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