linux-kernel - Re: [RFC PATCH 1/4] DRIVERS: IRQCHIP: Add crossbar irqchip driver

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Message-ID: <5239C5E1.4060807@ti.com>
Date:	Wed, 18 Sep 2013 20:55:21 +0530
From:	Sricharan R <r.sricharan@...com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>,
	Rajendra Nayak <rnayak@...com>
Subject: Re: [RFC PATCH 1/4] DRIVERS: IRQCHIP: Add crossbar irqchip driver

On Wednesday 18 September 2013 07:22 PM, Sricharan R wrote:
> Hi Thomas,
>
> On Tuesday 17 September 2013 05:56 PM, Linus Walleij wrote:
>> On Fri, Sep 13, 2013 at 4:24 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>>> So why can't you make use of irq domains and have the whole routing
>>> business implemented sanely?
>>>
>>> What's needed is in gic_init_bases():
>>> irq
>>>        if (of_property_read(node, "routable_irqs", &nr_routable_irqs) {
>>>           irq_domain_add_legacy(nr_gic_irqs);
>>>        } else {
>>>           irq_domain_add_legacy(nr_per_cpu_irqs);
>>>           irq_domain_add_linear(nr_routable_irqs);
>>>        }
>>>
>>> Now that separate domain has an xlate function which grabs a free GIC
>>> irq from a bitmap and returns the hardware irq number in the gic
>>> space. The map/unmap callbacks take care of setting up / tearing down
>>> the route in the crossbar.
>> This is obviously the right approach, it's exactly what .map should do
>> the only special thing here being that we have hardware to perform
>> the mapping ... bah why didn't I realize this :-(
>>
>> Yours,
>> Linus Walleij
> Thanks for the suggestion.
>
> So as i understand this, this implies using the GIC domain itself and
>  add the support for dynamically routable irqs (like crossbar) with in the
> GIC driver itself right ?
  Please ignore this. So the question was more of how to implement the
  call outs in the case of routable irqs from map/ unmap callbacks.
 I will look more here and come back.

Regards,
 Sricharan
 
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