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

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Date:	Thu, 14 May 2015 13:14:57 -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 Thu, May 14, 2015 at 3:32 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Wed, May 13, 2015 at 5:44 PM, Feng Kan <fkan@....com> wrote:
>
>> 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.
>
> OK I understand so much. SPISR is a status register of the state
> of the IRQ lines of shared peripherals.
>
> But surely the GPIO block has its own status register, so are
> you saying that this register is unreliable?

When the GPIO is used as interrupt, the gpio block does not report the
status anymore. Which leaves us stuck with SPISR.
>
> I can think of a few reasons, like transient IRQs etc but
> what is actually causing this?

I won't say the obvious.
>
> Techically the GIC would normally be higher up the food
> chain, i.e. one IRQ on the GIC is cascaded to sub-IRQs on
> the GPIO chip by virtue of its own struct irq_chip and
> irqdomain. The exception is typically only systems where
> the GPIO block is fused with the IRQ controller so that each
> GPIO line has its own unique IRQ line on the primary,
> top-level interrupt controller.
>
> Which GPIO driver is this? Is it upstream?
Yes, it is upstream. It is the xgene slimpro gpio driver. I am starting to
think that we ought to switch to use some gpio poll driver rather than
using gpio-key.
>
> Yours,
> Linus Walleij
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