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

[Stephen Boyd]

On 01/16, Lorenzo Pieralisi wrote:
> On Thu, Jan 16, 2014 at 01:38:40AM +0000, Stephen Boyd wrote:
> > On 01/15, Stephen Boyd wrote:
> > > 
> > > Ah sorry, I forgot to put the compatible property here like in
> > > the dts change. I'll do that in the next revision. Yes we need a
> > > compatible property here to match the platform driver.
> > > 
> > 
> > This is the replacement patch
> > 
> > -----8<------
> > From: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> > Subject: [PATCH v9] devicetree: bindings: Document Krait CPU/L1 EDAC
> > 
> > The Krait CPU/L1 error reporting device is made up a per-CPU
> > interrupt. While we're here, document the next-level-cache
> > property that's used by the Krait EDAC driver.
> > 
> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Kumar Gala <galak@xxxxxxxxxxxxxx>
> > Cc: <devicetree@xxxxxxxxxxxxxxx>
> > Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> > ---
> >  Documentation/devicetree/bindings/arm/cpus.txt | 58 ++++++++++++++++++++++++++
> >  1 file changed, 58 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt
> > index 91304353eea4..03a529e791c4 100644
> > --- a/Documentation/devicetree/bindings/arm/cpus.txt
> > +++ b/Documentation/devicetree/bindings/arm/cpus.txt
> > @@ -62,6 +62,20 @@ nodes to be present and contain the properties described below.
> >  		Value type: <u32>
> >  		Definition: must be set to 0
> >  
> > +	- compatible
> > +		Usage: optional
> > +		Value type: <string>
> > +		Definition: should be one of the compatible strings listed
> > +			    in the cpu node compatible property. This property
> > +			    shall only be present if all the cpu nodes have the
> > +			    same compatible property.
> 
> 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.

> 
> interrupts is a cpu node property and I think it should be kept as such.
> 
> I know it will be duplicated and I know you can't rely on a platform
> device for probing (since if I am not mistaken, removing a compatible
> string from cpus prevents its platform device creation), but that's an issue
> related to how the kernel works, you should not define DT bindings to solve
> that IMHO.

The interrupts property is also common for all cpus so it seems
fine to collapse the value down into a PPI specifier indicating
that all CPUs get the interrupt, similar to how we compress the
information about the compatible string.

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