On Fri, Jul 03, 2020 at 08:23:07PM +0530, Sai Prakash Ranjan wrote: > On 2020-07-03 19:07, Will Deacon wrote: > > On Mon, Jun 29, 2020 at 09:22:50PM +0530, Sai Prakash Ranjan wrote: > > > diff --git a/drivers/gpu/drm/msm/msm_iommu.c > > > b/drivers/gpu/drm/msm/msm_iommu.c > > > index f455c597f76d..bd1d58229cc2 100644 > > > --- a/drivers/gpu/drm/msm/msm_iommu.c > > > +++ b/drivers/gpu/drm/msm/msm_iommu.c > > > @@ -218,6 +218,9 @@ static int msm_iommu_map(struct msm_mmu *mmu, > > > uint64_t iova, > > > iova |= GENMASK_ULL(63, 49); > > > > > > > > > + if (mmu->features & MMU_FEATURE_USE_SYSTEM_CACHE) > > > + prot |= IOMMU_SYS_CACHE_ONLY; > > > > Given that I think this is the only user of IOMMU_SYS_CACHE_ONLY, then > > it > > looks like it should actually be a property on the domain because we > > never > > need to configure it on a per-mapping basis within a domain, and > > therefore > > it shouldn't be exposed by the IOMMU API as a prot flag. > > > > Do you agree? > > > > GPU being the only user is for now, but there are other clients which can > use this. > Plus how do we set the memory attributes if we do not expose this as prot > flag? I just don't understand the need for it to be per-map operation. Put another way, if we extended the domain attribute to apply to cacheable mappings on the domain and not just the table walk, what would break? Will
