From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755901AbdKNSae (ORCPT ); Tue, 14 Nov 2017 13:30:34 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:42320 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753132AbdKNSaZ (ORCPT ); Tue, 14 Nov 2017 13:30:25 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org F0EAA60818 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=vivek.gautam@codeaurora.org X-Google-Smtp-Source: AGs4zMYs8SQIL6Jzl3dVSzmHRFgjK0t0e/QoI35Yby0sPZsdfdC5S3gWwYiwOCtHlaA7a8rrMhFPhEbEk7YlHOM8xjg= 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: Vivek Gautam Date: Wed, 15 Nov 2017 00:00:21 +0530 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device To: Rob Clark , Robin Murphy , Will Deacon , "Rafael J. Wysocki" Cc: Sricharan R , Stephen Boyd , Joerg Roedel , Rob Herring , Mark Rutland , 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 Hi, On Mon, Aug 7, 2017 at 5:59 PM, Rob Clark wrote: > 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. Since the deferring the TLB maintenance doesn't look like the best approach [1], how about if we try to power-up only the smmu from different client devices such as, GPU in the unmap path. Then we won't need to add pm_runtime_get/put() calls in arm_smmu_unmap(). The client device can use something like - pm_runtime_get_supplier() since we already have the device link in place with this patch series. This should power-on the supplier (which is smmu) without turning on the consumer (such as GPU). pm_runtime_get_supplier() however is not exported at this moment. Will it be useful to export this API and use it in the drivers. Adding Rafael J. Wysocki for suggestions on pm_runtime_get_suppliers() API. [1] https://patchwork.kernel.org/patch/9876489/ Best regards Vivek > > BR, > -R > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation