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

From: Alexander Holler <holler@ahsoftware.de>
To: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Grant Likely <grant.likely@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	Linux-OMAP <linux-omap@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Enric Balletbo i Serra <eballetbo@gmail.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>,
	Santosh Shilimkar <santosh.shilimkar@ti.com>,
	Kevin Hilman <khilman@linaro.org>, Balaji T K <balajitk@ti.com>,
	Tony Lindgren <tony@atomide.com>,
	Jon Hunter <jgchunter@gmail.com>
Subject: Re: [PATCH] RFC: interrupt consistency check for OF GPIO IRQs
Date: Thu, 12 Sep 2013 13:26:54 +0200	[thread overview]
Message-ID: <5231A4FE.1070704@ahsoftware.de> (raw)
In-Reply-To: <5231A0F8.1070505@ahsoftware.de>

Am 12.09.2013 13:09, schrieb Alexander Holler:
> Am 12.09.2013 12:28, schrieb Alexander Holler:
>> Am 12.09.2013 12:11, schrieb Javier Martinez Canillas:
>>> On 09/12/2013 10:55 AM, Alexander Holler wrote:
>>
>> ...
>>>>
>>>> By the way, how do you define two GPIOs/IRQs from different
>>>> gpio-banks/irq-controllers wuth that scheme?
>>>>
>>>
>>> That is indeed a very good question and I don't have a definite answer.
>>>
>>>> Would that be like below?
>>>>
>>>>   ethernet@5,0 {
>>>>            compatible = "smsc,lan9221", "smsc,lan9115";
>>>>            interrupt-parent = <&gpio6>;
>>>>            interrupts = <16 8>;
>>>>            interrupt-parent = <&gpio7>;
>>>>            interrupts = <1 IRQF_TRIGGER_FALLING>; /* GPIO7_1 */
>>>>   };
>>>>
>>
>> ...
>>
>>> So, if I understood the code correctly the DT IRQ core doesn't expect
>>> a device
>>> node to have more than one "interrupt-parent" property.
>>>
>>> It *should* work though if you have multiple "interrupts" properties
>>> defined and
>>> all of them have the same "interrupt-parent":
>>>
>>>         interrupt-parent = <&gpio6>;
>>>         interrupts = <1 IRQF_TRIGGER_HIGH>; /* GPIO6_1 */
>>>         interrupts = <2 IRQF_TRIGGER_LOW>; /* GPIO6_2 */
>>>
>>> since of_irq_map_one() will be called for each "interrupts" and the
>>> correct
>>> "interrupt-parent" will get obtained by of_irq_find_parent().
>>
>> I assumed that answer. So to make such a scenario possible, something
>> like this might be neccessary:
>>
>>           interrupts = <&gpio6 1 IRQF_TRIGGER_HIGH>; /* GPIO6_1 */
>>           interrupts = <&gpio7 2 IRQF_TRIGGER_LOW>; /* GPIO7_2 */
>>
>> or, to be compatible
>>
>>           interrupts = <1 IRQF_TRIGGER_HIGH &gpio6>; /* GPIO6_1 */
>>           interrupts = <1 IRQF_TRIGGER_LOW &gpio7>; /* GPIO7_1 */
>>
>> Another problem is the naming. In all the above cases, the driver would
>> not know which IRQ he should use for what. Maybe the order defines it,
>> but that wouldn't be very verbose. And I think just changing the name
>> would make travelling the tree impossible, as only the driver itself
>> would know the name and it's meaning.
>
> On a second look, travelling the tree is still possible if the solution
> would be like above (without that interrupt-parent). So if a driver
> requires two interrupts he could use
>
>        interrupt-foo = <1 IRQF_TRIGGER_HIGH &gpio6>; /* GPIO6_1 */
>        interrupt-bar = <1 IRQF_TRIGGER_LOW &gpio7>; /* GPIO7_1 */
>
> And travelling the tree will still be possible because walking from the
> interrupt-controllers (those gpio) downwards would end up at the
> interrupt definitions, so the name of them isn't needed to find them in
> the tree.

I've just seen how they solved it for dma:

			dmas = <&edma0 16
				&edma0 17>;
			dma-names = "rx", "tx";

so it would be like

       interrupts = <1 IRQF_TRIGGER_HIGH &gpio6>; /* GPIO6_1 */
       interrupts = <1 IRQF_TRIGGER_LOW &gpio7>; /* GPIO7_1 */
       interrupt-names = "foo", "bar";

Or this would be possible:

       interrupt-parent = <&gpio6 &gpio7>;
       interrupts = <1 IRQF_TRIGGER_HIGH>; /* GPIO6_1 */
       interrupts = <1 IRQF_TRIGGER_LOW>; /* GPIO7_1 */
       interrupt-names = "foo", "bar";

Regards,

Alexander