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

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Date:	Tue, 19 May 2015 10:40:21 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Feng Kan <fkan@....com>, Marc Zyngier <marc.zyngier@....com>
Cc:	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 10:14 PM, Feng Kan <fkan@....com> wrote:
> On Thu, May 14, 2015 at 3:32 AM, Linus Walleij <linus.walleij@...aro.org> wrote:

>> 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.

Yeah I see your problem now :(

I think it's better to fix the access functions so that you can
cross-call to the GIC driver to get the SPISR flag out though.
Let's see what Marc says.

>> 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.

There is both gpio_keys_polled and IRQ-driven gpio_keys so yeah
that's possible. But honestly I think it's better to deal with this
problem for real because IRQ is more efficient.

So the way I perceive it this is the real problem:

+static int gic_irq_get_irqchip_state(struct irq_data *d,
+                                     enum irqchip_irq_state which, bool *val)
+{
+       switch (which) {
(...)
+       case IRQCHIP_STATE_ACTIVE:
+               *val = gic_peek_irq(d, GIC_DIST_ACTIVE_SET);
+               break;

Here it reads the status from 0x300 where DIST_ACTIVE_SET
is, so if you change GIC_DIST_ACTIVE_SET to
0xd04 (SPISR), does it start working?

I would *guess* that maybe you want to implement and
ask for IRQCHIP_STATE_LINE_LEVEL instead of
IRQCHIP_STATE_ACTIVE, and have that case: read
from 0xd04 (SPISR) instead, because that makes more
sense to me, or am I wrong at it?

+       case IRQCHIP_STATE_LINE_LEVEL:
+               *val = gic_peek_irq(d, GIC_DIST_SPISR);
+               break;

And then put a define into <linux/irqchip/arm-gic.h> for
GIC_DIST_SPISR.

Yours,
Linus Walleij
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