Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752476AbaBZMBP (ORCPT ); Wed, 26 Feb 2014 07:01:15 -0500 Received: from service87.mimecast.com ([91.220.42.44]:51912 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbaBZMBL convert rfc822-to-8bit (ORCPT ); Wed, 26 Feb 2014 07:01:11 -0500 Date: Wed, 26 Feb 2014 12:01:04 +0000 From: Lorenzo Pieralisi To: Kumar Gala Cc: Stephen Boyd , Borislav Petkov , "linux-kernel@vger.kernel.org" , "linux-arm-msm@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-edac@vger.kernel.org" , Mark Rutland , "devicetree@vger.kernel.org" Subject: Re: [PATCH v5 2/4] devicetree: bindings: Document Krait CPU/L1 EDAC Message-ID: <20140226120103.GA25326@e102568-lin.cambridge.arm.com> References: <20140115165623.GJ14405@codeaurora.org> <20140116013840.GA674@codeaurora.org> <20140116113332.GC25540@e102568-lin.cambridge.arm.com> <20140116180505.GA30925@codeaurora.org> <20140116183326.GG25540@e102568-lin.cambridge.arm.com> <20140116192617.GA13785@codeaurora.org> <20140117102109.GA22544@e102568-lin.cambridge.arm.com> <20140219002043.GE14769@codeaurora.org> <20140225111655.GA6855@e102568-lin.cambridge.arm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginalArrivalTime: 26 Feb 2014 12:01:12.0477 (UTC) FILETIME=[717CBCD0:01CF32EA] X-MC-Unique: 114022612010806701 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 25, 2014 at 08:48:38PM +0000, Kumar Gala wrote: > > On Feb 25, 2014, at 5:16 AM, Lorenzo Pieralisi wrote: > > > Hi Stephen, > > > > On Wed, Feb 19, 2014 at 12:20:43AM +0000, Stephen Boyd wrote: > >> (Sorry, this discussion stalled due to merge window + life events) > > > > Sorry for the delay in replying on my side too. > > > >> On 01/17, Lorenzo Pieralisi wrote: > >>> On Thu, Jan 16, 2014 at 07:26:17PM +0000, Stephen Boyd wrote: > >>>> On 01/16, Lorenzo Pieralisi wrote: > >>>>> On Thu, Jan 16, 2014 at 06:05:05PM +0000, Stephen Boyd wrote: > >>>>>> On 01/16, Lorenzo Pieralisi wrote: > >>>>>>> Do we really want to do that ? I am not sure. A cpus node is supposed to > >>>>>>> be a container node, we should not define this binding just because we > >>>>>>> know the kernel creates a platform device for it then. > >>>>>> > >>>>>> This is just copying more of the ePAPR spec into this document. > >>>>>> It just so happens that having a compatible field here allows a > >>>>>> platform device to be created. I don't see why that's a problem. > >>>>> > >>>>> I do not see why you cannot define a node like pmu or arch-timer and stick > >>>>> a compatible property in there. cpus node does not represent a device, and > >>>>> must not be created as a platform device, that's my opinion. > >>>>> > >>>> > >>>> I had what you're suggesting before in the original revision of > >>>> this patch. Please take a look at the original patch series[1]. I > >>>> suppose it could be tweaked slightly to still have a cache node > >>>> for the L2 interrupt and the next-level-cache pointer from the > >>>> CPUs. > >>> > >>> Ok, sorry, we are running around in circles here, basically you moved > >>> the node to cpus according to reviews. I still think that treating cpus > >>> as a device is not a great idea, even though I am in the same > >>> position with C-states and probably will add C-state tables in the cpus > >>> node. > >>> > >>> http://comments.gmane.org/gmane.linux.power-management.general/41012 > >>> > >>> I just would like to see under cpus nodes and properties that apply to > >>> all ARM systems, and avoid defining properties (eg interrupts) that > >>> have different meanings for different ARM cores. > >>> > >>> The question related to why the kernel should create a platform device > >>> out of cpus is still open. I really do not want to block your series > >>> for these simple issues but we have to make a decision and stick to that, > >>> I am fine either way if we have a plan. > >>> > >> > >> Do you just want a backup plan in case we don't make a platform > >> device out of the cpus node? I believe we can always add code > >> somewhere to create a platform device at runtime if we detect the > >> cpus node has a compatible string equal to "qcom,krait". We could > >> probably change this driver's module_init() to scan the DT for > >> such a compatible string and create the platform device right > >> there. If we get more than one interrupt in the cpus node we can > >> add interrupt-names and then have software look for interrupts by > >> name instead of number. > > > > As I mentioned, I do not like the idea of adding compatible properties > > just to force the kernel to create platform devices out of device tree > > nodes. On top of that I would avoid adding a compatible property > > to the cpus node (after all properties like enable-method are common for all > > cpus but still duplicated), my only concern being backward compatibility > > here (ie if we do that for interrupts, we should do that also for other > > common cpu nodes properties, otherwise we have different rules for > > different properties). > > > > I think you can then add interrupts to cpu nodes ("qcom,krait" specific), > > and as you mentioned create a platform device for that. > > > > Thanks, > > Lorenzo > > So I agree with the statement about adding compatibles just to create platform devices is wrong. However its seems perfectly reasonable for a cpu node to have a compatible property. I don't see why a CPU is any different from any other device described in a DT. I was referring to the /cpus node, not to individual cpu nodes, where the compatible property is already present now. Lorenzo -- 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/