Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752344AbdGMOzR (ORCPT ); Thu, 13 Jul 2017 10:55:17 -0400 Received: from mail-lf0-f67.google.com ([209.85.215.67]:33068 "EHLO mail-lf0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751267AbdGMOzN (ORCPT ); Thu, 13 Jul 2017 10:55:13 -0400 MIME-Version: 1.0 In-Reply-To: <60a56ae6-ed9d-57cd-130f-5bd9d32d4d58@codeaurora.org> 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> <60a56ae6-ed9d-57cd-130f-5bd9d32d4d58@codeaurora.org> From: Rob Clark Date: Thu, 13 Jul 2017 10:55:10 -0400 Message-ID: Subject: Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device To: Sricharan R Cc: Vivek Gautam , Stephen Boyd , Joerg Roedel , Robin Murphy , 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 Content-Length: 2842 Lines: 66 On Thu, Jul 13, 2017 at 9:53 AM, Sricharan R wrote: > Hi, > > On 7/13/2017 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). On the gpu side we >> opportunistically keep a buffer mapping until the buffer is freed >> (which can happen after gpu is disabled). Likewise, v4l2 won't unmap >> an exported dmabuf while some other driver holds a reference to it >> (which can be dropped when the v4l2 device is suspended). >> >> Since unmap triggers tbl flush which touches iommu regs, the iommu >> driver *definitely* needs a pm_runtime_get_sync(). > > Ok, with that being the case, there are two things here, > > 1) If the device links are still intact at these places where unmap is called, > then pm_runtime from the master would setup the all the clocks. That would > avoid reintroducing the locking indirectly here. > > 2) If not, then doing it here is the only way. But for both cases, since > the unmap can be called from atomic context, resume handler here should > avoid doing clk_prepare_enable , instead move the clk_prepare to the init. > I do kinda like the approach Marek suggested.. of deferring the tlb flush until resume. I'm wondering if we could combine that with putting the mmu in a stalled state when we suspend (and not resume the mmu until after the pending tlb flush)? BR, -R