linux-kernel - Re: [PATCH v2 3/6] ARM: dts: Device tree for AXM55xx.

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Date:	Mon, 28 Apr 2014 11:41:04 +0200
From:	Anders Berg <anders.berg@....com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Mike Turquette <mturquette@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/6] ARM: dts: Device tree for AXM55xx.

On Fri, Apr 25, 2014 at 01:50:25PM +0200, Linus Walleij wrote:
> On Fri, Apr 25, 2014 at 11:43 AM, Anders Berg <anders.berg@....com> wrote:
> > On Fri, Apr 25, 2014 at 11:16:18AM +0200, Linus Walleij wrote:
> >> On Thu, Apr 24, 2014 at 7:47 PM, Anders Berg <anders.berg@....com> wrote:
> >> > On Thu, Apr 24, 2014 at 03:24:14PM +0200, Linus Walleij wrote:
> >>
> >> >> One interrupt per CPU core?
> >> >>
> >> >> The drivers for these blocks will really just grab the first IRQ and
> >> >> then I guess they
> >> >> will only be able to execute on CPU0.
> >> >>
> >> >> It's definately correct to list all the IRQs here, but how do you envision
> >> >> the drivers making use of them in the long run?
> >> >
> >> > It's one interrupt line per input pin (so with the current driver only the first pin
> >> > is usable as interrupt source).
> >>
> >> Hm I'm not sure I understand what a "pin" is in this concept ...
> >> being maintainer of the pin control subsystem and all that really
> >> triggers my interest.
> >>
> >
> > Ok, maybe should replace "pin" with "GPIO" in my previous comment.
> >
> > So, a clarification. In one of the PL061 blocks (named gpio0 in the dts) there
> > is a separate interrupt per GPIO (I assume the motivation here is to enable to
> > control irq affinity per GPIO), where as the other block has a more standard
> > configuration with a single interrupt for all 8 GPIOs in that block.
> 
> OK! I get it. Thus this is not a stock PL061, but a version modified to
> generate a separate IRQ line per GPIO line.
> 

I believe it's an unmodified PL061. Looking at the TRM, the PL061 interface
signals include a GPIOMIS[7:0] in addition to the GPIOINTR. So I guess by
hooking up the GPIOMIS[7:0] signals to the interrupt controller, you can get
this one-irq-per-gpio setup.

> This means that you can only get a proper, working IRQ from the
> first line on gpio0 right? All other IRQs will be ignored.

Right.


/Anders

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