From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756322Ab2AMAbf (ORCPT ); Thu, 12 Jan 2012 19:31:35 -0500 Received: from mail-gx0-f174.google.com ([209.85.161.174]:51484 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756250Ab2AMAbb (ORCPT ); Thu, 12 Jan 2012 19:31:31 -0500 Message-ID: <4F0F7B60.5040701@gmail.com> Date: Thu, 12 Jan 2012 18:31:28 -0600 From: Rob Herring User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111124 Thunderbird/8.0 MIME-Version: 1.0 To: Grant Likely CC: linux-kernel@vger.kernel.org, Benjamin Herrenschmidt , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, Russell King , sfr@canb.auug.org.au, "linux-arm-kernel@lists.infradead.org" Subject: Re: [RFC 13/14] irq_domain: Remove 'new' irq_domain in favour of the ppc one References: <1326313337-24603-1-git-send-email-grant.likely@secretlab.ca> <1326313337-24603-14-git-send-email-grant.likely@secretlab.ca> <4F0DFC0F.2090005@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adding lakml... On 01/11/2012 03:27 PM, Grant Likely wrote: > On Wed, Jan 11, 2012 at 2:15 PM, Rob Herring wrote: >> Grant, >> >> On 01/11/2012 02:22 PM, Grant Likely wrote: >>> This patch removes the simplistic implementation of irq_domains and enables >>> the powerpc infrastructure for all irq_domain users. The powerpc >>> infrastructure includes support for complex mappings between Linux and >>> hardware irq numbers, and can manage allocation of irq_descs. >>> >>> This patch also converts the few users of irq_domain_add()/irq_domain_del() >>> to call irq_domain_add_legacy() instead. >> >> So what is the non-legacy way? Legacy implies we don't want to do it >> that way. I guess until we remove all non-DT platforms with GIC we are >> stuck with legacy. That seems like it could be a ways out until we get >> there. > > Non-legacy is letting the irq_domain manage the irq_desc allocations. > Some of the controllers will be easy to convert, some will be more > difficult. The primary thing that really blocks getting away from the > legacy method is anything that expects hardcoded #defined irq numbers. > The goal is to convert all users over to the linear revmap method. > So I gave this a spin on highbank. I ran into a couple problems. I had to revert "irqdesc: Consolidate irq reservation logic" which is in your branch, but not this series. irq_alloc_desc_from was returning -EEXIST. The GIC code did not work which I think is specific to using gic_of_init which makes irq_start = -1. With that it still doesn't work. It dies in gic_set_type... I've found one problem which I'll reply inline to, but I think this is a dead end path anyway. You have removed the irq_alloc_descs call from the GIC which is a step backwards. Several of the ARM DT enabled platforms are at the point they can fully support dynamic virq base for each irqchip. I changed the domain from legacy to linear and got things working. The issue with linear is for SPARSE_IRQ. The default behavior on ARM for SPARSE_IRQ is all nr_irqs are allocated at boot time before any controller is initialized. The only platform with a GIC and requiring SPARSE_IRQ is shmobile, but it is also the only one that calls irq_alloc_desc functions for it's interrupts. So I think we are okay there. The problem occurs when enabling SPARSE_IRQ for a non-DT platform with a GIC and with irqchips that don't call irq_alloc_desc for their irqs. IMHO, this should be an okay trade-off. There's no advantage to enabling SPARSE_IRQ on ARM for platforms that don't require it. All the platforms with a GIC have active work to convert to DT (except shmobile which I think is okay), so it's a temporary issue. Rob