From bae2c2d421cdea9dd8d62425eef99e389584cdb3 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Wed, 29 Jul 2015 19:46:05 +0100 Subject: iommu/arm-smmu: Sort out coherency Currently, we detect whether the SMMU has coherent page table walk capability from the IDR0.CTTW field, and base our cache maintenance decisions on that. In preparation for fixing the bogus DMA API usage, however, we need to ensure that the DMA API agrees about this, which necessitates deferring to the dma-coherent property in the device tree for the final say. As an added bonus, since systems exist where an external CTTW signal has been tied off incorrectly at integration, allowing DT to override it offers a neat workaround for coherency issues with such SMMUs. Signed-off-by: Robin Murphy Signed-off-by: Will Deacon --- Documentation/devicetree/bindings/iommu/arm,smmu.txt | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation/devicetree/bindings/iommu') diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt index 06760503a819..718074501fcb 100644 --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt @@ -43,6 +43,12 @@ conditions. ** System MMU optional properties: +- dma-coherent : Present if page table walks made by the SMMU are + cache coherent with the CPU. + + NOTE: this only applies to the SMMU itself, not + masters connected upstream of the SMMU. + - calxeda,smmu-secure-config-access : Enable proper handling of buggy implementations that always use secure access to SMMU configuration registers. In this case non-secure -- cgit v1.2.3