From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vivek Gautam Subject: Re: [PATCH 0/5] Qcom smmu-500 TLB invalidation errata for sdm845 Date: Wed, 5 Sep 2018 16:55:22 +0530 Message-ID: <3ac669af-a68e-874f-4c3e-91a2e9f676af@codeaurora.org> References: <20180814105528.20592-1-vivek.gautam@codeaurora.org> <20180814114009.GF28664@arm.com> <3f74124c-b09f-a92d-117d-a747d33a4561@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US 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: Rob Clark Cc: Mark Rutland , linux-arm-msm , Will Deacon , Linux Kernel Mailing List , Stephen Boyd , Bjorn Andersson , David Brown , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Andy Gross , Robin Murphy , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" List-Id: linux-arm-msm@vger.kernel.org On 9/5/2018 3:34 PM, Rob Clark wrote: > On Wed, Sep 5, 2018 at 5:22 AM Vivek Gautam wrote: >> >> On 8/14/2018 5:54 PM, Vivek Gautam wrote: >>> Hi Will, >>> >>> >>> On 8/14/2018 5:10 PM, Will Deacon wrote: >>>> Hi Vivek, >>>> >>>> On Tue, Aug 14, 2018 at 04:25:23PM +0530, Vivek Gautam wrote: >>>>> Qcom's implementation of arm,mmu-500 on sdm845 has a >>>>> functional/performance >>>>> errata [1] because of which the TCU cache look ups are stalled during >>>>> invalidation cycle. This is mitigated by serializing all the >>>>> invalidation >>>>> requests coming to the smmu. >>>> How does this implementation differ from the one supported by >>>> qcom_iommu.c? >>>> I notice you're adding firmware hooks here, which we avoided by >>>> having the >>>> extra driver. Please help me understand which devices exist, how they >>>> differ, and which drivers are intended to support them! >>> IIRC, the qcom_iommu driver was intended to support the static context >>> bank - SID >>> mapping, and is very specific to the smmu-v2 version present on >>> msm8916 soc. >>> However, this is the qcom's mmu-500 implementation specific errata. >>> qcom_iommu >>> will not be able to support mmu-500 configurations. >>> Rob Clark can add more. >>> Let you know what you suggest. >> Rob, can you please comment about how qcom-smmu driver has different >> implementation >> from arm-smmu driver? > sorry, I missed this thread earlier. But yeah, as you mentioned, the > purpose for qcom_iommu.c was to deal with the static context/SID > mapping. > > (I guess it is all just software, and we could make qcom_iommu.c > support dynamic mapping as well, but I think then it starts to > duplicate most of arm_smmu.c, so that doesn't seem like the right > direction) Thanks Rob for the response. I will wait for Will's response on how would he like this support be implemented. Best regards Vivek > > BR, > -R > >> Will, in case we would want to use arm-smmu driver, what would you >> suggest for >> having the firmware hooks? >> Thanks. >> >> Best regards >> Vivek