Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762089AbXERQww (ORCPT ); Fri, 18 May 2007 12:52:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757094AbXERQwe (ORCPT ); Fri, 18 May 2007 12:52:34 -0400 Received: from mithrandir.softwarenexus.net ([66.98.186.96]:4380 "EHLO mail.genesi-usa.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756867AbXERQwd (ORCPT ); Fri, 18 May 2007 12:52:33 -0400 Message-ID: <464DD9DD.8030603@genesi-usa.com> Date: Fri, 18 May 2007 17:52:45 +0100 From: Matt Sealey User-Agent: Thunderbird 2.0.0.0 (Windows/20070326) MIME-Version: 1.0 To: Kumar Gala CC: Thomas Gleixner , Sergei Shtylyov , linuxppc-dev@ozlabs.org, mingo@elte.hu, linux-kernel@vger.kernel.org, Robert Schwebel Subject: Re: [PATCH 2.6.21-rt2] PowerPC: decrementer clockevent driver References: <200705172142.26739.sshtylyov@ru.mvista.com> <8E44DB06-767D-4864-8D2C-6132E4D4370B@kernel.crashing.org> <464C99FF.8080404@ru.mvista.com> <135307ED-7125-4859-8594-4B5B900D92D6@kernel.crashing.org> <464C9E67.2020909@ru.mvista.com> <6E0D5E13-C939-4FCE-81A3-F29DFA6436A2@kernel.crashing.org> <464CA222.8000407@ru.mvista.com> <464D9E7E.3090605@genesi-usa.com> <464DADFC.3080802@ru.mvista.com> <464DB800.40702@genesi-usa.com> <1179499713.12981.75.camel@chaos> <32E780BE-58B7-4303-AA49-1852C4C7EB50@kernel.crashing.org> In-Reply-To: <32E780BE-58B7-4303-AA49-1852C4C7EB50@kernel.crashing.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1900 Lines: 48 Kumar Gala wrote: > > On May 18, 2007, at 9:48 AM, Thomas Gleixner wrote: > >> On Fri, 2007-05-18 at 15:28 +0100, Matt Sealey wrote: >>> >>> I think both the MPC52xx GPT0-7 and the SLT0-1 fulfil this fairly >>> easily. >> >> There is some basic work for MPC5200 available: >> >> http://www.pengutronix.de/oselas/bsp/phytec/index_en.html#phyCORE-MPC5200B-tiny >> > > I asked this earlier, but figured you might have a better insight. Is > their value in having 'drivers' for more than one clock source? I'd say > most (of not all) the PPC SoCs have timers on the system side that we > could provide drivers for, I'm just not sure if that does anything for > anyone. As I asked after, I'm also very intrigued as to what is going to end up using these timers, but likewise, not much use writing a driver if everyone can use the extremely high resolution decrementer all at once.. As I said before too, at least Intel has decided there is a great need for up to 256 high resolution timer sources on a system, but since this is a fairly new concept to Linux (and hrtimers and dynticks too) it only seems to be used in the case of i8254/RTC emulation, mostly on x86-64. I'm looking at it now and finding "users" of hrtimers is looking very thin on the ground. Maybe it's justified on the basis that more is better, and having support is preferable to not having it (even if nobody really uses it) but it seems the entire gamut of timing possibility in Linux can be handled through a simple, and single, high resolution timer and a queue of events.. So do we need some more? :D -- Matt Sealey Genesi, Manager, Developer Relations - 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/