linux-kernel - Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs

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Message-ID: <52644C88.5060608@wwwdotorg.org>
Date:	Sun, 20 Oct 2013 22:35:04 +0100
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Grant Likely <grant.likely@...aro.org>
CC:	Alexander Holler <holler@...oftware.de>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Linus Walleij <linus.walleij@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Enric Balletbo i Serra <eballetbo@...il.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...aro.org>,
	Balaji T K <balajitk@...com>,
	Tony Lindgren <tony@...mide.com>,
	Jon Hunter <jgchunter@...il.com>
Subject: Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs

On 10/20/2013 01:41 PM, Laurent Pinchart wrote:
> Hi Grant,
> 
> On Tuesday 17 September 2013 17:36:32 Grant Likely wrote:
>> On Thu, 12 Sep 2013 17:57:00 +0200, Alexander Holler wrote:
>>> Am 12.09.2013 17:19, schrieb Stephen Warren:
>>>> IRQs, DMA channels, and GPIOs are all different things. Their bindings
>>>> are defined independently. While it's good to define new types of
>>>> bindings consistently with other bindings, this hasn't always happened,
>>>> so you can make zero assumptions about the IRQ bindings by reading the
>>>> documentation for any other kind of binding.
>>>>
>>>> Multiple interrupts are defined as follows:
>>>> 	// Optional; otherwise inherited from parent/grand-parent/...
>>>> 	interrupt-parent = <&gpio6>;
>>>> 	// Must be in a fixed order, unless binding defines that the
>>>> 	// optional interrupt-names property is to be used.
>>>> 	interrupts = <1 IRQF_TRIGGER_HIGH> <2 IRQF_TRIGGER_LOW>;
>>>> 	// Optional; binding for device defines whether it must
>>>> 	// be present
>>>> 	interrupt-names = "foo", "bar";
>>>>
>>>> If you need multiple interrupts, each with a different parent, you need
>>>> to use an interrupt-map property...
...
>> Actually, I think it is solveable but doing so requires a new binding
>> for interrupts. I took a shot at implementing it earlier this week and
>> I've got working patches that I'll be posting soon. I created a new
>> "interrupts-extended" property that uses a phandle+args type of
>> binding like this:
...
>> device@...0 {
>> 	interrupts-extended = <&intc1 5> <&intc2 3 4> <&intc1 6>;
>> };
...
> Any progress on this ? I'll need to use multiple interrupts with different 
> parents in the near future, I can take this over if needed.
> 
> I've also been thinking that we could possibly reuse the "interrupts" property 
> without defining a new "interrupts-extended". When parsing the property the 
> code would use the current DT bindings if an interrupt-parent is present, and 
> the new DT bindings if it isn't.

interrupt-parents doesn't have to be present in individual nodes; it can
be inherited from the parent. That means you'd have to convert whole
sub-trees at once. It seems much more flexible to use a new property and
hence make it explicit what format the data is in.
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