[PATCH v2] arm64: dma-mapping: Fix dma_mapping_error() when bypassing SWIOTLB

Robin Murphy robin.murphy at arm.com
Wed Jan 25 10:31:31 PST 2017

When bypassing SWIOTLB on small-memory systems, we need to avoid calling
into swiotlb_dma_mapping_error() in exactly the same way as we avoid
swiotlb_dma_supported(), because the former also relies on SWIOTLB state
being initialised.

Under the assumptions for which we skip SWIOTLB, dma_map_{single,page}()
will only ever return the DMA-offset-adjusted physical address of the
page passed in, thus we can report success unconditionally.

Fixes: b67a8b29df7e ("arm64: mm: only initialize swiotlb when necessary")
CC: stable at vger.kernel.org
CC: Jisheng Zhang <jszhang at marvell.com>
Reported-by: Aaro Koskinen <aaro.koskinen at iki.fi>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>

v2: Get the return value the right way round this time... After some
    careful reasoning it really is that simple.

 arch/arm64/mm/dma-mapping.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index e04082700bb1..1ffb7d5d299a 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -352,6 +352,13 @@ static int __swiotlb_dma_supported(struct device *hwdev, u64 mask)
 	return 1;
+static int __swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t addr)
+	if (swiotlb)
+		return swiotlb_dma_mapping_error(hwdev, addr);
+	return 0;
 static struct dma_map_ops swiotlb_dma_ops = {
 	.alloc = __dma_alloc,
 	.free = __dma_free,
@@ -366,7 +373,7 @@ static struct dma_map_ops swiotlb_dma_ops = {
 	.sync_sg_for_cpu = __swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = __swiotlb_sync_sg_for_device,
 	.dma_supported = __swiotlb_dma_supported,
-	.mapping_error = swiotlb_dma_mapping_error,
+	.mapping_error = __swiotlb_dma_mapping_error,
 static int __init atomic_pool_init(void)

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