Re: [PATCH v2 00/10] arm64: tegra: Prevent early SMMU faults

[Thierry Reding <thierry.reding@gmail.com>]

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On Tue, Jun 01, 2021 at 01:26:46PM +0100, Will Deacon wrote:
> On Fri, May 28, 2021 at 07:05:28PM +0200, Thierry Reding wrote:
> > On Tue, Apr 20, 2021 at 07:26:09PM +0200, Thierry Reding wrote:
> > > From: Thierry Reding <treding@nvidia.com>
> > > 
> > > Hi,
> > > 
> > > this is a set of patches that is the result of earlier discussions
> > > regarding early identity mappings that are needed to avoid SMMU faults
> > > during early boot.
> > > 
> > > The goal here is to avoid early identity mappings altogether and instead
> > > postpone the need for the identity mappings to when devices are attached
> > > to the SMMU. This works by making the SMMU driver coordinate with the
> > > memory controller driver on when to start enforcing SMMU translations.
> > > This makes Tegra behave in a more standard way and pushes the code to
> > > deal with the Tegra-specific programming into the NVIDIA SMMU
> > > implementation.
> > > 
> > > Compared to the original version of these patches, I've split the
> > > preparatory work into a separate patch series because it became very
> > > large and will be mostly uninteresting for this audience.
> > > 
> > > Patch 1 provides a mechanism to program SID overrides at runtime. Patch
> > > 2 updates the ARM SMMU device tree bindings to include the Tegra186
> > > compatible string as suggested by Robin during review.
> > > 
> > > Patches 3 and 4 create the fundamentals in the SMMU driver to support
> > > this and also make this functionality available on Tegra186. Patch 5
> > > hooks the ARM SMMU up to the memory controller so that the memory client
> > > stream ID overrides can be programmed at the right time.
> > > 
> > > Patch 6 extends this mechanism to Tegra186 and patches 7-9 enable all of
> > > this through device tree updates. Patch 10 is included here to show how
> > > SMMU will be enabled for display controllers. However, it cannot be
> > > applied yet because the code to create identity mappings for potentially
> > > live framebuffers hasn't been merged yet.
> > > 
> > > The end result is that various peripherals will have SMMU enabled, while
> > > the display controllers will keep using passthrough, as initially set up
> > > by firmware. Once the device tree bindings have been accepted and the
> > > SMMU driver has been updated to create identity mappings for the display
> > > controllers, they can be hooked up to the SMMU and the code in this
> > > series will automatically program the SID overrides to enable SMMU
> > > translations at the right time.
> > > 
> > > Note that the series creates a compile time dependency between the
> > > memory controller and IOMMU trees. If it helps I can provide a branch
> > > for each tree, modelling the dependency, once the series has been
> > > reviewed.
> > > 
> > > Changes in v2:
> > > - split off the preparatory work into a separate series (that needs to
> > >   be applied first)
> > > - address review comments by Robin
> > > 
> > > Thierry
> > > 
> > > Thierry Reding (10):
> > >   memory: tegra: Implement SID override programming
> > >   dt-bindings: arm-smmu: Add Tegra186 compatible string
> > >   iommu/arm-smmu: Implement ->probe_finalize()
> > >   iommu/arm-smmu: tegra: Detect number of instances at runtime
> > >   iommu/arm-smmu: tegra: Implement SID override programming
> > >   iommu/arm-smmu: Use Tegra implementation on Tegra186
> > >   arm64: tegra: Use correct compatible string for Tegra186 SMMU
> > >   arm64: tegra: Hook up memory controller to SMMU on Tegra186
> > >   arm64: tegra: Enable SMMU support on Tegra194
> > >   arm64: tegra: Enable SMMU support for display on Tegra194
> > > 
> > >  .../devicetree/bindings/iommu/arm,smmu.yaml   |  11 +-
> > >  arch/arm64/boot/dts/nvidia/tegra186.dtsi      |   4 +-
> > >  arch/arm64/boot/dts/nvidia/tegra194.dtsi      | 166 ++++++++++++++++++
> > >  drivers/iommu/arm/arm-smmu/arm-smmu-impl.c    |   3 +-
> > >  drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c  |  90 ++++++++--
> > >  drivers/iommu/arm/arm-smmu/arm-smmu.c         |  13 ++
> > >  drivers/iommu/arm/arm-smmu/arm-smmu.h         |   1 +
> > >  drivers/memory/tegra/mc.c                     |   9 +
> > >  drivers/memory/tegra/tegra186.c               |  72 ++++++++
> > >  include/soc/tegra/mc.h                        |   3 +
> > >  10 files changed, 349 insertions(+), 23 deletions(-)
> > 
> > Will, Robin,
> > 
> > do you have any more comments on the ARM SMMU bits of this series? If
> > not, can you guys provide an Acked-by so that Krzysztof can pick this
> > (modulo the DT patches) up into the memory-controller tree for v5.14?
> > 
> > I'll send out a v3 with the bisectibilitiy fix that Krishna pointed
> > out.
> 
> Probably best if I queue 3-6 on a separate branch once you send a v3,
> then Krzysztof can pull that in if he needs it.

Patch 5 has a build-time dependency on patch 1, so they need to go in
together. The reason why I suggested Krzysztof pick these up is because
there is a restructuring series that this depends on, which will go into
Krzysztof's tree. So in order to pull in 3-6, you'd get a bunch of other
and mostly unrelated stuff as well.

Alternatively I can set this all up on stable branches and send out pull
requests for both you and Krzysztof to merge. Or if this is all too
complicated and you'd just prefer to ack the patches I could also take
this through ARM SoC via the Tegra tree.

Thierry

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