[PATCH 1/3] iommu/io-pgtable-arm: Support coherency for Mali LPAE

Will Deacon will at kernel.org
Mon Sep 21 13:57:19 EDT 2020

On Wed, Sep 16, 2020 at 12:51:05AM +0100, Robin Murphy wrote:
> Midgard GPUs have ACE-Lite master interfaces which allows systems to
> integrate them in an I/O-coherent manner. It seems that from the GPU's
> viewpoint, the rest of the system is its outer shareable domain, and so
> even when snoop signals are wired up, they are only emitted for outer
> shareable accesses. As such, setting the TTBR_SHARE_OUTER bit does
> indeed get coherent pagetable walks working nicely for the coherent
> T620 in the Arm Juno SoC.

I can't help but think some of this commentary deserves to be in the code
as well.

Do you know if this sort of thing is done for other SoCs too, or is this
just a Juno quirk?


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