On Thu, Aug 13, 2020 at 07:40:55PM -0700, Rob Clark wrote:

From: Rob Clark <redacted>

NOTE: Since Jordan was out today, and I wanted to keep things moving on
      this, I took the liberty of respinning his series (originally
      titled "iommu/arm-smmu: Add Adreno SMMU specific implementation")
      with updates based on Will's review comments, and some fixes and
      extra bits that I found in stress testing the series.  Original
      commit msg and updated version history below.

      In general I like the private interface between adreno-smmu and
      the GPU driver.  It should make for a more straightforward way
      to extend things to optimize TLB invalidation in the future, for
      example, rather than shoe-horning everything thru domain attrs.
      And it lets us describe the get_ttbr1_cfg/set_ttrb0_cfg dance
      more clearly.  Although it is going to make landing this via
      iommu vs drm tree a bit more difficult.  Maybe there are some
      arm-smmu parts of this series that could be pulled out to make
      it not conflicty to land the private interface and adreno-smmu
      bits via the drm tree?  (But I'm jumping a bit ahead here.  Just
      wanted to point out that issue.)

      The complete series can be found at:
      https://gitlab.freedesktop.org/drm/msm/-/commits/msm-next-pgtables

This series adds an Adreno SMMU implementation to arm-smmu to allow GPU hardware
pagetable switching.

The Adreno GPU has built in capabilities to switch the TTBR0 pagetable during
runtime to allow each individual instance or application to have its own
pagetable.  In order to take advantage of the HW capabilities there are certain
requirements needed of the SMMU hardware.

This series adds support for an Adreno specific arm-smmu implementation. The new
implementation 1) ensures that the GPU domain is always assigned context bank 0,
2) enables split pagetable support (TTBR1) so that the instance specific
pagetable can be swapped while the global memory remains in place and 3) shares
the current pagetable configuration with the GPU driver to allow it to create
its own io-pgtable instances.

The series then adds the drm/msm code to enable these features. For targets that
support it allocate new pagetables using the io-pgtable configuration shared by
the arm-smmu driver and swap them in during runtime.

This version of the series merges the previous patchset(s) [1] and [2]
with the following improvements:

v13: (Respin by Rob)
  - Switch to a private interface between adreno-smmu and GPU driver,
    dropping the custom domain attr (Will Deacon)
  - Rework the SCTLR.HUPCF patch to add new fields in smmu_domain->cfg
    rather than adding new impl hook (Will Deacon)
  - Drop for_each_cfg_sme() in favor of plain for() loop (Will Deacon)
  - Fix context refcnt'ing issue which was causing problems with GPU
    crash recover stress testing.
  - Spiff up $debugfs/gem to show process information associated with
    VMAs

I'll add the tags to Rob's code but in general I ack all these changes. I also 
like the private interface - it gives us the most flexibility without either
changing the IOMMU API or giving up entirely and making an internal SMMU
implementation inside drm/msm.

<snip>

Jordan

-- 
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