Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756891AbXEQTmW (ORCPT ); Thu, 17 May 2007 15:42:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757456AbXEQTmO (ORCPT ); Thu, 17 May 2007 15:42:14 -0400 Received: from h155.mvista.com ([63.81.120.155]:25494 "EHLO imap.sh.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756941AbXEQTmN (ORCPT ); Thu, 17 May 2007 15:42:13 -0400 Message-ID: <464CB071.5050504@ru.mvista.com> Date: Thu, 17 May 2007 23:43:45 +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: Segher Boessenkool Cc: linuxppc-dev@ozlabs.org, mingo@elte.hu, linux-kernel@vger.kernel.org, tglx@linutronix.de Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver References: <200705172142.26739.sshtylyov@ru.mvista.com> In-Reply-To: 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: 1662 Lines: 39 Segher Boessenkool wrote: >> + * We must write a positive value to the decrementer to clear >> + * the interrupt on the IBM 970 CPU series. In periodic mode, >> + * this happens when the decrementer gets reloaded later, but >> + * in one-shot mode, we have to do it here since an event handler >> + * may skip loading the new value... > Nothing special about 970 here -- on *every* PowerPC, > a decrementer exception exists as long as the high > bit of the decrementer equals 1. BookE is different > of course. Some other CPUs might deviate from the > architecture as well. Quoting "PowerPC Operating Environment Architecture": The Decrementer counts down. On POWER4, a Decrementer exception occurs when DEC0 changes from 0 to 1. On POWER4+, operation is as follows. The exception effects of the Decrementer are said to be consistent with the contents of the Decrementer if one of the following statements is true. * DEC0=0 and a Decrementer exception does not exist. * DEC0=1 and a Decrementer exception exists. If DEC0=0, a context synchronizing instruction or event ensures that the exception effects of the Decrementer are consistent with the contents of the Decrementer. Otherwise, when the contents of DEC0 change, the exception effects of the Decrementer become consistent with the new contents of the Decrementer reasonably soon after the change. > Segher 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/