From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.genesi-usa.com (mithrandir.softwarenexus.net [66.98.186.96]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 484EEDDEEE for ; Sat, 19 May 2007 02:52:26 +1000 (EST) Message-ID: <464DD9DD.8030603@genesi-usa.com> Date: Fri, 18 May 2007 17:52:45 +0100 From: Matt Sealey MIME-Version: 1.0 To: Kumar Gala 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 Cc: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Thomas Gleixner , mingo@elte.hu List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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