As discussed in the Qcom system cache support thread [1], it is imperative that we enable the support for non-cacheable page tables for SMMU implementations for which removing snoop latency on walks by making mappings as non-cacheable, outweighs the cost of cache maintenance on PTE updates.
This series adds a new SMMU device tree option to let the particular SMMU configuration setup cacheable or non-cacheable mappings for page-tables out of box. We set a new quirk for i/o page tables - IO_PGTABLE_QUIRK_NON_COHERENT, that lets us set different TCR configurations. This quirk enables the non-cacheable page tables for all masters sitting on SMMU. Should this control be available per smmu_domain as each master may have a different perf requirement? Enabling this for the entire SMMU may not be desirable for all masters. [1] https://lore.kernel.org/patchwork/patch/1020906/ Vivek Gautam (2): iommu/io-pgtable-arm: Add support for non-coherent page tables iommu/arm-smmu: Add support for non-coherent page table mappings drivers/iommu/arm-smmu.c | 7 +++++++ drivers/iommu/io-pgtable-arm.c | 17 ++++++++++++----- drivers/iommu/io-pgtable.h | 6 ++++++ 3 files changed, 25 insertions(+), 5 deletions(-) -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
