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

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Date:	Sun, 20 Oct 2013 14:41:41 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Grant Likely <grant.likely@...aro.org>
Cc:	Alexander Holler <holler@...oftware.de>,
	Stephen Warren <swarren@...dotorg.org>,
	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

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 (Google it for a more complete
> > > explanation I guess). Unlike "interrupts", "interrupt-map" has a phandle
> > > in each entry, and hence each entry can refer to a different IRQ
> > > controller. You end up defining a dummy interrupt controller node (which
> > > may be the leaf node with multiple IRQ outputs, which then points at
> > > itself as the interrupt parent), pointing the leaf node's
> > > interrupt-parent at that node, and then having interrupt-map "demux" the
> > > N interrupt outputs to the various interrupt controllers.
> > 
> > What a mess. I assume that is the price that bindings don't have to
> > change.
> > 
> > Thanks for clarifying that,
> > 
> > Alexander Holler
> 
> 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:
> 
> intc1: intc@...0 {
> 	interrupt-controller;
> 	#interrupt-cells = <1>;
> };
> 
> intc2: intc@...0 {
> 	interrupt-controller;
> 	#interrupt-cells = <2>;
> };
> 
> device@...0 {
> 	interrupts-extended = <&intc1 5> <&intc2 3 4> <&intc1 6>;
> };
> 
> 'interrupts-extended' will be proposed as a directly replacement of the
> 'interrupts' property and it will eliminate the need for an
> interrupt-map property. A node will be allowed to have one or the other,
> but not both.
> 
> I'll write up a proper binding document and post for review.

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.

-- 
Regards,

Laurent Pinchart
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