From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 153FBC46470 for ; Tue, 7 Aug 2018 14:25:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CD4872174B for ; Tue, 7 Aug 2018 14:25:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CD4872174B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389532AbeHGQka (ORCPT ); Tue, 7 Aug 2018 12:40:30 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:55088 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732639AbeHGQka (ORCPT ); Tue, 7 Aug 2018 12:40:30 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 325FA7A9; Tue, 7 Aug 2018 07:25:56 -0700 (PDT) Received: from [10.4.13.119] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ECB783F5B3; Tue, 7 Aug 2018 07:25:54 -0700 (PDT) Subject: Re: [PATCH 1/2] iommu/rockchip: Handle errors returned from PM framework To: Heiko Stuebner Cc: linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Joerg Roedel , Jeffy Chen References: <20180807085406.3863-1-marc.zyngier@arm.com> <2940317.dDZy1L4CDY@phil> <94b6aab1-e8d3-6929-a2e6-2f06c564bc70@arm.com> <3265383.PcPThIO4HC@phil> From: Marc Zyngier Organization: ARM Ltd Message-ID: <5aa8d184-0c58-3471-a661-8a66a93271c7@arm.com> Date: Tue, 7 Aug 2018 15:25:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <3265383.PcPThIO4HC@phil> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/08/18 14:15, Heiko Stuebner wrote: > Am Dienstag, 7. August 2018, 14:31:49 CEST schrieb Marc Zyngier: >> On 07/08/18 13:09, Heiko Stuebner wrote: >>> Hi Marc, >>> >>> Am Dienstag, 7. August 2018, 10:54:05 CEST schrieb Marc Zyngier: >>>> pm_runtime_get_if_in_use can fail: either PM has been disabled >>>> altogether (-EINVAL), or the device hasn't been enabled yet (0). >>>> Sadly, the Rockchip IOMMU driver tends to conflate the two things >>>> by considering a non-zero return value as successful. >>>> >>>> This has the consequence of hiding other bugs, so let's handle this >>>> case throughout the driver, with a WARN_ON_ONCE so that we can try >>>> and work out what happened. >>>> >>>> Fixes: 0f181d3cf7d98 ("iommu/rockchip: Add runtime PM support") >>>> Signed-off-by: Marc Zyngier >>> >>> I'm still not sure about the !CONFIG_PM case, as it was probably silently >>> working in that case before >> >> Do we agree that this is an orthogonal problem though? > > Nope ;-) .... I.e. right now the code ignores the -EINVAL from disabled PM > and continues, possibly even handling the irq correctly. Ah, I now see what you mean. Yeah, this is a bit rubbish. It would have been better if the API returned something more sensible in that case, but that's a bit late... > If it actually worked is a different matter, as I guess nobody really tried > with !PM in the past. I don't think anyone noticed. !CONFIG_PM on something like rk3399 probably isn't very popular, and certainly comes for free on a multiplatform kernel. > Now with error-handling we always return IRQ_NONE for !PM. Yup. >>> But on the other hand we're also already running over it in other places >>> like in the iommu-shutdown and I guess if someone _really_ disabled >>> CONFIG_PM, a lot of additional stuff would fail anyway. >>> >>> So should we wrap that in some #ifdef magic, just ignore it or simply >>> select PM similar to what Tegra, Renesas and Vexpress seem to do? >>> >>> I guess I like the 3rd option best ;-) >> >> It probably doesn't hurt. At what level do you want it? As a dependency >> to the IOMMU? or to the platform? > > I guess it might be best to go the Tegra, etc way. Whoever in their right > mind would want to drive a mobile platform without any form for power > management ;-) . > > I can do these patches for arm32+arm64 myself ... I just wanted to put > that thought out there - in case that was just a stupid idea of mine :-D . Not stupid at all. Regarding this very patch: where do you want me to take it? M. -- Jazz is not dead. It just smells funny...