From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Clark Subject: Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Date: Thu, 13 Jul 2017 07:50:31 -0400 Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4dbc938c-ac88-9bd4-cf00-458008ae24c1-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Sricharan R Cc: Mark Rutland , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Will Deacon , Stephen Boyd , Linux Kernel Mailing List , Stanimir Varbanov , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Rob Herring , Vivek Gautam , linux-arm-msm , linux-clk , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: linux-arm-msm@vger.kernel.org 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(). BR, -R From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752428AbdGMLus (ORCPT ); Thu, 13 Jul 2017 07:50:48 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:35719 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751935AbdGMLuo (ORCPT ); Thu, 13 Jul 2017 07:50:44 -0400 MIME-Version: 1.0 In-Reply-To: <4dbc938c-ac88-9bd4-cf00-458008ae24c1@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> From: Rob Clark Date: Thu, 13 Jul 2017 07:50:31 -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 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(). BR, -R From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 In-Reply-To: <4dbc938c-ac88-9bd4-cf00-458008ae24c1@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> From: Rob Clark Date: Thu, 13 Jul 2017 07:50:31 -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: 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(). BR, -R From mboxrd@z Thu Jan 1 00:00:00 1970 From: robdclark@gmail.com (Rob Clark) Date: Thu, 13 Jul 2017 07:50:31 -0400 Subject: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device In-Reply-To: <4dbc938c-ac88-9bd4-cf00-458008ae24c1@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> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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(). BR, -R