arm_iommu_get_sgtable can only describe buffers which came from arm_iommu_alloc_attrs, and returns -ENXIO for anything else. This is stricter than iommu_dma_get_sgtable(), which falls back to describing the buffer as a single chunk.
The difference shows up when a buffer is allocated for one device and mapped for another, as TegraDRM does. Buffers are allocated on the host1x logical device, which has no dma_configure and therefore uses direct DMA ops, and are then mapped for a display controller behind the SMMU. Add the same fallback as iommu_dma_get_sgtable(). Signed-off-by: Mikko Perttunen <[email protected]> --- arch/arm/mm/dma-mapping.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 91f12fb91509..22bde6acd1d3 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -1169,12 +1169,29 @@ static int arm_iommu_get_sgtable(struct device *dev, struct sg_table *sgt, { unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT; struct page **pages = __iommu_get_pages(cpu_addr, attrs); + struct page *page; + int ret; - if (!pages) - return -ENXIO; + if (pages) + return sg_alloc_table_from_pages(sgt, pages, count, 0, size, + GFP_KERNEL); - return sg_alloc_table_from_pages(sgt, pages, count, 0, size, - GFP_KERNEL); + /* + * The buffer was not allocated through these DMA ops. It may belong to + * a device which is not behind an IOMMU at all, which can happen when a + * buffer is allocated on one device and mapped for another. Describe it + * as a single chunk, as iommu_dma_get_sgtable() does. + */ + if (is_vmalloc_addr(cpu_addr)) + page = vmalloc_to_page(cpu_addr); + else + page = virt_to_page(cpu_addr); + + ret = sg_alloc_table(sgt, 1, GFP_KERNEL); + if (!ret) + sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0); + + return ret; } /* -- 2.55.0
