Users of IOMMU_QCOM_SYS_CACHE?

Will Deacon will at kernel.org
Thu Oct 24 10:51:51 UTC 2019


Hi all,

In commit 90ec7a76cc4b ("iommu/io-pgtable-arm: Add support to use system
cache") we added support for IOMMU_QCOM_SYS_CACHE which was merged into 5.3.
This allows non-coherent devices to request an outer cacheable memory
type.... except that nobody actually does this in mainline. I remember there
being a potential DRM user but I don't know what happened to it.

Given that this isn't actually exposed in the DMA API, I worry that we're
just carrying part of an out-of-tree hack here and propose that we drop
the flag altogether unless we get an upstream user, preferably by plumbing
this into the DMA API via a new attribute.

Thoughts?

Will


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