From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Mon, 16 Jan 2017 10:59:04 +0000
Subject: [RFC PATCH v2 10/10] dt-bindings: Document devicetree binding
 for ARM SPE
In-Reply-To: <20170113184352.GE2472@leverpostej>
References: <1484323429-15231-1-git-send-email-will.deacon@arm.com>
 <1484323429-15231-11-git-send-email-will.deacon@arm.com>
 <20170113184352.GE2472@leverpostej>
Message-ID: <20170116105904.GB1510@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Fri, Jan 13, 2017 at 06:43:52PM +0000, Mark Rutland wrote:
> On Fri, Jan 13, 2017 at 04:03:49PM +0000, Will Deacon wrote:
> > This patch documents the devicetree binding in use for ARM SPE.
> > 
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Rob Herring <robh@kernel.org>
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> > ---
> >  Documentation/devicetree/bindings/arm/spe-pmu.txt | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/arm/spe-pmu.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/arm/spe-pmu.txt b/Documentation/devicetree/bindings/arm/spe-pmu.txt
> > new file mode 100644
> > index 000000000000..d6540b491af4
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/arm/spe-pmu.txt
> > @@ -0,0 +1,20 @@
> > +* ARMv8.2 Statistical Profiling Extension (SPE) Performance Monitor Units (PMU)
> > +
> > +ARMv8.2 introduces the optional Statistical Profiling Extension for collecting
> > +performance sample data using an in-memory trace buffer.
> > +
> > +** SPE Required properties:
> > +
> > +- compatible : should be one of:
> > +	       "arm,arm-spe-pmu-v1"
> 
> The second "arm" here doesn't seem to add much. Should that be "armv8.2"
> instead?

I don't think armv8.2 is particularly helpful, because that effectively ties
together the SPE version and the architecture version, which I don't think
is strictly required. The reason I added it was so that you could describe
a partner implementation as something like:

  acme,arm-spe-pmu-v1

and know that it was acme's implementation of an ARM architectural feature.

If I drop the second "arm", I was worried that it might conflict with other
namespaces (e.g. acme's signal-processing-element's power-management-unit).

What do you reckon?

Will