linux-kernel - Re: [PATCH v2 2/4] irqchip: bcm2835: If a parent interrupt is registered, chain from it.

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Date:	Tue, 21 Jul 2015 20:08:29 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Eric Anholt <eric@...olt.net>
CC:	linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lee Jones <lee@...nel.org>, devicetree@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>
Subject: Re: [PATCH v2 2/4] irqchip: bcm2835: If a parent interrupt is registered,
 chain from it.

On 07/13/2015 07:35 PM, Eric Anholt wrote:
> The BCM2836 (Raspberry Pi 2) uses two levels of interrupt handling
> with the CPU-local interrupts being the root, so we need to register
> ours as chained off of the CPU's local interrupt.

Sorry for the slow review; laziness after vacation!

> diff --git a/Documentation/devicetree/bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt b/Documentation/devicetree/bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt

> +The BCM2836 contains the same interrupt controller with the same
> +interrupts, but the per-CPU interrupt controller is the root, and an
> +interrupt there indicates that the ARMCTRL has an interrupt to handle.
> +
>  Required properties:
>  
>  - compatible : should be "brcm,bcm2835-armctrl-ic"

Since there are some differences between the bcm2835 and bcm2836 HW
blocks, I'd expect the compatible value to be different for each. In
particular...

> +Optional properties:
> +- interrupt-parent : Specifies the parent interrupt controller when this
> +  controller is the second level.
> +- interrupts : Specifies the interrupt on the parent for this interrupt
> +  controller to handle.

I'd classify that as "additional required properties for
brcm,bcm2836-armctrl-ic"

... and with different compatible values for the two chips, you would
know when probe() should require vs. reject the property.
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