On Wed, Sep 5, 2018 at 5:22 AM Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx> 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) 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
