MontaVista Software Inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.7.2) Gecko/20040803 X-Accept-Language: ru, en-us, en-gb MIME-Version: 1.0 To: Benjamin Herrenschmidt Cc: Ingo Molnar , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, dwalker@mvista.com Subject: Re: [PATCH] 2.6.18-rt7: PowerPC: fix breakage in threaded fasteoi type IRQ handlers References: <200611192243.34850.sshtylyov@ru.mvista.com> <1163966437.5826.99.camel@localhost.localdomain> <20061119200650.GA22949@elte.hu> <1163967590.5826.104.camel@localhost.localdomain> <4560BDF5.400@ru.mvista.com> <1163968376.5826.110.camel@localhost.localdomain> In-Reply-To: <1163968376.5826.110.camel@localhost.localdomain> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hello. Benjamin Herrenschmidt wrote: >> I must not that this whole ack() vs eoi() stuff is misleading. For example, >>in 8259 driver, mask_ack() method actually sends EOI to PIC, not ACK's an IRQ >>-- the actual ACK is implicit on x86 and is used to read the interrupt vector >>form 8259 on PPC. So, IMO, there probably should only have been either ack() >>or eoi() method in the first place. Though I'm not familiar with ARM from >>which genirq stuff originated... > They are different concepts. Ack clears the event on the PIC, it's > tyically necessary for resetting the edge detection logic for edge > interrupts and has to happen before the handler is called. I know 8259. :-) It also resets the corresponding IRQ bit in IRR, and sets it in ISR where it's then cleared on EOI command. > On MPIC or XICS, this is implicit by reading the vector. On some more > dumb controllers, this has to be done explicitely. This is not implicit -- CPU has to read INTACK reg. on OpenPIC. Really implicit method is in action on x86 where CPU issues dual ACK bus cycle to get the vector form 8259... > 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. > Ben. WBR, Sergei