Subject: [PATCH v7 0/6] iommu/arm-smmu: Enable split pagetable support

From: Jordan Crouse <[email-masked]>
Date: Thu, 4 Jun 2020 14:57:04 -0600

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(-)

-- 
2.17.1

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