Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754196Ab2JBPDq (ORCPT ); Tue, 2 Oct 2012 11:03:46 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:33036 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753412Ab2JBPDl (ORCPT ); Tue, 2 Oct 2012 11:03:41 -0400 Date: Tue, 2 Oct 2012 16:03:33 +0100 From: Dave Martin To: Lorenzo Pieralisi Cc: Mark Rutland , Russell King , "linux-doc@vger.kernel.org" , Marc Zyngier , "devicetree-discuss@lists.ozlabs.org" , Will Deacon , Rohit Vaswani , Rob Herring , "linux-kernel@vger.kernel.org" , Grant Likely , Bryan Huntsman , Rob Landley , Daniel Walker , David Brown , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2 RESEND 2/2] ARM: local timers: add timer support using IO mapped register Message-ID: <20121002150333.GC2108@linaro.org> References: <1347694914-1457-1-git-send-email-rvaswani@codeaurora.org> <1347694914-1457-2-git-send-email-rvaswani@codeaurora.org> <5062013F.8050507@codeaurora.org> <20120928122858.GD9472@e106331-lin.cambridge.arm.com> <20120928155746.GB2253@linaro.org> <20120928171549.GA29991@e102568-lin.cambridge.arm.com> <20121002112704.GA2410@linaro.org> <20121002134444.GB28600@e102568-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121002134444.GB28600@e102568-lin.cambridge.arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2690 Lines: 58 On Tue, Oct 02, 2012 at 02:44:44PM +0100, Lorenzo Pieralisi wrote: > On Tue, Oct 02, 2012 at 12:27:04PM +0100, Dave Martin wrote: > > On Fri, Sep 28, 2012 at 06:15:53PM +0100, Lorenzo Pieralisi wrote: > > > On Fri, Sep 28, 2012 at 04:57:46PM +0100, Dave Martin wrote: > > [...] > > > > There must be a common way for all devices to link to the topology, though. > > > > > > The topology must be descriptive enough to cater for all required cases > > > and that's what Mark with PMU and all of us are trying to come up with, a solid > > > way to represent with DT the topology of current and future ARM systems. > > > > > > First idea I implemented and related LAK posting: > > > > > > http://lists.infradead.org/pipermail/linux-arm-kernel/2012-January/080873.html > > > > > > Are "cluster" nodes really needed or "cpu" nodes are enough ? I do not > > > know, let's get this discussion started, that's all I need. > > > > One thing which now occurs to me on this point it that if we want to describe > > the CCI properly in the DT (yes) then we need a way to describe the mapping > > between clusters and CCI slave ports. Currently that knowledge just has to > > be a hard-coded hack somewhere: it's not probeable at all. > > That's definitely a good point. We can still define CCI ports as belonging > to a range of CPUs, but that's a bit of a stretch IMHO. > > > I'm not sure how we do that, or how we describe the cache topology, without > > the clusters being explicit in the DT > > > > ...unless you already have ideas ? > > Either we define the cluster node explicitly or we can always see it as a > collection of CPUs, ie phandles to "cpu" nodes. That's what the decision > we have to make is all about. I think that describing it explicitly make > sense, but we need to check all possible use cases to see if that's > worthwhile. How is the cache topology described today (forgive my laziness in not answering this question for myself)? The issues are somewhat similar. I still have some misgivings about describing clusters in terms of sets of CPUs. For example, when we boot up a cluster, we have to set up ... the cluster. This is a distinct thing which we must set up in addition to any of the actual CPUs. There is a strict child/parent relationship between clusters and CPUs, so a tree of nodes does seem the most natural description ... but I'm not aware of all the background to this discussion. Cheers ---Dave -- 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/