From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753225AbdHGMaF (ORCPT ); Mon, 7 Aug 2017 08:30:05 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:36211 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752156AbdHGMaD (ORCPT ); Mon, 7 Aug 2017 08:30:03 -0400 MIME-Version: 1.0 In-Reply-To: References: <1499333825-7658-1-git-send-email-vivek.gautam@codeaurora.org> <1499333825-7658-4-git-send-email-vivek.gautam@codeaurora.org> <20170712225459.GZ22780@codeaurora.org> <5ee0bacd-e557-a6c4-a897-844fb12ea6ae@codeaurora.org> <4dbc938c-ac88-9bd4-cf00-458008ae24c1@codeaurora.org> From: Rob Clark Date: Mon, 7 Aug 2017 08:29:59 -0400 Message-ID: Subject: Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device To: Vivek Gautam Cc: Robin Murphy , Sricharan R , Stephen Boyd , Joerg Roedel , Rob Herring , Mark Rutland , Will Deacon , Marek Szyprowski , "iommu@lists.linux-foundation.org" , "devicetree@vger.kernel.org" , Linux Kernel Mailing List , linux-clk , linux-arm-msm , Stanimir Varbanov , Archit Taneja , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 7, 2017 at 4:27 AM, Vivek Gautam wrote: > On Thu, Jul 13, 2017 at 5:20 PM, Rob Clark wrote: >> On Thu, Jul 13, 2017 at 1:35 AM, Sricharan R wrote: >>> Hi Vivek, >>> >>> On 7/13/2017 10:43 AM, Vivek Gautam wrote: >>>> Hi Stephen, >>>> >>>> >>>> On 07/13/2017 04:24 AM, Stephen Boyd wrote: >>>>> On 07/06, Vivek Gautam wrote: >>>>>> @@ -1231,12 +1237,18 @@ static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova, >>>>>> static size_t arm_smmu_unmap(struct iommu_domain *domain, unsigned long iova, >>>>>> size_t size) >>>>>> { >>>>>> - struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops; >>>>>> + struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); >>>>>> + struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops; >>>>>> + size_t ret; >>>>>> if (!ops) >>>>>> return 0; >>>>>> - return ops->unmap(ops, iova, size); >>>>>> + pm_runtime_get_sync(smmu_domain->smmu->dev); >>>>> Can these map/unmap ops be called from an atomic context? I seem >>>>> to recall that being a problem before. >>>> >>>> That's something which was dropped in the following patch merged in master: >>>> 523d7423e21b iommu/arm-smmu: Remove io-pgtable spinlock >>>> >>>> Looks like we don't need locks here anymore? >>> >>> Apart from the locking, wonder why a explicit pm_runtime is needed >>> from unmap. Somehow looks like some path in the master using that >>> should have enabled the pm ? >>> >> >> Yes, there are a bunch of scenarios where unmap can happen with >> disabled master (but not in atomic context). > > I would like to understand whether there is a situation where an unmap is > called in atomic context without an enabled master? > > Let's say we have the case where all the unmap calls in atomic context happen > only from the master's context (in which case the device link should > take care of > the pm state of smmu), and the only unmap that happen in non-atomic context > is the one with master disabled. In such a case doesn it make sense to > distinguish > the atomic/non-atomic context and add pm_runtime_get_sync()/put_sync() only > for the non-atomic context since that would be the one with master disabled. > At least drm/msm needs to hold obj->lock (a mutex) in unmap, so it won't unmap anything in atomic ctx (but it can unmap w/ master disabled). I can't really comment about other non-gpu drivers. It seems like a reasonable constraint that either master is enabled or not in atomic ctx. Currently we actually wrap unmap w/ pm_runtime_get/put_sync(), but I'd like to drop that to avoid powering up the gpu. BR, -R