linux-kernel - Re: [PATCH] genirq: Introduce irq_read

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Date:	Tue, 28 Oct 2014 08:41:50 -0700
From:	Bjorn Andersson <bjorn@...o.se>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>
Subject: Re: [PATCH] genirq: Introduce irq_read_line()

On Sat, Oct 25, 2014 at 2:22 AM, Marc Zyngier <marc.zyngier@....com> wrote:
> On Sat, Oct 25 2014 at 12:12:55 am BST, Bjorn Andersson <bjorn@...o.se> wrote:
>> On Fri, Oct 24, 2014 at 10:59 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>>> I just pushed out a branch:
>>> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git
>>> irq/irqchip_state
>>>
>>> Please let me know if that's useful for you.
>>>
>>
>> I think that my irq_read_line() would be equivalent of
>> irq_get_irqchip_state(IRQCHIP_STATE_PENDING), i.e. the state of the
>> interrupt ignoring masking. And the rest would be EINVAL.
>> So I think this would work out just fine for us!
>
> Excellent.
>

Hi Marc,

We gave this some more thought and read up on what "pending" and
"active" means according to the ARM GIC - PENDING is not what we want
:(

In the Qualcomm pmic we have two interrupt status registers
"interrupt" and "real-time". I think the "interrupt" status register
would be the one related to your defined constants. However what we
need to access in our use cases are the "real-time" status register,
which basically is a representation of the input to the interrupt
logic.

As far as I can see the GIC does not offer anything like that, but I
hope we could add another constant to your enum list and utilise your
api for this.

I'm not entirely sure what we should call it though,
IRQCHIP_STATE_LEVEL seems somewhat conflicting with level trigger and
the Qualcomm name IRQCHIP_STATE_REALTIME isn't very self describing.
Maybe IRQCHIP_STATE_LINE_LEVEL?

Regards,
Bjorn
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