From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] ARM: OMAP: irqs: Fix NR_IRQS value to handle PRCM interrupts Date: Tue, 28 Feb 2012 14:36:14 +0000 Message-ID: <20120228143614.GA5627@n2100.arm.linux.org.uk> References: <4F4CD231.4030709@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:33472 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932085Ab2B1Og1 (ORCPT ); Tue, 28 Feb 2012 09:36:27 -0500 Content-Disposition: inline In-Reply-To: <4F4CD231.4030709@ti.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: "Cousson, Benoit" Cc: tony Lindgren , linux-omap , "linux-arm-kernel@lists.infradead.org" , "Nayak, Rajendra" On Tue, Feb 28, 2012 at 02:10:09PM +0100, Cousson, Benoit wrote: > The following commit: 2f31b51659c2d8315ea2888ba5b93076febe672b > Author: Tero Kristo > Date: Fri Dec 16 14:37:00 2011 -0700 > > ARM: OMAP4: PRM: use PRCM interrupt handler > > introduced the PRCM interrupt handler and thus the need > for 64 more interrupts. Since SPARSE_IRQ is still not fully > functional on OMAP, the NR_IRQS needs to be updated to avoid > the failure that happen during irq_alloc_descs call inside > the PRCM driver: > > [ 0.208221] PRCM: failed to allocate irq descs: -12 > > Later the mux framework is then unable to request an IRQ from > the PRCM interrupt handler. > > [ 1.802795] mux: Failed to setup hwmod io irq -22 This is fine for rc, but longer term... Do any of these have hard-coded interrupt numbers associated with them? If not, just enabling sparse IRQ will sort this out. As I tried to explain yesterday, there are two modes for IRQ allocation: 1. Without sparse IRQ enabled, irq_alloc_descs(-1, from, num, -1) will allocate IRQs _within_ the existing from..NR_IRQS range, and will fail if there is insufficient IRQs available. 2. With sparse IRQs enabled, irq_alloc_descs(-1, from, num, -1) will allocate IRQs starting at max(from, NR_IRQS) and working upwards. In either case, irq_alloc_descs(start, 0, num, -1) will allocate 'num' IRQs at 'start' or fail if the range is already in use (and 0..NR_IRQS is defined as 'being in use' when sparse IRQs are enabled.) So, if the PRCM interrupts aren't statically assigned (the code suggests that they aren't) then it's already sparse-IRQ compliant, and enabling sparse IRQ support will mean that they will be allocated above NR_IRQS. Therefore, I suggest rather than raising NR_IRQS, you instead enable SPARSE_IRQ now so that anyone using the dynamic IRQ allocation can benefit from sparse IRQ support without having to have a large NR_IRQS. So, you don't have to wait until everything is converted to use sparse IRQ. You just need to make sure that nothing uses irq_alloc_descs(start, from, num, ...) where start < NR_IRQS, and nothing using that requires statically defined IRQ numbering.