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 65962DDEA2 for ; Fri, 18 May 2007 22:39:04 +1000 (EST) Message-ID: <464D9E7E.3090605@genesi-usa.com> Date: Fri, 18 May 2007 13:39:26 +0100 From: Matt Sealey MIME-Version: 1.0 To: Sergei Shtylyov 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> In-Reply-To: <464CA222.8000407@ru.mvista.com> Content-Type: text/plain; charset=UTF-8 Cc: linuxppc-dev@ozlabs.org, tglx@linutronix.de, mingo@elte.hu, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sergei Shtylyov wrote: > Hello. > > Kumar Gala wrote: > >>> Kumar Gala wrote: > >>>> I haven't looked at all the new clock/timer code, is there any >>>> utility in having support for more than one clock source? > >>> Of course, you may register as many as you like. > >> Sure, but is there any utility in registering more than the decrementer >> on PPC? > > Not yet. I'm not sure I know any other PPC CPU facility fitting for > clockevents. In theory, FIT could be used -- but its period is measured in > powers of 2, IIRC. Wouldn't it be possible to use SoC timer functionality, too, and not limit this to what is only present on the CPU die? I guess the real question is, how high resolution does a high resolution timer need to be, and how often do you want to be handling interrupts? The 52XX has 8 general purpose timers and 2 slice timers. Both will generate an interrupt once the clock hits a preset value, the timing of which is determined by prescalers and the IPB clock.. -- Matt Sealey Genesi, Manager, Developer Relations