linux-kernel - Re: DT connectors, thoughts

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Message-Id: <2C63DCA2-385A-4EE3-A957-F1DBEF7929F8@konsulko.com>
Date:	Thu, 21 Jul 2016 22:15:36 +0300
From:	Pantelis Antoniou <pantelis.antoniou@...sulko.com>
To:	Rob Herring <robh+dt@...nel.org>
Cc:	David Gibson <david@...son.dropbear.id.au>,
	Frank Rowand <frowand.list@...il.com>,
	Stephen Boyd <stephen.boyd@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Rutland <mark.rutland@....com>,
	Matt Porter <mporter@...sulko.com>,
	Koen Kooi <koen@...inion.thruhere.net>,
	Guenter Roeck <linux@...ck-us.net>,
	Marek Vasut <marex@...x.de>, Wolfram Sang <wsa@...-dreams.de>,
	devicetree <devicetree@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: DT connectors, thoughts

Hi Rob,

> On Jul 21, 2016, at 22:09 , Rob Herring <robh+dt@...nel.org> wrote:
> 
> On Thu, Jul 21, 2016 at 9:14 AM, Pantelis Antoniou
> <pantelis.antoniou@...sulko.com> wrote:
>> Hi David,
>> 
>>> On Jul 21, 2016, at 16:42 , David Gibson <david@...son.dropbear.id.au> wrote:
>>> 
>>> On Wed, Jul 20, 2016 at 11:59:44PM +0300, Pantelis Antoniou wrote:
>>>> Hi David,
>>>> 
>>>> Spent some time looking at this, and it looks like it’s going to the right direction.
>>>> 
>>>> Comments inline.
>>>> 
>>>>> On Jul 18, 2016, at 17:20 , David Gibson <david@...son.dropbear.id.au> wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> Here's some of my thoughts on how a connector format for the DT could
>>>>> be done.  Sorry it's taken longer than I hoped - I've been pretty
>>>>> swamped in my day job.
>>>>> 
>>>>> This is pretty early thoughts, but gives an outline of the approach I
>>>>> prefer.
> 
> [...]
> 
>>>>>            i2c: i2c@... {
>>>>>            };
>>>>>            intc: intc@... {
>>>>>                    #interrupt-cells = <2>;
>>>>>            };
>>>>>    };
>>>>> 
>>>>>    connectors {
>>>>>            widget1 {
>>>>>                    compatible = "foo,widget-socket";
>>>>>                    w1_irqs: irqs {
>>>>>                            interrupt-controller;
>>>>>                            #address-cells = <0>;
>>>>>                            #interrupt-cells = <1>;
>>>>>                            interrupt-map-mask = <0xffffffff>;
>>>>>                            interrupt-map = <
>>>>>                                    0 &intc 7 0
>>>>>                                    1 &intc 8 0
>>>>>> ;
>>>>>                    };
>>>> 
>>>> This is fine. We need an interrupt controller node.
>>> 
>>> Actually I think we only need an interrupt nexus, not an interrupt
>>> controller (in IEEE1275 terminology).  (An interrupt controller would
>>> generally require it's own driver, to ack/mask irqs, whereas this just
>>> demonstrates the routing to an existing interrupt controller).  Which
>>> makes that example slightly incorrect (it shouldn't have the
>>> interrupt-controller property).
>> 
>> Hmm, as far as I can tell we only have a concept of an interrupt controller
>> in the kernel. An interrupt nexus is something new. We should get by without
>> a driver but hacking the interrupt lookup path at DT.
> 
> Interrupt nexus is the interrupt-map property which is fully
> supported. I'd expect we'll end up with a gpio nexus (i.e. gpio-map)
> for connector gpios, too.
> 

Is interrupt-map enough to cover all our cases? On all the cases that I see it
used is in the context of PCI or some sort of bus.

Is the example above well defined? As far as I can tell interrupt-controller is not
needed.
 
> Rob

Regards

— Pantelis