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

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Date:	Mon, 01 Dec 2014 11:19:41 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Liviu Dudau <Liviu.Dudau@....com>
CC:	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.

Hi Russell,

On 01/12/14 11:03, Russell King - ARM Linux wrote:
> On Mon, Dec 01, 2014 at 10:46:13AM +0000, Liviu Dudau wrote:
>> On Mon, Dec 01, 2014 at 10:41:45AM +0000, Russell King - ARM Linux wrote:
>>> On Fri, Nov 28, 2014 at 05:55:40PM +0000, Liviu Dudau wrote:
>>>> +	/*
>>>> +	 * PPIs are optionally configurable, but we cannot distinguish
>>>> +	 * between high and low, nor falling and rising. Change the
>>>> +	 * type so that it passes the next check.
>>>
>>> This comment could do with a /lot/ of improvement.  It sounds like the
>>> only reason this code exists is to bypass the check.  If that's all
>>> that's being done, there's better ways to code it.
>>
>> Hi Russell,
>>
>> You are right, all I want to do is bypass the next check because *if*
>> the PPIs can be configured, then any combination is valid (edge 
>> raising/falling, level low/high). In real systems, PPIs tend to be
>> configured with active level low. That falls the existing check.
> 
>  "fails" :)
> 
> 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).

Thanks,

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