linux-kernel - Re: [PATCH v3 3/7] irqchip: gic: Support hierarchy irq domain.

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Message-ID: <4904191.xcTM1nFGH7@wuerfel>
Date:	Mon, 13 Oct 2014 21:51:18 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	"Joe.C" <yingjoe.chen@...iatek.com>,
	Mark Rutland <Mark.Rutland@....com>,
	"arm@...nel.org" <arm@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"srv_heupstream@...iatek.com" <srv_heupstream@...iatek.com>,
	"yingjoe.chen@...il.com" <yingjoe.chen@...il.com>,
	"hc.yen@...iatek.com" <hc.yen@...iatek.com>,
	"eddie.huang@...iatek.com" <eddie.huang@...iatek.com>,
	"nathan.chung@...iatek.com" <nathan.chung@...iatek.com>,
	"yh.chen@...iatek.com" <yh.chen@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Olof Johansson <olof@...om.net>,
	Pawel Moll <Pawel.Moll@....com>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Matt Porter <mporter@...aro.org>,
	Marc Carino <marc.ceeeee@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Sricharan R <r.sricharan@...com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/7] irqchip: gic: Support hierarchy irq domain.

On Monday 13 October 2014 13:10:32 Marc Zyngier wrote:
> On 13/10/14 11:43, Joe.C wrote:
> > On Thu, 2014-10-09 at 17:59 +0100, Marc Zyngier wrote:
> >> On 09/10/14 15:29, Joe.C wrote
> >>> @@ -952,7 +988,11 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
> >>>  
> >>>     gic_irqs -= hwirq_base; /* calculate # of irqs to allocate */
> >>>  
> >>> -   if (of_property_read_u32(node, "arm,routable-irqs",
> >>> +   if (IS_ENABLED(CONFIG_IRQ_DOMAIN_HIERARCHY) &&
> >>> +           of_find_property(node, "arm,irq-domain-hierarchy", NULL))
> >>> +           gic->domain = irq_domain_add_linear(node, gic_irqs,
> >>> +                                   &gic_irq_domain_hierarchy_ops, gic);
> >>
> >> I really think that looking for a property is the wrong thing to do. If
> >> "node" is non-NULL, then we're pretty sure that we're initializing from
> >> DT, and that a pure linear domain should be the right thing, leaving the
> >> legacy stuff for the few non-DT platforms that are still around.
> >>
> >> Thanks,
> >>
> >>      M.
> > 
> > The only reason I introduce "arm,irq-domain-hierarchy" property is
> > trying to keep original behavior when hierarchy irq domain is not used.
> > Without this, when a board init GIC with DT, all driver will have to use
> > devicetree. I'm not sure we want to break things like this.
> 
> I don't think we want to support a "middle of the road" setup, where the
> GIC is probed by DT, but some devices have hardcoded interrupts.

Agreed. We should work on making GIC DT-only by converting the few remaining
users instead, and certainly should not add any new board files that
might use the domain hierarchy code.

	Arnd
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