Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936Ab3IRWcB (ORCPT ); Wed, 18 Sep 2013 18:32:01 -0400 Received: from www.linutronix.de ([62.245.132.108]:33356 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751661Ab3IRWb7 (ORCPT ); Wed, 18 Sep 2013 18:31:59 -0400 Date: Thu, 19 Sep 2013 00:31:57 +0200 (CEST) From: Thomas Gleixner To: Santosh Shilimkar cc: linus.walleij@linaro.org, Sricharan R , LKML , devicetree@vger.kernel.org, linux-doc@vger.kernel.org, LAK , linux-omap@vger.kernel.org, Russell King , Tony Lindgren , rnayak@ti.com Subject: Re: [RFC PATCH 1/4] DRIVERS: IRQCHIP: Add crossbar irqchip driver In-Reply-To: <5239C19E.1090609@ti.com> Message-ID: References: <1379000351-15672-1-git-send-email-r.sricharan@ti.com> <1379000351-15672-2-git-send-email-r.sricharan@ti.com> <523228B5.5070507@ti.com> <5232457A.8080709@ti.com> <52326D6B.2010003@ti.com> <52332772.5040203@ti.com> <5239C19E.1090609@ti.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2037 Lines: 54 On Wed, 18 Sep 2013, Santosh Shilimkar wrote: > On Friday 13 September 2013 10:55 AM, Santosh Shilimkar wrote: > > On Friday 13 September 2013 10:24 AM, Thomas Gleixner wrote: > > [...] > > >> Before you dig into MSI, lets talk about irq domains first. > >> > >> GIC implements a legacy irq domain, i.e. a linear domain of all > >> possible GIC interrupts with a 1:1 mapping. > >> > >> 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(): > >> > >> 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. > >> > >> Thoughts? > >> > > This sounds pretty good idea. We will explore above option. > > Thanks Thomas. > > > After further looking into this, the irqdomain approach lets us > setup the map only once during the init. This is similar to > the earlier approach of cross-bar driver where at probe time > the router was setup. The whole debate started with the fact > that we shouldn't fix the irq mapping at probe and should > dynamically change the mapping based on [request/free]_irq() > to be able to maximize the use of the IP. Well, that's what irq_of_parse_and_map() resp. irq_create_mapping and irq_dispose_mapping() are for. It requires changes to drivers, but you can't get that thing for free. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/