linux-kernel - Re: [PATCH v4 2/3] irqchip: GIC: Add support for irq_{get,set}_irqchip

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Message-ID: <CAL85gmC4ovR99wQQYoKs=oo24So80jZ_guxDDFhi-1MXXj0uSw@mail.gmail.com>
Date:	Wed, 13 May 2015 08:44:44 -0700
From:	Feng Kan <fkan@....com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>, Phong Vo <pvo@....com>,
	Tin Huynh <tnhuynh@....com>, Y Vo <yvo@....com>,
	Thomas Gleixner <tglx@...utronix.de>, Toan Le <toanle@....com>,
	Bjorn Andersson <bjorn@...o.se>,
	Jason Cooper <jason@...edaemon.net>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH v4 2/3] irqchip: GIC: Add support for irq_{get,set}_irqchip_state

On Wed, May 13, 2015 at 4:58 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Wed, May 13, 2015 at 4:25 AM, Feng Kan <fkan@....com> wrote:
>
>> Marc:
>>
>> Sorry for top posting. It seems with GIC-400, the get_irqstate is not a reliable
>> way of accessing the GPIO status. In our case, the gpio interrupt status can
>> only be read correctly with the SPISR register. So it seems we have to go
>> back to the old way of mapping the SPISR portion of the GIC in our GPIO
>> driver. We wanted to ask you if that is acceptable since SPISR in not
>> standard in all GIC, perhaps we can treat it differently.
>
> As GPIO maintainer I am curious about what this is...
>
> Can you describe the scenario where your GPIO (!) driver needs
> to be poking around in the GIC SPISR?

We are using the gpio driver with gpio_key for power button. The gpio
status can only be retrieved from the GIC register when the gpio is
acting as a interrupt. Marc had provided a patch which allow the
getting of the irq status
using the PENDING_SET register, however it seems it is not reliable.
Another register in the GIC call the SPISR always give the correct
status but it is only available in the GIC-400 and hence not likely to
be incorporated into the general GIC code. We would like to go back
the version 1 of the patch and ioremap the region in the gpio driver
and access the status that way. Please let us know what you think.

>
> Yours,
> Linus Walleij
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