linux-kernel - interrupts-extended only allowed with different parents? [Was: Re: [PATCH 3/4] ARM: dts: imx28-tx28: fix interrupt flags and use interrupts-extended property]

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Date:   Mon, 16 Oct 2017 11:03:56 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Lothar Waßmann <LW@...O-electronics.de>
Cc:     Fabio Estevam <fabio.estevam@....com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Sascha Hauer <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: interrupts-extended only allowed with different parents? [Was: Re:
 [PATCH 3/4] ARM: dts: imx28-tx28: fix interrupt flags and use
 interrupts-extended property]

On Mon, Oct 16, 2017 at 10:56:32AM +0200, Lothar Waßmann wrote:
> Hi,
> 
> On Mon, 16 Oct 2017 09:17:26 +0200 Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Wed, Oct 11, 2017 at 01:05:38PM +0200, Lothar Waßmann wrote:
> > > diff --git a/arch/arm/boot/dts/imx28-tx28.dts b/arch/arm/boot/dts/imx28-tx28.dts
> > > index 211e67d..3c852f7 100644
> > > --- a/arch/arm/boot/dts/imx28-tx28.dts
> > > +++ b/arch/arm/boot/dts/imx28-tx28.dts
> > > @@ -328,8 +328,7 @@
> > >  		reg = <0x20>;
> > >  		pinctrl-names = "default";
> > >  		pinctrl-0 = <&tx28_pca9554_pins>;
> > > -		interrupt-parent = <&gpio3>;
> > > -		interrupts = <28 0>;
> > > +		interrupts-extended = <&gpio3 28 IRQ_TYPE_NONE>;
> > >  		gpio-controller;
> > >  		#gpio-cells = <2>;
> > >  		interrupt-controller;
> > 
> > While interrupts-extended looks nice,
> > Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> > has:
> > 
> > 	"interrupts-extended" should only be used when a device has
> > 	multiple interrupt parents.
> > 
> > If this is still true, this patch is wrong.
> >
> Thanks for the hint. It really helps to read the documentation
> sometimes, rahter than relying on existing code only...
> 
> A quick check shows, that more than 100 of the 130 uses of
> interrupts-extended are wrong. :(

That's why I honestly consider that these documentation bits are stale.
I adapted the Subject to maybe catch the attention of the devicetree
guys.

(BTW: The current wording is likely imprecise. I'd expect that it really
should mean "Use interrupt-parent + interrupts if possible", but the
following still fulfills the documented condition:

	interrupts-extended = <&gpio3 28 IRQ_TYPE_NONE &gpio3 29 IRQ_TYPE_NONE>

while it can be expressed without interrupts-extended.)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |