linux-kernel - Re: [PATCH v4 2/2] dt/bindings: Add bindings for Layerscape external irqs

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Message-ID: <6186117d-ff4f-a64f-9b5e-c3b3fac8bb88@arm.com>
Date:   Fri, 9 Feb 2018 09:47:00 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Rob Herring <robh@...nel.org>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Mark Rutland <mark.rutland@....com>,
        Andy Tang <andy.tang@....com>,
        Alexander Stein <alexander.stein@...tec-electronic.com>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 2/2] dt/bindings: Add bindings for Layerscape external
 irqs

On 08/02/18 15:08, Rasmus Villemoes wrote:
> On 2018-02-05 07:07, Rob Herring wrote:
>>> +Example:
>>> +	scfg: scfg@...0000 {
>>> +		compatible = "fsl,ls1021a-scfg", "syscon";
>>> +		...
>>> +		extirq: interrupt-controller {
>>> +			compatible = "fsl,ls1021a-extirq";
>>> +			#interrupt-cells = <3>;
>>> +			interrupt-controller;
>>> +			interrupt-parent = <&gic>;
>>> +			offset = <0x1ac>;
>>
>> Use reg here instead (with a length).
> 
> Hm, ok, but what does the length buy us? Should the driver just ignore
> it, or should it check that it is 4 and bail out if not?
> 
>>> +			interrupts = <163 164 165 167 168 169>;
>>
>> These don't look like GIC interrupt cells. Building this with current 
>> dtc will have errors.
> 
> Indeed, they are not. They simply record which interrupt lines on the
> GIC the external interrupt lines IRQ0...IRQ5 map to (the arm64 socs
> apparently have 12 such lines, but I don't know what they map to). I
> originally had that mapping in the driver, but I was asked to move it to
> DT. Is the problem the use of the name "interrupts" for this property?
> I'm happy to use something else (parent-interrupts, interrupt-mapping,
> ...) I find it very hard to figure out which property names have
> magic/reserved meanings.
> 
> I don't see any warnings/errors from dtc in the 4.14 tree I'm working
> on. Does it require an even newer dtc than that?

Most interrupt controllers use a private property, potentially with a
range (see the recent example of the Qualcomm PDC [1]).

Thanks,

	M.

[1] https://patchwork.kernel.org/patch/10208037/
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