Merge branches 'arm/exynos', 'arm/omap', 'arm/rockchip', 'arm/mediatek', 'arm/smmu...

[mirror_ubuntu-artful-kernel.git] / arch / arm / mm / dma-mapping.c

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 63eabb06f9f17551695e89efc0ed59e0ce6ba186..386f41ced733b4f84691e73c8e860702d5aae5cf 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -935,13 +935,31 @@ static void arm_coherent_dma_free(struct device *dev, size_t size, void *cpu_add
        __arm_dma_free(dev, size, cpu_addr, handle, attrs, true);
 }
 
+/*
+ * The whole dma_get_sgtable() idea is fundamentally unsafe - it seems
+ * that the intention is to allow exporting memory allocated via the
+ * coherent DMA APIs through the dma_buf API, which only accepts a
+ * scattertable.  This presents a couple of problems:
+ * 1. Not all memory allocated via the coherent DMA APIs is backed by
+ *    a struct page
+ * 2. Passing coherent DMA memory into the streaming APIs is not allowed
+ *    as we will try to flush the memory through a different alias to that
+ *    actually being used (and the flushes are redundant.)
+ */
 int arm_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
                 void *cpu_addr, dma_addr_t handle, size_t size,
                 unsigned long attrs)
 {
-       struct page *page = pfn_to_page(dma_to_pfn(dev, handle));
+       unsigned long pfn = dma_to_pfn(dev, handle);
+       struct page *page;
        int ret;
 
+       /* If the PFN is not valid, we do not have a struct page */
+       if (!pfn_valid(pfn))
+               return -ENXIO;
+
+       page = pfn_to_page(pfn);
+
        ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
        if (unlikely(ret))
                return ret;
@@ -2390,6 +2408,15 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
        const struct dma_map_ops *dma_ops;
 
        dev->archdata.dma_coherent = coherent;
+
+       /*
+        * Don't override the dma_ops if they have already been set. Ideally
+        * this should be the only location where dma_ops are set, remove this
+        * check when all other callers of set_dma_ops will have disappeared.
+        */
+       if (dev->dma_ops)
+               return;
+
        if (arm_setup_iommu_dma_ops(dev, dma_base, size, iommu))
                dma_ops = arm_get_iommu_dma_map_ops(coherent);
        else