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authorChristoph Hellwig <hch@lst.de>2019-08-06 15:01:38 +0300
committerChristoph Hellwig <hch@lst.de>2019-09-04 11:13:19 +0200
commit249baa54790171438524ba97e8e0485dd6aa2762 (patch)
treecf5dc669ac064a93a37912f25aa7910d7e8db58d /kernel/dma/mapping.c
parentd9295532d5725e5926d76470acdfd239c8d2aad3 (diff)
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dma-mapping: provide a better default ->get_required_mask
Most dma_map_ops instances are IOMMUs that work perfectly fine in 32-bits of IOVA space, and the generic direct mapping code already provides its own routines that is intelligent based on the amount of memory actually present. Wire up the dma-direct routine for the ARM direct mapping code as well, and otherwise default to the constant 32-bit mask. This way we only need to override it for the occasional odd IOMMU that requires 64-bit IOVA support, or IOMMU drivers that are more efficient if they can fall back to the direct mapping. Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma/mapping.c')
-rw-r--r--kernel/dma/mapping.c30
1 files changed, 10 insertions, 20 deletions
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 285de5fbc8e9..64a3d294f4b4 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -271,25 +271,6 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
}
EXPORT_SYMBOL(dma_mmap_attrs);
-static u64 dma_default_get_required_mask(struct device *dev)
-{
- u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
- u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
- u64 mask;
-
- if (!high_totalram) {
- /* convert to mask just covering totalram */
- low_totalram = (1 << (fls(low_totalram) - 1));
- low_totalram += low_totalram - 1;
- mask = low_totalram;
- } else {
- high_totalram = (1 << (fls(high_totalram) - 1));
- high_totalram += high_totalram - 1;
- mask = (((u64)high_totalram) << 32) + 0xffffffff;
- }
- return mask;
-}
-
u64 dma_get_required_mask(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -298,7 +279,16 @@ u64 dma_get_required_mask(struct device *dev)
return dma_direct_get_required_mask(dev);
if (ops->get_required_mask)
return ops->get_required_mask(dev);
- return dma_default_get_required_mask(dev);
+
+ /*
+ * We require every DMA ops implementation to at least support a 32-bit
+ * DMA mask (and use bounce buffering if that isn't supported in
+ * hardware). As the direct mapping code has its own routine to
+ * actually report an optimal mask we default to 32-bit here as that
+ * is the right thing for most IOMMUs, and at least not actively
+ * harmful in general.
+ */
+ return DMA_BIT_MASK(32);
}
EXPORT_SYMBOL_GPL(dma_get_required_mask);