linux-kernel - Re: [PATCH 5/5] DT: arm,gic-v3: Documment PPI partition support

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Message-ID: <20160412162937.GA25932@rob-hp-laptop>
Date:	Tue, 12 Apr 2016 11:29:37 -0500
From:	Rob Herring <robh@...nel.org>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 5/5] DT: arm,gic-v3: Documment PPI partition support

On Mon, Apr 11, 2016 at 09:57:55AM +0100, Marc Zyngier wrote:
> Add a decription of the PPI partitioning support.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  .../bindings/interrupt-controller/arm,gic-v3.txt   | 34 ++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> index 007a5b4..4c29cda 100644
> --- a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> +++ b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
> @@ -11,6 +11,8 @@ Main node required properties:
>  - interrupt-controller : Identifies the node as an interrupt controller
>  - #interrupt-cells : Specifies the number of cells needed to encode an
>    interrupt source. Must be a single cell with a value of at least 3.
> +  If the system requires describing PPI affinity, then the value must
> +  be at least 4.

You're winning for cell count...

One alternative that would save adding a cell and keep it contained 
within would be just list the affinities in the GIC node in the form of 
'<PPI#> <count> <cpu phandles>':

ppi-affinity = <1 2 &cpu2 &cpu3>,
		<5 1 &cpu4>,
		...

This would be harder to parse though if you have a large number of PPIs 
with affinities.

That said, I've got no real issue with this as is.

Rob