Date:	Fri, 29 May 2015 17:57:50 -0700
From:	Gregory Fong <gregory.0xf0@...il.com>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	linux-gpio@...r.kernel.org, Alexandre Courbot <gnurou@...il.com>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH v2 3/6] dt-bindings: brcmstb-gpio: document properties for wakeup

On Fri, May 29, 2015 at 5:36 PM, Brian Norris
<computersforpeace@...il.com> wrote:
> On Thu, May 28, 2015 at 07:14:07PM -0700, Gregory Fong wrote:
>> Some brcmstb GPIO controllers can be used to wake from suspend, so use the
>> de facto standard property 'wakeup-source' to mark the nodes of controllers
>> with that capability.
>>
>> Also document interrupts-extended, which will be used for wakeup handling
>> because the interrupt parent for the wake IRQ is different from the regular
>> IRQ.
>>
>> Signed-off-by: Gregory Fong <gregory.0xf0@...il.com>
>> ---
>> New in v2.
>>
>>  .../devicetree/bindings/gpio/brcm,brcmstb-gpio.txt | 26 +++++++++++++++++++++-
>>  1 file changed, 25 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/gpio/brcm,brcmstb-gpio.txt b/Documentation/devicetree/bindings/gpio/brcm,brcmstb-gpio.txt
>> index 435f1bc..568814f 100644
>> --- a/Documentation/devicetree/bindings/gpio/brcm,brcmstb-gpio.txt
>> +++ b/Documentation/devicetree/bindings/gpio/brcm,brcmstb-gpio.txt
>> @@ -33,6 +33,12 @@ Optional properties:
>>  - interrupt-parent:
>>      phandle of the parent interrupt controller
>>
>> +- interrupts-extended:
>> +    Alternate form of specifying interrupts and parents that allows for
>> +    multiple parents.  This takes precedence over 'interrupts' and
>> +    'interrupt-parent'.  This probably must be used if the wakeup-source
>> +    property is provided because that may have a different interrupt parent.
>> +
>
> "This probably must be used" seems a little awkward, especially when
> you're just explaining an implementation detail of our SoCs, rather than
> something unique about this binding. Maybe:
>
>   "Wakeup-capable GPIO controllers often route their wakeup interrupt
>   lines through a different interrupt controller than the primary
>   interrupt line, making this property necessary."

That wording does seem better, will change.

>
>>  - #interrupt-cells:
>>      Should be <2>.  The first cell is the GPIO number, the second should specify
>>      flags.  The following subset of flags is supported:
>> @@ -48,7 +54,10 @@ Optional properties:
>>      Marks the device node as an interrupt controller
>>
>>  - interrupt-names:
>> -    The name of the IRQ resource used by this controller
>> +    The names of the IRQ resources used by this controller
>
> If you're specifying names, you should list them here.

I was wondering about that.  Some bindings have them listed, some
don't.  In this case I know what names currently exist but there could
certainly be different ones in the future.  How does that work?  Or am
I misunderstanding what this field is used for?  Where are the
documented rules for this?

>
>> +
>> +- wakeup-source:
>> +    GPIOs for this controller can be used as a wakeup source
>>
>>  Example:
>>       upg_gio: gpio@...0a700 {
>> @@ -63,3 +72,18 @@ Example:
>>               interrupt-names = "upg_gio";
>>               brcm,gpio-bank-widths = <0x20 0x20 0x20 0x18>;
>>       };
>> +
>> +     upg_gio_aon: gpio@...172c0 {
>> +             #gpio-cells = <0x2>;
>> +             #interrupt-cells = <0x2>;
>
> Might use decimal instead of hex for the above 2 lines?

Sure.

>
>> +             compatible = "brcm,bcm7445-gpio", "brcm,brcmstb-gpio";
>> +             gpio-controller;
>> +             interrupt-controller;
>> +             reg = <0xf04172c0 0x40>;
>> +             interrupt-parent = <0xc>;
>
> That should be a phandle, not an int (I realize phandles resolve down to
> an integer, but we're speaking DTS, not DTB).

OK.

>
>> +             interrupts = <0x6>;
>> +             interrupts-extended = <0xc 0x6 0xa 0x5>;
>
> Same here (phandles).
>
> Also, even though the interrupt binding semantics specify precedence
> between interrupts and interrupts-extended, I'd think an example should
> stick to one or the other, no?

This is the output that we actually get from the bootloader.  But
regardless, IMO the example should have both cases: precedence is
well-defined, both sets of information are valid, and the driver can
handle the case where interrupts-extended is not an understood
property.

>
>> +             interrupt-names = "upg_gio_aon", "upg_gio_aon_wakeup";
>> +             wakeup-source;
>> +             brcm,gpio-bank-widths = <0x12 0x4>;
>> +     };
>
> Reviewed-by: Brian Norris <computersforpeace@...il.com>

Thanks for the review,
Gregory
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