Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757112AbcCRJy5 (ORCPT ); Fri, 18 Mar 2016 05:54:57 -0400 Received: from hqemgate16.nvidia.com ([216.228.121.65]:13725 "EHLO hqemgate16.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751924AbcCRJys (ORCPT ); Fri, 18 Mar 2016 05:54:48 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Fri, 18 Mar 2016 02:53:16 -0700 Subject: Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type fails To: Geert Uytterhoeven References: <1458224359-32665-1-git-send-email-jonathanh@nvidia.com> <1458224359-32665-5-git-send-email-jonathanh@nvidia.com> <56EAC761.1040801@nvidia.com> <20160317151800.GH1184@io.lakedaemon.net> <56EAD93B.7040105@nvidia.com> CC: Jason Cooper , Thomas Gleixner , Marc Zyngier , =?UTF-8?Q?Beno=c3=aet_Cousson?= , Tony Lindgren , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , "Kumar Gala" , Stephen Warren , "Thierry Reding" , Kevin Hilman , Grygorii Strashko , Lars-Peter Clausen , Linus Walleij , , "linux-omap@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , From: Jon Hunter Message-ID: <56EBD061.6030502@nvidia.com> Date: Fri, 18 Mar 2016 09:54:41 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.21.132.114] X-ClientProxiedBy: UKMAIL101.nvidia.com (10.26.138.13) To UKMAIL101.nvidia.com (10.26.138.13) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3652 Lines: 74 On 18/03/16 09:20, Geert Uytterhoeven wrote: > On Thu, Mar 17, 2016 at 5:20 PM, Jon Hunter wrote: >> On 17/03/16 15:18, Jason Cooper wrote: >>> On Thu, Mar 17, 2016 at 03:04:01PM +0000, Jon Hunter wrote: >>>> On 17/03/16 14:51, Thomas Gleixner wrote: >>>>> On Thu, 17 Mar 2016, Jon Hunter wrote: >>>>>> Setting the interrupt type for private peripheral interrupts (PPIs) may >>>>>> not be supported by a given GIC because it is IMPLEMENTATION DEFINED >>>>>> whether this is allowed. There is no way to know if setting the type is >>>>>> supported for a given GIC and so the value written is read back to >>>>>> verify it matches the desired configuration. If it does not match then >>>>>> an error is return. >>>>>> >>>>>> There are cases where the interrupt configuration read from firmware >>>>>> (such as a device-tree blob), has been incorrect and hence >>>>>> gic_configure_irq() has returned an error. This error has gone >>>>>> undetected because the error code returned was ignored but the interrupt >>>>>> still worked fine because the configuration for the interrupt could not >>>>>> be overwritten. >>>>>> >>>>>> Given that this has done undetected and we should only fail to set the >>>>>> type for PPIs whose configuration cannot be changed anyway, don't return >>>>>> an error and simply WARN if this fails. This will allows us to fix up any >>>>>> places in the kernel where we should be checking the return status and >>>>>> maintain back compatibility with firmware images that may have incorrect >>>>>> interrupt configurations. >>>>> >>>>> Though silently returning 0 is really the wrong thing to do. You can add the >>>>> warn, but why do you want to return success? >>>> >>>> Yes that would be the correct thing to do I agree. However, the problem >>>> is that if we do this, then after the patch "irqdomain: Don't set type >>>> when mapping an IRQ" is applied, we may break interrupts for some >>>> existing device-tree binaries that have bad configuration (such as omap4 >>>> and tegra20/30 ... see patches 1 and 2) that have gone unnoticed. So it >>>> is a back compatibility issue. > > Indeed (also for sh73a0 and r8a7779). Thanks. I was wondering if there are others. Do you know what the correct setting should be? Ie. should it be IRQ_TYPE_EDGE_RISING as well? I can then include this with OMAP and Tegra. >>> This sounds like a textbook case for adding a boolean dt property. If >>> "can-set-ppi-type" is absent (old DT blobs and new blobs without the >>> ability), warn and return zero. If it's present, the driver can set the >>> type, returning errors as encountered. >> >> True. However, if we did have this "can-set-ppi-type" property set for a >> device, it really should never fail (unless someone specified it >> incorrectly). So I am trying to understand the value in adding a new DT >> property. > > Do we really want to add properties that basically indicate that a description > in DT is correct? > > Alternatively, it can be fixed in the kernel in a DT quirk (if SoC == xxx then > fix TWD). I am not sure I fully understand your proposal, but please note that it may not be just limited to the TWD (although this does appear to be the one client that is wrong for a lot of SoCs). PPIs are also used for the armv7/8 timers as well. The problem is that we have a lot of SoCs with twd-timers and I have no way to test all of these to know which could be a problem. So I thought that warning would be a good first step to fixing them. However, I am still trying to see the real value in returning an error in this case. May be I am the only one with that perspective? Cheers Jon