Another iteration of the split-pagetable support for arm-smmu and the Adreno GPU SMMU. After email discussions [1] we opted to make a arm-smmu implementation for specifically for the Adreno GPU and use that to enable split pagetable support and later other implementation specific bits that we need.
On the hardware side this is very close to the same code from before [2] only the TTBR1 quirk is turned on by the implementation and not a domain attribute. In drm/msm we use the returned size of the aperture as a clue to let us know which virtual address space we should use for global memory objects.
There are two open items that you should be aware of. First, in the implementation specific code we have to check the compatible string of the device so that we only enable TTBR1 for the GPU (SID 0) and not the GMU (SID 4). I went back and forth trying to decide if I wanted to use the compatbile string or the SID as the filter and settled on the compatible string but I could be talked out of it.
The other open item is that in drm/msm the hardware only uses 49 bits of the address space but arm-smmu expects the address to be sign extended all the way to 64 bits. This isn't a problem normally unless you look at the hardware registers that contain a IOVA and then the upper bits will be zero. I opted to restrict the internal drm/msm IOVA range to only 49 bits and then sign extend right before calling iommu_map / iommu_unmap. This is a bit wonky but I thought that matching the hardware would be less confusing when debugging a hang.
[1] https://lists.linuxfoundation.org/pipermail/iommu/2020-May/044537.html [2] https://patchwork.kernel.org/patch/11482591/
Jordan Crouse (6): iommu/arm-smmu: Pass io-pgtable config to implementation specific function iommu/arm-smmu: Add support for split pagetables dt-bindings: arm-smmu: Add compatible string for Adreno GPU SMMU iommu/arm-smmu: Add implementation for the adreno GPU SMMU drm/msm: Set the global virtual address range from the IOMMU domain arm6: dts: qcom: sm845: Set the compatible string for the GPU SMMU
.../devicetree/bindings/iommu/arm,smmu.yaml | 4 ++ arch/arm64/boot/dts/qcom/sdm845.dtsi | 2 +- drivers/gpu/drm/msm/adreno/adreno_gpu.c | 13 ++++++- drivers/gpu/drm/msm/msm_iommu.c | 7 ++++ drivers/iommu/arm-smmu-impl.c | 6 ++- drivers/iommu/arm-smmu-qcom.c | 38 ++++++++++++++++++- drivers/iommu/arm-smmu.c | 32 +++++++++++----- drivers/iommu/arm-smmu.h | 29 ++++++++++---- 8 files changed, 108 insertions(+), 23 deletions(-)