linux-kernel - Re: [PATCH v5 2/4] devicetree: bindings: Document Krait CPU/L1 EDAC

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Message-ID: <20140219002043.GE14769@codeaurora.org>
Date:	Tue, 18 Feb 2014 16:20:43 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 2/4] devicetree: bindings: Document Krait CPU/L1 EDAC

(Sorry, this discussion stalled due to merge window + life events)

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.

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