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

[Will Deacon]

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 at 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.

Will