Messages in this thread | | | Date | Fri, 03 Jul 2020 22:29:16 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCHv3 7/7] drm/msm/a6xx: Add support for using system cache(LLC) |
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On 2020-07-03 21:34, Rob Clark wrote: > On Fri, Jul 3, 2020 at 7:53 AM Sai Prakash Ranjan > <saiprakash.ranjan@codeaurora.org> wrote: >> >> Hi Will, >> >> 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? > > It does appear that the downstream kgsl driver sets this for basically > all mappings.. well there is some conditional stuff around > DOMAIN_ATTR_USE_LLC_NWA but it seems based on the property of the > domain. (Jordan may know more about what that is about.) But looks > like there are a lot of different paths into iommu_map in kgsl so I > might have missed something. > > Assuming there isn't some case where we specifically don't want to use > the system cache for some mapping, I think it could be a domain > attribute that sets an io_pgtable_cfg::quirks flag >
Ok then we are good to remove unused sys cache prot flag which Will has posted.
Thanks, Sai
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