On Wed, Aug 07, 2019 at 04:21:38PM -0600, Jordan Crouse wrote: > (Sigh, resend. I freaked out my SMTP server) > > This is part of an ongoing evolution for enabling split pagetable support for > arm-smmu. Previous versions can be found [1]. > > In the discussion for v2 Robin pointed out that this is a very Adreno specific > use case and that is exactly true. Not only do we want to configure and use a > pagetable in the TTBR1 space, we also want to configure the TTBR0 region but > not allocate a pagetable for it or touch it until the GPU hardware does so. As > much as I want it to be a generic concept it really isn't. > > This revision leans into that idea. Most of the same io-pgtable code is there > but now it is wrapped as an Adreno GPU specific format that is selected by the > compatible string in the arm-smmu device. > > Additionally, per Robin's suggestion we are skipping creating a TTBR0 pagetable > to save on wasted memory. > > This isn't as clean as I would like it to be but I think that this is a better > direction than trying to pretend that the generic format would work. > > I'm tempting fate by posting this and then taking some time off, but I wanted > to try to kick off a conversation or at least get some flames so I can try to > refine this again next week. Please take a look and give some advice on the > direction. Will, Robin - Modulo the impl changes from Robin, do you think that using a dedicated pagetable format is the right approach for supporting split pagetables for the Adreno GPU? If so, then is adding the changes to io-pgtable-arm.c possible for 5.4 and then add the implementation specific code on top of Robin's stack later or do you feel they should come as part of a package deal? Jordan > Jordan Crouse (2): > iommu/io-pgtable-arm: Add support for ARM_ADRENO_GPU_LPAE io-pgtable > format > iommu/arm-smmu: Add support for Adreno GPU pagetable formats > > drivers/iommu/arm-smmu.c | 8 +- > drivers/iommu/io-pgtable-arm.c | 214 ++++++++++++++++++++++++++++++++++++++--- > drivers/iommu/io-pgtable.c | 1 + > include/linux/io-pgtable.h | 2 + > 4 files changed, 209 insertions(+), 16 deletions(-) > > -- > 2.7.4 > > _______________________________________________ > Freedreno mailing list > Freedreno@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/freedreno -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
