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

From: Thierry Reding <thierry.reding@gmail.com>
To: Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Joerg Roedel <joro@8bytes.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: Jon Hunter <jonathanh@nvidia.com>,
	Nicolin Chen <nicolinc@nvidia.com>,
	Krishna Reddy <vdumpa@nvidia.com>,
	linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 00/10] arm64: tegra: Prevent early SMMU faults
Date: Fri, 28 May 2021 19:05:28 +0200	[thread overview]
Message-ID: <YLEi2FonP568wYrE@orome.fritz.box> (raw)
In-Reply-To: <20210420172619.3782831-1-thierry.reding@gmail.com>

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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.

Thanks,
Thierry

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