linux-kernel - Re: [PATCH 4/6] edac: Document Krait L1/L2 EDAC driver binding

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Message-ID: <20131030003805.GC3268@kartoffel>
Date:	Tue, 29 Oct 2013 17:38:06 -0700
From:	Mark Rutland <mark.rutland@....com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Kumar Gala <galak@...eaurora.org>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"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>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 4/6] edac: Document Krait L1/L2 EDAC driver binding

On Tue, Oct 29, 2013 at 06:00:59PM +0000, Stephen Boyd wrote:
> On 10/29/13 01:21, Kumar Gala wrote:
> > On Oct 28, 2013, at 7:31 PM, Stephen Boyd wrote:
> >
> >> The Krait L1/L2 error reporting device is made up of two
> >> interrupts, one per-CPU interrupt for the L1 caches and one
> >> interrupt for the L2 cache.
> >>
> >> Cc: <devicetree@...r.kernel.org>
> >> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> >> ---
> >> .../devicetree/bindings/arm/qcom,krait-cache-erp.txt     | 16 ++++++++++++++++
> >> 1 file changed, 16 insertions(+)
> >> create mode 100644 Documentation/devicetree/bindings/arm/qcom,krait-cache-erp.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/arm/qcom,krait-cache-erp.txt b/Documentation/devicetree/bindings/arm/qcom,krait-cache-erp.txt
> >> new file mode 100644
> >> index 0000000..01fe8a8
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/arm/qcom,krait-cache-erp.txt
> >> @@ -0,0 +1,16 @@
> >> +* Qualcomm Krait L1 / L2 cache error reporting
> >> +
> >> +Required properties:
> >> +- compatible: Should be "qcom,krait-cache-erp"
> >> +- interrupts: Should contain the L1/CPU error interrupt number and
> >> +  then the L2 cache error interrupt number
> >> +
> >> +Optional properties:
> >> +- interrupt-names: Should contain the interrupt names "l1_irq" and
> >> +  "l2_irq"
> >> +
> >> +Example:
> >> +	edac {
> >> +		compatible = "qcom,krait-cache-erp";
> >> +		interrupts = <1 9 0xf04>, <0 2 0x4>;
> >> +	};
> > Why wouldn't we have these as part of cache nodes in the dts?  (which begs the question why we don't have cache nodes?)
> >
> 
> I can certainly add cache nodes and cpu nodes and then put the
> interrupts in those nodes. I was thinking along those same lines when I
> ported this driver but figured it would be good to get something out
> there. The only question I have is how am I supposed to hook that up
> into the linux device model? Will the edac driver bind to the device
> created for the cpus node and the cache node? I guess it will have to be
> a driver that binds to two devices.
> 
> One could argue that we should put the cp15 based architected timers in
> the cpus node also but so far nobody has done that and I think there was
> some reasoning behind that, Mark?

The architected timer binding was created at a time I wasn't involved in kernel
development, and I'm not aware of any particular reasoning. I've heard that
there was a decision to not duplicate banked resources, which would explain not
having the timer under /cpus/cpu@N, but doesn't imply that having it under
/cpus is bad.

Do we have precedent for putting any devices other than CPUs in /cpus?

Thanks,
Mark.
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