Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757847AbXERNkM (ORCPT ); Fri, 18 May 2007 09:40:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754497AbXERNkA (ORCPT ); Fri, 18 May 2007 09:40:00 -0400 Received: from h155.mvista.com ([63.81.120.155]:31159 "EHLO imap.sh.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1753949AbXERNj7 (ORCPT ); Fri, 18 May 2007 09:39:59 -0400 Message-ID: <464DAD06.2060504@ru.mvista.com> Date: Fri, 18 May 2007 17:41:26 +0400 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: Dave Liu , linuxppc-dev@ozlabs.org, tglx@linutronix.de, mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver References: <200705172142.26739.sshtylyov@ru.mvista.com> <464CB071.5050504@ru.mvista.com> <9095839480a9686d9c40aa6143edb804@kernel.crashing.org> <464CB460.40905@ru.mvista.com> <97d47c2261fe9cd3f1a6c864278a6ab6@kernel.crashing.org> <1179464690.32247.370.camel@localhost.localdomain> <1179466769.3658.0.camel@localhost.localdomain> <1179472096.32247.394.camel@localhost.localdomain> In-Reply-To: <1179472096.32247.394.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 Content-Length: 1455 Lines: 41 Hello. Benjamin Herrenschmidt wrote: >>>>Yes, on some implementations there can be other conditions that >>>>make a decrementer exception go away; there is no contradiction >>>>here (thankfully). My wording was sloppy. >>>Some CPUs have the DEC exceptions basically edge triggered (yeah I know >>for example? >>>it sucks). That's why, among others, the IRQ soft-disable code has code >>>to re-trigger DEC exceptions ASAP (by setting it to 1.. note that we >>>could probably use 0 here, we've been a bit conservative). Yeah, the classic decrementer is programmed off-by-one. > I'm not 100% certain... Paulus thinks all the old 6xx are like that, and > maybe POWER4. If I look at the oldest BookIV I can find (the 601), it From the "PowerPC Operating Environment Architecture" that I've already quoated t follows that POWER4-compatible decremented exception *must* be edge triggered. > says that an exception is generated when the MSB transitions from 0 to > 1. It's not clear wether the exception sticks while that bit is 1 or is Freescale MPC 7450 manual says the same, for example. > indeed considered as an "edge" event that gets cleared as soon as > delivered. > Ben. WBR, Sergei - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/