From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753974AbcGFI7L (ORCPT ); Wed, 6 Jul 2016 04:59:11 -0400 Received: from foss.arm.com ([217.140.101.70]:56698 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752568AbcGFI7D (ORCPT ); Wed, 6 Jul 2016 04:59:03 -0400 Subject: Re: [RFC PATCH v1] irqchip: add support for SMP irq router To: Thomas Gleixner References: <577542D1.4070307@laposte.net> <577A5260.3070001@free.fr> <577BA854.6090503@laposte.net> <20160705144151.GE3348@io.lakedaemon.net> <577BCFD2.8060203@laposte.net> <20160705155306.GG3348@io.lakedaemon.net> <577BE288.70200@laposte.net> <577BE4D8.2040601@arm.com> <577BE75B.4070109@laposte.net> <577BEABE.2010204@arm.com> Cc: Sebastian Frias , Jason Cooper , Mason , LKML From: Marc Zyngier X-Enigmail-Draft-Status: N1110 Organization: ARM Ltd Message-ID: <577CC83E.5080203@arm.com> Date: Wed, 6 Jul 2016 09:58:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/07/16 20:24, Thomas Gleixner wrote: > On Tue, 5 Jul 2016, Marc Zyngier wrote: >> On 05/07/16 17:59, Sebastian Frias wrote: >>> Well, if you the domains should not be described in the DT and that they should >>> be somehow hardcoded into the drivers' code, it should not be hard indeed. >> >> Hardcoded? No way. You simply implement a route allocator in your >> driver, assigning them as needed. And yes, if you have more than 24 >> interrupts, they get muxed. > > There is one caveat though. Under some circumstances (think RT) you want to > configure which interrupts get muxed and which not. We really should have that > option, but yes for anything which has less than 24 autorouting is the way to > go. Good point. I can see two possibilities for that: - either we describe this DT with some form of hint, indicating what are the inputs that can be muxed to a single output. Easy, but the DT guys are going to throw rocks at me for being Linux-specific. - or we have a way to express QoS in the irq subsystem, and a driver can request an interrupt with a "make it fast" flag. Of course, everybody and his dog are going to ask for it, and we're back to square one. Do we have a way to detect which interrupt is more likely to be sensitive to muxing? My hunch is that if it is requested with IRQF_SHARED, then it is effectively muxable. Thoughts? Thanks, M. -- Jazz is not dead. It just smells funny...