linux-kernel - Re: [PATCH] irqchip: gic: Allow interrupt level to be set for PPIs.

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Message-ID: <547C5179.5020505@arm.com>
Date:	Mon, 01 Dec 2014 11:31:05 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Liviu Dudau <Liviu.Dudau@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] irqchip: gic: Allow interrupt level to be set for PPIs.

On 01/12/14 11:23, Russell King - ARM Linux wrote:
> On Mon, Dec 01, 2014 at 11:19:41AM +0000, Marc Zyngier wrote:
>> Hi Russell,
>>
>> On 01/12/14 11:03, Russell King - ARM Linux wrote:
>>> If all you want to do is to bypass the following check, what's wrong
>>> with actually doing that:
>>>
>>> -	if (type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
>>> +	if (gicirq >= 32 && type != IRQ_TYPE_LEVEL_HIGH &&
>>> +	    type != IRQ_TYPE_EDGE_RISING)
>>> 		return -EINVAL;
>>>
>>
>> I think that will require some additional changes to gic_configure_irq
>> (in irq-gic-common.c).
> 
> I don't think so - gic_configure_irq() will treat it as a no-op as far
> as trying to configure the IRQ settings.

I agree. But that's following ARM's tradition of making PPIs
non-configurable. I seem to remember that there is at least one
occurrence of a GIC with configurable PPIs (Qualcomm, IIRC).

With this use case in mind, Liviu's patch allows an active-low interrupt
to be correctly configured as level, for example.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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